Your blood group—A, B, AB, or O—is essential for transfusions, but researchers have also been studying whether it could be linked to long-term disease risk, including cancer. Several large epidemiological studies suggest small statistical associations between the ABO blood system and certain types of cancers, though experts stress these findings must be interpreted with caution.
Research, including a 2014 meta-analysis published in the Asian Pacific Journal of Cancer Prevention, found that people with blood group A may have a slightly higher risk (around 20%) of digestive cancers such as stomach and pancreatic cancer. In contrast, individuals with blood group O appear to have a modestly lower risk for some of these conditions. Results for blood groups B and AB vary depending on the type of cancer studied, with some studies—such as one published in Oncotarget in 2017—suggesting a possible increased liver cancer risk for group AB.
However, scientists emphasize that these differences are relatively small. Risk variations typically range between 10% and 25% and do not mean that a blood group causes or prevents cancer. Lifestyle and environmental factors remain far more influential.
Researchers propose several possible explanations. ABO antigens are found not only on red blood cells but also on other tissues, and they may influence inflammation and immune responses. Infections such as Helicobacter pylori, a known risk factor for stomach cancer, may also interact differently depending on blood type. Genetic proximity between the ABO gene and other immune-related genes may further explain observed correlations.
Institutions such as Inserm and Institut national du cancer continue to study these complex interactions, while also reinforcing that major cancer risks remain tied to modifiable factors like smoking, alcohol consumption, obesity, inactivity, and poor diet.
Public health agencies such as Santé publique France also stress that blood type does not determine cancer fate—being group O does not protect against cancer, just as group A does not mean someone will develop it.
