A popular diet claims that you need to eat right for your blood. What’s the evidence?
Something that may have come up in your discussion group is the blood-type diet, a concept developed by writer and naturopathic physician Peter D’Adamo. I’ve gotten a lot of questions from other listeners about whether we should base our diet on our blood type, such as this one from Don in L.A.:
I was wondering whether you subscribe to the blood type diet. It seems to be really popular these days. I’m just concerned because it seems that a lot of the foods that I’m supposed to avoid are foods that you and other nutritionists say are great for me. There are a lot of fruits and vegetables that don’t fit my blood type. What’s your take on the whole thing?
The Theory Behind the Blood Type Diet
As dietary concepts go, the blood-type diet is one of the more interesting ones I’ve seen. The basic idea is that your blood type may be the key to what type of diet is best for you, and that you won’t feel as well or be as healthy if your diet is inappropriate for your blood type.
The different blood types—O, A, B, and AB—are genetic variations that appeared at various points in human evolution. Type O blood is thought to be the oldest surviving blood type, corresponding with the hunter-gatherer period. Type A blood appeared roughly twenty thousand years ago, coinciding with the dawn of primitive agriculture and the introduction of things like legumes and cereal grains to the human diet.
The other blood types emerged even later, when humans were not only farming but also keeping livestock and consuming dairy products. They’d also begun to travel the globe, interbreed, and encounter a much wider variety of food species.
Dr. D’Adamo’s central hypothesis is that you will be best nourished by the diet that was predominant when your blood type emerged. In other words, Type O folks thrive on lots of meat and very few grains and dairy products. People with Type A blood will be healthier eating a more plant-based diet. And the lucky Types B and AB can pretty much eat anything!
Of course, because this is a five-minute podcast, this is a vast over-simplification of Dr. D’Adamo’s argument. Check the show notes for a link to a much more detailed summary of the principles. Or, of course, you can check out one of Dr. D’Adamo’s books, such as the best-selling Eat Right For Your Blood Type. In his books, he’s also laid out detailed lists of foods that are good and bad for each blood type.
What’s the Evidence to Support the Blood-Type Diet?
As I said, it’s a very interesting hypothesis. But the evidence to support it is somewhat, well, incomplete.
Your blood type is determined genetically, and things like your predisposition to various diseases and conditions are also, in part, genetic. And there is some evidence that certain conditions occur more frequently in those of certain blood types. For example, people with Type A blood are more likely to suffer from a lack of stomach acid. But people eating a plant-based diet, as people with Type A blood are advised to do, need less stomach acid than people whose diet is higher in protein. Interesting…
Dr. D’Adamo has dug through a century’s worth of medical literature and culled out a handful of findings like this one that support various parts of his argument. But you’d never get a conviction based on evidence like this in a court of law. It’s circumstantial at best. Strong, substantive evidence for the benefits of eating a diet based on blood-type is lacking.
Nonetheless, there are plenty of people who have tried this system and found it life-changing. I am not one of them. I have Type O blood, so according to D’Adamo, I should thrive on eating lots of meat and almost no grains or dairy products.