Blood Type: “Unrelated to Personality, But Closely Related to Disease”

The word is in: type O’s are strong against viral diseases, while type A’s and type B’s are strong against bacterial diseases. The preservation of the four different blood types enables humankind to defend against both classes of ailments.

ABO blood types are determined by sugar chains that adhere to the surface of red blood cells. A study of patients who have contracted the measles virus shows that the virus attaches a sugar chain identical to the host’s blood type to its own body as it multiplies inside the host. That is, the virus, like human blood, takes on a type A or a type B.

Dr. Seymour explains, “Because type O blood has antibodies against types A, B, and AB, it is able to swiftly attack invading viruses that mimic these other blood types.” By contrast, type A’s and others are relatively deficient in antibodies, and therefore more vulnerable to viral infection.

When people with type O blood become too numerous due to viral diseases, it’s time for bacterial diseases to attack these type O’s and reduce their number. Bacteria recognize the sugar chains on the surface of cells, like sign posts. They attach themselves to these chains and infect the cells. An excess of type O’s leads to the proliferation of bacteria that fasten themselves on type O sugar chains, thus infecting a higher number of type O hosts. This decreases the number of type O’s and increases the remaining types.

The fact that certain blood types are more vulnerable to particular kinds of diseases gradually became known after the 1960s. In a study conducted in the late 1980s, type O’s were more easily infected with cholera while type AB’s were the most resistant. AB blood types could even drink cholera-containing water without being easily affected with diarrhea. On the other hand, type O people, while weak against cholera, proved somewhat stronger against malaria and various kinds of cancer.

British science writer Matt Ridley states in his book entitled “Genome” that the reason modern American Indians are mainly type O whereas ancient Indian mummies are mostly types A and B might have to do with sexually-transmitted diseases. Type O’s are less sensitive to venereal disease than other blood types, and there are traces of a large outbreak of venereal diseases in ancient Indian settlements.

The distribution of blood types varies slightly according to race.

Koreans have the largest number of type A’s (34 percent), followed by type O’s (28 percent), type B’s (27 percent), and type AB’s (11 percent). Type A’s are the most common among the Japanese (38 percent), while the Chinese comprise a particularly large number of type O’s (42 percent), except in the Beijing area, where type B’s are the majority (32 percent). In Europe, on the other hand, type O’s are the most common among the British (47 percent), and type A’s the most common among the French (47 percent). Compared to Asians, Europeans include a notably smaller number of type B’s and type AB’s. Could there have been some factor that made it hard for “type B men” to survive in Europe, like there may have been for American Indians?

According to the Blood Bank at the Asan Medical Center in Seoul, the type A person—the type most often found in Korea—has a slightly higher chance of getting stomach cancer or coronary arterial disease, whereas the type O person is more at risk for duodenal ulcers. “Even microorganisms known to cause diseases have their own blood types,” says Professor Kwon Seok-un of the Ulsan University Medical School, “and certain microorganisms can more easily invade people with similar blood types to its own.” He added, “Animals also have blood types. Dogs have A and B types largely identical to humans’ and have to be matched by blood type in dog-to-dog transfusions.”

Scientists are far more skeptical regarding the claim that blood types have their corresponding personality types, the majority viewing them to be as absurd as astrological personality studies. Professor Seo Eun-guk of the psychology department at Yonsei University remarked, “There was a scientific study in Britain on the relationship between blood types and personalities, and the results showed that the two were completely unrelated.”

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