The blood type diet is a diet advocated by Peter D'Adamo, a naturopathic physician, and outlined in his book Eat Right 4 Your Type. D'Adamo's claim is that ABO blood type is the most important factor in determining a healthy diet, and he promotes distinct diets for people with O, A, B, and AB blood types.

Throughout his books D'Adamo cites the works of biochemists and glycobiologists who have researched blood groups, claiming or implying that their research supports this theory. Nevertheless, the consensus among dieticians, physicians, and scientists is that the theory is unsupported by scientific evidence.^{[1][2][3][4][5][6][7]} D'Adamo responds to some of the criticisms on his website.^[8]

Contents 1 Description 2 Scientific criticism 2.1 Research evidence 2.1.1 Questions of lectin actions 2.1.2 Lack of clinical trials 2.2 Blood type evolution issues 3 Further reading 4 See also 5 References 6 Internal links 7 External links

[edit] Description

D'Adamo's premise is that human blood type is key to the body's ability to differentiate self from non-self. Lectins in foods, he asserts, react differently with each ABO blood type and to a lesser extent with an individual's secretor status. In his book, Eat Right 4 Your Type, "Lectins: The Diet Connection", and in following chapters, lectins which interact with the different ABO type antigens are described as incompatible and harmful, therefore the selection of different foods for A, AB, B, and O types is important to minimize reactions with these lectins.

D'Adamo bases his ideas on the ABO classification of Karl Landsteiner and Jan Janský, and some of the many other tissue surface antigens and classification systems, in particular the Lewis antigen system for ABH secretor status.^[9]

On page 20 of "Eat Right 4 Your Type", D'Adamo states: "at this point, you might be wondering about other blood type identifiers, such as positive/negative, or secretor/non-secretor. ... These variations or subgroups within blood types play relatively insignificant roles. More than 90% of the factors associated with your blood type are related to your primary blood type, O, A, B, or AB. "

The evolutionary theory of blood groups, which is also used by D'Adamo, stems from work by William C. Boyd, an immunochemist and blood type anthropologist who made a worldwide survey of the distribution of blood groups. In his book Genetics and the races of man: An introduction to modern physical anthropology, published in 1950, Boyd describes how by genetic analysis of blood groups, human races are populations that differ according to their alleles. On this basis, Boyd divided the world population into 13 geographically distinct races with slightly different frequency distributions of blood group genes.

D'Adamo groups those thirteen races together by ABO blood group, each type within this group having unique dietary recommendations:

• Blood group O is believed by D'Adamo to be the hunter, the earliest human blood group. The diet recommends that this blood group eat a higher protein diet. D'Adamo bases this on the belief that O blood type was the first blood type, originating 30,000 years ago.
• Blood group A is called the cultivator by D'Adamo, who believes it to be a more recently evolved blood type, dating back from the dawn of agriculture, 20,000 years ago. The diet recommends that individuals of blood group A eat a diet emphasizing vegetables and free of red meat, a more vegetarian food intake.
• Blood group B is, according to D'Adamo, the nomad, associated with a strong immune system and a flexible digestive system. The blood type diet claims that people of blood type B are the only ones who can thrive on dairy products and estimates blood type B arrived 10,000 years ago.
• Blood group AB, according to D'Adamo, the enigma, the most recently evolved type, arriving less than 1,000 years ago. In terms of dietary needs, his blood type diet treats this group as an intermediate between blood types A and B.

[edit] Scientific criticism

D'Adamo's Blood Type Diet has met with criticisms for many different reasons,^{[1][2][3][4][5][6][7]} some of which have been addressed publicly by D'Adamo.^[8]

[edit] Research evidence

One criticism of D'Adamo's hypotheses and recommendations claims that he provided inadequate evidence.^[7] For example, his first book, Eat Right 4 Your Type, published in 1997, contains only a bibliography. While his subsequent books have provided thorough references for the classifications of various foods within his categories of "beneficials", "neutrals" and "avoids", his specific process and reasons for reaching these conclusions of classification remain undocumented.

Also, by limiting the very complex human beings to just four limiting stereotypes, the blood type diet has been likened to a "blood type astrology".^[10]

[edit] Questions of lectin actions

D'Adamo claims there are many ABO specific lectins in foods.^[11] This claim is unsubstantiated by established biochemical research, which has not found differences in how the lectins react with a given human ABO type. In fact, research shows that lectins which are specific for a particular ABO type are not found in foods (except for one or two rare exceptions, e.g. lima bean), and that lectins with ABO specificity are more frequently found in non-food plants or animals.^[12][13]

The Nachbar Study^[14] has been cited in support of D'Adamo's theories, because it reports that the edible parts of 29 of 88 foods tested, including common salad ingredients, fresh fruits, roasted nuts, and processed cereals were found to possess significant lectin-like activity (as assessed by hemagglutination and bacterial agglutination assays). However, almost all of the 29 foods agglutinated all ABO blood types, and were not ABO blood type specific. Since D'Adamo's theory has to do with lectins in food that are "specific for a certain ABO blood type", this study does not support his claim that there are many ABO specific lectins in foods.

D'Adamo has remarked in the past that it is an oversimplification of his work with blood groups to simply apply the lectin-blood group specifics ad hoc to his work, since that "would not be following the Blood Type Diet, but rather a lectin-avoidance diet". He has been quoted many times as saying that the Blood Type Diet is characterized more by "what you eat rather than what you avoid", and that "the lectin connection was only a part of a much larger picture." However, this is not clear in his books.

[edit] Lack of clinical trials

Another criticism is that there are no clinical trials of the Blood Type Diet. In his first book Eat Right 4 Your Type, D'Adamo mentions being in the eighth year of a 10 year cancer trial,^[15] but the results of this trial have never been published. In his book Arthritis: Fight It With the Blood type Diet, D'Adamo mentions an impending clinical trial of the Blood Type Diet in order to determine its effects on the outcomes of patients with rheumatoid arthritis,^[16] but the results of this 12 week trial have never been published.

A self-reported internet survey with 6627 respondants conducted by D'Adamo's website reported that individuals following the Blood Type Diet for a period of one month or more, in 71-78% of cases, had significant improvement in a variety of health conditions. The most common reported improvement was with weight.^[17] These results, however, are "self-reported," and include no reference to how this information was gathered.

[edit] Blood type evolution issues

In a Brazilian medical research journal, Luiz C. de Mattos and Haroldo W. Moreira point out that D'Adamo's assertion that the O blood type was the first human blood type requires that the O gene evolved before the A and B genes in the ABO locus.^[18] However, phylogenetic networks of human and non-human ABO alleles show that the A gene was the first to evolve.^[19] The authors argue that, in the evolutionary sense, it would be extraordinary for normal genes (those for types A and B) to have evolved from abnormal genes (for type O).

Yamamoto et al. further note:

Although the O blood type is common in all populations around the world,^[20] there is no evidence that the O gene represents the ancestral gene at the ABO locus. Nor is it reasonable to suppose that a defective gene would arise spontaneously and then evolve into normal genes.^[21]

Another study from 2004 concluded that: "Assuming constancy of evolutionary rate, diversification of the representative alleles of the three human ABO lineages (A101, B101, and O02) was estimated at 4.5 to 6 million years ago."^[22] This finding directly contradicts D'Adamo's assertion of blood type evolution.

However, the author has stated in the past that it is an oversimplification to characterize his description of the evolution of the blood groups as a matter of mutational selection, and that this often represents attempts to discredit the theory by cherry-picking obfuscations that inevitably result when one is forced to depict scientifically complex material in context of a mass-market diet book. D'Adamo has been quite clear in the past that these conclusions were drawn from studies of the epidemiologic effects of migration patterns and infectious disease susceptibility in relation to blood groups distribution^[23] and the migration patterns, not natural selection via mutation in any Mendelian sense.^[24]

[edit] Further reading

• D'Adamo, P. (with additional material by Catherine Whitney) (1996). Eat Right 4 your Type. Putnam. ISBN 0-399-14255-X
• D'Adamo, P. (with additional material by Catherine Whitney) (2000). Live Right 4 your Type. Putnam. ISBN 0-399-14673-3
• D'Adamo, P. (with additional material by Catherine Whitney) (2002). The Eat Right 4 Your Type Complete Blood Type Encyclopedia. Riverhead. ISBN 1-57322-920-2
• D'Adamo, P. "Nontransfusion Significance of ABO and ABO-Associated Polymorphisms" Chapter 43 In: Pizzorno JE, Murray MT (Eds.) Textbook of Natural Medicine, 3rd Edition, Volume 1 (2006) Elsevier. ISBN 0-443-07300-7 [1]
• D'Adamo, P. "Metabolic and immunologic consequences of ABH secretor and Lewis subtype status." Altern Med Rev. 2001 Aug;6(4):390-405. [2]
• Weissberg, Steven M. and Joseph Christiano (1999). The Answer is in Your Bloodtype. Personal Nutrition USA. ISBN 0-967-01250-3

[edit] See also

• List of diets
• Japanese blood type theory of personality

[edit] References

[edit] Internal links

• Blood type

[edit] External links

• The official website of the Blood Type Diet
• Eat right 4 your Blood Type - another Diet Fad?.
• Dr. Arpad Pusztai comments on the Blood Type Diet.
• Quackwatch Book Review
• blood type diet: The Skeptic's Dictionary