In 1996, a man named “Dr.” Peter J. D’Adamo published Eat Right For Your Type. This book promoted the “blood type diet.” It claimed that your diet should be based on your ABO blood type (type A, B, AB, or O). The ABO system of blood typing is important in blood transfusion. Getting a transfusion of the wrong type of blood can kill you. However, there is no scientific evidence that your blood type has anything to do with how your body reacts to food. People of any blood type thrive on a low-fat, plant-based diet.
The things that D’Adamo says about the natural history of the different blood types are wrong. So are the things he says about the effects of blood type on the body. Worst of all, D’Adamo gives particularly bad dietary advice to the people with the most common blood type. I suspect that his book has been so popular because he has been telling a lot of people exactly what they want to hear. He has been telling the people with the most common blood type that they need to eat a lot of fatty meat.
The Blood Type Diet theory
D’Adamo claims that type O was the original blood type of cavemen. Supposedly, modern-day people with type O blood should therefore avoid eating grains, especially wheat. Instead, they should supposedly eat a meat-based diet. D’Adamo also claims that type A blood resulted from the rise of agriculture. It supposedly allows people to eat a high-carbohydrate diet. He argues that people with type A blood can therefore eat a Mediterranean style diet based on grains and vegetables.
D’Adamo claims that type B arose in Asia, among Mongolian herdsmen. Thus, he argues that people with type B blood should eat a lot of cultured dairy products. D’Adamo argues that people with type AB blood should eat a mixed diet. However, he thinks that they should avoid eating starches and proteins in the same meal.
D’Adamo also sells a broad range of products. D’Adamo sells kits for testing your blood and saliva. He sells a broad range of foods, teas, and dietary supplements. He also sells skin care products. Of course he does! The fact that he has such an extensive product line is a bad sign. Every single nutrition textbook I have ever read says that we should get our nutrients from food, not pills. Be wary of taking any nutritional advice from someone who sells supplements!
But gorillas have type B blood!
Of course, D’Adamo is totally wrong about the history of blood types. You can find types A and B in monkeys and apes. All of the African and Asian primates have some version of the ABO blood types. Modern-day gorillas usually have something similar to human type B. A few have something like human type O, but none have human type A. Modern-day baboons and orangutans have a version of type A. Most chimpanzees also have a version of type A, but a few have something similar to human type O. There is a lot of debate about this topic. However, the consensus is that the ancestral blood type was type A and that type B may have evolved separately several times. The human AB blood type is just the result of someone inheriting the type A gene from one parent and the type B gene from the other.
Why is type O so common in modern humans? Scientists are still not sure. One theory is that having type O blood makes you more likely to survive a case of falciparum malaria, which is the worst form of malaria.
D’Adamo insists that people with type O blood should eat a meat-based Paleo-style diet. He insists that only people with type A blood should eat a vegetarian or vegan diet. Yet there is no evidence that anyone would have better general health on a Paleo-style diet. Extremely low-carb (ketogenic) diets are sometimes used as a treatment for severe epilepsy in children. These diets work by mimicking the effect of fasting, but without causing the person to starve. However, these low-carb diets are not good for the child’s general health. In fact, they can stunt the child’s growth. The ketogenic diet can even cause severe side-effects, such as pancreatitis.
ND stands for “not a doctor”
D’Adamo is often called “doctor.” But he is not a medical doctor (MD). Nor does he have a doctor of philosophy (PhD) or a doctor of science (DSc) degree. Instead he has a doctor of naturopathic medicine (ND) degree from Bastyr University. Bastyr is a school for people who want to go into an alternative health trade, such as naturopathy or acupuncture. D’Adamo has taught at some other schools, but they are just other naturopathy schools. In the early 20th century, the schools of naturopathy lost their ability to grant MD degrees, because they refused to provide a good enough science education. Nevertheless the naturopaths have been fighting hard to get licensure to practice as primary care providers. For information about naturopathy, see Naturopathic Diaries, the blog of ex-naturopath Britt Marie Hermes.
D’Adamo describes himself as a researcher. However, real researchers write articles about their research. Those articles then get published in scientific and medical journals. When I searched for P. J. D’Adamo in MEDLINE, I couldn’t find even one citation. In other words, D’Adamo has never written even one article that any scientific or medical journal has seen fit to print. When I searched for his name in www.clinicaltrials.gov, I couldn’t find him listed as the main investigator of even one clinical study.
The real science of blood typing
The blood type diet is just an attempt to hijack the prestige of some real scientific advance. The ABO blood typing system was discovered in 1900 by an Austrian immunologist named Karl Landsteiner. Landsteiner eventually won the Nobel Prize for this discovery.
Your blood type is extremely important if you need a blood transfusion. Even if you get blood that is well-matched to your own, you could suffer from fever and chills, as your immune system reacts to some unfamiliar proteins from the donor. However, if you get red blood cells of the wrong ABO blood type, your body may mistake those red blood cells for a dangerous foreign invader. As a result, your body’s antibodies could attack and kill those donated red blood cells. In severe cases, the immune system will tear the foreign red blood cells apart. This problem, called an acute hemolytic transfusion reaction, can kill you by causing severe blood clotting.
The ABO system was the first set of blood types to be discovered. Later researchers revealed the Rh types (positive and negative). People with AB-positive blood (ABO type AB and Rh-positive) can receive blood transfusions from practically anyone. People with O-negative blood can donate to practically anyone.
Blood typing is also important in forensic medicine. Before the days of DNA testing, it was often used to rule out suspects in certain kinds of crimes. If you know that the perpetrator had type A blood, you can rule out suspects with type O, B, or AB blood. In the days before DNA testing, blood typing was important in paternity cases. If a child has type A blood but his mother has type O blood, you know that the father must have had type A blood.
In other words, blood typing is extremely important in transfusion medicine and has been important in forensic medicine. However, there is no reason to believe that the different blood types represent different stages in human evolution. Nor is there any reason to believe that your blood type will let you predict how you will react to a particular diet. D’Adamo claims that a low-fat, vegan diet should be reserved for people with type A blood. In reality, it’s the best diet for people with any blood type.
Photo by GreenFlames09