You may have heard of the blood type diet, also known as the blood group diet. It was made popular back in 1996 by Dr. Peter D’Adamo, a naturopathic physician. His book, a New York Times bestseller became extremely popular, and still is today. He believes that the ideal diet for a person depends on their blood type. D’Adamo claims that, genetically, each blood type has traits from our ancestors. He therefore designed a diet for each blood type based off of what type of diet its ancestors ate. His methods are also based on a theory about proteins called lectins that can bind sugar molecules and are considered to have a negative effect on the lining of the gut. This theory states that there are many lectins in the diet that are specifically harmful for different blood types, and eating the wrong types of lectins can do damage.
The 4 different blood type diets are generally broken down as follows:
Type A is called the agrarian, or cultivator. This diet should be rich in plants. It also must be completely free of red meat which is considered toxic, and closely reminds us of a vegetarian diet.
Type B is called the nomad. This diet should consist of eating plants, most meat; excluding chicken and pork, and some dairy. It completely avoids wheat, corn, lentils, tomatoes, and a few other foods.
Type AB is called the enigma. This diet is a mix of type A and type B. It includes eating seafood, tofu, dairy, beans, and grains. It excludes kidney beans, corn, beef, and chicken.
Type O is called the hunter. This is a high-protein diet that consists mostly of meat, fish, poultry, certain fruits and vegetables. It limits grains, legumes and dairy, and closely reminds us of the paleo diet.
What Does The Research Say?
As far as evidence-based research goes, there really is not much there that supports this theory. The research that exists on ABO blood types strongly suggests that people with certain blood types are at higher or lower risk for some diseases, however, no studies have shown any connection at all with blood types and the diet. In fact, in 2013, there was a major review study where researchers were not able to find a single well designed study that looked at the health effects of the blood type diet. A comprehensive review published in the American Journal of Clinical Nutrition found no evidence to support the Blood Type Diet and called for properly designed scientific studies to address it.
As for the lectins theory, there is actually some evidence that shows a small percentage of lectins that are found in raw legumes can have specific effect on certain blood types. However, the research also shows that the majority of these lectins react with all ABO blood types, basically meaning that most of these dietary lectins not blood-type specific.
As for Dr. D’Adamo, his claims were disproved as having no basis in current scientific literature, and when really examined, all of the evidence that his book is based on is filled with errors, incorrect evolutionary information, mixed up dates in history, and assumptions that turn out to be wrong.
So, Where Does This Leave Us?
The question we are left with is, if there is no evidence that supports this diet, why has it been so popular? The truth is, it has worked for some people, more specifically about 44-62% of the population. The reason being that the dietary suggestions that are made for each blood type are overall healthier and real foods, regardless of blood type. This includes removing the majority of unhealthy processed foods and junk food, so it is automatically an improvement for most people’s diets. Finding that this diet works for you does not suggest that it is because of your blood type, but by all means you are doing something right, and there is no need to change it.
My belief is that there is no “Ideal” diet for all or any group of people, but rather a diet that specifically works for each individual. It is hard to believe that there are billions of us on the planet, and that there are 4 different types of diets that work for all of us. To me, the ideal diet should be designed for each individual, and should be based off of eating to meet our specific needs. So whether you swear by this diet, or are unimpressed by the lack of evidence that backs it up, find a diet that works well for your needs and metabolism, and stick with it !