The Blood Type Diet is a diet plan that was popularized by naturopathic doctor Peter D’Adamo.
D’Adamo claims that your blood type determines which foods your body is adapted to eat and which you should eliminate from your diet.
By eating according to these principles, he says, you can optimize your health and avoid a wide range of maladies.
Is this true, though? Can you really boost your health by eating a diet based on blood type?
Learn the answer in this article.
Table of Contents
The Blood Type Diet, also commonly referred to as “the blood group diet,” is a diet plan that encourages you to eat according to your blood type.
It was popularized in the mid-1990s by naturopathic doctor Peter D’Adamo (a naturopathic doctor is someone who attempts to use natural remedies to help the body heal itself), who published a book titled Eat Right 4 Your Type detailing the diet’s theoretical basis and how to follow it successfully.
According to D’Adamo’s book, we should use our blood type to determine what kinds of foods our ancestors evolved to eat, then eat similar foods so that we thrive the way our forebears did.
The book also claims that failing to do this leads to the agglutination (clumping together) of red blood cells, which causes several medical issues.
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Your blood type is hereditary (determined by the genes passed on from your parents) and commonly classified using two systems: the ABO and Rh systems.
The ABO system categorizes blood types into four groups: A, B, AB, or O. The Rh system classifies your blood type into two further subgroups—positive or negative (A-, for example). Thus, when you combine these two systems, there are eight possible blood types.
The Blood Type Diet doesn’t factor the Rh system into its recommendations. Instead, it uses just the ABO system to recommend one of four diet plans: the type A blood diet, type B blood diet, type AB blood diet, and the type O blood diet.
D’Adamo refers to people with type A blood as “agrarians” or “cultivators.”
These people are predisposed to illnesses such as heart disease, cancer, and diabetes and should only eat select fruits, vegetables, nuts, seafood, seeds, legumes, beans, and grains.
According to D’Adamo, people who follow the A Blood Type Diet should almost wholly avoid dairy products to prevent “insulin reactions” and meat since their “low stomach acid content” means that they “store meat as fat.” They should also limit wheat intake, or their “muscle tissue will become overly acidic.”
D’Adamo recommends people with type A blood engage in calming exercises such as yoga and tai chi, hiking, swimming, and bicycling, and avoid vigorous exercise because “the heightened sensitivity of the nervous system gradually frays the person’s delicate protective antibodies.”
D’Adamo refers to people with type B blood as “nomads.”
These people are able to “resist” most diseases or survive them if they do contract them, but are prone to immune system disorders, such as chronic fatigue syndrome (ME), multiple sclerosis, and lupus.
They can eat most fruits, vegetables, seafood, dairy products, and meats (though not chicken, for some reason), and select nuts, seeds, beans, legumes, and grains.
According to D’Adamo, Type Bs should do exercises that are neither too aerobically intense nor completely aimed at mental relaxation, such as hiking, biking, the less aggressive martial arts, tennis, and aerobics.
D’Adamo refers to people with type AB blood as “enigmas.”
The AB diet is the most complex of all D’Adamo’s Blood Type Diets, because it’s a mix of type A and B.
Type ABs should avoid all meats except lamb, rabbit, turkey, pheasant, and some animal livers, but can enjoy many types of seafood. They can eat most fruits, vegetables and cereals, and select nuts, dairy products, beans, and pulses.
For exercise, Type ABs should follow a similar regimen to Type As and focus mainly on yoga and tai chi.
D’Adamo refers to people with type O blood as “hunters.”
Type Os thrive on animal protein (the only meats they should avoid are bacon, goose, ham, and pork) but should avoid dairy products and grains. They can also eat most fruits and vegetables, and select beans, nuts, and seeds.
D’Adamo believes that the best way for Type Os to deal with stress and maintain a healthy weight, emotional balance, and strong-self image is doing regular intense exercise, such as weightlifting, martial arts, stair climbing, and contact sports.
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D’Adamo believes that your blood reacts with specific types of proteins in the food you eat called lectins.
Lectins are a class of protein molecules that bind to particular carbohydrates, including glucose (blood sugar), sucrose (table sugar), and cellulose (fiber). They’re present in almost all life forms, from plants to animals to microorganisms like bacteria, viruses, and fungi.
According to D’Adamo, when you consume lectins that are incompatible with your blood type, the lectins target an organ or bodily system and begin to clump blood cells in that area, causing a long list of adverse effects including irritable bowel syndrome, cirrhosis of the liver, or reduced circulation through the kidneys, to name a few.
Your blood type dictates how your body reacts to different foods and the lectins they contain. As such, D’Adamo suggests you should tailor your diet based on your blood type to avoid lectins that may harm your body.
No studies support any of D’Adamo’s claims about the Blood Type Diet, and as such it’s essentially a collection of his opinions about how you should eat, not a science-based approach to dieting.
Some folks with a more accepting cast of mind toward fad diets might say it’s unfair to dismiss the Blood Type Diet, because we don’t have studies to refute D’Adamo’s claims. And to that I’d say, that’s not how science works.
An important pillar of the scientific method is that extraordinary claims require extraordinary evidence to match, and if that evidence isn’t present, the assumption is that the claims aren’t valid (this is technically known as the null hypothesis).
At the very least, you’d expect D’Adamo to muster a strong mechanistic argument for why his particular diet regimen works (for instance, showing that chicken proteins cause clumping of type B red blood cells in a test tube), but he hasn’t even scaled this meager hurdle.
D’Adamo also claimed in two of his books published in 1996 and 2004 that we’d have scientific evidence supporting his diet recommendations shortly after their publication, but as yet, there’s scant evidence on the diet at all, and none that inspires confidence.
For instance, one review study conducted by scientists at Belgian Red Cross-Flanders combed through thousands of studies that might provide clues on how the Blood Type Diet affects health. After garnering 1,415 relevant studies, they found that only 16 were designed in a way that would provide useful answers, and only 4 of these involved a diet that was remotely similar to the Blood Type Diet.
As they dug further, they had to remove three studies that were riddled with methodological flaws, and the one study left (again, out of almost 1,500) involved a protocol that was a far cry from the Blood Type Diet (it explored how LDL cholesterol levels changed when people with different blood types followed a low-fat diet and used the MNS blood type system, not the ABO system).
Unsurprisingly, the researchers concluded that “no evidence currently exists to validate the purported health benefits of blood type diets.”
Another more recent observational study conducted by scientists at the University of Toronto provides more reasons to doubt the benefits of the Blood Type Diet.
This study showed that people who followed the type A diet improved several markers of health, including BMI, waist circumference, blood pressure, cholesterol, and triglycerides. Those that followed the type AB and type O diets also experienced some positive changes, though they weren’t quite as impressive.
There’s a twist, however. While some blood type diets were associated with improved cardiometabolic health, these associations were independent of each person’s ABO blood type.
In other words, anyone who followed the type A, type AB, and type O diets showed improvements regardless of whether they ate the correct diet for their blood type or not.
And this makes perfect sense.
Most Americans eat an abysmally poor diet. If you took the average American and substituted their diet for any of D’Adamo’s Blood Type Diets, which are rich in healthy foods such as fruits and vegetables, minimally-processed meats, dairy, grains, and eggs, they’d see improvements in their health regardless of their blood type.
Chances are, though, they’d see even better results if they didn’t impose nonsensical restrictions on themselves that force them to consume foods they dislike and cut out foods they enjoy.
The real “secret” to better health, then, isn’t eating a diet according to your blood type—it’s eating a diet that contains nutritious, minimally-processed food.
And if you’d like advice about how many calories, how much of each macronutrient, and which foods you should eat to reach your health and fitness goals, take the Legion Diet Quiz, and In less than a minute, you’ll know exactly what diet is right for you. Click here to check it out.
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There’s no evidence that eating a diet according to your blood type has any positive effect on your health.
There’s no such thing as a “best diet for your blood type.”
Regardless of your blood type, you can optimize your health by eating a diet that’s rich in nutritious foods such as fruits, vegetables, whole grains, lean meats, fish, dairy, pulses, nuts, seeds, legumes, and plant oils.
Maybe, but not because there’s anything special about how the foods in the A positive Blood Type Diet react with your blood type.
If you currently eat a standard Western diet that includes a lot of highly processed, high-fat, high-calorie foods, switching to the A positive Blood Type Diet may help you maintain a calorie deficit and lose weight because it contains a lot of nutritious, low-calorie foods that are harder to overeat.
If you switch to the A positive Blood Type Diet and continue to eat the same number of calories that you currently consume, the A positive Blood Type Diet won’t help you lose weight.
There are plenty of O positive blood type diet meal plan templates online, but they’re unlikely to help you lose weight or improve your health.
If you’d like specific advice about which diet you should follow to reach your health and fitness goals, including detailed information about how many calories, how much of each macronutrient, and which foods you should eat, take the Legion Diet Quiz, and in less than a minute, you’ll know exactly what diet is right for you. Click here to check it out.
In D’Adamo’s Blood Type Diet, foods are categorized in two ways: By type (meat, vegetables, fruit, and so on) and by how beneficial they are for your blood type. For example, for Type Os, beef is “highly beneficial,” chicken is “neutral,” and goose should be “avoided.”
Since each diet contains several hundred food recommendations, it can be difficult to remember which foods you’re “allowed” to eat and which you should avoid. A blood type diet chart condenses all of this information into a clear table. A clear table of dubious advice.