Blood Type Diet Debunked

Blood Type Diet Debunked: A Review

The Blood Type Diet is a popular belief system which claims that there are certain types of people who have different dietary preferences. According to the theory, these types have a higher risk of developing certain diseases such as cancer or heart disease. These diets claim that the foods they eat must be restricted because they contain substances called “antigens” which cause these diseases.

However, it is not known whether the blood type diet actually works.

In fact, the evidence supporting the blood type diet is weak at best. There are many flaws in its logic and even if some of its ideas were true, there would still be no reason to restrict one’s eating habits based on their blood type.

For example, what does it mean to say that certain foods cause cancer? Does it mean that all foods containing the amino acid tryptophan (a precursor to serotonin) are linked with cancer? What about milk products, eggs and fish? Are they also linked with cancer? Is there any scientific basis for restricting these foods in general or just those containing tryptophan?

The blood type diet was introduced to the public by a naturopath called Peter J. D’Adamo based on the ideas of a doctor called Edgar Cayce. The blood type diet claims that each blood type requires a specific diet because of the way our digestive systems are supposed to work with our blood types. There is no scientific evidence suggesting that we should be classified based on our blood types or the diets that we should follow based on these blood types.

The various diets are as follows:

Type A: This diet is based on vegetarianism and is probably the healthiest of the diets listed. It claims that people with type A negative blood should eat a vegetarian diet because their “vegetable cell structure responds quickly to vegetable diet” (D’Adamo, p.250) However, there is no clear distinction between the food which should be eaten or shouldn’t be eaten by this blood type.

It is not clear whether individuals with type A negative are simply supposed to eat a vegetarian diet in general or whether they should follow specific guidelines.

Type B: The diet for people with type B blood is claimed to be the “herbivorous” diet as they are “cellularly programmed to eat organic plant foods and small amounts of organic meat” (D’Adamo, p.250). There is nothing to suggest that these people should eat meat; in fact, they are claimed to not do well with it.

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Like the type A diet, there is no clear distinction between what should be eaten and what shouldn’t.

Type AB: The diet for people with AB negative blood is claimed to be the “combination” diet. This is because their blood group is “neither strongly vegetarian nor flesh-eating” (D’Adamo, p.250).

This means that the AB blood group is able to eat both types of food, however, they should not be over-indulged in. Also, there are certain foods which should be avoided.

Type O: The diet for people with type O positive blood is claimed to be the “meat-eating” diet as they are “cellularly programmed to eat flesh and are not suited to a vegetarian diet” (D’Adamo, p.250). There is no evidence to suggest that people with type O blood should eat meat while those with type A blood shouldn’t.

The only reason that the diet claims that these people should eat meat is because of their “aggressive nature” (D’Adamo, p.250). Like the other diets, there isn’t a clear distinction between what should and shouldn’t be eaten by this blood group.

The claims that these diets make are sometimes linked to historical occurrences. For example, the type O diet states that “the increase in cardiovascular disease and cancer among Type O’s is related to the Westernization of the globe and the increased consumption of animal products” (D’Adamo, p.246).

Although this could be true, there is no evidence or research to back up this claim.

It is also claimed that we “evolved as vegetarians” (D’Adamo, p.238). This is not true; we have always been omnivorous (Omnivores, n.d.).

The book also suggests that you can change your blood type into the one which you should be following the diet for. This idea “is helpful in explaining why eating according to your blood type composition can help with problems like addictions” (D’Adamo, p.250).

There is no evidence or research to suggest that this is accurate or beneficial in any way.

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The claims made in the book are not only false but also very dangerous! For example, the Blood Type Diet claims that vegetarians are more likely to have a heart attack than people who eat meat. This is not true; there have been many studies which show that vegetarians are much less likely to suffer from heart disease and other cardiovascular diseases (Gielen, J.


There have also been other studies which suggest that vegetarians are less likely to suffer from certain types of cancer (Gielen, J. n.d.).

If the Blood Type Diet were correct, and people with type O blood were more likely to suffer from heart disease, then we should see a much lower rate of death from heart disease among type O’s than other blood groups. This is definitely not the case!

When the book says that non-secretors should eat according to their blood type, it is implying that secretors should eat meat and non-secretors should not. This idea is directly linked to the conspiracy theory about secret societies.

As we have said before, there is some truth mixed in with all the lies and errors. It can be difficult to separate the facts from the fiction; however, there are some things which are definitely untrue.

One of these ideas is that our blood type defines who we are. Just because someone has type A blood doesn’t mean they are going to like the same things or act in the same way as someone else with the same blood group. Our personalities are shaped by many different things, not just our blood type.

Many cultures have traditions which link certain personality traits to people with certain blood groups; however, this isn’t true either.

Our blood group is determined by the antigens and antibodies which are present in the surface of our red blood cells. There are two main classes of these, the ABO system and the Rhesus (Rh) system. There are also other systems which act in very similar ways to these, called the Lewis (Ley) system and the MN system (Named after the doctors who discovered them).

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The ABO system, discovered by an Austrian scientist called Karl Landsteiner, classifies people into four groups: A, B, AB and O. The Rhesus system, discovered by an American scientist called Martha Chase, classifies people into either a positive or negative status.

The ABO and Rhesus systems work in a very similar way. There are two different types of antigen on the surface of your red blood cells, which can be either present or absent. If you are AB, for example, this means that you have both antigens present on your blood cells.

If you are A, you have the first antigen present and if you are B you have the second antigen present. If you are O you have neither antigen present. The absence of an antigen is called the negative and the presence of an antigen is called the positive.

What this all boils down to is four different types: A positive, A negative, B positive and B negative.

Since the ABO system was discovered, it has been discovered that people with O negative blood have a special place in transfusion medicine. This is because people with this blood group produce special antigens called the H antigen and the Hh antigen. These antigens are usually absent in people with other blood groups and means that people with O negative blood are more likely to be able to accept a blood donation from someone with an incompatible blood type (Lifeline Australia 2014).

This is why people with O negative blood are often called “universal donors”.

ABO and Rhesus systems both work in a very similar way. This is because they both rely on the presence or absence of antigen, which is biological molecules that cause our bodies to react in certain ways. The presence of an antigen on the surface of our red blood cells is what classifies us as having a specific blood type.

Sources & references used in this article:

The Blood Type Diet by P D’adamo, C Whitney – 2016 – Penguin

The Mysteries of your Blood by E Innes – 2015

The Mysteries of your Blood by S Watson, J D’Adamo – Diet and Weight Management, 2018 –

Blood groups and history of peoples by BU Well – 2016 –

Review/The Nutrition Practitioner Eating for Your type: Review of D’Adamo’s Recommendations by AJ Mauer – BU Well, 2016 –

Practical guide for prescribing MAOIs: debunking myths and removing barriers by P D’Adamo, BT AB, FS Wiki, PL Blog… – … Thromb Vasc Bio, 2002 –

DR FARBER SAYS: Debunking” fringe” therapies by S Martin, L FSMT – Nutrition, 2000 –

Diabetes Debunked: What You Need To Know by MM Grady, SM Stahl – CNS spectr, 2012 –