Separately, people with A, B, and AB blood types are considered to be at greater risk of developing gastric cancer compared to those with type O. Type A individuals are said to face the highest risk within this group, a pattern researchers attribute in part to the greater prevalence of H. pylori infections among type A individuals. This bacterium, commonly found in the stomach, is known to cause inflammation and ulcers.
Type O is not risk-free: ulcers and a specific bacterial vulnerability
Type O blood is often highlighted for its universal donor status, but it comes with its own documented health associations. Studies have shown that people in the type O group face a higher risk of developing peptic and duodenal ulcers compared to those in other blood type groups.
Peptic ulcers are painful open sores that form in the stomach lining and upper intestine. The elevated risk in type O individuals is linked to an enhanced binding of Helicobacter pylori — the same bacterium associated with gastric cancer risk in type A — to epithelial cells in those belonging to the type O group.
Gastric cancer itself remains a significant global health burden: it is the 5th most diagnosed cancer worldwide and the 3rd leading cause of cancer-related death globally, underscoring why understanding blood type associations with digestive health carries real clinical weight.
Taken together, the research reviewed here suggests that blood type — long considered relevant mainly for transfusions — may also serve as one indicator among many in assessing susceptibility to conditions ranging from heart failure to cognitive decline. For type A and B individuals, the cardiovascular risk figures from the American Heart Association study are the most precisely documented: an 8% higher heart attack risk and a 51% greater chance of deep vein thrombosis compared to other groups.
