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Should I “eat right for my blood type?”

A recent grad from Institute for Integrative Nutrition applied for the GreenSmoothieGirl Health Coaches certification and said this:

“I’ve studied over 100 nutritional plans, and the 12 Steps to Whole Foods program is the most comprehensive, practical, grounded approach I have found.”

(That’s the goal. I think I’ve studied all those nutrition plans, too. Most have a kernel of truth, or lots of truth, along with, usually, some problems. And many of the diet plans appeal to popular tastes – such as Atkins, South Beach, The Zone, etc. — rather than being supported by evidence.)

One of the more frustrating diet plans, to me, is the blood type diet. The idea is that you have a certain blood type because your ancestors were from a certain place, so they adapted to a specific diet. You are then instructed, based on having O, A, B, or AB blood, to eat according to the prescription. Vegetarian, highly carnivorous, a mix of the two, grains or no grains, etc.

The diet has no real science backing it. Only a very dubious theory. The theory collapses when you consider that every indigenous population of the world has all the blood types: A, B, AB, and O. It’s also highly problematic when you consider how much genetic mixing and nomadism we’ve had in recent centuries. Few people have both parents going back to the same origins.

Peter D’Adamo fathered the first blood typing program (based on the theory of his father James, both naturopaths) that gave rise to a set of nutrition principles. But others have leveraged the same concept, with different recommendations. It’s tempting, financially, to author a new diet, since those books sell well. I know this all too well, since I waged an epic war with my publisher over the name of my bestseller, The Green Smoothies Diet. I hate the word diet because “diets” don’t work. I wanted to teach good principles, towards a sustainable lifestyle, but my publisher said,

“But American love diet books. They fly off the shelves.”

I lost the war and, in so doing, probably gained financially, as my book was instantly a bestseller for my publisher. It wasn’t a hill I was going to die on, because if it gets the same message out, I can “sell out” on the fairly minor point of a title. (Mostly, I just wanted, on principle, to name my own book!) And Ulysses Press was right—Americans do, apparently, want to “go on” yet another diet.

The whole idea of blood typing does call legitimate attention to the fact that we are all different, with different needs. This doesn’t obviate the fact that there are certain classes of foods that are nutritious to just about everyone. Just because you feel weak if you try to eat only plants, after a lifetime of eating animals, doesn’t mean that for you, vegetables are bad food.

It could mean you are transitioning and cleansing, and that is uncomfortable in the short- to mid-term. It could mean that because degenerative gut problems are nearly ubiquitous (everyone who has indulged in the S.A.D. suffering from them to one extent or another), many of us have developed sensitivities to specific foods. Some of those sensitivities are to good foods. This doesn’t mean that food X or Y is necessarily “bad” for you personally—it may mean that you have a problem to rectify so your body can accept and utilize nutrition from that food class.

Some people are reading this article and preparing to scream at me that I’m wrong because they went on the blood type diet and feel much better. I believe that! But not because you’re eating “correctly” for your blood type.

You feel better because the author of the nutrition program eliminates gluten from the type O diet. That will make everyone feel better, as grains have been hybridized and are causing many people problems. And he tells all type A’s to eat vegetarian, which is actually a good diet for most, if not all, people.

(As always, I refuse to take a stand on whether a limited amount of animal protein is good or desirable or at least acceptable—but it’s clear that more plants, and less animals, is across the board, more environmentally sustainable and more health-promoting.)

You feel better because regardless of your blood type, you’re told to eliminate processed foods such as white flour.

D’Adamo’s theory gets really silly when he tells Type A’s to meditate, Type O’s to do aerobics, etc. (Does this mean Type O’s shouldn’t meditate, and Type A’s shouldn’t exercise their hearts?) He delves into stereotyping personality and character based on blood type, too. It’s really nonsense but can “look” true because some true principles are involved.

Many other experts have soundly debunked D’Adamo’s reasoning and recommendations. He claims type O is the oldest blood type, but in fact, A is. This decimates the crux of his theory. Also, agriculture developed in different parts of the world independently, and his theory is based on unilateral development worldwide and positive outcomes for that development, neither of which is fact.

Most of his theory rests on lectins, proteins on the surfaces of foods that can cause cells or molecules to stick together. But a number of doctors object to the hypotheses the D’Adamos make, saying that there is no documentation of the health effects they predict if you eat “wrong” for your blood type, which virtually everyone does, of course. Michael Klaper, M.D. said that the effects he describes would be fatal for millions of people, if D’Adamo were correct in his theory.

The diets D’Adamo advocates for are not particularly harmful or out-of-the-ordinary, and all of them eliminate the worst of the bad in the Standard American Diet. (He isn’t telling any of the blood types to eat Twinkies or Cocoa Puffs. He is just making certain recommendations within whole-foods groups and macronutrients. Most Americans, of course, are eating Twinkies and Cocoa Puffs! Any  involves less processed food is likely to result in health improvement.)

As a culture, we need better critical thinking skills. We have a long love affair with personality testing and typing, horoscopes, and other ways to try to categorize and make sense of our world. But blood-typing theory is flawed on so many levels. I believe that individuals have specific dietary needs that may fall slightly – not massively — outside a prescribed set of guidelines.

Looking to blood type does not provide those answers. As logic might suggest to you, only experimentation and intuition do.

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