Vitamin E mainly functions in the body as an antioxidant, which helps prevent damage caused by free radicals—rogue forms of oxygen that wreak havoc with the fats found in the outer layer, or membrane, of all cells.

As nutrients go, vitamin E is more complex than most: there are actually eight forms of vitamin E found naturally in foods, each with a different level of biological activity in the body. However, alpha-tocopherol is the only form that is known to meet the body’s requirement for vitamin E, and it is the form on which the recommended dietary allowance (RDA) is based.