When an old colleague alerted me that Dr. Alan Gaby had written an editorial (Townsend Letter, September 2018) critical of my theories regarding the use of ABO expression in the gut as a potential indicator of certain dietary relationships, I was of course quite concerned. Dr. Gaby is a well-regarded authority on nutritional science, and our relationship goes quite far back. In fact he, and Drs. Bland, Pizzorno and Wright were the four nutrition instructors I had in my time at the then John Bastyr College. Frankly I question the need and timeliness of Dr. Gaby’s review, and why exactly my simple theories make this esteemed physician so apoplectic; especially since the Blood Type Diet, despite its ongoing popularity, is a mass-market book –with all the limitations therein– that I wrote over two decades ago.
However, a quick reading soon gave way to relief and then wry amusement, as Dr. Gaby’s criticisms of my work essentially amounted to a 1000 word logical fallacy commonly known as ‘an appeal to ignorance.’
But before I reply to Dr. Gaby’s editorial, I’d like to advance a simple concept that some readers may not be familiar with; something called a ‘heuristic’. Most of us probably know how to complete the phrase, ‘If at first you don’t succeed…’ For those who don’t, the traditional answer is to then ‘try, try, again.’ Not a bad rule, since most of the time giving something a second try is reasonable piece of advice. However, in certain circumstances, this could be a terrible recommendation. Thus our little aphorism qualifies as a heuristic, a probabilistic solution that, while not being perfect, is better than random.
Now, to my way of thinking, the Blood Type Diets are classically heuristic. They’re all fundamentally healthy; the entry requirements are quite minimal (the popularity of the theory has probably sent more healthy people to the Red Cross to give blood and get typed than any terrorist attack, earthquake or flood) and while the evidence is circumstantial, it’s based in some pretty compelling physiology (although it is physiology that Dr. Gaby neglects to mention). They don’t work in everybody, but they work in a surprisingly significant number of people, a percentage that cannot possibly be explained by Dr. Gaby’s claim that they are merely working by other methods.
On to Dr. Gaby’s editorial. I’ll first begin by mentioning what Dr. Gaby conveniently did not: The consistent, significant variations in digestive secretions that are predictable by ABO and secretor (FUT2) genetic variations. Let’s take one for example, intestinal alkaline phosphatase (IAP). Although often outshone by his isoenzyme cousins, IAP is responsible for the detoxifying of bacterial endotoxin, regulation of the Intestinal microbiome and, perhaps most importantly, regulation of intestinal lipid absorption.  Serum ALP levels vary significantly by ABO and FUT2 polymorphism, with type O secretors having up to 3-4 fold greater levels of this enzyme. I’ll leave it to the readers to draw the obvious conclusions.
Curiously, the first paper to report this, a 1996 editorial in the Lancet, was used by Gaby to criticize the associations between blood groups and gastric hydrochloric acid production and which, despite his slant, did in fact jive with my reporting. However he chose to make no mention of much stronger IAP link in his editorial at all.  It’s alarming when the choices available to gauge the action of a authoritative figure are limited to whether they are either disingenuous or sloppy.
The study Dr. Gaby highlights as proof positive of the lack of a scientifically validated correlation was one by El-Sohemy, et al at the University of Toronto. In 2015 they published a very similar study in PLOS One.  I’ll summarize it for you here: Their study conclusively proved that if young, healthy research subjects self-report eating potato chips, sandwiches, pizza, ‘beans,’ mac-and-cheese, French Fries and processed meat products, all the while doing 13.7% of the Blood Type Diet for six weeks, their final cardiometabolic markers will probably not vary much by blood type.  I had a very interesting series of back and forth with the lead investigator in the comments section of another blog I used to write.  Perhaps some readers might enjoy reading it.
I’d like to address a serious deficiency in Dr. Gaby’s understanding of my linking recommendations regarding certain dietary lectins to particular ABO phenotypes. Although he accuses me of ‘misunderstanding biochemistry and immunology’ in fact Dr. Gaby may well be the one in need of some remedial study, in particular the argument that ‘the ABO system is one of only 30 or so cell surface markers that have been identified on erythrocytes.’ This is in fact true, but is totally irrelevant. ABO and FUT2 polymorphisms are two of the most important genetic determinants of the tissue glycosylation of the gut. This characteristic is not to be found in any of the other blood grouping systems or as a predictable factor in other genetic polymorphisms. Any basic textbook in glycobiology would bear this assertion out.
The editorial ends with a whiz-bang that sets a new bar for irony: The claim that the blood type diets restrict certain foods, which might ‘inconvenience people and deprive them of healthful foods.’ Now, it seems obvious, at least to to me, that in a particular blood type, the point of this whole exercise is that they might not be all that healthful after all. Concerning the former, all I will say is that during the time I knew Dr. Gaby, he was quite fond of putting virtually all his patients on ‘elimination diets’ which, upon comparison, would make any variant of the blood type diet feel like a Roman vacation in hedonism.
It’s sad to see someone you respect heading in this direction, and it’s hard for me to believe he could be so duplicitous. But perhaps he is. I remember attending two of his lectures over the last few years and leaving the second lecture in amazement from the realization that both had the same identical slides, cursory, facile analysis and outdated references. This despite the fact that the lectures were years apart. Long before that I bought a paperback he wrote that basically recommended people take pyridoxine (vitamin B6) as a panacea for everything and anything.
So what if he’s a bit lazy, kinda sloppy and heavy-handedly tried to write an entire diet book best seller about a single vitamin? Prior to the diatribe your are currently reading I’ve never felt there was any sort of need on my part to haul him out over it. That’s his karma, not mine. However reading this review of my work makes me wonder exactly what his needs and motives are. The relentless fault-finding reminded me of another emperor, the Flavian Domitian, described by his contemporary the historian Seutonius, as being ‘his most content when he had impaled a fly with his stylus so that he could then pull their wings off.'
The doctor doth protest too much, methinks: If all the manufactured risks and dangers of following the BTD were as serious as he portrays, then given the length of time and large numbers of people involved, shouldn’t we have heard reports from other sources besides Dr. Gaby?
Critical reviews are not my forte, nor do they interest me all that much. Too busy with my own stuff. However, if I were to write a criticism of something, I think I would try to contact the responsible person directly, and openly and honestly tell them of my concerns about certain aspects of their work. Maybe take them to lunch if they lived close by. I would also tell them that I hope to learn more about it from their side, and allow them an opportunity to convert my skepticism into curiosity. After all, they’re probably the expert on the subject, even if they happen to be the expert in something I disagree with. It would have been nice to have had that opportunity, considering how far back I go with the guy, but I guess the popularity of my books just made the opportunity of grabbing a quick headline too irresistible.
Finally, I’d like to offer a closing heuristic, one that is likely more pertinent than the first:
Whenever you read words or phrases like ‘debunked’ or ‘illogical thinking’ in a review or criticism, you are more than likely being fed from an agenda. Whenever the other side of the issue is excluded and absent, today’s weather will be gotcha-nonsense, with an increasing chance of bullshit-vending later in the day.
Getting all science-like and preachy about a mass-market book in which virtually every line of text had to be simplified, massaged and democratized for the average man in the street is just bullying low-hanging fruit. Frat boys with sophomoric tendencies can not automatically be trusted to write modulated opinion pieces. Perhaps Dr. Gaby would care to list his own uniquely creative contributions to human happiness. Not stuff other people did that you can co-opt or sit around and pontificate about. Even just one single, useful, previously undiscovered, wholly-owned, important idea without a prior precedent.
Let’s start there.
8. “Inter initia principatus cotidie secretum sibi horarum sumere solebat nec quicquam amplius quam muscas captare ac stilo praeacuto configere, ut cuidam interroganti, essetne quis intus cum Caesare, non absurde responsum sit a Vibio Crispo, ne muscam quidem.” (Suetonius, The Lives of the Caesars)