Your blood type means a lot more to your health than understanding which you’d need in a medical emergency. It can also affect whether you die of malaria or have a heart attack.

Red blood cells have certain sugars on their surfaces, known as antigens. You can have A or B antigens for Type A or Type B blood, both for Type AB, or neither for Type O. They are involved in how your immune system responds to foreign invaders because they tell it which cells are your own and which are different from the rest. But SciShow host Olivia Gordon explains that they do things other than signal antibodies.

Read: How a Blood Transfusion Changes Your DNA

The A and B antigens also make it easier for malaria-infected red blood cells to adhere to healthy ones, Gordon says. That makes the disease more dangerous because clumps could block blood flow as well as make your immune system’s job harder.

In that case, Type O blood is an advantage. In others, Type O is a disadvantage, like when the A and B antigens help your body fight off cholera in your intestines, according to SciShow.

The differences between blood types are significant because they mean different people have different needs. Type O is the most common, followed by Type A, the American Red Cross says, but exact distributions vary between races. For example, more than half of Hispanics and blacks in the United States have Type O blood, while about a quarter of blacks compared to a third of Hispanics have Type A. Those number differences lead to a larger gulf between their populations with Type B blood — almost 20 percent for black people but only about 10 percent for Hispanic people.

See also:

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