Vitamin C

Vitamin C is one of the safest and most effective nutrients, experts say. Though it may not be the cure for the common cold, the benefits of vitamin C may include protection against immune system deficiencies, cardiovascular disease, prenatal health problems, eye disease, and even skin wrinkling. The tolerable upper intake level (or the maximum amount you can take in a day that likely won’t cause harm) is 2000 mg a day for adults.