What are reasons why there are different blood types and what do they do?

Do nothing: Blood groups do not do any thing, with rare exceptions. They are variations in the genetic make up of different individuals. It is just like having different eye or hair colors. The different colors do not do anything and the same is true for blood groups. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk prodFor good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.