scientific explanation
A study done all the way back in 1978 showed that people who are blood type O have a much faster response time to gastrin than the non-O blood types. Gastrin is the hormone that signals your stomach to release hydrochloric acid and pepsinogen upon the arrival of food (especially meat). After a meal, it only took 10 minutes for the body to respond to gastrin in type O subjects, but 40 minutes in A and B subjects.
Another study found that type Os have much higher levels of Pepsinogen A than people who are type A. Hydrochloric acid in the stomach activates pepsinogen, turning it into pepsin- which is the enzyme that breaks protein into peptides and amino acids.
Epidermal Growth Factor (EGF) is a protein that binds to specialized receptors on the surface of cells. EGF, interestingly, also has the effect of decreasing stomach acid secretion. One of the reasons that people who are type A have less stomach acid might have to do with the fact that the blood type A antigen is also capable of binding to the EGF receptors, leading to a decrease in acid production. Therefore, just being blood type A means a person’s stomach cells respond to these A-antigens that turn off stomach acid.
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