Jan 17 2014

Unbelievable Facts


A study purporting to ‘debunk’ the blood type diet theory has recently been published. [1,2] However, a closer look at the study’s experimental design raises serious questions about its conclusions, including whether in fact the participants were actually following the blood type diet at all, and given its other parameters, would it have even been possible for the study to have any other outcome.

In response, I’ve written about some of my concerns with the design of the study and consequently the strength of what conclusions can be drawn from it. I’ve also asked a few colleagues who are versed in research evaluation to read the article, look at the data, and weigh-in on the conclusions. Let’s take a look at some of the more serious flaws in the study:

1. None of the subjects actually followed the Blood Type Diet.

The study was done on 1,455 participants of the Toronto Nutrigenomics and Health study. The study’s subjects simply kept diet diaries and a ‘diet score’ was calculated to determine their adherence to the respective diet for their blood type. This is how the researchers calculated the subject’s adherence to the blood type diet:

“Based on the food items listed in the ‘Blood-Type’ diets, subjects received one positive point for consuming one serving of each recommended food item and one negative point for consuming one serving of an item on the list of foods to avoid. Foods that are listed as ‘Neutral’ were not included in the equation and do not contribute to the final score.”

From the start it should be obvious that this method is a gross simplification. For example, a type A subject eating 12 ounces of high-fat hamburger three times per week would have a ‘0’ rating if they garnished the hamburger with onions. Simply giving +1 and -1 values for following or not following the food choices will most likely result in the subject’s results simply marching backwards and forwards and often just canceling out.

Dr. Ryan Partovi: “My problem with this methodology is that two people —one who eats mostly neutrals and a few beneficials could end up with the same score as someone who eats heaps of avoids and then just covers them up with a slightly greater number of beneficials. That’s not the way I’ve found the BTD to work. You can’t offset avoids with beneficials.”

Dr. Natalie Colicci: “I’m fairly certain you do not recommend white bread and potato chips to any patients”.

Dr. Ryan Partovi: “I think one of the biggest issues that I see is one of food quality. The difference between a grass-fed, grass-finished beef steak and a corn-fed beef steak is as large as the difference between a corn-fed beef steak and a piece of salmon. The average reader/researcher is clueless to those distinctions as well as their impact on what they seem most interested in measuring (lipids, weight, and blood sugar regulation).

The researchers themselves point to the limitations of this model, admitting that “Since the scoring system in the present study only assessed relative adherence to each of the four ‘Blood-Type’ diets, we could not determine the absolute number of people who strictly followed any of the diets.” [1]

Dr. Joseph Veltman: “Whenever I see a researcher using a food frequency questionnaire to evaluate someone’s nutrition, the results and conclusions are meaningless. The American Dietetic Association has said as much too. Research subjects who use this instrument bias their intake on what they think the researchers want them to eat.”

The study misclassifies numerous foods or lumps them into impossible-to-categorize groups. For example, ‘Mac and Cheese’ is listed as neutral for types A, B and AB. However, ‘mac and cheese’ is almost universally made with processed American cheese, which is listed as an avoid for those types. ‘Other grains’ (whatever they are) is listed as neutral for types A, B and AB, which effectively removes the majority of lectin specificities.

Dr. Ryan Partovi: “Many of the food values they used are also flat out wrong. Generic hotdogs (almost always pork) beneficial for O’s? Fried potato chips neutral for B’s and AB’s? Fried corn chips neutral for A’s? Sandwiches beneficial for O’s?! Did they look at the typical ingredients of any of these foods?! Fish clumped up into fish cakes, Dark meat fish, Other fish, and assigned random values? You can’t conclude anything from this nonsense.”

If this wasn’t bad enough, the very design of the study resulted in almost the entire study population being high compliance with the AB diet. So in essence, this study is trying to find a relation between blood type and the blood type diet in a study population that is largely on the AB diet.

2. The study used healthy young adults.

The study was performed on young adults aged 20 to 29. Using a population comprised sole of heathy young adults is virtually guaranteed to produce very negligible differences between the blood types, especially since each of the blood type diets is fundamentally healthy whole-foods diet. A much more useful study would have looked at a more health-compromised population, for example individuals with digestive disorders. Most chronic illness is accompanied by changes in cell glycosylation and host micro-biome, and it is these changes that sharply define the differences in how each blood type might benefit from a specific diet.

Dr. Natalie Colicci: “These people are healthy and it would seem unlikely that you’d see much variation due to genetic differences in as short a time as one month.”

Dr. Todd LePine: “Is the Blood Type Diet the cure of all ailments? No, but food affects the immune system directly and indirectly via the interaction with lectins on the gut mucosa and how the food shifts bacterial populations which in turn affects host metabolism.”

3. The study was conducted over a very short period of time.

The study analyzed what the subject reported eating over a one-month period. Even under the best of conditions, this is a very short period of time to observe any difference as subtle as variation between individuals. Our observations have consistently shown that a minimum three-month period is required for even the earliest demonstrable differences to be discerned.

Dr. Natalie Colicci: “I don’t think 30 days is enough to cause a sustained improvement. I’ve always said that superficially the blood type diet is a whole foods diet. That can’t be argued with. So of course taking any one blood type and mismatching it to one of the diets would show improvement in 30 days to some extent just because you are ‘cleaning’ up someone’s diet, especially if their current diet was contributing to elevated cardio risk factors.”

Dr. Todd LePine: “Measuring a few ‘biomarkers’ in a month’s span that are associated with cardiovascular disease and which take years to develop is like observing just one mole on the skin not change in a month’s time and saying you can predict the probability of melanoma.”

4. The diets actually benefited many of the subjects.

Given even its very short length the study’s authors themselves admit that the diets produced positive effects: “However, the observed results showed that even relatively high adherence to Type-A, Type-AB and Type-O diets were associated with favorable levels of cardio-metabolic disease risk factors, albeit in an ABO-independent manner.” [1]

Dr. Ryan Partovi: “I did find it interesting that the Type O diet lowered triglycerides (much more of a problem for Type O’s anyway) much better than the Type A diet, which was better at lowering cholesterol (much more of a Type A problem anyway).”

5. The study’s scope was overly simplistic.

As previously discussed, nobody in the study actually followed the blood type diet. In addition, if the researchers were truly interested in whether there were differences between individuals of different blood types (in such a short time frame) were truly significant, they should have also included the subject’s secretor status in their workup, as I have repeatedly stressed in my subsequent writings. [3] Since ABO type was determined genomically, adding this additional data (and adjusting food values to include variations based on secretor status) would have minimally added to the cost and complexity of the study but might have produced observable differences in the short (30 day) time frame.

Dr. Todd LePine: What is the Blood Type Diet? As I’ve always understood it, it was based on both ABO status and secretor status. I don’t see that they measured secretor status in the paper.

Dr. Mitchell Stargrove: “On first pass it seems to have a narrow set of evaluation factors, and a shallow comprehension of what actually constitutes adherence; let alone missing out on deeper approaches such as secretor status.”

6. When you go looking for something (or not), you very often find it.

Dr. Todd LePine: “In the study the ‘drug’ was the food, for which they did not fully control.”

Dr. Ryan Partovi: “This is a retrospective study. When you know the data set ahead of time, it’s fairly easy to structure a study that ends up with the result that you’d like to find. Because there is no control group, and this is only a retrospective study based on general trends in a person’s eating, there’s no way to really say for certain that the people who were following a diet of avoids for their blood type weren’t doing much worse than the average. Put another way, this study looked at the wrong thing. I’d say that the fact that they didn’t involve you, the author of the blood type diet books, in the study design is evidence enough that they weren’t serious about figuring out what the diets can do for cardiovascular disease.”

7. Possible conflicts of interest.

According to the disclosed ‘competing interests’ section of the article, one of the study’s principle investigators, Ahmed El-Sohemy, holds shares in Nutrigenomix Inc., a genetic testing company for personalized nutrition. Nutrigenomix  markets a variety of nutrigenomic  test kits, genotyping and customized reports to  dietitians. [4] Although the article states that Dr. El-Sohemy holds shares in Nutrigenomix, in reality he is actually the founder of the company.  It should not be too difficult to imagine the possible benefits to invalidating the blood type diets under these circumstances.

8. Conclusions.

This study had the opportunity to shed new light on a complex topic in nutrigenomics.  However, its definition of what actually constitutes following the Blood Type Diet was  simplistic to the point of uselessness. In addition, the length of the study was too short  and the significance of its negative results over-extrapolated. Far from proving the ineffectiveness of the blood type diet, it simply demonstrates the previously known fact that,  in the short term, there  are a multitude of approaches to eating healthy –if you are an already healthy young person.

In addition, pejorative elements in the article’s syntax, such as the continued  use of the phase “Blood Type Diets” in quotation throughout the article;  the simultaneous  publication of a press release hailing the ‘debunking’ of the blood type diet, and the direct links between the principal investigator and other nutrigenomic business interests call into question, at least in my mind, if the study’s outcome was an already pre-ordained forgone conclusion.

Dr. Todd LePine: “From this study you can’t conclude anything, except that the Blood Type Diet was beneficial and not harmful in all cases. But in this limited time-frame, relatively unscientific study we don’t have the power or time-frame to conclude much of anything. The thousands of real patients, who have followed the diet for a myriad of aliments, especially those with inflammatory and autoimmune issues, benefit in the real world of do I feel better, think better and move more easily.”


  1. ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors
  2. ‘Popular blood type diet debunked’
  3. Metabolic and immunologic consequences of ABH secretor and Lewis subtype status.
  4. Nutrigenomix Scientific Advisory Board



63 responses so far

63 Responses to “Unbelievable Facts”

  1. Edna W. says:

    Excellent, substantive and comprehensive debunking of the supposedly debunking study, which was, in fact, TOTAL BUNK!

    • Ahmed El-Sohemy says:

      Author of PLoS One study responds:

      As I stated earlier, your blog lists a number of false, misleading and irrelevant comments about our study and I provide a point by point response here to the major comments made by you and your colleagues. I want to clarify that our study was based on the recommendations made in the Eat Right 4 Your Type book (1996), which is what I will refer to in my comments when I make reference to “your book” or “the book”. Regardless of subsequent writings you may refer to, this book continues to be sold alongside numerous products that are marketed as offering a unique benefit to individuals based on their ABO blood type alone. So, the large number of individuals who might be affected (7 million copies sold) deserve to know that the only study to test the blood type hypothesis shows that any benefits of the blood type diet have nothing to do with a person’s blood type.

      Comment: “1. None of the subjects actually followed the Blood Type Diet.”

      The findings of our study show that those who had high adherence scores for the A, AB and O type diets did better off on a number of health indicators. But, the benefits had nothing to do with a person’s blood type. You issued a press release yesterday on PR Newswire where you clearly agree with us:
      “From this study you can’t conclude anything, except that the Blood Type Diet was beneficial in all cases.”

      How can you claim that the Blood Type Diet was beneficial to all, yet also claim that none of the subjects actually followed the Blood Type Diet? If we accept your press release that the Blood Type Diet worked in our study, but was the same regardless of what a person’s blood type is, then we can draw only two possible conclusions:
      1. The blood type diet hypothesis is false.
      2. You disagree with our method of determining blood type (i.e. DNA genotyping, which is the gold standard).

      Comment (by Natalie Colici): “I’m fairly certain you do not recommend white bread and potato chips to any patients”

      We never claimed that you do. We are aware that white bread and potato chips are not recommended for any of the blood type diets, but some people eat them, so we assigned them either a negative or neutral score depending on how they were classified in your book.

      Comment (by Ryan Partovi): “I think one of the biggest issues that I see is one of food quality. The difference between a grass-fed, grass-finished beef steak and a corn-fed beef steak is as large as the difference between a corn-fed beef steak and a piece of salmon.”

      The book makes no recommendations on beef consumption based on whether the cow was fed grass, corn or anything else. Yet, Partovi considers “one of the biggest issues” with our study to be something that’s not even part of the blood type diet. Partovi makes reference to salmon, but it looks more like just a red herring.

      Comment: (by Joseph Veltman): “Whenever I see a researcher using a food frequency questionnaire to evaluate someone’s nutrition, the results and conclusions are meaningless.”

      The food frequency questionnaire was used in a population-based study, not to asses an individual’s nutritional status. It’s a widely accepted and validated tool for assessing relative intake and has been described in hundreds of studies published in JAMA, New England Journal of Medicine, American Journal of Clinical Nutrition and many other top ranked scientific and medical journals. Food frequency questionnaires have been used to demonstrate many associations between diet and various health outcomes, including effects of diet that occur in controlled clinical trials (For an example, see study by Dr. Willett’s group from Harvard in Am J Epidemiol 2001;154:1107–12). Indeed, our food frequency questionnaire was able to demonstrate that those who follow an A, AB or O type diet have lower levels of biomarkers of cardiometabolic disease risk, which you conveniently touted in yesterday’s press release. What you failed to mention was that those beneficial effects had nothing to do with anyone’s blood type. Unless you have an issue with how we determined blood type, this selective omission of our key finding is incredibly misleading.

      Comment: “If this wasn’t bad enough, the very design of the study resulted in almost the entire study population being high compliance with the AB diet.”

      This is false. Look at Figure 1B in our paper. There were those with low compliance, medium compliance and high compliance with the adherence score ranging from -40 to +80.

      Comment: “2. The study used healthy young adults.”
      “Using a population comprised solely of healthy young adults is virtually guaranteed to produce very negligible differences between the blood types”

      Despite using a generally young and healthy population we still showed that adhering to either the A, AB or O type diets was associated with statistically significant effects on various health outcomes, which you seemed to praise in your press release. For example, those who adhered to the type A diet had lower blood pressure, insulin and cholesterol. But, this was observed whether you had type A blood or any other blood type. If the blood type diet hypothesis had any merit, wouldn’t we have seen no effect (or even adverse effects) in those with type O blood, who according to Dr. D’Adamo’s blog post (Gnomic Advice, June 3, 2013) should be “following diametrically differing diets”?

      Comment: “3. The study was conducted over a very short period of time.”

      “The study analyzed what the subject reported eating over a one-month period. Even under the best of conditions, this is a very short period of time to observe any difference as subtle as variation between individuals. Our observations have consistently shown that a minimum three-month period is required for even the earliest demonstrable differences to be discerned.”

      This is a complete contradiction of what you wrote in your book:
      “…try your Blood Type Diet for at least two weeks. Most of my patients experience some results within that time period” – Peter D’Adamo (p XVIII (Introduction), Eat Right 4 Your Type, 1996)

      Shifting the goal posts seems to be a common theme in response to inconvenient observations that you’re not able to counter.

      Comment: “4. The diets actually benefited many of the subjects.”

      Absolutely. This is precisely the point. Three of the 4 blood type diets displayed some of the benefits you claim. But, those benefits exist even for those who follow one of those blood type diets, but have a different blood type. This means your theory of unique benefit of a particular diet for a specific blood type is wrong (unless you have an issue with how we determined blood type). It also means that you no longer seem to have an issue with our method of determining dietary intake.

      Comment: (by Ryan Partovi): “I did find it interesting that the Type O diet lowered triglycerides (much more of a problem for Type O’s anyway) much better than the Type A diet, which was better at lowering cholesterol (much more of a Type A problem anyway).”

      Not correct. The book states that triglycerides and cholesterol are both a problem for Type A, and neither is a problem for Type O (p.260). This is another example of either shifting the goal posts or as Dr. Steven Novella notes on his blog about the blood type diet “appears to me to be the naturopathic tradition of just making stuff up.”

      Comment: “5. The study’s scope was overly simplistic”
      “they should have also included the subject’s secretor status in their workup, as I have repeatedly stressed in my subsequent writings.”

      The recommendations in your book are based solely on whether you have A, B, AB or O blood type, not secretor status. It appears that it wasn’t until you started selling a test to determine secretor status that you shifted the goal posts yet again. Remember that in your Eat Right 4 Your Type book you made big claims about benefits within 2 weeks, doubling survival rate among cancer patients and seeing benefits in more than four thousand patients, all based on ABO blood type, not secretor status.

      Comment: “6. When you go looking for something (or not), you very often find it.”

      We went looking to see if following the blood type diets had a different effect based on a person’s blood type and didn’t find it.

      Comment: “7. Possible conflicts of interest.”
      “Although the article states that Dr. El-Sohemy holds shares in Nutrigenomix, in reality he is actually the founder of the company. It should not be too difficult to imagine the possible benefits to invalidating the blood type diets under these circumstances”

      This comment is simply an attempt to discredit a scientist when you clearly have not been able to discredit the science. It is also an insult to the other co-authors (who have no ties to Nutrigenomix), especially the lead author Jingzhou Wang who had complete access to all of the data and conducted all of the original analyses. You should also recognize that the Nutrigenomix test kit is not a competitor of the blood type diet. You sell your products directly to consumers and to naturopaths and chiropractors. Nutrigenomix testing is available only through registered dietitians and I have yet to meet a dietitian who promotes the blood type diet. That’s because dietitians practice evidence-based nutrition and, as you know, there’s no evidence for the blood type diet.

      We have shown that the blood type diets have the intended effects on various biomarkers of health, but there is nothing special about how a person’s blood type affects their response. I have provided a response to each of the so-called ‘flaws’ and shown that they are false, misleading or irrelevant.

      Question for Dr. D’Adamo:
      Although I would have preferred to limit this discussion to the methods of our study, the results and their interpretation, you chose to issue a press release yesterday that was nothing short of a personal attack on my integrity. By the way, I’ve never heard of someone issuing a press release that they posted something on their blog. Bravo. You start this blog with the headline “Something Fishy”, so let’s talk about something fishy. You continue to skirt around the issue of providing scientific evidence by first claiming in your book that you are doing a study, then stating on your blog that a study can’t be done, then launching personal attacks on a scientist who actually did it and found that your theory just doesn’t work. My question to you, Dr. D’Adamo, is what happened to that 10 year trial on blood type diet and cancer remission you described in your book?:

      “Even now, as I write this, I am beginning the eighth year of a ten-year trial on reproductive cancers, using the Blood Type Diets. My results are encouraging. So far, the women in my trial have double the survival rate published by the American Cancer Society. By the time I release the results in another two years, I expect to make it scientifically demonstrable that the Blood Type Diet plays a role in cancer remission.” – Peter D’Adamo (p 307, Eat Right 4 Your Type, 1996).

      Where are the results of this study? I have not seen them published anywhere. If they have not been published, it would mean one of 3 things:
      1. You are a very slow writer and you need more than 15 years to write up this study and release the findings.
      2. You refuse to report the findings because the results showed that the Blood Type Diet didn’t work, or worse yet, may have caused harm.
      3. This study never existed.

      So, which is it Dr. D’Adamo? Those who bought one of the 7 million copies of your book deserve an answer. Especially those vulnerable cancer patients who were swayed by this ‘research’ of yours and bought your supplements, shakes and other blood type-specific products because you claimed that your program could double the survival rate.


      • Thank you for taking the time to respond.

        I will prepare my own response and publish it shortly.

      • Agnieszka says:

        Dear Mr El-Sohemy,

        I have read Dr D’Adamo’s blog and your response and I decided to share my experience with you. I think it might be of interest to you.

        My husband (blood type A) has followed the Blood Type Diet for 10 years, and me (blood type 0) – a few years longer.

        Both of us noticed a very significant change in our health and the way we felt very soon after we started following the diet (or – the way of eating, I prefer to call it, because “diet” sounds to me like a short-term thing and the Blood Type Diet is more like a way of life.

        I am not a dietician but I have always been interested in biology, health and nutrition. I never followed any trendy diets because they seemed unnatural and stupid to me. Already in primary school I was taught that to be healthy, we need to eat proteins, carbohydrates, fats, vitamins. So even before I learnt more about nutrition, popular diets that aimed to eliminate all fats or all sugars seemed tricky to me. Once I tried being a vegetarian, as an experiment. Although my diet was varied and seemingly healthy and I was definitely eating enough, after three weeks I was extremely weak, couldn’t concentrate and felt cold all the time. No surprise – I am type 0, so the vegetarian diet is not for me.

        What convinced me to try Dr D’Adamo’s diet was first of all the fact that I was sure it wouldn’t do me harm. There were foods from all nutritional groups on the recommended and neutral lists. I wasn’t supposed to eat pork but I could eat most other meats; I couldn’t eat wheat but I could eat rice. No oranges – but so much other fruit was allowed. Cauliflower was banned – no problem, there were so many other vegetables on the list. I had to avoid cow milk, which was hard because although I didn’t drink milk, I ate cheese, but sheep and goat milk cheese was allowed. This made this diet seem both doable and safe.

        Also, it convinced me that I read that for a healthy person it was not a problem to make an exception now and then and eat something from the avoid list. It makes it easier to follow a diet if you don’t have to feel bad or worried when you make an exception by mistake, out of necessity (nothing gluten-free, potato-free, pork-free, peanut-free and cashew-free at a gas station in the middle of the night, and you’re hungry and still have a long drive to do) or just because you feel like it. I soon realised that there were foods I had to absolutely avoid and never make exceptions, for example wheat and pork. After eating even just a little bit of wheat, I just started feeling discomfort all the way through my digestive tract, starting already in my mouth. It was so uncomfortable I preferred not to eat anything at all than eat a wheat sandwich if nothing else was available. Another of these foods was pork. It has happened to me I think four times in over 10 years that I had a little pork by mistake: when the food I bought was made of mixed minced meat and not beef, as the seller claimed, when there was pork fat (and who knows, maybe also meat) added to burgers which I ate at a festival where there was nothing else I could eat and twice when there was pork added to kebab and the seller told me it was only beef. In each of these cases I did not know I was eating pork so it was not a psychological effect that I got really sick. It was an indescribable rotten feeling in my whole body, nausea, headache, sweat, feeling hot and cold at the same time, unquenchable thirst. It lasted for about 12 hrs. I never eat pork, wheat and several other foods because it is just not worth it. When there is nothing substantial that I can eat available, for example while travelling, I eat an apple or a handful of nuts or even nothing. I find it much more bearable than eating something I really should avoid, even when I am at a party when everyone around me is eating fries, burgers, cakes and I am really hungry. Even then I stay away from what I should avoid. Some “avoid” foods I find acceptable in very small amounts, mixed with other food (potato flour in gluten-free products, corn, small amounts of potato, cabbage). Some “avoid” foods I sometimes eat and I have a feeling (could be misleading) they are not bad for me – like cow yoghurt, but only one brand and only the organic and fat-free variety. Of course, I can’t say if they are not doing any harm, but I don’t feel discomfort after eating them.

        It is true what Dr D’Adamo said in his book about feeling some results already 2 weeks after starting the diet. I would say, at least if your type is 0, you feel the result much earlier, already after a few days, if you stop eating wheat, potatoes and pork. It just changes your quality of life so much. Suddenly you realise that you don’t have to feel pain and discomfort after eating. All my childhood I hated having lunch or dinner because of the pain and discomfort afterwards. Suddenly, it was gone. What is more, I can eat whenever I feel like it and as much as I feel like eating and I never have trouble with my weight. I never eat too much, either. I just don’t feel hungry when I have had enough. In the times when I ate wheat, I would have a big sandwich and then an hour later I was hungry again. I would keep myself from having another one because I knew I shouldn’t, but it meant I was hungry all the time. I understand why so many people with type 0 who eat wheat are overweight. It makes you want to eat more and more, and if you don’t, you just constantly feel hungry and not everyone can stand this feeling.

        I will shortly tell you about my husband. Everyone in his family has (or had) problems with too high cholesterol and he did too when we met. When I told him about the Blood Type Diet, he realised he did feel uncomortable after the foods that he was supposed to avoid (wheat, milk, pork, shrimps) and decided to try it. About a year later he did a blood test. His uncle, who is a doctor, said it was unbelievable he was in the same family: there was no cholesterol problem at all. He has had good results since then, all these years. He also lost weight, his skin improved and he has stopped getting sick. He ever catches a cold or ‘flu and he used to catch them often.

        What is more, what Dr D’Adamo says about the type of exercise that is good for our blood types is true about us. I need to get tired, physically exhausted, I love hiking, cross-country skiing, working out in the gym and I feel trapped and stressed if I don’t get it. My husband prefers more acrobatic sports and running. Our body types also match Dr D’Adamo’s description: I have big muscles that grow from hardly any exercise and he has small muscles, no matter how much he exercises. I know it is not very relevant to this discussion but I find it interesting that also these details agree.

        Why am I telling you this story?

        Because you asked Dr D’Adamo for evidence that his diet worked. I think my husband and I are your evidence. We have followed the diet for 10 and over 10 years. We noticed what happened to us when we really stuck to it and when we made exceptions. We live in Europe, we don’t really follow nutritional debates, we are not selling Dr D’Adamo’s books and we have no agenda. I think we are reliable evidence, and you can read testimonies of more people in Dr D’Adamo’s book or on his Facebook page. You could also try to follow the diet yourself.

        It is very far from the truth that there is no evidence Dr D’Adamo’s diet works. What could be better evidence than all those experiences of real people who were helped by the diet?

        I don’t know about Nutrigenomics as I have only read about it today. I understand it is based on a similar principle as Dr D’Adamo’s diet. But while you need to do a test to determine what is the individual diet the patient should follow, Dr D’Adamo’s diet is a much simpler key. Personally, I suppose it is not completely accurate because even people with the same blood type are not completely the same and may react slightly differently to some foods, but still, just following the diet according to their type will improve their health and make them feel better. In the last 10 years, I have told a lot of people about this diet. I don’t know many people who follow it as strictly as I do because most people find it too much hassle (or can’t resist some foods), but I don’t know a single person who has tried it and said it didn’t work. Not a single one.

        I am a busy and quite healthy person and I don’t go to the doctor unless I have to. I would probably not go to take a test to find out what I can eat just out of curiosity, only if I felt uncomfortable after what I ate and/or I had some unexplained health problems. I would also never go to a dietician who was not familiar with, and respectful of, the Blood Type Diet. I think at this point, so many years after it started being developed, not being familiar with it if you work in the medical sector is ignorance, and denying that it works without getting familiar with it (including trying it and/or talking to people who consequently and correctly follow it) is suspicious.

        I will quote you: you say that “the Nutrigenomix test kit is not a competitor of the blood type diet. You sell your products directly to consumers and to naturopaths and chiropractors. Nutrigenomix testing is available only through registered dietitians and I have yet to meet a dietitian who promotes the blood type diet. That’s because dietitians practice evidence-based nutrition and, as you know, there’s no evidence for the blood type diet.” To be honest, I think it sounds a bit arrogant to me. I don’t know how many studies have been done on the BTD but how come all the testimonies of the people who follow the diet are not considered evidence? They should be, at least in some way, and I think it would be more practical if your dietitians got familiar with Dr D’Adamo’s findings and had respect for them at least while dealing with the patients because otherwise you might lose customers. Ordinary people don’t want to pick sides, they just want to be healthy and feel good and they will follow whatever is convenient for them and whatever seems to work. I can imagine it could be good for your business if Dr D’Adamo’s diet was really “debunked” because then people would think, ah, it’s not enough to simply follow the diet for my type, it turns out I have to do the (expensive?) test to really know what I can eat. So, yes, Dr D’Adamo’s diet is a competitor for you in a very obvious way but you can’t prove it false with such a short and poorly thought out experiment. You accuse Dr D’Adamo of not presenting unbeatable evidence that his diet works – well, you are also not able to provide evidence that it doesn’t and you won’t because it has helped so many people.

        As big an enthusiast of this diet as I am, I don’t claim that Dr D’Adamo’s diet is perfect and complete and that everything is known because nothing is perfect and nothing ever is completely examined. Science is a process and I believe Dr D’Adamo keeps finding out more about his diet all the time, even at this stage. But already just eating according to the four blood types improves people’s health, and for many of these people it is good enough, or more than that.

        Perhaps you could carry out an independent, unbiased study on the effect of GMO on human health. Feed one group of people with GMO and the other, with the same foods but GMO-free. For a few years. That would be a fantastic and much needed study, much more beneficial to humanity than “debunking” Dr D’Adamo’s diet.

        • Ahmed El-Sohemy says:

          Your post was cleverly disguised as one that seemed sincere, but I wonder what your true motivation is by fixating on a company that I hold shares in. If I owned shares in Kraft or Nestle, I suppose you’d say that I have a conflict of interest because the blood type diet does not promote the consumption of processed foods and so the results are somehow suspect because it may impact my dividends? Insulting the scientist because you have no ability to criticize the science seems rather desperate. Dr. D’Adamo claimed in his book that he was able to double the survival rate in cancer patients so I merely asked him to show us the evidence. You seem to feel qualified to claim that our study is “such a short and poorly thought out experiment”. Yet, when I ask Dr. D’Adamo for his evidence you defend him by claiming “I think my husband and I are your evidence.” Not very scientific.

      • “Nutrigenomix testing is available only through registered dietitians and I have yet to meet a dietitian who promotes the blood type diet. That’s because dietitians practice evidence-based nutrition and, as you know, there’s no evidence for the blood type diet.”

        I see that some folks out there are not terribly enamored about the evidence for your Nutrigenomix gene/diet panel as well.


        ‘This smells of pseudoscience.’

        ‘As presented here, however, this doesn’t seem far removed from astrology.’

        Pretty harsh words.

        • Ahmed El-Sohemy says:

          That’s the best your sleuthing could come up with? Some blogger. She states “Where is this research?”. Here it is (and just a sample for just one of the tests, and shown by 2 independent research groups):

          Coffee, CYP1A2 genotype, and risk of myocardial infarction

          CYP1A2 genotype modifies the association between coffee intake and the risk of hypertension

          As you stated in a previous post “With all due respect, perhaps it is time to stop surfing my website and get cracking” by answering the simple question about that 10 year study you referred to in your book. I’ve provided links above to some of our published research (and you can find the rest on Pubmed) so why won’t you show us the data for this remarkable study that you claimed doubled cancer survival?

        • Yes harsh words, they come easy. The difference is that the words are merely an opinion while the thousands of gene x diet interaction studies are a reality.

          This from AJCN in 2002:

          “With the identification of polymorphisms, or common mutations, in vitamin metabolism, large percentages of the population may have higher requirements for specific vitamins.” And the MTHFR work, plus many others since, have withstood repeated studies

          Yes be sceptical, then investigate, if you find no evidence then continue to be sceptical, otherwise…

          And to help sift through the rubbish in nutrition and the potentially useful, this site is good


        • Peter, pleass check comment stuck moderation again … did not say shut up this time (but did use “harsh words” literally!)

      • Ahmed,

        In specific response to your response to my points, I can only ask why you seem to have limited your reading at Eat Right for Your Type (ER)? Not only is that book the most elementary presentation of the Blood Type Theory, grossly simplified for the reader with no more than an 8th grade education; it’s also the oldest of Dr. Peter J. D’Adamo’s published books— although still in first edition hardcover, I might add.

        For the sake of argument though, let’s look at your assertion that, “The book makes no recommendations on beef consumption based on whether the cow was fed grass, corn or anything else.” Let’s turn to Page 52 of ER, where you’ll find the following:

        “… most of the meat consumed today is shot through with fat and tainted by the indiscriminate use of hormones and antibiotics. ‘You are what you eat’ can take on an ominous meaning when you’re talking about the modern meat supply.
        Fortunately, organic and free-range meats are becoming more widely available. The success of the Type O Diet depends on your use of lean, chemical-free meats, poultry, and fish.”

        Then, on page 345:

        “Although more expensive, try to find free-range meats that have been raised without the excessive use of antibiotics and other chemicals. Our ancestors consumed rather lean game or domestic animals that grazed on alfalfa and other grasses; today’s high-fat meats are produced by using high amounts of corn feed.”

        It may seem obvious in 2014, but Dr. D’Adamo was actually the first to recommend organic, free-range, grass-fed animal products in a diet book when ER was published back in 1996; and even then, he made clear that, “The success of the Type O Diet depends on your use of lean, chemical-free meats, poultry, and fish.”

        If distinguishing grass-fed from grain-fed meats proves too daunting, perhaps you would be best served by sticking to your red herring (although fresh would be best)— provided that you’re not a Type A Secretor, of course!

        On to your claim that, “The book states that triglycerides and cholesterol are both a problem for Type A, and neither is a problem for Type O (p.260).” I reread page 260, and I found no such claim. Dr. D’Adamo does say that Type O’s tend to have the highest level of the enzyme that breaks down dietary fats, which are the most significant source of blood cholesterol. He goes on to say that Type A’s and AB’s have consistently higher levels of serum cholesterol and triglycerides than O’s and B’s. He does not, however, discuss the relative impact of these lipid markers on cardiovascular disease risk based on blood type, i.e. how much of a “problem” they are for each blood type in ER.

        However, Dr. D’Adamo dedicates an entire chapter to just that question in his second book on the Blood Type Theory, Live Right for Your Type (LR), published a mere three years later in 1999. In Chapter 4, “Metabolic Synchrony: Blood Type’s Biochemical Influence” (pp. 61-73), Dr. D’Adamo lays out in detail the interaction between cholesterol, triglycerides, metabolic syndrome, dyslipidemia, and the ABO blood groups. I would especially refer you to the section entitled “The Cardiovascular Connection” on pp. 65-73.

        To paraphrase the late, great Dr. James D’Adamo, originator of the Blood Type Theory, perhaps this is a case of one man’s “shifting the goal posts” is someone else’s “slam dunk.”

        Best wishes,


  2. Ahmed El-Sohemy says:

    Thank you for turning on the Comments section here. I will prepare a response to your criticisms of our study in PLoS One and post it here soon. Please stay tuned.

    • Tom Martens says:

      Your study on the Blood Type Diet could have been applied to the Vegan diet, Atkins diet, Paleo diet or any other diet out there. All you would have to do is swap the title and you would have ended up with the same or worse results. There’s no mention of a control group and you parameters for compliance are poor.

      In the interest of science, you should retract your findings until an actual scientific research project can be completed.


      Tom Martens

      • Ahmed El-Sohemy says:

        Tom, I see that you’re a sales affiliate for the Eat Right 4 Your Type (www.decidetolivebetter.com/), and make a 20% commission on sales from blood type diet-related products, so I understand why you’re not pleased with the results of our study. But, I’d suggest you actually read our study because your comment about replacing the title with Atkins, Paleo etc is nonsensical. You should also familiarize yourself with a cross-sectional study design before asking questions about our control group. Your comment about parameters of compliance is also without merit. Be clear with what you consider a limitation of our study. Making grand proclamations without any evidence or citation adds little to a discussion on science.


  3. Jack H. says:

    Since you are criticizing Nutrigenomics for better health and diet, than which or who do you suggest to follow that pinpoints the gene types and gives you an accurate result attached with a diet for better health an living than Nutrigenomics?

  4. Ahmed El-Sohemy says:

    Your blog lists a number of false, misleading and irrelevant comments about our study that was published in PLoS One. Let me remind your readers that our study is the first ever to test the blood type diet hypothesis and was published in a reputable, peer-reviewed scientific journal. Although you’ve claimed previously, and on many occasions, that there are thousands of studies that support the blood type diet hypothesis, you acknowledged only recently that there’s never actually been any research on the topic. This admission was made in your blog post (Gnomic Advice, June 3, 2013) in response to the systematic review that was published last year in the American Journal of Clinical Nutrition, which concluded that there was no evidence to support the blood type diet (http://n-equals-one.com/blogs/2013/06/03/gnomic-advice/):

    “It is no great news to hear that there is a lack of published studies on following a diet based on one’s blood type: I’ve proselytized for just these types of studies for over two decades. All the authors did was conclude, as did I many years ago, that there is a lack of direct research on the subject.” and “Does this lack of ‘evidence’ bother me? Not really.”– Peter D’Adamo

    Our study in PLoS One was assigned to an impartial editor and reviewed by 3 independent and anonymous expert reviewers before it was accepted for publication. In contrast, you’ve “asked a few colleagues who are versed in research evaluation to read the article, look at the data, and weigh-in on the conclusions.” I did a Pubmed and Google Scholar search and could not find a single original research article published by any of them. Instead, I found that two of them (Partovi and Colicci) are naturopaths who offer (and presumably profit from) blood type diet-related products and services. Readers of this blog should have been informed of this clear and direct conflict of interest (something you raise yourself, which I will address).

    I will prepare a point-by-point response to the major comments made by you and your colleagues and post those here shortly.


    • Dr. El-Sohemy,

      I will await your point-by-point rebuttal.

      In the meantime I’ll just say that putting up a wall of ad hominems is not a very convincing counterpoint. It’s your study: so defend it. Trashing the qualifications of those who criticize it is not a defense.

      In addition, the use of the logical fallacy of ‘arguing from authority,’ by citing the level of expertise of your reviewers as a justification, is likewise unhelpful and proves nothing.


      • Ahmed El-Sohemy says:

        Dr. D’Adamo,

        In your own response to critics of your book (http://www.dadamo.com/science_critic.htm), you start off by stating that each “has not authored any peer-reviewed scientific papers on blood groups, nutrition or lectins.” Surely you consider having published a study to be a relevant point. Why else would you indicate this about your critics? Perhaps you can point specifically to where in my comment I was “trashing” anyone’s qualifications. I simply stated that none of them have published a single original study in a peer-reviewed journal (on any topic for that matter).

        I also made no reference to the “level of expertise” of the reviewers of our paper. I simply stated that they were experts, which means they were asked to serve as reviewers because they had published on related topics, which you consider to be something worth noting about critics of your book.

        I would prefer to limit this dialogue to ‘scientific evidence’ rather than obfuscate the discussion with philosophical arguments about fallacies and ad hominems, which are likewise unhelpful and prove nothing.


        • AE,

          With all due respect, perhaps it is time to stop surfing my website and get cracking on that point-by-point rebuttal. In particular, I’m interested in the usage of the category ‘grains, other,’ since one would think that species-specific grain values were at the heart of many food-lectin relationships, and when in fact no such category exists in any of my writings.


  5. Andrea Cayea says:

    I am a long time follower of Dr. D’Adamo, and his work which spans over 20 years. Your study really makes me laugh, how do you conclude that the diets BTD A, O, B, AB and also take into account secretor status plus initial health status in a study such as yours? It really makes me question your ability to truly understand Dr. D’Adamo’s work which has taken decades to discover and understand ( have you read his textbook or his consumer books of which he wrote over 10), but you claim to have designed a study that considers all the variables. Do you know someone who is following this diet and you felt you needed to disprove it? Or is Dr. D’Adamo a financial threat to you somehow? Sadly you wasted your time and I suspect someone’s money. So many of Dr. D’Adamo’s fans will continue to follow his diet advice regardless of your “study”, and new people will also be helped by his advice. Sadly you may actually keep people from health by your “study” which is really the saddest part of you, one day when you are old you will realize that health is what matters and how the patient achieves that does not matter. Your comment sounds angry and I wonder why would you write a point by point rebuttal to a blog Dr. D’Adamo wrote? After all it is just a blog. I will pray for you that you would open your heart to curiosity and understanding.

    • Ahmed El-Sohemy says:

      Hello Andrea,

      Thank you for your prayers. I’m sorry that you felt my “comment sounds angry”. Perhaps you can pray for me to see which words in my response convey anger.

      I do not know anyone who follows the BTD, but I also did not feel the need disprove it as you claim. In science, we test hypotheses. Let me explain the motivation behind conducting this research. I’ve given over 100 invited talks on the topic of nutrigenomics and personalized nutrition around the world and almost every time I have someone in the audience ask me “So, is this like the blood type diet?” My response has always been “No. I’m not aware of any study that has shown that differences in the ABO gene make people respond differently to different diets”. So, I decided that we need to test the hypothesis empirically to see if there is any validity to it. Our findings showed that adherence to either the A, AB or O type diets was associated with some beneficial effects (I would’ve thought that proponents of the BTD would be pleased to know this). However, these effects had nothing to do with an individual’s blood type. So, if a person followed the type A diet, they would see similar health benefits regardless of whether they had A, B, AB or O type blood. The diets are generally prudent, healthy diets (eg A type diet is mostly a vegetarian diet, which has long been known to promote health). This explains why so many people swear that that the BTD works. But, the benefits don’t seem to have anything to do with a person’s blood type. This is the only scientific evidence we have to date. If you prefer to ignore scientific evidence and simply believe someone’s ideas then we’ve reached the end of a discussion. If, however, you have specific concerns about certain aspects of our study design, I would be happy to address them. I will provide a point by point response to the comments made on this blog because, as I stated above, it is full of misinformation. Don’t you think readers of a blog deserve accurate information?


  6. MS says:

    Mr Sohemy

    Obviously you have a bias against the blood type diet since you are a principle shareholder in Nutrigenomix and would benefit greatly if the Blood Type Diet never existed for you would surely sell more of your “Eat according to your Genes” testing kits. I would like to see a follow up study on the results from your own genetic diet testing with the same parameters, level of compliance and age group you used in this study. I’m sure we would find the same less than satisfactory results…but then again there would still be a bias. If your gene test happens to help someone feel better, then we’re all on the same page as far as I’m concerned.


    • Ahmed El-Sohemy says:

      I normally don’t respond to those who are too cowardly to reveal their full and true names instead of initials, but I’ll make an exception here. The Blood Type Diet products (the books, supplements, shakes, teas, apps, test kits, bars, etc…) are all sold directly to consumers online or through naturopaths and chiropractors who can sign up as ‘Sales Affiliates’ to get a 20% cut from whatever they can convince their patients to buy. Nutrigenomix does not sell anything directly to consumers or to naturopaths or chiropractors. It sells only 1 genetic test kit that’s available only through a registered dietitian and is based on findings from studies published in only the top peer-reviewed scientific and medical journals. The company also does not sell any supplements or other products with its kit because the science is not there to support that. That’s a company that cares more about integrity than peddling supplements and shakes without valid scientific evidence just to make a buck.

      A typical strategy for those who have no valid arguments against the science is to attempt to slander the scientist. Classy.

      • Ahmed,

        I’m uncertain if you are making much of a case here. For one, I think you needn’t bother with responding to these types of comments. Maybe try and stay on point a bit more. Second, consider knocking off with the digs and slights about naturopaths. You seem to know little about their qualifications, and it weakens your claims that you yourself are the victim of slurs, when you in turn slur back. Finally, whether someone sells diet software, high-top sneakers, gene testing kits, weather vanes or vitamins, it doesn’t really matter. Money is money and I doubt that Nutrigenomix pays you in peanut shells.


  7. Carla N. says:

    As Dr. D’Adamo pointed out in the earlier blog post you cite:

    “There is a big difference between an absence of evidence and evidence of absence. There is good science behind the blood type diets, just like there was good science behind Einstein’s mathematical calculations that led to the Theory of Relativity. However Einstein’s theory required very specific and particular conditions to occur (solar eclipses at a certain time in a certain part of the world) before it could be subjected to testing and confirmation.

    Just like Einstein’s math, the theoretical and empirical evidence behind the blood type diets is pretty good. Spend some time reading my books or this blog and you will understand.”

    Mr. Sohemy do you actually make the time to read these? Is it at all possible you may be sweeping this under the rug because you were awarded grant money to conduct testing “your way” and beat Dr. D’Adamo to the proverbial “finish line” of empirical evidence?

    Are you aware of your own blood type/secretor status/genotype based upon Dr. D’Adamo’s work, and have made the necessary changes to this diet and lifestyle yourself? If you aren’t, then you don’t have the experiential underpinnings critical to set up said test, and it is a waste your time trying to explain point by point on this blog. There are many egocentric soreheads out there who exist (understandably) to conduct testing in a skewed way only if it would contribute to their own personal recognition, and bring them more grant money to continue on said course to prove anything, yet still using the same flawed base of “results.”

    What I think everyone on this blog CAN heartily agree on is that forging ties with competent colleagues in your area of study (such as Dr. D’Adamo) will produce more lasting work and recognition in a quicker amount of time, and with a more satisfactory result, than regarding them as having nothing whatsoever to offer.

    • Ahmed El-Sohemy says:

      I think even Dr. D’Adamo must be scratching his head after reading your post. It’s clear you don’t understand what he means by “There is a big difference between an absence of evidence and evidence of absence.” He was referring to the review last year in the American Journal of Clinical Nutrition that found no studies to support the blood type diet. He was disputing the headlines that said the blood type diet does not work. He argued (and I agree with him) that the ‘absence of evidence’ (which means there have been no studies – that’s what no evidence means) is not the same as ‘evidence of absence’ (which means a study – which is evidence – shows that the effect is absent.). His statement, however, is no longer applicable because we have now provided the ‘evidence of absence’.

      I can’t really comment on Dr. D’Adamo equating his work with Einstein’s. Only history will show whether this is the case or whether they are polar opposites.
      As for knowledge of my blood type/secretor status, yes, I have known my blood type since I was a child, but I don’t know my secretor status. Other than whoever sells Dr. D’Adamo’s secretor status kit for their 20% cut, I’m not aware of any medical clinic in the world that offers such testing. If there was any scientific evidence that knowledge of secretor status had any clinical utility, surely medical labs around the world would be offering it, no? We know they offer ABO blood typing because of its importance in blood transfusions and Rh factor for its importance during pregnancy. Why not secretor status? Let me guess. Because they haven’t read Dr. D’Adamo’s ‘work’, right? Sorry, a ‘book’ based on an idea is not considered scientific evidence.

      • Natalie Colicci says:

        Medical facilities around the world do offer it. Secretor status can be determined for most individuals by the Lewis antigen system. Lewis A and Lewis B antigen testing can be ordered with all conventional laboratories, hospitals, and blood banks like the Red Cross. It is a simple blood test. There is research correlating the clinical significance of these antigens. Just search pubmed.

      • Tom Greenfield says:

        Dr. El-Sohemy,

        Apart from the public saliva secretor status test available in the US, and the many laboratories worldwide which test for Lewis blood group as part of a blood grouping panel, my own laboratory tests for secretor status via Lewis blood group specifically for our own patients to adhere to a more refined version of the Blood Type Diet. We also receive blood samples from doctors and practitioners throughout Europe for the same reason. In addition, Dr. Jason Malia ND PhD in Australia also tests for secretor status in this way, and I know of other doctors and practitioners who use Lewis blood grouping for testing the secretor status of their own patients in their own laboratories. Just because you are not aware of them does not mean they do not exist.
        The Lewis blood group test is mentioned on pp. 367-8 of Eat Right For Your Type, and explained in more detail with separate diets for secretor and non-secretor throughout the later book Live Right For Your Type and others. When conducting such a study as you did, it would seem pertinent to pay attention to such facts, especially since the secretor gene modifies the expression of the blood group antigens so significantly in the gut.
        With regard to your comments about making a profit from selling secretor tests, I wonder whether any dieticians might possibly make a profit selling your tests to their patients?

        • Ahmed El-Sohemy says:

          I see you’re also a naturopath who contributes regularly to Dr. D’Adamo’s blog: http://www.dadamo.com/B2blogs/blogs/index.php?blog=14

          Your gave me the impression that you operate a medical laboratory that runs testing independently of Dr. D’Adamo’s site, but it appears that what you really do is process the samples for the secretor status test sold through the D’Adamo Personalized Nutrition website. So, it makes sense that you cite other naturopaths who do the same thing. So, you’re either using the test that Dr. D’Adamo sells or you use a different assay because it’s cheaper or better.
          Regardless, I’ve clearly let myself get sucked in by yet another red herring. The Eat Right For Your Type does not make any dietary recommendations based on secretor status, as you have acknowledged (even pp. 367-8 that you cite does not). I am aware that at least one of the subsequent 18 books that Dr. D’Adamo has written gives further advice based on secretor status, but this original book that sold 7 million copies and continues to be sold. Despite the comment by Natalie above yours claiming published studies on Pubmed, not a single one shows secretor status modifies response to diet as claimed in D’Adamo’s subsequent book(s).
          If you’re now telling us that ABO blood type alone is irrelevant then doesn’t that mean all those claims made by Dr. D’Adamo in his original book are false?

      • “If there was any scientific evidence that knowledge of secretor status had any clinical utility, surely medical labs around the world would be offering it, no?”

        Again with the logical fallacy of appealing to authority. But for the record, here are a few studies that link FUT2 to ‘clinical utility’:

        FUT2 in inflammatory bowel disease


        ABO/FUT2 Modulates predisposition to Crohn’s disease and affects disease behavior


        Fucosyltransferase 2 (FUT2) non-secretor status is associated with Crohn’s disease.


        Association of Lewis and Secretor gene polymorphisms and Helicobacter pylori seropositivity among Japanese-Brazilians.


        ABO blood type, Lewis and Secretor genotypes, and chronic atrophic gastritis: a cross-sectional study in Japan.


        Common variants of FUT2 are associated with plasma vitamin B12 levels.


        Secretor genotype (FUT2 gene) is strongly associated with the composition of Bifidobacteria in the human intestine.


        Gut microbiota: FUT2 genotype influences the gut microbiota in patients with Crohn’s disease and healthy individuals.


        Genetically dictated change in host mucus carbohydrate landscape exerts a diet-dependent effect on the gut microbiota


        Genome-wide association study of vitamin B6, vitamin B12, folate, and homocysteine blood concentrations.


        Involvement of intestinal alkaline phosphatase in serum apolipoprotein B-48 level and its association with ABO and secretor blood group types.


        Changes in intestinal alkaline phosphatase isoforms in healthy subjects bearing the blood group secretor and non-secretor.


        Total serum alkaline phosphatase (SAP) and serum cholesterol in relation to secretor status and blood groups in myocardial infarction patients.


        Triglyceride fatty acid chain length influences the post prandial rise in serum intestinal alkaline phosphatase activity.


        • Ahmed El-Sohemy says:

          Dr. D’Adamo,

          It was a mistake for me to think I could engage in an honest academic dialogue with you. You continue to mislead your followers by citing irrelevant studies with relevant-sounding titles so your readers think “wow, there really is scientific evidence to support the blood type diet”. If a single one of these studies supports the recommendations in your book then you would have quoted a relevant section from that study. But, you can’t because none of them do, so what’s the purpose of posting them when they do not support your hypothesis? As the saying goes, if you can’t convince them, confuse them.


          • Ahmed,

            I did not post them as proof of my diet; I posted them after your professed your ignorance of the fact that FUT2 had any ‘clinical utility.’

            Your words, not mine.


            • By the way, 23andMe tests for FUT2:


              Something you may to think about for your own panel.

              • Ahmed El-Sohemy says:

                Sorry, but the FDA declared that 23andME can no longer offer this test. Just read the very first sentence from the link you just sent. Not very helpful to your argument about clinical utility. You just cite articles showing that the genetic variants are linked to some health outcome, but clinical utility refers to the result of the test determining the clinical management of that patient. I’m not sure what kind of fallacy this is called, but none of those studies you cite show that the result of a secretor status test alters the course of treatment or management. If it does, then quote the part of the study that shows this.

  8. Regarding these personal attacks regarding conflict of interest – they are out of place and not justified. I’m sure Prof El Sohemy can look after himself but these attacks are a huge insult and offense to the co-authors or the paper and the editors and (unpaid) reviewers of the journal. As Prof El Sohemy states, the paper was peer reviewed for content and for process and judged by independent peers to be sound and valid.

    The process is extremely transparent, PloS One is open access, all the material is available, feel free to attempt to pick apart the study but leave the accusations aside. This applies especially to the author of this blog, Dr D’Adamo, if you have any evidence of fraud (because that is what you are at least implying) then come out with it.

    There is another thing here – you have all missed the point so far about nutrigenetics and nutrigenomics. The “Blood Type” or any of the other hundreds of diets, are not a threat at all. It is not either / or. I am also involved in nutrigenomics research and also commercial aspects. If there was (independently reviewed) published scientific evidence that supported the BD that would be fine, it would be great, it would be no problem at all for nutrigenetics. We use genetic information to personalise ANY type of diet. I have also published studies on the ketogenic diet – and we apply nutrigenetics to this diet system (which by the way is supported by hundreds of independent validated studies).

    We will not recommend the BD until there is proper evidence for it. It does not have to be randomised clinical trial (which is difficult with nutrition), but there are many other valid methods for evidence based nutrition (see for example http://1.usa.gov/1bLjzmU).

    Dr D’Adamo needs to do the studies and he also needs to shut up about the personal attacks on people who don’t agree with him. He has claimed in the past that he can’t conduct studies because opponents would just say that they are not reliable because he did them. Why? I really don’t think that would be the case. If he published a proper scientific study in a good peer reviewed journal I bet it would be well received. Probably there would be some comments and snide remarks about conflict of interest, but only from the ignorant minority.

    We have experience, there were a lot of critics and sceptics about nutrigenetics. We (Sciona, a commercial company) published the first trial in 2007 in Nutrition Journal (http://bit.ly/4Yk4Wg) – it was EXTREMELY well received – as far as I know the question of conflict of interest was only raised by an ignorant minority of one. Why? Because it was a transparent study, apparently well designed, and it was published in a reputable, independent and transparent journal.

    Dean Ornish has no such reaction to the studies he publishes.

    Dr D’Adamo believes in the BD, and so do most of the commenters here. But for now that is all it can be, a belief, a faith, that it works. You all claim it brings great health benefits – then Dr D’Adamo you are doing a great disservice to mankind by not conducting proper studies. You should do so, and if they are positive they will be followed by further independent studies. If you ever want this BD to be accepted that is the minimum you should do

    • Carla N. says:

      This is very odd; asking Dr. D. to “shut up” while on his blog?
      Hopefully Mr. Grimaldi you don’t think I am Dr. D’Adamo. If you did, I am simply Carla (just stating for the record.)

      • I’m happy for Dr D’Adamo to speak on his blog of course! My request was simply referring to the knee-jerk “conflict of interest” accusations. These statements about connections to commercial interests can only mean one thing – that the study was not fair, objective, well done or honest. That is an insult to all those involved including the co-authors, editors and reviewers and is completely unjustified and this is where the “shut up” applies. If any of you have evidence that the study was polluted by commercial interests then say so clearly and show the evidence, otherwise, well, you know…

    • Eric says:

      “You all claim it brings great health benefits – then Dr D’Adamo you are doing a great disservice to mankind by not conducting proper studies. You should do so, and if they are positive they will be followed by further independent studies.”

      I’ve been a follower of D’Adamo and my Type O diet for the better part of a decade, and I agree with this statement wholeheartedly. I am a scientist by ideology and a skeptic by nature. I know the diet works for me, otherwise I wouldn’t have wasted the last 8 years of my life. However, I cannot intellectually honestly tell other skeptics that the diet “works” by the same method we know other things work like cosmology and vaccines. There is still a bit of a leap of “faith” if you like. It’s not that the science isn’t there – in fact, if you read Dr D’Adamo’s literature and work through the sources, you will find an unbelievable amount of evidence for blood type as a factor in a host of metabolic and physiological functions. But I, too, wish the ball would get rolling on the research. Because I know that this is the only way it will gain any sense of credibility – as it should be. We need peer review and all of the wonderful mechanisms that the scientific method employs; otherwise we might as well still be throwing rocks at each other and seeing the witch doctor. I do appreciate your honest arguments Keith, and I apologize for the hostility you’ve felt here.

  9. Natalie Colicci says:

    Please let me clarify for you, Ahmed El-Sohemy, and the readers of this blog if I may. The result of your search is correct in that I have not published a research article. This however does not make my knowledge and experience with the Eat Right 4 Your Type (Blood Type Diet) and Dr. Peter D’Adamo’s work any less than fact, as I have incorporated it into the prescriptions of thousands of cases. You basically took a bastardized version of your concept of his work, conducted a research study with no control and concluded you debunked the diet. You state that your research had independent and expert reviewers. Did you or they even look at the Eat Right 4 Your Type book to see if you actually had your study participants following the diet? If you or they had, clearly you would see that your study is based on some diet, but it is not Eat Right 4 Your Type. Let us not even delve into the fact that the book also suggests exercise and lifestyle changes as well as dietary changes – none of which were incorporated into the study.

    You refer to me as a “naturopath,” as if that makes me any less of a physician licensed to practice medicine after attending four years of medical school and passing board exams. I also hold a Master of Science in Clinical Human Nutrition and am licensed as a nutritionist as well. Putting our advanced degrees and whether or not one is published aside, you do not have to have a doctorate degree to see the study participants simply did not follow the food compliance guidelines as defined by the Eat Right 4 Your Type book, just the ability to read. As far as a direct conflict of interest, I do not directly profit from Dr. D’Adamo’s products or services. Along with my education and continued research, his concepts in individualized nutrition are all incorporated together as tools in my practice to benefit my patients.

    I find it quite unfortunate that this study wasn’t better designed. Perhaps consultation with Dr. D’Adamo to ensure the diet was correctly implemented in the study would have been wise. I am sure he would have been more than happy to assist. His work in individualized nutrition has benefited hundreds of thousands of people worldwide. You may have debunked something, but it wasn’t the Blood Type Diet.

  10. James Palmer says:

    Dr. El-Sohemy,

    I see you reference a lot of Dr. D’Adamo’s prior statements. But, from all the readings I’ve done on Dr. D’Adamo’s work, one of the main thing he stresses, is that there hasn’t been a major study done on the diet because of cost constraints. That being said, since you know this already…. Was your study done in a controlled atmosphere? Did you monitor your participants for every morsel of food they put into their mouth? Did you watch every thing they did, to make sure they were following the recommended life-style habits? And on a side note, I have to say one month, just doesn’t cut it.

    • Ahmed El-Sohemy says:


      I agree that Dr. D’Adamo has stated that there hasn’t been a major study done on the blood type diet. Then how do you explain this:
      “Even now, as I write this, I am beginning the eighth year of a ten-year trial on reproductive cancers, using the Blood Type Diets. My results are encouraging. So far, the women in my trial have double the survival rate published by the American Cancer Society. By the time I release the results in another two years, I expect to make it scientifically demonstrable that the Blood Type Diet plays a role in cancer remission.” – Peter D’Adamo (p 307, Eat Right 4 Your Type, 1996).

      Wouldn’t you say this is a major study? That was about 15 years ago, and two years have come and gone. Perhaps Dr. D’Adamo can explain where he published these results.

      You state that one month just doesn’t cut it, right? Well then how do you explain this:
      “…try your Blood Type Diet for at least two weeks. Most of my patients experience some results within that time period” – Peter D’Adamo (p XVIII, Eat Right 4 Your Type, 1996)


      • Tom Martens says:

        Almost all of the people who start using ERFYT have health issues. ERFYT was created to help with digestive issues with weight loss as a by-product. If they were 100% compliant, 70-80% of them would notice a positive change in 2 weeks or less. Because Secretor status play a huge role in overall health, the 20-30% of the rest may or may not respond that fast or at all. Isn’t it interesting that 15-20% of the population are non secretors?

  11. My comment is still in moderation – is there a reason? other posts have since appeared

    • Keith,

      I believe the program automatically quarantined your post because you used the phrase ‘shut up.’ I’ve since approved it.

      Regarding your post: May I suggest that you stick to the point, i.e. did the experimental design properly model individuals actually doing what was recommended in my book?

      In response to your accusations of my great disservice to humanity: Which, I ask you, has the greater potential for disservice: a simple set of guidelines for a variety of healthy diets that would appear to work better in some than in others; that uses a biomarker that is low-cost, or even free of charge, or a study that purports to have definitively debunked those guidelines, despite containing questionable elements in its experimental design, and whose only effect will be to poison the well with regard to future inquiry?

      • The problem is that there are myriad “guidelines for a variety of healthy diets that would appear to work better in some than in others” that are not supported by scientific studies so there is no way of knowing which are really any good.

        If the BD is really good and useful it will pass scrutiny, if it is not, it won’t. At the moment thousands, millions (?) use it and really do NOT know if it the best option, if it is the optimal nutrition for them. So yes it would be a good service to test it properly. Therefore regarding your question I go for the former. An open, honest and transparent scientific study is never a bad thing – it will not poison any well, it can’t.

        • I agree with you. Problem is, even if the article is ‘open, honest and transparent,’ did it in fact test the hypothesis properly? If not, its consequences are actually worse than simply being wrong.

          • Eric says:

            I think this is the point. We’re all arguing for the same thing, just from different sides. Research is good; nay, critical. But in all fairness, the Canadian study was just not a proper way to set up the Blood Type Diet. Let’s try it again and see what happens.

  12. Carla N. says:

    I am still hoping Mr. Sohemy will respond as to whether he has knowledge of his own blood type/secretor status/genotype, in order to understand how to set up the proper hypothetical testing for individuals “the next time there is a study, ” because this would be a very positive thing.

  13. Tom Martens says:

    Have you performed the same study on your Nutrigenomics hypothesis (diet?)

    It would only make sense that if your are promoting a hypothetical Nutrigenomics (diet) as a way of eating, that you would do testing and a study to see if your hypothesis was correct before you would apply the same test to another diet.

  14. Maurice says:

    I received the Eat Right BT book last Xmas… I have had bloodwork before/after (8 weeks) – I did not see any changes, but perhaps if I followed longer?

    After reading this I am curious – why didn’t Dr D’Adamo publish even the preliminary data from 8 years of data collecting? That might have elucidated something right? The data looked promising for cancer remission so what happened next?? There must be some evidence to share?

    Thank you.

    • Tom Martens says:

      Hi Maurice, I can’t answer to Dr. D’Adamo’s cancer work, but would like to learn more about your situation. Did your blood work give you your blood type and secretor status? What are your health issues and how compliant were you?

  15. James Palmer says:

    Dr. El-Sohemy,

    I could cherry pick words and sayings to any study and find flaws with it; but, that’s not what my question was intended for. You were the Senior Author of the study, I am merely trying to find out if it meets my expectations of a study to base facts off of; especially, since the article says you found no evidence at all that the Blood Type Diet Works. I have no affiliation with Dr. D’Adamo, I make no money off of him, and I’ve never met the man–In case you were wondering. In full disclosure, I do follow The Blood Type Diet’s facebook page. I make comments on there from time to time; regarding my own personal habits (which a lot of the time do not go in a straight line with the Blood Type Diet).

    I find in life, when a question that was intended to be answered with a Yes or No question, isn’t answered that way, Politics is involved. I will not assume the answers to my questions are “No,” which I could easily do (it also doesn’t mean it’s bad); but, I will give you a second chance at answering the questions. This of course is just the start of my questions; I need concrete answers to continue with the rest.

    • Ahmed El-Sohemy says:

      It’s not that I said the blood type diets don’t work; it’s that they appear to work no matter what your blood type is. So, if you follow the type A diet, you’ll benefit just as much if you have A type blood or O type blood. It’s understandable that those who try one of these diets and see a benefit are convinced that Dr. D’Adamo’s theory is right. But, if someone with a completely different blood type tried the same diet they would have likely benefitted just the same. That’s why the theory is false. I don’t see how that’s so difficult to follow.
      My apologies for not answering your Yes/No questions on your previous post, and it’s most gracious of you to give me a second chance. Here are your questions again and my answers follow:

      1. “Was your study done in a controlled atmosphere?”

      Answer: Yes. There were no meteorological disruptions during the course of our study. We also happened to have a control group, in case you’re wondering, which consisted of individuals who did not adhere to each of the blood type diets as evidenced by their low adherence scores.

      2. “Did you monitor your participants for every morsel of food they put into their mouth? Did you watch every thing they did, to make sure they were following the recommended life-style habits?”

      Answer: No. Previous studies that used to monitor every morsel of food a person put in their mouth and watched all of their life-style habits were done on institutionalized individuals (eg. prison populations), and Research Ethics Boards no longer approve such studies. By life-style habits, I assume you mean the exercise recommendations where one blood type should do vigorous aerobics, and another blood type should stick to yoga and golf, right? (I forgot, which yoga-inducing antigens bind to which specific blood cell type?). The title of the book is ‘Eat Right 4 Your Type’ and the claims made in the book refer to the benefits of the diets alone. Are we now to believe that the diets become ineffective if the person is not doing yoga/golf or aerobics as well?


      • James Palmer says:

        Thank you for replying. I will wait for your follow up to Dr. D’Adamo’s new blog; since, it may answer other questions I may have.

  16. Child w/Autism Mother; Tracy Shirley says:

    HeseMy family has been on the BTD since November 2013.
    Yes, because of health reasons in members of the family.
    Our son, Reed, who is 4 has Autism and development delay
    has responded Very well by sticking to this diet! His story is long
    so I will not go into great lengths about it but since sticking
    to this diet he has begun to do things he has Never done
    before. These are huge steps for a child who has Autism
    like my son. Reed’s eye contact is wonderful now, he looks at
    the person talking to him when spoken to 8 times out of 10,
    he has begun to mimic sounds, thus giving the signs he will
    in fact begin to talk, he doesn’t always have a blank stare, he
    has an actual light in his eyes! He has taken interest in trying to use the pedals of his tricycle, he’s now pushing a toy truck down the hallway and not throwing it, his bowels are regular now and transitioning from one thing to another is getting easier for him. Reed still has a long way to go but these changes we’ve seen in him have been all since we began using them BTD! No one can convince my family that the BTD is not beneficial or doesn’t work because we know first hand that it does! Dr. D ‘Adamo, though we have not met him or even spoke to him and all his research over the years is a blessing and we are so grateful we found his books and chose to follow the diet.
    Rank You Dr. D’Adamo! Tracy Shirley

  17. Thomas Oellrich says:

    Regarding the supposedly non-existing conflict of interest, if a ‘scientific’ study were to convince people that the Blood Type Diet was a scam, what would a lot of people who would otherwise have given it a try do? Go see a dietician maybe?

  18. Ray Dibb says:

    I am intrigued and also dismayed by both sides of the ‘argument’ in relation to the efficacy of the Blood Type Diet. Peter D’Adamo came up with a theory of how a range of foods were tolerated by persons of different blood types. He apparently felt strongly enough by his theory that he decided to publish a book as a means of sharing his theory with any member of the public that wanted to know about it. It still remains a theory, and I must profess that I consider it to be a worthy theory.

    Sadly, my observation is that ego seems to play a very big part in these kinds of debates. Each side tends to make subtle and even overt negative comments about the integrity, qualifications and independence of the other side.

    Most health conscious people realise that they must take personal responsibility for pursuing their best possible health outcome. The BTD offers a theory, which seems to me to have a great upside and no discernable downside. Like most things in life, it’s up to the individual to decide what to make of a theory or a concept. Good on anyone that takes the initiative to seek out ways to better themselves. If persons try out the BTD and find that it does nothing positive for them, then they will likely move on in search of something that might work for them. My point is that it is most unlikely that such persons will have suffered any detriment in having given this theory a go.

    I can’t help but feel that Ahmed El-Sohemy believes that a theory that is not validated by clinical trials, as well as being peer reviewed, is not worth considering.

    Ahmed El-Sohemy has relied on a non-randomized, observational, cross-sectional study, which apparently used subjects that were mainly young and healthy to complete questionnaires on their food consumption. From such a study Ahmed El-Sohemy concluded with apparent confidence in saying that the blood type diet hypothesis was false. The assumption to be derived from Ahmed El-Sohemy as well as Steven Novella and Co is that the BTD Theory is rubbish, and that anyone that gives credence to it is foolish and gullible.

    I applaud Peter D’Adamo’s theory. I have followed it for some considerable time, ceased following it also for a considerable time, and then re-followed it in a more disciplined way over the past 12 months. All I can conclude from this is that it has worked for me in a spectacular way. I guess the same could be said by the many thousands of people that contribute to the BTD forums. If one needs to be foolish or gullible in order to feel better, then I say go for it.

    I personally do not feel that an irrefutable clinical trial could be conducted on this kind of theory, as it would involve unlimited variables and would need to rely on artificial constraints. So what? So it’s a leap of faith. Who cares? I don’t. Why? Because I suffered no harm in trying it. Furthermore, I guess Peter D’Adamo could have sent surveys or questionnaires to any number of the many thousands of BTD advocates in order to obtain a meaningful assessment of the validity of the theory in action. Why would he? I doubt that Ahmed El-Sohemy and his peers would accept this as a valid process.

    If one wants to suggest that I got ripped off in buying Peter D’Adamo’s book or his App then I say get real. Such a petty little amount for a worthwhile pursuit of better health could not possibly be what Ahmed El-Sohemy wants to protect us from. Ahmed El-Sohemy needs to keep in mind that the theory does not require proponents to spend money on special plans, on consultants or on supplements etc. It does not have to cost anything to follow the theory.

    The major reason I am critical of Ahmed El-Sohemy is that he chose to try to ‘debunk’ a theory that does no harm but may do good. So why would he choose to do this? So what if seminar participants associate what he is peddling with the BTD. To me, that alone tells me that he sought for an outcome that would discredit the BTD theory.

    If Ahmed El-Sohemy wants to do a service to humanity, then maybe he should pursue trials that ‘debunk’ the efficacy of chemotherapy, of statins, of certain vaccines, etc. These are high profile controversies that are crying out for independent and honest assessment. It goes without saying that the death, health complications and expense associated with these issues are massive. In contrast, I would like Ahmed El-Sohemy to inform of the death, health complications and expense that have been associated with people that have followed the BTD.

    But that is only if Ahmed El-Sohemy wants to keep making academic contributions. Then again, if Ahmed El-Sohemy really wants to ‘debunk’ the holy grail of theories, then I suggest he start putting his claws into the theory behind all the various religions. Is this not the ultimate in ‘leap of faith’?

    Let’s just allow the followers of the BTD to enjoy their improved health, even if it is no more than a placebo effect from following various dietary templates. Please do not suggest or imply to the BTD followers that they should go and see their doctor for dietary advice, or go to Jenny Craig, or to rely on pharmaceutical remedies. Please also, do not subliminally send the message to BTD followers that it is okay to indulge in processed and fast foods.

    My message is about the greater good as opposed to bowing to big egos.

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