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Test Drive Diet No. 2: The Blood Type Diet

Timothy Boyer Ph.D.'s picture
Blood Type Diet explains why not all diets work for everyone.

Here’s the latest research news on a popular Dr. Oz-recommended diet that is based on the premise that feeding your body the right type of foods for your blood type will lead to weight loss. Discover what this blood type weight loss diet is all about, what foods to match with your blood type; and, what a new study has to say about Blood Type Dieting.


Why “Test Drive Dieting”

With the holiday season here, now might seem like the worst time to start a diet. However, rather than approach dieting and a healthier lifestyle with a rigid “just-do-it” approach on the first day of the New Year, now is the perfect time to get a taste of a variety of diets as a test run to understand how it works (or doesn’t) for you before you commit to a New Year weight loss resolution or goal.

This month, we will focus on a wide range of dieting plans, techniques, and recommendations for weight loss that you can research and test drive at home to help you decide on which dieting plan is the right choice for you.

Today, we will take a look at another Dr. Oz previously-recommended diet plan called the “Blood Type Diet.”

The Blood Type Diet

The Blood Type Diet, popularized nearly a decade ago when Dr. Oz promoted it as an exciting weight loss program, is still used by dieters today and is the focus of recent research that wanted to determine if the diet really works under scientific scrutiny; or, if it was just another dieting fad that is more myth than fact.

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The promise of the diet is that it can help dieters who are failing to lose weight through popular dieting methods that appear to work for others but not for themselves. The blood type diet does this by helping dieters discover why those diets did not work for them and how they can become slim just by eating foods based on their ancestry; and therefore—their blood type.

The originator of the blood type diet is Peter D'Adamo, a naturopathic physician who is also an author, researcher-educator, and considered by some to be a world expert in glycobiology with emphasis on the components responsible on blood cell surfaces that are the signatures of our blood types.

As the author of his book “Eat Right 4 Your Type” D'Adamo achieved national acclaim when the media and The Dr. Oz Show learned about his diet plan and how it explained why one person on one diet can lose weight, but another person on the same diet cannot. The reason according to D'Adamo is that the success or failure of a particular diet is actually rooted to our ancestry.

How Ancestry Determines Diet Success and Failure

The foundation of the blood type diet is built on the idea that the gut biomes we carry today are a result of whether our ancestors were hunter-gatherers (Type O), farmers (Type A), domesticated-animal herding nomads (Type B), or some more modern mix of hunters and herders. The theory is that gut biomes in our early ancestors evolved in accordance with the foods they primarily lived on be it meat, vegetable, grain, dairy or some combination of all four food groups—or types of foods within groups.

So, what is the connection between our gut bacteria and our blood types? According to the blood type diet, our red blood cells are present not just in our veins and arteries, but are actually found in other areas such as the intestinal tract where specific bacterial colonies live and feed off of the surface of red blood cells.

Red blood cells it turns out, possess blood type antigens (A, B, AB or O) made up of amino acids and basic sugars that are food for the gut bacteria. These gut bacteria have presumably evolved as matches for the specific blood type on our red blood cells. In other words, if an early ancestor is the originator of blood type O who was a hunter-gatherer that consumed primarily red meat, then it is expected their gut biome would have evolved to efficiently handle a meat-rich diet.

However, if the gut biome were to have a blood type mismatched diet, say feeding a meat-eating Type O hunter-gather a diet heavy in carbohydrates, then the gut and the rest of the body would be less healthy based on the idea that the gut bacteria were not be evolutionarily optimized to handle the carbohydrate load.

This concept has been analogized as attempting to run a vehicle on different types of fuel. Most fuels are petroleum products just as most foods provide energy for the body. However, if you try to run an unleaded fuel engine with diesel fuel, then you will have problems. Hence, if you feed the gut biome with the wrong type of diet, your body will suffer for it.

The Gut Biome and Health

The aforementioned reasoning of the possible connection between blood types and gut biomes is not so far-fetched. For years now, scientists have been finding associations between the bacteria in our digestive tract and our health—particularly with inflammation in the body that can lead to all sorts of health issues including digestive problems and obesity.

In fact, some studies report favorable outcomes when a patient is able to change the type of bacteria in their gut through fecal transplants or eating probiotics.

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Examples of Recommended Diet Changes Based on Blood Type

The blood type diet works by changing your diet according to a blood type/food chart that provides essential “what to eat” and “what not to eat” recommendations.

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For Type O Blood—a blood type dieter would eliminate wheat and gluten, cow milk and other dairy, and pork from their diet and replace it with spelt/brown rice bread, almond milk, and lean grass-fed beef. He or she would also forego corn, catfish and cabbage; but, add kale, cod and broccoli to their diet.

For Type A Blood—a blood type dieter would stop consuming beef, bananas and cow milk; but, replace the food items with salmon, figs and soy milk. In addition, tomatoes, eggplants and oranges would be substituted with beets, Portobello mushrooms and grapefruit.

For Type B Blood—a blood type dieter would give up chicken, corn and wheat bread; but replace it with lamb, broccoli and oat bread. Likewise, crab, coconut and coffee would be exchanged for cod, bananas and green tea.

For Type AB Blood—a blood type dieter would eliminate ice cream, corn flakes and American cheese from their diet; and, substitute it with kefir, oatmeal and mozzarella cheese. Red meat, kidney beans and corn are out, but turkey, pinto beans and kale are in.

There are many more examples of foods to eliminate and match with your blood type that are best referred to via D'Adamo’s book “Eat Right 4 Your Type,” which provides the rationale why some foods make the blood type cut and others do not.

What Recent Research Says About the Blood Type Diet

According to a new study published in the Journal of the Academy of Nutrition and Dietetics by researchers with the Physicians Committee for Responsible Medicine, the blood type diet is bunk. In other words, their researchers have found no association between blood types and the effects of a plant-based diet on body weight, body fat, plasma lipid concentrations, or glycemic control.

Using data from an earlier study that determined that following a plant-based diet causes a person’s metabolism to significantly increase following meals, the researchers conducted a secondary analysis of whether the effects of a plant-based dietary intervention on body weight, blood lipids, and glycemic control are associated with ABO blood type.

According to the news release, an association between diet and blood types does not hold water under scientific scrutiny based on their statistical analysis.

"We found that blood type made no difference," says study author Neal Barnard, MD, president of the Physicians Committee. "While the blood type diet says that a plant-based diet should be better for blood type A and less so for blood type O, it turned out to be beneficial for people of all blood types, and there was no evidence that meaty diets are good for anyone.

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"Our research shows that all blood types benefit equally from a vegan diet based on the consumption of fruits and vegetables, legumes and whole grains, looking specifically at weight loss and cardiometabolic health in overweight adults," he says.

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The conclusion of the paper states, “These results indicate that blood type is not associated with the effect of a plant-based diet on body weight, body fat, plasma lipid concentrations, or glycemic control.”

While some pro-blood type dieters may argue that this is just one study and is not necessarily damning, the authors of the study include earlier similar studies with the shared conclusion that, “… although adherence to certain dietary practices was associated with changes in certain physical variables, these associations were not related to an individual’s blood type.”

In Conclusion

While the Blood Type Diet may not be entirely accurate; at the very least, it does recommend some sensible dietary recommendations and offers a non-harmful proactive approach to dieting and providing dieters with hope that achieving weight loss is possible.

For more about test driving a diet for weight loss, be sure to check out this Dr. Oz Recommended 21-Day Weight Loss Plan article.

Timothy Boyer has a Ph.D. in Molecular and Cellular Biology from the University of Arizona. For 20+ years he has been employed as a freelance health and science writer. Today, with an eye on the latest news, Timothy continues writing about science with a focus on what you need to know for healthier living. For continual updates about health, you can also follow Timothy on Twitter at TimBoyerWrites.

Image Source: Courtesy of 200 Degrees from Pixabay


New study debunks blood type diet” Physicians Committee For Responsible Medicine news release 4 Dec. 2020’

Blood Type Is Not Associated with Changes in Cardiometabolic Outcomes in Response to a Plant-Based Dietary Intervention” Neal D. Barnard, MD et al, Journal of the Academy of Nutrition and Dietetics 4 Dec. 2020.

Sept. 2011 issue of For Women First Dr. Oz headlined article titled “Why the Blood: weight loss discovery” article posted on the Dr. D'Adamo website.