Blood type diet: what's behind this nutritional method

Can you lose weight according to your blood group? Although scientifically highly controversial, the notion continues to enjoy popularity. We explain what lies behind the blood type diet and which foods can be eaten by which blood group.

Soraya Laurenza

27 May 2022 | 3 Min. Reading Time

What is the blood type diet?

The blood type diet was devised by Peter D'Adamo. The American naturopath developed the theory in the 1980s and quickly gained popularity with his book a few years later. According to D‘Adamo, your blood group determines which foods you tolerate. The idea of the diet isn't primarily to lose weight, but rather to prevent or even cure medical conditions with a change of diet.

Blood type diet and evolutionary theory

Historical background

The roots of the different blood groups and the blood type diet are said to come from the Stone Age. D'Adamo claims that blood group O originated first: that of typical hunter-gatherers. At a later point in time, in the Neolithic Age, blood group A is said to have emerged, coinciding with the beginning of agriculture. Blood group B, whose origins lie in the steppes of Eurasia, arose as peoples intermixed. And blood group AB only emerged 1'000 years ago, from a combination of blood groups A and B.

What lectins have to do with the blood type diet

D'Adamo claims that protein-carbohydrate compounds called lectins can, in a worst case scenario, seriously damage our bodies. In best case scenarios, the opposite is true. Lectins are found in food and, in certain respects, are similar to our red blood cells. According to the blood type diet, the structure of the lectins that we take in through food should be similar to the structure of our own blood group. This is said to avoid adhesions of the blood cells, which can lead to health problems. And the conclusion of the theory is? People tolerate certain foods differently depending on their blood group and should therefore tailor their diet accordingly.

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The right foods for each blood group

With the blood type diet, eating plans are tailored to the diets of these ancestors.

Blood group O: focus on protein

The hunter-gatherers from the early Stone Age mainly ate meat, fish, fruit and vegetables. So what should blood group O carriers definitely not go without? Animal protein. Red meat, in particular, shouldn't be missing from their menus. On the other hand, they're advised to stay away from milk products and to steer clear of whole wheat grain products.

Blood group A: mostly fruit and vegetables

According to the blood type diet, carriers of this blood group – former crop farmers – have a sensitive gastrointestinal tract and should therefore eat meals containing plenty of fruit and vegetables. In addition to a mostly vegetarian diet, A-types can eat small amounts of fish. Pulses shouldn't present a problem, but eating meat isn't advised.

Blood group B: milk, vegetables, fish – all permitted

This group can consider themselves lucky, as they are said to have a resistant digestive tract. They can easily tolerate dairy products, most vegetables and almost any meat. Is anything off-limits? Cereals and chicken.

Blood group AB: Wheat? No problem!

According to D'Adamo, AB types tolerate practically all the fruits and vegetables tolerated by A and B types. Interestingly, carriers of this blood type are said to be the only ones who can tolerate wheat products. Dairy products also seem to be fine. Pork, on the other hand, is an absolute no-go.

Depending on their blood group, people tolerate certain foods differently and should tailor their diets accordingly.

What do researchers say about the blood type diet?

Peter D'Adamo hasn't proven that lectins lead to the clumping of blood cells, and evidence is also lacking for his theory on the origin of blood groups. In addition, numerous questions about the health benefits of this diet remain scientifically unanswered. But that's not all: according to experts, the blood type diet even has several disadvantages.

Disadvantages of the blood type diet

Being one-sided and unbalanced, this diet can lead to deficiency symptoms in the long term.
The selection of recommended foods is very limited.
Many of the foods are fancy or even exotic and therefore not available everywhere.
The diet is also difficult to integrate into everyday life.

A balanced diet is preferable

People looking to lose weight or simply to live more healthily should aim to eat a balanced diet and get enough exercise on a long-term basis. However, where the blood type diet sets a good example is in advocating home-cooked meals which, unlike ready-made meals, are more nutritious and free of flavour enhancers and added sugar. Science also shows that people of all blood types benefit equally well from a plant-based diet.

Vegan diet