Most people do not give much thought to the blood running through their veins. However, it may pay to learn more about blood type, as it can affect your overall health in a variety of ways.

What is blood type?

The American Red Cross says there are four main blood types, which are determined by the presence or absence of A and B antigens on the surfaces of red blood cells and the presence of antibodies in the blood plasma. Blood type is further affected by a protein called the Rh factor, which can be present (+) or absent (-). Here’s a further breakdown:

Type A: Only the A antigen on red cells (and B antibody in the plasma).

Type B: Only the B antigen on red cells (and A antibody in the plasma).

Type AB: Both A and B antigens on red cells (but neither A nor B antibodies in the plasma).

Type O: Neither A nor B antigens on red cells (but both A and B antibodies in the plasma).

COVID-19

Studies examining how blood type affects overall health are ongoing, and such research garnered extra attention from the general public during the COVID-19 pandemic. Recent research indicates that blood type can affect one’s risk of contracting COVID-19 as well as the severity of symptoms. A key finding of the genetics company 23andme indicated that people with type O had lower incidences of COVID-19 positive tests. Evidence held even when researchers took into account age, sex, body mass index, and other factors. In a study published in March 2020, researchers in China found that “blood group A was associated with a higher risk for acquiring COVID-19 compared with non-A blood groups.”

Researchers at Columbia University reported similar risks associated with type A blood.

Heart disease

The protective nature of type O blood also applies to heart disease. WebMD reports that risk for coronary heart disease is lower among the O group as opposed to other types.

Stomach cancer

Individuals with A, B and AB blood types are more likely to get stomach cancer. The link may lie in the presence of H. pylori infection, which tends to be more common in people with type A blood, according to Northwestern Medicine.

Stress

Northwestern also reports that those with type A blood may have more trouble handling stress due to heightened levels of the stress hormone cortisol.

Kidney stones

More than five million people in Sweden were studied to determine the link between blood type and health risks. Those with type O and type B were more likely to get kidney stones.