Evidence stating there is no difference between natural and synthetic vitamins has now been challenged — at least in the case of Vitamin E.

Vitamin E supplements should be taken in natural formulations in preference to synthetic, according to Cornell University's May issue of "Food and Fitness Advisor."

"With the exception of Vitamin E, it usually doesn't matter if you take synthetic or natural formulations," the newsletter reported. "But Vitamin E is better absorbed in its natural form, so you need less of it — 100 to 200 IU (international units) as compared to 200 to 400 IU of synthetic E."

The Cornell recommendation follows numerous scientific findings that Vitamin E, made from soybeans in its natural form, is more effective than the synthetic version, usually made from petrochemicals. Consumers have been advised to read labels closely — natural Vitamin E will read "d alpha tocopherol," while the synthetic version reads "dl alpha tocopherol."

Vitamin supplements, including Vitamin E, should be taken with food, "preferably after the largest meal of the day, and with a meal that contains some fat," according to the Cornell newsletter.

Dr. Kevin Vigilanti of Brown University warns low-fat diets can impair absorption of fat-soluble vitamins such as Vitamin E.

In a separate article, the health letter noted "It is difficult to get enough Vitamin E from foods alone, and multivitamins do not usually contain sufficient amounts."