Picture of blood type characatures

I get questions sometimes from readers about the Eat Right for Your Blood Type diet plan. Published in 1996, Eat Right 4 Your Blood Type suggests that your blood type dictates your diet based upon ancestral styles of eating.

Basics of the Blood Type Diet

The basic reasoning is this: people with the same blood type share a common genetic heritage, while those with different blood types do not. Therefore, according to the author’s reasoning, people with Type O blood have different nutritional and exercise requirements than those who are Type As, and they are also susceptible to different diseases and health issues.

For example, according to the plan, people with blood Type O have emerged from caveman hunter ancestors, and therefore they require a high animal protein/meat diet.

The author also suggests that certain blood types should avoid some foods at all costs, because to eat foods that are genetically inappropriate causes lectin deposits that agglutinate your blood. In other words, substances that naturally occur in the foods you eat cause blood clumping that diminishes blood flow and clogs vessels and organs.

Unfortunately, the reasoning in this popular diet plan is flawed and not backed by research or studies.

The result is that people who adhere to this type of an eating plan may be eating foods that do not contribute to good health – no matter what your blood type. Furthermore, the people that have experienced positive results from the plan may simply be cutting out some processed and allergenic foods that anyone would improve from, regardless of their blood type.

About Blood Type

There are eight basic blood types. The most common type, O+, is present in about 39 percent of the population.

This is followed closely by A+ and B+. Your blood type is determined by the type of antigens existing on the surface of the red blood cells.

Picture of a bottle with AB on it

These antigens determine whether blood type is A, B, AB, or O. The other factor that types blood is the Rh factor, which is expressed as + or -.

Blood type is genetically inherited from both parents; however, it is slightly more complex than just directly passing on one or the other blood types of the parents.

For example, according to the Red Cross, a child with both parents having the AB blood type can have A, B, or AB. A child with parents who both have a blood type of B may have either Type O or Type B blood, and so on.

Blood type is important for blood donation. For example, someone with Type A blood can’t donate to someone with Type B. This is because when the body receives an incompatible blood type, it sees the foreign blood as an invader.

This leads to an immune response that causes clotting. How the blood type affects our body’s response to the foods we eat, however, is much less clear.

Debunking the Diet

One of the claims in the blood type diet is that Type O is the very first blood type that existed, present among early hunters. Microbiological research, on the other hand, suggests that the original blood type was A. 

Since the blood type diet begins with such a flawed premise, it is not surprising that its hypotheses and recommendations are flawed, as well.

Picture of a label that states, "Debunked - Myth"

One of the biggest flaws in the diet I see is this: The author suggests that the human species as a whole does not have an ideal diet.

Rather, he states that subgroups within this species (in this case humans separated by blood type) each have distinct ideal diets that vary extensively. This is not something found in nature.

In fact, if you look at the animal kingdom, every species has an ideal diet that suits the entire species.

For example, consider gorillas or cats. All gorillas or cats do best with a certain diet, and that doesn’t change wherever you’re feeding one. Why should people be any different?

Every human being has the same anatomy and digestive tract, and therefore the way we process the foods we eat are roughly the same. While genetic inheritance and upbringing may give rise to certain things such as susceptibility to disease, allergies, food sensitivities, and many others, reactions to food have more to do with individual genetic tendencies.

That’s why you can and should determine and eat the specific foods do best for your body. But to apply those to a broad group of people based on blood type is false, and it can mislead people into eating foods that aren’t best for humans as a species and avoiding those that are.

Another claim the blood type diet makes is that lectins from specific foods only cause agglutination of specific blood types. Research seems to show the opposite. Very few plant foods contain lectins that react with specific blood types; however, animal foods are more likely to be blood type specific. 

Likewise, lectins are in virtually every food human beings eat – plants, animals, grains, nuts – so avoiding them is nearly impossible unless you eat a grossly restrictive diet.

Humans have been eating lectin-containing foods since the beginning, yet many of the health issues of civilization (diabetes, metabolic syndrome, etc.), have only come about in relatively recent human history.

Many experts also refute the blood type diet, saying that it lacks solid backing in research.

The bottom line is this: the blood type diet lacks solid, controlled studies to back up the author’s reasoning.

Likewise, much of the diet’s reasoning is based on a faulty premise. It also doesn’t fall in line with the laws of nature whereby a species as a whole has a general, ideal natural diet, based on its anatomy, digestive tract, etc.

How to Eat

I am an advocate of plant-based diets, which are tailored to the human digestive system and meet human nutritional needs ideally. I believe anyone, regardless of blood type, can benefit from an alkaline plant-based diet rich in enzymes and nutrients to achieve optimal health.

You can keep a small amount of animal protein in your diet, if you would really like to, but this should be limited, no matter what your blood type.

If you eat too much meat your body will become overly acidic.

See which foods your body digests the best and that you feel the best on, and avoid the ones that don’t specifically work for you. Keep meals more simple, for better digestion.