Blood type diet

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The blood type diet is a diet advocated by Peter D'Adamo and outlined in his book Eat Right 4 Your Type. Its basic premise is that ABO blood type is the most important factor in determining a healthy diet. The diet is widely derided by dieticians, physicians, and nutritional scientists as having no scientific basis.

The cornerstone of his theory is D’Adamo’s premise that lectins in foods react differently with each ABO blood type. Throughout his books he cites the works of various biochemists and glycobiologists who have researched blood groups, claiming or implying that their research supports this theory. 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 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. ^[2]

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 these supposedly muscular, active people eat a meat-rich diet.
• 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. 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.
• Blood group AB, per D'Adamo, the enigma, the most recently evolved type. In terms of dietary needs, his blood type diet treats this group as an intermediate between blood types A and B.

Criticism

D'Adamo's Blood Type Diet has met with several criticisms. The fundamental criticisms are, for one, that none of his hundreds of citations to others' research on blood groups directly support his claims of differential food tolerances and, secondly, that he provides no comparative clinical trials demonstrating efficacy of his diet.

Evidence

One criticism of D'Adamo's hypotheses and recommendations claims that he provided inadequate evidence. For example, his first book, Eat Right 4 Your Type, published in 1997, contains only a bibliography. Most of his subsequent books, however, have been thoroughly referenced as far as his general theory. However, despite his providing general reasons for the classifications of various foods within his established categories of "beneficials", "neutrals" and "avoids", his specific process for reaching these conclusions of classification remain undocumented.

Although D'Adamo claims there are many ABO specific lectins in foods, this claim is, for a number of his cited cases, unsubstantied by established biochemical research, which has not found differences in how the lectins react with a given human ABO type. A common criticism is that lectins which are preferential 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.

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, but no results of this trial have ever 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, but no results of this trial have yet been published.

Blood type evolution

In the article "Genetic of the ABO blood system and its link with the immune system", 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. Instead, phylogenetic networks of human and non-human ABO alleles show that the A gene was the first to evolve. 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, 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.

In May 2004, Transfusion published a study which 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." This finding declares that ABO did not evolve in the near past, essentially contradicting that which D'Adamo suggests.