Blood Type Diet Debunked

The blood type diet has garnered quite a following since its introduction, but a new study suggests it might not actually work. In fact, it seems maybe we should all eat similar diets.

Eat Right for your Type, the 1997 book by Peter D’Adamo, has sold millions of copies. D’Adamo claims that our dietary needs differ by blood type. People with type A blood should eat mostly vegetables and eschew meat. Those with type O blood should eat more meat. Type B and AB are moderate, falling somewhere between the extremes. But does science back up these claims?

“Of course not!” said a recent study in PLOS One. Researchers examined data from a large study in Toronto that collected data from almost 1,500 participants, who recorded their dietary habits in detail. Then the researchers compared participants’ habits to their blood type and general markers of health, like cholesterol and blood pressure. Would those who ate right for their blood type have better health than those who did not? Not a chance.

But here’s the best part. Those who ate according to the type A, type AB, or type O diet all had better health markers – it just didn’t matter whether their diets were matched to their actual blood types. Anyone who ate the type A or AB diet showed lower blood pressure and lower triglycerides. Type A dieters even had a smaller waist. Anyone who ate the type O diet showed lower triglycerides.

How can this be? Because each of the blood type diets contains some recommendation for either increased lean meat or vegetables. And that’s going to improve your health regardless of your blood type. So while matching your diet to your blood type is a futile exercise, eating according to any of the recommended blood type diets can actually result in positive progress.

I’m not sure why anyone ever believed that different blood types have different dietary needs. I suspect it’s rooted in the idea that we are all special, when in fact, we are not. I know you probably feel like you have a unique situation that has never been faced by anyone else. Your blood type is AB negative. You don’t like the taste of fish. And your son, Faustian, must be driven to soccer practice three times per week on a route that passes Taco Bell. Guess what? Nature doesn’t care. You’re just a homo sapien. Your genes are programmed to respond to your every decision about diet and lifestyle, and nothing gets you a free pass from the consequences. We aren’t a society of special snowflakes. We are a society of people who are remarkably similar in needs. The sooner we all accept this, the better off we’ll be.


1. Jingzhou Wang, et al. ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. PLOS One. Published: January 15, 2014. DOI: 10.1371/journal.pone.0084749

Photo courtesy of Shutterstock.

Be the smartest person in your gym

Everything you need to know about strength in in your inbox.