Your blood type, Carl Zimmer explains, may predispose you to certain types of illness:
Doctors first began to notice a link between blood types and different diseases in the middle of the 20th century, and the list has continued to grow. “There are still many associations being found between blood groups and infections, cancers and a range of diseases,” Pamela Greenwell of the University of Westminster tells me.
From Greenwell I learn to my displeasure that blood type A puts me at a higher risk of several types of cancer, such as some forms of pancreatic cancer and leukaemia. I’m also more prone to smallpox infections, heart disease and severe malaria. On the other hand, people with other blood types have to face increased risks of other disorders. People with type O, for example, are more likely to get ulcers and ruptured Achilles tendons.
These links between blood types and diseases have a mysterious arbitrariness about them, and scientists have only begun to work out the reasons behind some of them. For example, Kevin Kain of the University of Toronto and his colleagues have been investigating why people with type O are better protected against severe malaria than people with other blood types. His studies indicate that immune cells have an easier job of recognizing infected blood cells if they’re type O rather than other blood types.