Could your blood group determine your risk of major cancers, infertility and stomach ulcers, as well as diseases such as cholera and malaria? A growing number of studies is revealing how our blood groups may make us more prone to lethal illnesses — or even protect us from them. Researchers at Pennsylvania University discovered this benefit in a study involving 20,000 people. Their research, to be published in The Lancet, found that most people who have a gene called Adamts7 face a significantly raised risk of suffering a heart attack. But in people with blood group O who have the Adamts7, there is no raised risk.