Vitamin E is a blanket term for eight different naturally occurring nutrients—four different tocopherols and four different tocotrienols. Each of these vitamin E-types is considered a fat-soluble antioxidant and all eight are found in varying degrees in our daily diet. You may sometimes hear all eight molecules being referred to collectively as “tocochromanols.”
The most famous of the vitamin E group is alpha-tocopherol. Both with respect to diet and high-dose supplementation, it is among the most intensely studied of nutrients. This is because its ability to help prevent free radical damage is well documented Public health recommendations for vitamin E are typically measured in milligram equivalents of alpha-tocopherol equivalents, or mg ATE.
However, despite the current prominence of alpha-tocopherol in public health recommendations and nutrition research, scientists are also interested in potential health benefits associated with lesser studied members of the vitamin E family, especially the tocotrienols. Like tocopherols (including alpha-tocopherol), tocotrienols are naturally occurring forms of vitamin E. Since they cannot be converted by humans into alpha-tocopherol, the tocotrienols are not considered relevant in meeting vitamin E needs. However, preliminary studies suggest that tocotrienols can provide us with health benefits in a way that is distinct from alpha-tocopherol, as well as other tocopherols.
In this introductory description of vitamin E, it is also worth mentioning the unusually confusing nature of its units of measurement. There is really no such thing as “milligrams of vitamin E” since this description fails to explain what forms of the vitamin were considered when making the determination.
Vitamin E is a potent antioxidant. Because it is fat soluble, we see it offer protection against damage to the fats that line the outside of every cell of our body.
When the fats in our membranes become damaged, important cell functions become compromised. Based on this important mechanism, researchers have studied whether diets low in vitamin E are associated with many diseases associated with aging.
We also see vitamin E protect fats from free radical damage before we eat them. We’ll talk about the role of vitamin E in protecting foods during storage below in the Impact of Cooking, Storage, and Processing section.
Vitamin E helps protect LDL cholesterol (sometimes referred to as “bad” cholesterol) from free radical damage. Free radical damage typically involves an unwanted interaction with a reactive oxygen-containing molecule. When vitamin E is deficient—and under some other circumstances as well—it is possible for LDL cholesterol to become insufficiently protected and damaged by oxygen. When damaged in this way, the LDL cholesterol is often referred to as “oxidized LDL.” If the process continues, it is possible for oxidized LDL to accumulate in blood vessel walls and create the early stages of hardening of the arteries (atherosclerosis).
Diets rich in vitamin E from vegetables, fish, and plant oils—like the Mediterranean diet for example—have been linked to cardiovascular prevention in large health surveys. Understand, though, that the potential benefits of this diet are not limited to or fully explained by vitamin E, and that dietary supplements of vitamin E (in comparison to vitamin E in food) have not demonstrated the same sort of preventive benefit that researchers hoped to see.