The blood type diet has received an enormous amount of exposure in the past decade for its purported health benefits. Based on the work of naturopathic doctor Peter D'Adomo, the basic premise of the blood type diet is that you can achieve improved health and well-being by eating foods that are "correct" for your blood type. To date, no clinical evidence supports the diet's use, nor is there any specific scientific evidence against the blood type diet.
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About the Diet
The essential idea behind the blood type diet is that certain compounds in foods, known as lectins, cause a reaction with molecules that determine different blood types. Lectins are proteins that bind with sugar molecules and are most commonly found in grains, beans and seeds. The diet postulates that individual blood types evolved based on the availability of certain foods over the course of history and that the ability to digest and metabolize lectins is different for each type. Essentially, your ancestral type determines what you should be eating. Type O reported by D'Adomo to be the first blood type to evolve, is associated with the "hunter," requiring a diet of protein-rich foods. In a 2008 interview with NPR News, Dr. Christine Cserti-Gazdewich, a hematologist at the University of Toronto, states that the A blood type was actually the first blood type to evolve in prehistoric humans. Type A is associated with the development of agriculture and is believed to require a diet leaning towards vegetarianism. Type B is the "nomad," thought to have an increased tolerance for many types of foods, including dairy products. Finally, type AB is thought to require a combination of foods recommended for the A and B blood types.
The Case Against Lectin
While there are no clinical studies supporting or refuting D'Adomo's claims that eating for your blood type can promote health, the diet has received much criticism from medical professionals, particularly with regard to the lectin premise. In an article for EarthSave, a nonprofit agency that promotes healthy eating in underprivileged individuals and families, Dr. Michael Kapler points out that there is no solid scientific evidence to support D'Adomo's idea that lectin reactions are ultimately responsible for ill health and other types of bodily disruptions. For example, in an article for his website, D'Adomo claims that type O blood types cannot tolerate wheat or dairy products. However, he does not specify what this actually means and attributes it to blood type instead of confirmed medical issues such as gluten intolerance or wheat allergies.
Blood Type and Medical Conditions
Another key assertion made by D'Adomo is that certain blood types are more vulnerable to specific diseases and should therefore avoid certain foods that can cause or aggravate these conditions. Although a number of credible, scientific studies have attempted to examine the proposed link between blood type and certain diseases, there isn't a lot of evidence to support the specific link between diet, blood type and disease. One study, published in 2002 in the journal, "Medicina," found a link between the B blood type and an increased risk of coronary atherosclerosis in women. However, there is no scientific evidence to support claims that following the blood type diet can mitigate this or any other condition.
Major medical centers and teaching hospitals such as the NYU Langone Medical Center do not recommend following the blood type diet, due to a lack of solid scientific evidence and because the diet severely restricts the types of foods you can eat. A wiser choice is to follow a healthy, well-balanced diet plan that meets all your nutritional requirements. Consult your doctor if you need a recommendation for a healthy diet that suits your specific needs.