Results of recent studies suggest that natural vitamin E is more bioavailable and is retained in body tissues significantly longer than synthetic vitamin E. These studies show that previously accepted differences were underestimated and that the bioavailability of natural vitamin E is about twice that of synthetic vitamin E compounds.

Natural vitamin E is derived from vegetable oils, primarily soybean oil. Synthetic vitamin E is produced from petrochemicals. A key difference scientists are examining is the structure of the compounds.

Natural vitamin E is a single stereoisomer, while synthetic E is a mixture of eight stereoisomers -- only one of which is the same as natural vitamin E.

The other seven stereoisomers have different molecular configurations and lower biological activities.

Consumers will find natural vitamin E by looking on the product's list of ingredients on the label: natural is "d" alpha-tocopherol, while synthetic is "dl" alpha-tocopherol

The researcher of a study that shows humans strongly discriminate between natural and synthetic vitamin E believes anyone taking vitamin E should be taking the natural form.

"Our studies suggest without question that natural vitamin E delivers at least twice the impact as synthetic E," said Robert Acuff, PhD, Professor and Director, Center for Nutrition Research at East Tennessee State University, "In the case of vitamin E, the natural form is clearly the one our bodies were designed to use."