Blood Type Diet: Latest Diet Scam
We are naturopathic physicians. We are also vegan as are our children. The practice of naturopathy as originally described by Dr. Benedict Lust includes "the elimination of...habits such as over-eating, alcoholic drinks and...meat eating" (Joseph Pizzorno, N.D. & Michael Murray, N.D., Encyclopedia of Natural Medicine, Prima Publishing, Rocklin, CA, 1991,p.5). When we attended the John Bastyr College of Naturopathic Medicine (now Bastyr University) the work of Henry Lindlahr, M.D. was required reading. Dr. Lindlahr defined the philosophy of Nature Cure or naturopathy as favoring a "strict vegetarian diet" because of the "morbid nature" of the "alkaloids of putrefaction" which "every piece of animal flesh is saturated with" (Henry Lindlahr, M.D., Nature Cure, Nature Cure Publishing, Chicago, Illinois, 1924, p.273).
Peter D'Adamo, N.D. has recently published a popular book in which he encourages a diet based on his interpretation of the ABO blood groups and health. This blood type diet theory encourages daily consumption of animal flesh by people of blood type O and blood type B. Together these two blood types make up between 56% and 69% of population of the United States (Kickler et al in The Principles and Practice of Medicine, 22nd edition, Appleton, Norwalk, CT, 1988, p.465). Schools of naturopathic medicine have begun to include this theory in their curriculum and our colleagues often recommend a diet including daily consumption of animal flesh to vegan/vegetarian patients of blood type O or B.
The wise, health-promoting nutritional advice offered by the vegetarian doctors who defined naturopathy as well as the recent research detailing the benefits of vegan/vegetarian diet on our kind done by Pritikin & Ornish (heart), Wahlqvist and Aldercreutz (menopause), Lindahl (asthma), Barsotti (kidney disease), the Farm Collective (uncomplicated home births) and Chen, Peto et al (general health, cancer) is being ignored by naturopathic physicians who subscribe to the blood type diet theory.
We feel this is a mistake.
The foundation for the blood type diet theory is comprised of three "legs" as the author himself points out. As we read them the individual legs contain inaccuracies which render each one scientifically and logically flawed. The diet theory they support is, then, rendered invalid.
"Leg One" is the lectin hypothesis. The foods we eat contain lectins. Because of how lectins clump (or "agglutinate") other molecules they have the capacity to create health problems for human beings. Botulism toxin has a lectin, ricin, that is so deadly you would never encourage someone to consume it. On page 27 of the book explaining the blood type diet, it is stated that certain lectins "agglutinate cells in the affected blood type" as "visible under the microscope". The author assumes that this same clumping seen in office on a slide beneath a microscope occurs in the bodies of people of particular blood type, making them unwell if they don't choose their foods as recommended by the blood type diet theory. Extrapolating from results observed in a test done on a laboratory slide to effects in a human being has several disadvantages. Observed in vitro morphological changes in blood are controversial regarding their "validity and reproducibility" as well as "the most common criticism" that "the technique is susceptible to the subjective judgments of technicians and that the methods used by different labs produce widely varying results" (Stephen Barrie, N.D. in A Textbook of Natural Medicine by Joseph Pizzorno, N.D. and Michael Murray, N.D., John Bastyr College Publications, Seattle 1987, Sect II Supplemental Diagnostic Procedures, p. II:FoodAl 2).
A laboratory slide differs significantly from the environment of the intestine. This is especially important when you realize that fasting or abstinence from alcohol will alter intestinal villus morphology and brush border membrane enzymes (Can J Physiol Pharmacol, 1985 Oct, 63:10, 1312-20) and that the combination of foods chosen at a meal will alter transport properties of individual nutrients due to changes in the composition of brush membrane lipids (Diabet Res, 1991 Mar, 16:3, 127-38). These important changes in tissue, enzymes, absorption and transport at the intestinal tract will not be mirrored in a slide of blood taken from the arm or fingertip. Additionally and perhaps most importantly, in response to in vivo challenge of the gastrointestinal tract with a food, human beings produce natural antibodies to dietary lectins such as soy, wheat and peanut. These antibodies do not interfere with the agglutination properties of the lectins but they are a significant part of our immune repertoire (FEBS Lett, 1996 Nov, 397:2-3, 139-42). The in vivo protection against any potential lectin-induced damage afforded by such antibodies is not quantifiable or apparently observable by in vitro microscopic analysis of agglutination, so an investigator or technician would miss it. Analogously, if we saw a house ablaze in a section of a city with closely-packed homes without knowing there was a nearby and reliable fire department, we could erroneously assume that an entire block of homes would go up in flames. This is decidedly not the case in nearly every major metropolitan area. Similarly, conclusions drawn about the impact of soy, peanut and wheat lectins from observed agglutination on a slide without knowing the extent of the innate protection our bodies generate in response to these lectins are most likely mistaken.
"Leg Two" of the blood type theory addresses the effect of foods on each blood type with regards to their interactions with intestinal bacteria and the mucous secretions of the gut (the largest source of blood type antigens other than red blood cells). This is referred to as the "polyamine part". Polyamines are chemicals which can be measured by a urine indican test. The urine indican test, as employed by conventional labs and some natural health doctors, does reflect bacterial activity in the small and large intestines. Elevated levels of urine indicans are considered, by some natural health care doctors, to be an indicator of "intestinal toxemia" and "overgrowth of anaerobic bacteria" (Dirk Powell, N.D. in A Textbook of Natural Medicine by Joseph Pizzorno, N.D. and Michael Murray, N.D., Section II Supplemental Diagnostic Procedures, p. II :Indic-1).
The conditions which, according to Dirk Powell, N.D., are confirmed as resulting in elevated levels of urine indican are the following: "inflammatory bowel disease, celiac disease, hypochlorhydria, gastric ulcer, biliary & intestinal obstruction, jejunal diverticulosis, scleroderma, gastrectomy, Hartnup's disease, pancreatic insufficiency, diminished peristalsis and blue diaper syndrome". Urine indican is recognized as valuable for detecting intestinal integrity, absorption and protein catabolism (Jacobs et al, Laboratory Test Handbook, Mosby, St Louis, 1984, p. 589). It is possible to draw oblique conclusions about the impact of diet on colon health using the urine indican test. The blood type diet theory hypothesizes, as stated on pages 27-8 of the book, that the urine indican test "shows that a carcinogen entering your system is magnified to ninety times the effect of someone for whom it is not toxic". There is no evidence that we could find which substantiates this remark. Also, there is evidence that enzymes such as intestinal transglutaminase, secreted in response to certain lectins, repair lectin-induced damages to the microvilli and gut epithelium (Biochem Biophys Acta, 1996 Nov, 1314:1-2, 66-70). In so doing these enzymes would inhibit and occasionally eliminate the potential for the chronic intestinal inflammation, bacterial overgrowth and illness ascribed to eating "wrong" for your blood type.
"Leg Three" addresses the secretory differences with regard to digestive juices (enzymes & acids) amongst the blood types. On page XVI of the blood type book, it is explained that higher than average stomach acid levels are to be expected in people with blood type O. The tendency of this blood type to peptic ulcer of the duodenum is cited as evidence of this. The book also notes, on page XVI, that in the practice of the naturopathic doctor who first coined the blood type theory it was observed that "type O patients did well on animal products and protein diets --- foods that require more stomach acid for proper digestion". It is known that not all men and women of blood type O hypersecrete HCl, a considerable percent secrete normal levels of stomach acid and some hyposecrete stomach acid; peptic ulcer of the duodenum does not have to be coincident with excess secretion of stomach acid and the localized rather than diffuse histopathology of a peptic ulcer of the duodenum cannot be explained as due to only excess stomach acid secretion, something additional is adversely affecting the duodenal health of patients so prone (McGuigan in "Harrison's Principles of Internal Medicine" 13th edition & McKusick in "The Principles & Practice of Medicine" by Harvey, 22nd edition). Dietary strategies for type O patients as outlined by the blood type theory are intended, in large part, to treat people who hypersecrete stomach acid. As we have explained this is often not the case and such diet strategies will not be appropriate care for quite a number of people who are blood type O.
More to our focus as regards "Leg Three", stomach acid does not digest protein, pepsin does. On page 55 of the blood type diet book it is stated that "type O's can efficiently digest meats" (animal flesh)"because they tend to have high stomach acid content". Hydrochloric acid is necessary for the conversion of pepsinogen (inactive) to pepsin (active). Nonetheless it is pepsin which is responsible for protein digestion, not stomach acid. The optimum pH for pepsin's protein-digesting activity is 2.0, a gastric pH consistent with what is realized by most non-doudenal ulcer patients. When the pH of the stomach drops to below 2.0 and especially at a pH of less than 1.5 (a pH more consistent with HCl hypersecretion) pepsin becomes demonstrably less effective at digesting protein (Lehninger, Biochemistry 2nd edition, p.196). Theoretically a person who hypersecretes HCl would be less able to digest protein. Given this, a "one size fits all" diet theory lumping every blood type O person into a HCl hypersecretor/high animal protein diet will not be health promoting.
A second aspect of the "Third Leg" of the blood type diet theory involves the blood type variability in the secretion of intestinal alkaline phosphatase. Blood type O and B secrete this enzyme while its secretion is negligible in the other two blood types. The blood type diet theory contends that intestinal alkaline phosphatase is an enzyme whose primary function is to split cholesterol and long chain fatty acids. On his website, the author of the blood type theory has stated that intestinal alkaline phosphatase is "an enzyme whose sole function is to break down dietary cholesterol" (11/13/97 post at 07:17:24 by author to S. Shapiro). This is not true. In the 1960's intestinal alkaline phosphatase was believed to be involved in lipid absorption, due to its ability to hydrolyze phosphate esters. In the 1970's reports suggested a different primary function for intestinal alkaline phosphatase, namely, that it is involved in calcium absorption (Gastroenterology, March 1972 62:3, P. 452-8). Observations by the researchers Norman and Hanssler independently confirmed a two to three-fold increase in intestinal alkaline phosphatase activity after vitamin D administration coupled with a rise in calcium transport. Recently intestinal alkaline phosphatase has been shown to also play an important role in thiamin transphosphorylation (Arch Physiol Biochem, 1995 Apr, 103:1, 33-8) and the hydrolysis of FMN and FAD in addition to being involved in riboflavin transport (Int J Vitam Nutr Res, 1983, 53:1, 109-14). At the very least intestinal alkaline phosphatase is involved in much more than the function heralded by the blood type theory. The possible significance of its varying secretion re: blood type to an involvement in cholesterol metabolism is overemphasized by the blood type theory to support an unhealthy recommendation for cholesterol-laden animal proteins.
In our opinion, the blood type theory of diet doesn't have a leg to stand on.
Deirdre B. Williams, N.D.