'Eat Right for Your Type' by Peter J. D'Adamo has become widely known as the blood type diet. Since I am constantly asked to give my input on this dieting system, I have decided to add my comments here.
I agree with and respect quite a few of D'Adamo's insights and perspectives but have major reservations about others. The book suggests that you use your blood type to determine which foods you should be eating. According to the theory, when you eat foods that 'agree' with your blood type, you reduce the risk of cancer, heart disease, diabetes, infections and liver disease. Type A people supposedly had ancestors that were farmers. If you are of this type, you should be a vegetarian and avoid meat and dairy products. According to the author, people with Type B blood had ancestors that were nomads; therefore they should eat red meat and fish. Those with Type O blood had ancestors that were hunters and gatherers; This means they should eat lots of animal protein and few carbohydrates. Finally, those with Type AB blood, had mixed ancestry, and are supposedly to eat a combination of the Type A and B diet. Does this mean, for example, that all nomads used to have the blood type 0, and all farmers used to have type A blood? What about people who did not farm and who did not move from place to place?
Unfortunately, these theories are not supported by scientific literature, traditional knowledge and records of the world's oldest medical systems, such as Chinese Medicine and Ayurveda. D'Adamo's discoveries have not been confirmed anywhere else. There is little or no distinction made between individuals who have lived in the Andes, the tropical rain forests, or plains of Africa for hundreds of thousands of years. The Indian subcontinent thrived and flourished for thousands of years on a vegetarian diet, and so has most of the world's population. And where does ancestry begin anyway? Two thousand years ago, 100 centuries ago, or 60 million years ago? How far do we go in the bloodline of our ancestors to determine our dietary needs? When the last Ice Age began, many vegetarians living in formerly tropical lands were suddenly forced to eat animals in order to survive. Some ate a mixed diet, because of more moderate climates. Others in the all-year-round tropical places of the Earth continued with vegetarian foods until quite recently. The proposed theory is highly inconclusive about all of these facts.
When I went on the high protein diet (very similar to the type O diet plan) at age 5, I felt great for about 18 months, as do so many others who go on the popular Atkins diet. Then I started developing stones in my liver, a dangerous arrhythmia and juvenile rheumatoid arthritis, among other diseases. I had no idea that these ailments were due to protein poisoning. Ten years later I switched to a balanced vegan diet, and most of my illnesses went away within a matter of weeks. However, I still had to live with the many stones that had been produced in my liver and gallbladder as a result of what is known today as the O-type blood diet. Forty gallbladder attacks later, I did a series of liver and gallbladder flushes, which cleared out these vital organs. Finally, I was free of any illness or discomfort.
You will not notice the effects of a high protein diet until the blood vessel walls are well-thickened with excess protein. Eating lots of animal protein triggers a powerful immune response in order to get rid of the foreign DNA and the dead, coagulated and damaged protein of meat, fish, eggs, poultry and dairy products. This immune response involves a powerful release of energy, thereby cleaning out impurities, improving skin functions and making you feel more grounded. However, as soon as the immune system is exhausted by the constant excess activity, which took a mere 18 months in my case, the situation begins to backfire and the body becomes unexpectedly congested.
The blood type diet theory is flawed in the sense that it does not recognize the basic body type requirements generated by the three forces / humors of nature (Vata, Pitta and Kapha) that control the physicality of matter and the body of humans and animals. Only a fraction of the body's energy requirements are met through food, and there are many more effects on the body than one's blood type. The 6,000-year old medical system of Ayurveda accounts for most of these influences. One's constitutional body type is not as simply and easily determined as one's blood type. The theory of blood type foods is really based on guesswork, not on science or time-tested traditional knowledge as found in Ayurveda, Chinese Medicine, Greek medicine or ancient Egyptian medicine.
If concentrated protein foods were a necessary part of the human diet, as the blood type diet advocates for the O-type, for example, why does nature not reflect that need when it formulates human milk in a mother's breast? Its protein content is a mere trace amount of 1.1-1.6 percent, provided to a baby at the time of its largest growth spurt. Would not O-type babies die if they lived on so little protein for up to 18 months, since most babies in the natural world only get mother's milk as food? On the contradiction, the babies actually develop perfect organs and systems, and are emotionally the most content. If nature's most perfect food does not give you much protein at the time when you are growing more rapidly than at any other time in your life, why would you need to eat concentrated proteins, such as meat, when you are older and no longer growing?
If you are on the blood type diet and decide to continue following it, I recommend that you be vigilant about how your body feels. If you start feeling a dull sensation in your gallbladder or pain in your joints, muscles or head, or if you develop mucus and sinus problems, a covered tongue or other signs of congestion, you may need to reconsider your diet regimen.