However, researchers from the American Institute of Oncology have discovered that the risks of cancer death among smokers are directly linked to the concentration of vitamin E in their blood. Individuals with higher concentration of vitamin E in the body run lower risk of developing cancer and cardiac diseases, in comparison to those with lower levels of vitamin E in their blood. The optimum concentration of vitamin E in the bloodstream is thirteen or fourteen milligrams per liter. Vitamin E is contained in most nuts and seeds, full-grain bread, and dark-leafed vegetables. It should be noted, however, that the only way to reduce the risks to their minimum is to quit smoking.