Synthetic vs. Natural Vitamin E
(An interview with Robert V. Acuff, Ph.D. by Nature’s Impact magazine)
NI: Can you explain more about the chemical difference between natural and synthetic vitamin E?
RA: For consumers, it can be a little tricky to find authentic natural vitamin E in a supplement. People have to find “d-alpha tocopherol” in the list of ingredients on bottles of vitamin E. Some brands confuse consumers by suggesting that they’re buying natural vitamin E when they’re actually buying the synthetic form.
Let’s start with some basics. There are eight naturally occurring compounds with vitamin E activity. These are closely related molecules. Four are tocopherols and four are tocotrienols. The form with the greatest biological activity in people is unquestionably the alpha tocopherol form. The others play minor roles in human health.
When you buy a natural vitamin E supplement, the d-alpha form, you are getting a single chemical structure. Synthetic vitamin E has a different chemical structure and, in fact, actually consists of eight different stereoisomers of alpha tocopherol. The problem is that only 12.5 percent of synthetic vitamin E is the same as natural vitamin E; the other seven stereoisomers have lower activities in the body. Isomers are molecules with the same atoms, but in a different arrangement. The arrangement of atoms influences the properties and the biological activity of a substance.
Nl: Can you explain the difference in how natural and synthetic vitamin E are absorbed and retained in the body?
RA: It’s a very important difference, and there’s some interesting history leading up to my research and that of my colleagues. Historically, researchers have believed that natural vitamin E in the acetate form, milligram for milligram, is 1.36 times (or 36%) more biologically active than the synthetic form.
However, you may know that virtually all the vitamin E supplements sold on the market are measured in international units (IU), not milligrams (mg). The IU standard was developed as a way of leveling the playing field between synthetic and natural vitamin E. So while natural vitamin E per milligram is more potent, the theory was that natural and synthetic vitamin E in IU should be equal.
Nl: Why do you believe natural vitamin E is absorbed better than synthetic?
RA: There has been some excellent research in this area by Maret Traber, Ph.D., of Oregon State University, and Angelo Azzi, Ph.D., of the University of Bern, Switzerland. Vitamin E doesn’t just float through the blood by itself. The transport of vitamin E through the body depends on a protein called tocopherol-binding protein, which is produced in the liver. After you consume vitamin E, it moves from the digestive tract to the liver, which is the body’s chemical processing plant. It’s in the liver that tocopherol-binding protein hooks up specifically with the natural d-alpha tocopherol form of vitamin E instead of other natural forms and synthetic vitamin E. The fact that tocopherol-binding protein prefers the natural d-alpha tocopherol indicates that this is the form of the vitamin the body principally uses.