If you want to tone up or lose weight, common sense dictates that all you have to do is watch what you eat and exercise. However, the latest dieting fad proposes that following a diet specific to your blood type is the key to losing weight, feeling healthier, and lowering one’s risk of developing many diseases.
At least that is what Peter D’Adamo, a naturopath and creator of the Blood Type Diet, claims in his book Eat Right 4 Your Type. Considering its simplicity, it is little wonder that this supposedly brilliant and revolutionary idea is a favourite of celebrities such as Liz Hurley, Martine McCutcheon, and Courtney Cox-Arquette. While these stars might be ardent fans of the diet, most medical practitioners and nutritionists are not quite so enthused.
D’Adamo’s theory is based on the distinctive antigen patterns that mark each blood group: A, B, and AB, as well as O, which has no marker. Attached to the antigens is a sugar-based molecule, called a lectin, which is involved in triggering immune responses. D’Adamo claims that each antigen reacts badly with certain types of foods, potentially leading to health problems. He also claims that levels of stomach acidity and digestive enzyme imbalances can be directly linked to blood groups.
These findings could be considered plausible were it not for D’Adamo’s claim that, since blood types have evolved at different times in human history, an individual’s diet should be based on the types of food that our ancestors ate at the time that particular blood type evolved. In addition, he says that the diet should be supplemented with exercise similar to what our ancestors were doing at the time of emergence of the blood type.
This oversimplifies the issue. The Blood Type Diet suggests that each antigen evolved when it was ideal for the human body to receive it. However, the exact function of antigens and lectins is not completely understood, and to say that there is an advantage for certain antigens at certain times in human history is misleading.
In short, here is D’Adamo’s blood type system:
• The O blood type evolved around 50,000 BC and hence has a hunter-gatherer ancestry. As such, people with that blood type should eat a high-protein, low-carbohydrate diet with lots of meat and fish, but no dairy products, wheat or grains. They must also do lots of aerobic exercise.
• Blood type A emerged next, around 15,000 BC. By this time, humans had settled into quasi-farming communities, so the Type A diet should be primarily vegetarian. People should still avoid dairy products, but engage in more calming and sedentary exercises, such as golf and yoga.
• Type B evolved around 10,000 BC, when our ancestors were nomadic. Therefore, very few foods need to be avoided. Activities that have a mental component are recommended, such as hiking and tennis.
• Type AB, which D’Adamo claims evolved just 1,000 years ago, marks the era of modern man. But since AB is a combination of both A and B alleles, a combination of both A and B diets and exercise is recommended.
The blood type diet is flawed on several levels. Firstly, neither D’Adamo’s book nor his website provide any evidence of documented research-indeed, many of his claims are debatable at best.
Secondly, antigens have very little to do with the metabolism of foods. On a social science level, there is much debate over when and in which order the different blood groups evolved. It makes very little sense to claim that AB evolved only 1,000 years ago, when both A and B alleles are co-dominant, meaning that the AB blood type should have been expressed earlier, when parents with A and B blood types produced offspring.
Let’s assume for a moment that D’Adamo is right in supposing that a particular antigen was better at protecting the body from foreign contaminants at one point in time, and was therefore passed down through the generations. Our modern health needs are different from a nomad’s or a hunter-gatherer’s, however, so by his logic these “ancient” antigens should be disappearing in favour of ones that benefit our modern lifestyle.
Besides the lack of scientific proof, the blood type diet fails to provide a varied or balanced diet and gives no indication of how much weight-loss users should expect, or in what time-frame.
There are very few, if any, benefits to this diet. One certainly would lose weight, no matter one’s blood type, since the diet essentially eliminates bread and dairy products. However, the cons are simply too numerous-the lack of scientific evidence, an unbalanced diet, and the near-impossibility of planning a meal for the entire family or friends makes this approach to dieting unrealistic.
One cannot help but wonder what Dr. D’Adamo would say if a new blood type evolved in our time. He would probably call it Type J, and recommend that people with that type eat only junk food. Now how scientific is that!
