To Your Health
I get confused about the various kinds of vitamin E on the vitamin labels. Why can't labels just say "tocopherol"?
A. Most nutrients are chemically defined molecules, but when vitamins were first being discovered no one knew which specific molecule was the vitamin. In the beginning, an extract of some food was said to have "vitamin activity" and it took many decades of research to define a vitamin. Today vitamin B-2 is understood to be a specific molecule, riboflavin. For all the minerals and most of the vitamins we have clear definitions, but vitamin E is one of the exceptions.
The first form of vitamin E discovered in 1922 was called simply "tocopherol," from the Greek words tokos, offspring, and pherein, to bear. Rats deficient in tocopherol could not bear young. Complications arose almost immediately. Shortly after tocopherol was discovered, other fractions were found. The first or "alpha" fraction was found to be the most potent, so other fractions were named beta, gamma, and delta, with potencies 60, 25, and 27% that of alpha, respectively. Since more than one molecule had vitamin E activity, it could no longer be called merely "tocopherol."
Isolating vitamins from foods turns out to be a rather expensive process, so there was a monetary incentive to synthesize alpha tocopherol. This was done, but it generated yet more complications. Molecules that have similar chemical characteristics but which differ slightly in structure are called "isomers." Synthesized alpha tocopherol contains eight isomers, most of which are virtually useless as vitamins. So now in addition to having four fractions of tocopherols, each with different potencies, we have eight isomers of the most common of these fractions. The label on vitamin bottles usually distinguishes between these forms of vitamin E by calling the mixture of the four naturally occurring fractions "mixed tocopherols" and calling the mixture of synthetic isomers "dl-alpha tocopherol." If only natural alpha tocopherol fraction is present it is called "d-alpha tocopherol."
Research just published (May 2002) in the Journal of Cardiovascular Pharmacology describes Swedish research on alpha tocopherol alone compared to mixed tocopherols. While both alpha tocopherol and the mixture shielded red cells from damage to the cell, mixed tocopherols were much more powerful than alpha tocopherol alone. Researchers attributed this observation to a greater cellular uptake of gamma and delta tocopherols. It appears that mixed tocopherols are better than d-alpha tocopherol, which in turn is better than dl-alpha tocopherol.
It gets even more complicated. A new class of substances with vitamin E activity has been found. Called tocotrienols, they are less potent than tocopherols when measured by the old "rat fertility" method but possess at least six times the antioxidant power of d-alpha tocopherol. In one way tocotrienols are better than tocopherols but not as good in another way. Gamma tocotrienol, for instance, has a cholesterol-lowering effect equal to that of the "statin" drugs, and without the complications, while alpha tocopherol outperforms tocotrienols in the classic rat fertility assay.
It apparently boils down to this: As insurance against our ignorance about vitamin E and its various functions, a mixture of several forms of vitamin E is the best way to maintain our health.