Jun 03 2013
I object, your honor! This trial is a travesty. It’s a travesty of a mockery of a sham of a mockery of a travesty of two mockeries of a sham.
— Fielding Melish
“Blood Type Diets Don’t Work,” “No Science Behind Blood Type Diets,” scream headlines on mass media sites like Reuters and NewsMax, who report the results of a study published in the latest edition of the American Journal of Clinical Nutrition (AJCN).
Now, you might think that a scientific article that could generate that type of headline actually went ahead and did what is normally done to subject a theory to scientific scrutiny: Test the theory clinically, preferably by some sort of randomized, controlled trial on a significant number of test subjects. In fact the AJCN researchers did nothing of the sort. They simply went into PubMed (the medical online database) and searched for any prior studies that have been published on the blood type diets.
Not surprisingly, they didn’t find any. Had they contacted me prior to the study I could have saved them a lot of extra work. I’ve looked high and low and also never found one. That’s how original this theory is.
Since I became interested in the ABO blood groups three decades ago I’ve collected, archived and categorized virtually every scientific article on blood types (excluding the large number of articles that dealt solely with transfusion) going way back to the early twentieth century. I also own many articles in languages other than English, some of which I have paid to have translated. Finally, my collection includes a large number of articles written in the years 1940-1966, long before the time when medical articles became electronically indexed. And I fully concur with the researchers, that there is indeed not one article of value in all that time that ever linked anything regarding a person’s blood type with nutrition. 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.
But here is where the dishonesty begins.
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 mathmatical 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. ABO blood type is a significant influence on the digestive tract, from stomach acid levels to intestinal enzymes to the particular strains of bacteria that grow inside of us. Much of the immunologic reactivity of many foods varies by blood type.
The connection between blood types and food lectins was universally maligned, except by some very accomplished lectin scientists, who obviously knew better. Especially vicious were the ‘paleolithic diet experts,’ who then conveniently rediscovered the lectin connection when it became evident that it could be used to justify their grain-phobic worldview. Virtually every skeptic I’ve ever discussed the theory with was completely ignorant of these facts, despite the notion that virtually all of the original studies (minus the pre-1966 stuff) can be perused on PubMed.
The delightful fantasy that everything in modern medicine has a strong evidence basis is just that–a delightful fantasy. For example, many medical agents are often employed ‘off-label’ for uses other than those originally intended as a result of their original study –even if they lack the high degree of scientific scrutiny are routinely reserved for pharmaceuticals.  Most herbal medicines, many used successfully since antiquity and the basis for many modern drugs, also have a weak evidence basis in modern science. About 30% of drugs prescribed to children have never actually been tested on children. We continually live and work in a world of knowledge insecurity, typically for the very same reasons you don’t see any studies on blood types and nutrition: Little institutional interest and even less available money.
Long-term diet studies are renowned for their difficulties. Subjects would have to follow a prescribed diet for a significant period of time, perhaps as long as one year, as many of these differences would be rather slight in the short term. Other subjects would have to follow a control or ‘sham’ diet. Both groups would have to include a reasonable number of subjects, and since we are talking about comparing outcomes between the four basic blood groups, we’d have to take this total number of subjects and then quadruple it. Subjects would have to be paid, constantly monitored, and their food prepared and supplied to them. Since we are studying a complete food plan, versus a single food or even a single drug, the cost of doing an ongoing study of this sort would be enormous.
So what is empirically self-evident when employed on a day-in, day-out basis, (“Hey Doc, three weeks on the diet and my psoriasis is clearing up!”) becomes an uncontrollable, insupportable, unsustainable mess when subjected to what is normally the scientific gold standard; a paradigm much better suited for a clean, get-in, get-out, trial of a single agent or intervention, like a drug or a specific medical procedure.
We’ve done some very simple polling (for which I make no special claims to be scientific) that show that, in a rather large number of internet responders, the level of satisfaction following one of the four blood type specific diets runs consistently at about 85% across all four blood types. What made this observation interesting is not the degree of satisfaction, since that is subject to bias, but rather the constancy of that number across the four different blood type groups, especially since they are all following diametrically differing diets to a certain degree.
So, are the headlines truthful? Do the diets not work? Is there no science behind them?
A sure sign that things are turning jaundiced occurs when the registered dietician gets wheeled out for the requisite Parthian Shot. As is expected, the preferred slur here is ‘fad diet’ which is a truely ludicrous accusation since the main book about the blood type diets, Eat Right for Your Type has been in mass publication for almost two decades. A two-decade old fad. One can only wonder just how long something has to be around before it is no longer a fad. Now, with all due respect, your average dietician is simply in no position to comment on the technical basis of how blood groups influence digestive physiology. Sorry, but it’s advanced, high level glycomics/glycobiology stuff and they just don’t do that in these types of programs.
On the up-side, each of the specific diets recommended for each of the blood types is, in itself, a pretty healthy diet. Indeed, somewhere in the nutrition literature, someone is claiming that the scientific evidence supports the use of such a one-size-fits-all diet in everyone. Perhaps the only reasonable claim is that the blood type diets can help predict which healthy diet, among the many out there, is particularly healthy for you.
Should this type of study be performed? Absolutely. But unfortunately, every once in a while there comes along a theory that must remain, at least for the foreseeable future, as a simple thought experiment; a heuristic; a useful rule-of-thumb for those willing to try it. Sort of like chicken soup for a head cold.
Does this lack of ‘evidence’ bother me? Not really. In fact, I’ve moved on from my obsession with the ABO blood groups years ago, although I still keep an eye on new developments.
“Science.” so the quote goes. “If you’re not pissing people off, you’re doing it wrong.”
So I guess the Blood Type Diet is scientific after all.
1. (Literary & Literary Critical Terms) consisting of, containing, or relating to gnomes or aphorisms
2. (Literary & Literary Critical Terms) of or relating to a writer of such sayings
- Walton SM, Schumock GT, Lee KV et al., “Prioritizing future research on off-label prescribing: results of a quantitative evaluation,” Pharmacotherapy 2008; 28(12):1443-52.