Research 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. 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.[citation needed]
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".[15]
There is a lack of scientific evidence on the associations between disease states and ABO blood types as mentioned in Peter D'Adamo's website.[16] A search of PubMed under the author's name does not yield any peer-reviewed articles with data to support his claims. For example, his claim that elderberry can be used as a remedy for the common flu lacks scientific evidence and may be misleading. A review article by Dr. Guo and colleagues, published in the American Journal of Medicine, reports "the effectiveness of any complementary and alternative therapy for treating or preventing seasonal influenza is not established beyond reasonable doubt.[citation needed] Current evidence from randomized controlled trials is sparse and limited by small sample sizes, low methodological quality, or clinically irrelevant effect sizes."[17]
