What is the thinking behind the blood type diet?

What is the thinking behind the blood type diet?

Dr D’Adamo’s scientific basis for the blood type diet is broken down as follows:

  • Molecular mimicry: A variety of microorganisms produce markers (antigens) in the body which are unique to one type of blood group or another. Depending on the blood grouping, these antigens are given different advantages unique to one of the different blood types. In just the same way, these markers can also be a source of trouble in their own right, according to a blood type grouping (i.e. working for or against your body according to your blood type grouping).
  • Energy source: Bacteria appears to have a preference for certain blood type groupings and consumes blood type antigens as a source for energy. By-products of this may or may not be beneficial to the digestive tract of a particular person (depending on their blood type).
  • Adhesion: Blood type antigens found in cells and in the mucus of the digestive lining, can be used by microorganisms, attaching themselves to tissues and cells throughout the body. In this way, it is believed that certain infections and conditions are directly linked with specific blood type groups (i.e. your blood type may make your more susceptible to certain conditions and ailments). Symptom ranges may vary, however from mild to severe.
  • Inappropriate responses: Unexpected immune system responses may be triggered by certain microorganisms and directly relates to individual blood type groups (i.e. responses are different for each group). Infections (viral or bacterial) may affect different blood type groups in an excessive manner (i.e. leading to high levels of inflammation, and compromising the body’s response to combatting the infection) or generate additional shock or increased levels of stress.

Lectins and the blood type diet

When it comes to the blood type diet, much of the debate centres around lectins, which are protein compounds in foods that react with the molecules (binding themselves to sugar molecules) in the body.

Dr D’Adamo’s theory is that most human blood types evolved as the availability of different foods (i.e. food sources) changed over the course of history. Our ability to digest and metabolise lectins, in particular, changed through time and according to the blood types which developed.

The thinking ties in with the idea that our ancestral blood type is the fundamental factor that determines what we should be eating. The blood type O is labelled as ‘the hunter’ and is, according to Dr D’Adamo, classified as the oldest of the four main groups. ‘The hunter’ requires a diet that is rich in protein. Others disagree and feel strongly that Type A was actually the first blood group to evolve in prehistoric human history. Type A’s tolerate veggie diets better and are thought to have come about as a blood group with the development of agriculture, which in turn influenced eating habits.

Type B is classified as ‘the nomad’ and developed when society had a need for increased tolerance for a variety of different food types (when societies began consuming more dairy products). AB blood groups led to the need for combination dietary requirements (i.e. a combination of the requirements of both A and B blood types).

Dr D’Adamo makes the argument that the effect of lectins (chemical reaction) based on foods we eat and our individual blood type groups is inherently part of our genetic make-up. Our digestive and immune systems effectively maintain a ‘favouritism’ for foodstuffs that our blood group ancestors ate (due to their agglutinating properties).

These proteins act like super glue by attaching themselves to cells in the liver’s bile ducts and the mucus linings throughout the body. If you eat food containing lectins that are believed to be incompatible with your blood type (antigens), the protein then targets the bodily systems (organs like your liver, kidneys, stomach and gut).

Interactions with tissues can have a distressing effect on the body (i.e. leading to the development of a health concern or medical condition). Blood type A individuals could consume a bowl of butter beans (a legume also known as lima beans). The beans would normally digest through an acid hydrolysis process. Lectin proteins are resistant to this process in a type A group and as such, don’t effectively digest in the stomach, rather staying intact or with some nutrients being absorbed in the bloodstream. The intact protein then settles somewhere inside the body and becomes something like a magnet for the cells in that area. This causes clumping, which in turn has a negative effect for the area of the body this occurs in. This can lead to conditions such as irritable bowel syndrome (IBS) or cirrhosis of the liver, food allergies or perhaps problems with the kidneys if a blockage of blood flow occurs.

Young woman in pain holding her stomach

Other signs of a lectin problem in the digestive system can include things such as flatulence or bloating following a meal, bowel habit changes, hormonal fluctuations, skin breakouts, achy joints or muscles, or fatigue.

Dr D’Adamo explains that approximately 95% of the immune system in the human body protects us from lectin proteins, with much of these being absorbed from the food we consume. The remaining 5% filters through the bloodstream and have the aforementioned types of reactions, effectively destroying white and red blood cells.

Lectins, as part of the debate, are seemingly a complex issue, as the nature of these proteins varies widely. It all comes down to their source. Lectins found in wheat are different from those found in soy foodstuffs. Thus, they attach differently to various cells/areas in the body, and by extension will have different effects on the bodies of different blood types. According to the doctor, the effect of this is beneficial to one type group but destructive for another. Hence the need for completely different and structured diet plans. For instance, he suggests that lectins in soy are beneficial for the immune system of a blood type A person, guarding against cellular changes, which would otherwise be problematic in the body for those with other blood groups.

Some problem foods high in lectin, for each main blood type group, according to Dr D’Adamo are:

  • Type O: Wheat, soy, Kidney beans and peanuts
  • Type A: Tomatoes, eggplant (aubergine), lima beans and garbanzo beans (chickpeas)
  • Type B: Soy, lentils, chicken and corn
  • Type AB: Bell peppers, corn, chicken and Fava beans (broad beans)

Various legumes on porcelain spoons (beans, legumes, lentils)

To date, the diet disagreement centres around the notion that lectin reactions in the body are solely responsible for poor health and body disruptions, and are directly related to different blood type groups. Dr D’Adomo takes the stand that type O blood groups are wheat and dairy intolerant and thus have systems that cannot handle these foodstuffs very well, making them more prone to gluten intolerance or suffering wheat allergies.

Counter arguments take the stance that the effects are not solely due to blood type groupings alone. Lectins are considered antinutrients and the small percentage that has any agglutinating activity (i.e. elicit the clumping of red blood cells) affects all ABO blood types, not just one specific group. Thus, it is argued that the effects can’t be specific to one blood group and not another.

Negative effects are also specifically attached to the consumption of raw legumes, but is argued that this carries little weight as most are hardly ever eaten in this state, and are rather soaked and cooked before being consumed. Thus, any small percentage of lectins are destroyed anyway.

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