Eating according to your blood type seems to be the hottest idea in nutrition today. Despite negative reviews in nearly every mainstream publication - nearly all of whom have proclaimed the diet to be “no bloody good” - Eat Right 4 Your Type by Peter J. D’Adamo, N.D. (Putnam, 1996) has become a bestseller.
Fad diets, of course, come and go, rarely earning kudos from anyone other than publishers and their publicists. Dr. D’Adamo’s book, however, has won the respect of fellow naturopathic doctors, many of whom now offer $20 blood typing tests to determine whether their clients are Type O, A, B or AB. After all, Dr. D’Adamo claims 4,000 case studies of people who achieved radiant good health after learning to “eat right for their type.” Supporters include Ann Louise Gittleman, M.S., C.N.S., Christiane Northrup, M.D., Bruce West, M.D., Jonathan Wright, M.D.,and scores of other respected physicians and nutritionists.
Why then have others - Brian Clement, Director at the Hippocrates Institute, Robert Crayon, M.S. of Designs for Health, and this writer, among others - seen little or nothing that clinically or scientifically supports the theory? Blood type as a factor in illness? Certainly. More than 1,000 scientific studies exist suggesting this is so.
Blood type as a factor in deciding what to eat? D’Adamo bases his theories on the assumption that early man had Type O blood, and that the A, B, and AB bloodtypes came long after. He claims that these later bloodtypes are genetically predisposed towards grains and milk products, foods that came in with agriculture and the domestication of animals, while Type Os are natural meat eaters. The evidence is less than convincing. Anthropologists can point to evidence that all four blood types existed back in the hunter/gatherer Paleolithic era1 a fact that deflates Dr. D’Adamo’s entire theoretical structure.
That so many people have done well on Dr. D’Adamo’s blood type diet theory suggests that there is at least a drop of truth in it. Could the system work though the theories are faulty? Would that answer were as simple as four blood types, four diets!
Whether we are blood type A, B, AB or O is determined by chemical markers called antigens that lie on the surface of our red blood cells. If foreign blood enters the body - as occurs with an improperly matched blood transfusion - the immune system’s “security police” step up to check the antigen ID card to determine whether or not it should be welcomed. If not, the immune system generates antibodies to lock onto the foreign blood cells, causing them to clump together or “agglutinate.” Bodily “garbage collectors” then round up the glued-together trespassers to usher them out of the body.
Most people are familiar with this particular immune system scenario. It’s the reason why wrong blood transfusions cause hemolysis and death.
Less well known is the fact that plants and foods also contain blood-specific agglutinins known as lectins. A powerful example is a lectin known as ricin, found in the seeds of castor oil plants. If injected into the bloodstream, it agglutinizes so quickly with red blood cells that massive blood clots form and death is nearly instantaneous.
Reactions to the protein lectins in food are rarely so life threatening. (Or so unlikely, given that few people would ever think of eating the seeds of the castor oil plant much less inject them into the bloodstream.) Dr. D’Adamo, however, reports that hundreds of common food lectins are capable of causing health problems when eaten by people of the wrong blood type. Milk, he says, has “B-like qualities; if a person with Type A blood drinks it, his system will immediately start the agglutination process in order to reject it.” He reports that similar consequences accrue to Type O wheat eaters, Type B chicken eaters, Type AB anchovy eaters, and so forth. In short, there is a long list of foods that he says are best avoided by each blood type.
Such clumping, according to Dr. D’Adamo’s theory, is not just a form of “corpuscle punishment;” it disrupts digestion, metabolism, nutrient absorption, insulin utilization and a host of other vital processes, which, in turn, may contribute to everything from postprandial lethargy to chronic fatigue, diabetes, arthritis, irritable bowel syndrome, cancer and other ills. If so, it only makes sense to “eat right 4 your type.”
When we take a careful look at this theory it appears a bit “sticky.” The majority of scientific studies linking blood types and lectins have involved lectins added to blood isolated in test tubes.2 But foods are NOT supposed to be injected directly into the blood stream. Mother Nature designed the digestive system to process them for safe transport through the bloodstream and for easy assimilation into our cells.
A healthy body with full digestive and assimilative capabilities is completely capable of handling food lectins. In fact, this is borne out by numerous studies which suggest that lectins are either dismantled by enzymes - which are abundantly present in raw and fermented foods - or by cooking, which destroys the helpful enzymes but compensates by denaturing complex proteins so that they can more easily be broken down during the rest of the digestive process. 3
Few people today, however, can boast fully functioning digestive systems. Two health problems that have undoubtedly contributed to the ability of food lectins to slip uninvited into the bloodstream are: widespread hydrochloric acid (HCl) and trypsin deficiencies, which make it difficult for people to properly digest protein, and “leaky gut” syndrome, a condition in which large undigested or partially digested protein molecules “leak” out of the GI tract and into the bloodstream, where they do not belong and where they are likely to provoke an immune system response.
Many popular health writers, including Adelle Davis and Linda Clark, have identified problems caused by widespread HCl deficiencies, especially after the age of 40. As Davis put it, “Too little hydrochloric acid impairs protein digestion and vitamin C absorption, allows the B vitamins to be destroyed and prevents minerals from reaching the blood to the extent that anemia can develop and bones crumble.” Strong words, but backed by studies she cites from 1939 to 1961.4
More recently Robert Atkins, M.D., has taken up the cry. In Dr. Atkins’ Vita-Nutrient Solution (Simon & Schuster, 1998), he writes, “A lack of stomach acid is commonplace, the result of aging genetics, use of certain medications, and a variety of other factors.” Citing 11 studies, Dr. Atkins contends that the inability to properly digest protein contributes to asthma, diabetes, food allergies, osteoporosis, iron deficiency anemia, pernicious anemia, candida, rheumatoid arthritis, intestinal infections, psoriasis, vitiligo, hives, eczema, dermatitis, herpetiformis and acne.5
Why are people so short of HCl? For the body to manufacture HCl, it needs ample supplies of protein and zinc, ingredients that are in short supply in the popular low protein/high carbohydrate vegetarian and near vegetarian diets so popular today. Low HCl levels lead people to eat less meat (because they have trouble digesting it), which, in turn, leads to still lower HCl production. Once this cycle is set in motion, declining health is inevitable.
Adelle Davis did not make a link between HCl deficiencies and blood type; and Dr. Atkins does not consider blood type when he tailors programs to his clients, according to Joel Pescatore, Ph.D., a nutritional counselor at the Atkins Center.6 So it is possible that most of the people with this problem are all Type As or ABs, the types Dr. D’Adamo feels are predisposed to chronic shortfalls of HCl. The people with ample HCl may all be Type Os, as Dr. D’Adamo claims. Yet the identification of age-related deficiencies coupled with reports of failing health suggest a gradual decline of HCl over time. If so, HCl deficiency is a preventable and correctable problem, regardless of blood type.
Less well known is that people with digestive problems tend to suffer from shortfalls of pancreatic enzymes, particularly the protein digesting protease trypsin. If this is not secreted in sufficient quantities, protein molecules are improperly broken down. The greater the pancreatic insufficiency, the more undigested and partially digested protein molecules that enter the system and the more likely an immune system reaction. Indeed a connection between pancreatic enzyme insufficiency and multiple food allergies was made back in 1935.7
If trypsin deficiencies are on the rise today, the culprit might be the growing popularity of soy products such as tofu, soy milk and products made with soy protein isolate, all of which contain trypsin inhibitors. Although many nutritionists believe that these inhibitors are deactivated by processing and cooking, Robert L. Anderson and Walter J. Wolfe of the USDA’s National Center for Agricultural Utilization Research in Peoria, IL, have shown that the ONLY way to completely deactivate trypsin inhibitors is through the old-fashioned fermentation techniques used to make tempeh, miso and natto. Otherwise some trypsin inhibitors ALWAYS remain.8 If soyfoods are only eaten occasionally, the pancreas will kick in to produce extra trypsin. A constant barrage of soyfoods, however, will cause the pancreas to become overworked over time.
The problem colloquially known as “leaky gut” syndrome occurs when the mucus membranes of the intestinal tract are damaged and no longer provide an effective barrier to pathogenic gut bacteria and macro food molecules such as undigested or partially digested large proteins.
Once these macromolecules “leak” into the system, they are either attacked as foreign antigens or join “immune complexes” that lodge elsewhere in the body, causing havoc. When food and other antigens are allowed to enter the system in excessive amounts - as is always the case in individuals with leaky gut syndrome - sensitization of the immune system occurs, contributing to, if not actually causing, auto-immune diseases.
As might be expected, permeability of the intestinal lining correlates with numerous disorders, including food and environmental allergies; bowel problems such as IBS, Crohn’s disease and celiac disease; inflammatory joint diseases such as rheumatoid arthritis; dermatological diseases such as psoriasis, and many forms of cancer.9
Foreign proteins that pass through a “leaky gut” include not only Dr. D’Adamo’s pet lectins but also saponins and other blood factors. As clinical allergist Vincent Mark, M.D, points out, “Lectins are only another aspect of food intolerances or hyperreactivity and cannot stand alone diagnostically as its advocates imply.”10
Though Dr. D’Adamo seems well aware of the differences between food allergies (which trigger reactions of IgE antibodies), food sensitivities (which trigger delayed reactions by IgA, IgG and IgM antibodies) and lectin-related agglutinations, the bottom line is that the foods marked most often for avoidance by people of all four blood types are the very same ones that are most likely to trigger allergic reactions. Nowhere is this more true than of the Type Os, who are forbidden wheat, corn, sugar, dairy products and yeast - five of the “sinister seven” foods identified by the late Stuart Berger, M.D., as the foods most likely to cause allergies and damage the immune system.”11 As for Dr. Berger’s other two “sinister” foods, soy and eggs, Dr. D’Adamo considers soy a “neutral” that should not be eaten in quantity and advises that eggs are “generally a poor source” for the O blood type.
Dr. D’Adamo may well be correct in saying that the foods he has matched to each of the four main blood types would create no reaction in the body. More likely, such foods cause LESS of a reaction. Types A, B, AB, and O, after all, only represent the major blood types. More than 400 other blood markers exist, most of which are minor and admittedly occur only in limited geographic areas. Even so, the myriad markers mean that people have blood configurations that are as unique as their fingerprints. Take the lectin theory to its ultimate conclusion, and each of us would require a one-of-a-kind custom diet. Not four blood types, four diets, but an infinite number. It doesn’t take an IV league degree to know that this is an unworkable solution.
Wouldn’t it be wiser to clear up the problems that are causing “leaky gut” syndrome to begin with? The causes of “leaky gut” are many. More than half of the 68 million people who take nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen (best known under the brand names Advil, Motrin and Nuprin), naproxen, eiflunisal, profen, undomethacin, salicylate and tolmetin report some degree of digestive upset, including irritation, bleeding and ulceration. The drugs interfere with the protective mucus that nature designed to coat the GI tract.12
Other factors that contribute to leaky gut syndrome include HCl and trypsin deficiencies13, alcoholism14 and trauma.15 Aging also plays a role. As D. Hollander wrote in Gerontology, “the intestinal barrier to the absorption of potentially harmful environmental substances may be less efficient in aging animals.”16
Less publicized is the importance of diet. As Loren Cordain, Ph.D. - a proponent of the hunter/gatherer Paleo-Diet has pointed out - cereal grains, legumes, dairy products, yeast-containing foods and other products of the agricultural era all contain lectins that bind intestinal epithelial cells and change the permeability of those cells.17 These are the very foods tagged for elimination in most of the four blood type diets!
Dr. D’Adamo guaranteed the phenomenal success of his book when he told people of Type O, A and B to “just say €˜no” to all commercially-made breads, bagels, muffins, flours, cakes, cookies, pastas and cereals. Whether made from refined flours or the seemingly healthier version of whole grains, these gluten-containing products injure the gut. Eliminating them from the diet is the first step in giving the injured intestinal lining a chance to rest and recover. In that the three blood types O, A and B represent 96 percent of Anerica’s white population and 93 percent of the black population, it’s no wonder that so many people have benefited mightily from Dr. D’Adamo’s diets.18
Surely another component of Dr. D’Adamo’s success is the fact that many of his clients had been eating the same foods over and over, week after week for years. A rabbi who ate kasha day in and day out, for example. A boy whose favorite foods were corn and fried chicken. A woman suffering from lupus and kidney failure who ate “substantial amounts” of dairy and wheat. It is well known that people with “leaky gut” syndrome become more and more sensitive to their favorite foods as time goes on, and that people with food allergies and sensitivities are often advised to stick to “rotation diets.”
Why else might Dr. D’Adamo’s programs work? It could be as simple as the fact that all four diets eliminate chips, candy, donuts, cinnamon rolls and other junk foods comprised of sugar, wheat, salt, hydrogenated fats, and other known health destroyers. For Americans on the Standard American diet (SAD), adoption of any of the four diets would represent a considerable improvement.
Those who would like to enjoy high energy and radiant health without subscribing to the restrictive blood type diets nor to a rigid grain-free, dairy-free and bean-free Paleolithic diet, might consider the following:
First determine if you have “leaky gut” syndrome. One diagnostic tool is the intestinal permeability test available through Great Smokies Diagnostic Laboratory in Asheville, N.C. For healing, what’s generally required is the elimination of wheat and other gluten-containing grain products - as well as other problematic foods such as dairy and soy - for a period of four months to a year, depending on severity of the condition. Although diet alone can sometime heal a wounded GI tract, healing is facilitated with an appropriate supplement plan.
People who have had a “leaky gut” for some time tend to be seriously deficient in vitamins and minerals, betaine-HCl, digestive enzymes, beneficial gut bacteria, and many beneficial fatty acids. Two supplements that almost always work wonders are MSM (methylsulfonylmethane) and bovine cartilage. Detoxification programs, candida cleanses and parasite purge programs are often advisable as well. Coconut cream and coconut oil - which D’Adamo says should be avoided by everybody - can be particularly helpful in combatting pathogens in the gut and in restoring proper fatty acid balance.
Upon completion of these programs - not before - I have found that people of all blood types seem able to eat MODEST amounts of nearly anything, including wheat and other grain products. The operative word, of course, is “modest,” meaning one or two small servings a day, not the whopping 6-11 servings of breads and grains currently recommended by the U.S.D.A. Food Pyramid.
To maintain ongoing gut health, breads and grains MUST be prepared for easy digestion using the soaking, fermenting and cooking instructions described in Nourishing Traditions by Sally Fallon (NewTrends Publishing, 2000). Better yet, start making gelatin-rich soup broths, as per Fallon’s recipes.
Scientific studies dating back to the turn of the century suggest that gelatin improves the digestion of grains, beans, meat and dairy products and that it can normalize cases of hydrochloric acid deficiency. In addition, gelatin can soothe, protect and nourish the intestinal lining. As Erich Cohn of the Medical Polyclinic of the University of Bonn wrote back in 1905, “Gelatin lines the mucous membrane of the intestinal tract and guards against further injurious action on the part of the ingesta.” 19
Further support of gelatin came in 1937 when Francis Pottenger noted, “Even foods to which individuals may be definitely sensitive, as proven by the leucopenic index and elimination diets, frequently may be tolerated with slight discomfort or none at all if gelatin is made part of the diet.”20
The obvious conclusion is that proper soaking and cooking, and the use of gelatin, can make the blood-type diets irrelevant. Type Os find they can eat grains. Type A people - whom Dr. D’Adamo believes are natural vegetarians because they typically lack the abundant secretions of HCl necessary for easy digestion of meats - find meats easier to digest if they are served with a gelatin-based gravy, stewed in their own broth or served along with a cup of soup. And gelatin can alleviate the allergic reactions and sensitivities that numerous research studies have connected to blood Types B and AB.
Those who don’t care to keep their stock pots simmering, can achieve similar benefits by taking bovine cartilage supplements. More than 40 years of studies by the late John F. Prudden, M.D., D.Sci., showed that cartilage can soothe inflammation anywhere in the body, particularly the GI tract.21
Follow these simple, old-fashioned rules and those pesky lectins will be dismantled in your healthy gut and never cause problems in the bloodstream. If so, you’ll have the high energy and good health needed to mine yet another vein of the blood type controversy - the possible link between blood type and personality. Since 1920, it’s been a hot subject in Japan, where political candidates advertise their blood type, where dating services inform prospective partners about each other’s antigens and where a TV sitcom was entitled “I Am Type O.” Even condoms are sold by blood type and come packaged with little “success cards” advising which types will make red-blooded romantics.
- E-mail from Ruediger Hoeflechner on the subject of the Paleodiet, September 14-24, 1998.
- Freed, D. L.F., “Dietary Lectins and Disease,” Chapter 21 from Section B. “Non-Allergic Effects of Food,” pp. 375-381 from an unidentified medical textbook in the collection of Vincent Mark.
- Davis, Adele, Let’s Get Well (Signet, 1972), p. 142.
- Atkins, Robert, Dr. Atkins’ Vita-Nutrient Solution (Simon & Schuster, 1998), pp. 234-235.
- Author’s conversation with Joel Pescatore at the American College of Clinical Nutrition’s annual convention, Albuquerque, N.M., October 2, 1998.
- Oelgoetz, A.W, “The Treatment of Food Allergy and Indigestion of Pancreatic Origin with Pancreatic Enzymes,” American Journal of Digestive Disturbances Nutrition, 1935, Volume 2, pp. 422-426.
- Anderson, Robert L., and Wolf, Walter, J., “Compositional changes in trypsin inhibitors, phytic acid, saponins and isoflavones related to soybean processing,” The Journal of Nutrition, March 1995, pp. 518S-588S.
- For 52 references see the 1996 manual Assessing Physiological Function published by the Great Smokies Diagnostic Laboratory, Interpretive Guidelines, Intestinal Permeability, p. 6.
- Correspondence of Vincent Mark, M.D., to Pat Connolly, February 19, 1998.
- Berger, Stuart, Dr. Berger’s Immune Power Diet (New American Library, 1985).
- Margolis, Simeon and Flynn, John A., Arthritis: The Johns Hopkins White Papers 1997 (Baltimore, MD, Johns Hopkins Medical Institutions, 1997), pp. 15-19.
- Mack, David R.; Flick, Jonathan A.; et al; “Correlation of intestinal lactulose permeability with exocrine pancreatic dysfunction,” Journal of Pediatrics, 1992, Volume 120, pp. 696-701.
- Bjarnason, Ingvar; Ward, Kevin; and Peters, Timothy; “The leaky gut of alcoholism: possible route of entry for toxic compounds,” The Lancet, January 28, 1984, pp. 179-182.
- Freed, D.L.F., p. 380.
- Hollander, D and Tarnawski, H., “Aging-associated increase in intestinal absorption of macromolecules,” Gerontology, 1985, Vol.31, No. 3, pp. 133-137.
- E-mail from Loren Cordain on the subject of Paleo diets, March 29-30, 1998.
- The incidence in the white population is: type A, 41 percent; type B, 10 percent; type AB, 4 percent; type O, 45 percent. Among blacks, the frequencies are: Type A, 27 percent; Type B, 20 percent; Type AB, 7 percent; Type O 46 percent. Source: Tortora, Gerard, J., and Anagnostakos, Nicholas P., Principles of Anatomy and Physiology, Sixth Edition, (Harper & Row, 1990), p. 563.
- Gotthoffer, N. R., Gelatin in Nutrition and Medicine (Grayslake, IL, Grayslake Gelatin Company, 1945).
- Ibid, p. 62.
- Pottenger, F. M., “Hydrophilic Colloid Diet,” PPNF Health Journal, Spring 1997, Vol. 21, no. 1, p. 17.
- Prudden, John F., and Balassa, Leslie L.,”The Biological Activity of Bovine Cartilage Preparations,” Seminars in Arthritis and Rheumatism, Vol. III, No. 4, Summer 1974