Natural Vitamin E retained two times better than synthetic
atural vitamin E is retained in humans two times greater than the synthetic form of the supplement, according to a new study published in the April 1998 American Journal of Clinical Nutrition (AM J Clin Nutr 1998;67:669-84). The research, conducted with volunteer subjects in Canada and the United States, is the second such study reported in the past two months.
"What we found was that, first in blood, and then eventually in organ levels, levels of natural vitamin E were almost double those of synthetic vitamin E, and they were consistently so," said Graham W. Burton, Ph.D., one of the study's principal investigators and a researcher at the National Research Council of Canada, Ottawa.
Natural and synthetic vitamin E are not the same. Previous research has shown natural vitamin E is better retained and more biologically active than synthetic. To identify the kind of vitamin E in a supplement, it is necessary to read the ingredients listed on the label. Natural vitamin E begins with "d," as in "d-alpha-tocopherol." The synthetic version begins with "dl."
In this new study, five healthy men and women, ages 20 to 59, were given a single 30 mg dose of vitamin E half natural and half synthetic. A month later, the same subjects took the same 30 mg dose daily for eight days. Another five subjects took a single dose of 300 mg of vitamin E and, a month later, also took the same dose daily for eight days. Half of this vitamin E was natural and the other half was synthetic.
When researchers measured the amount of vitamin E in the subjects' blood, they found twice the amount of natural vitamin E compared with synthetic regardless of how much and how often the mixed supplement was given. The 30 mg dose was equivalent to 35 international units (IU), or a little more than double the recommended dietary allowance (RDA) for vitamin E. The higher dose was equivalent to 354 IU, closer to the 400 IU commonly sold as supplements. This amount has been found effective in reducing the risk of coronary heart disease.
The same trend showed up in blood obtained from 22 patients hospitalized for various surgical procedures who took the "half and half" vitamin E supplement for up to 6 weeks. Two terminally ill patients were also given the same mixture for 1 to 2 years.
However, the levels of natural vitamin E were not as high in the tissue samples obtained from the elective surgery group. In contrast, levels of natural vitamin E were twice as high in all of the tissues of the terminally ill patients. "It is clear that it takes some time for the tissues to catch up to the difference observed between natural and synthetic vitamin E levels in blood," Burton said. "Both forms of vitamin E are absorbed equally well through the gut, but the liver clearly prefers the natural form, transferring it to lipoproteins to be transported through the blood for deposition into the tissues. The natural vitamin E is retained by a two-to-one ratio over the synthetic."
The findings are significant, Burton added, because it has long been believed that natural vitamin E, milligram for milligram, provides 36 percent more vitamin than the synthetic. The international unit standard was established years ago to account for this difference and to create a level playing field in terms of dosage. However, Burton's research suggests a far greater disparity between natural and synthetic vitamin E, demonstrating that synthetic supplements are retained only half as well as the natural. "Natural vitamin E may cost 2 to 3 times more, but it is twice as effective," Burton said.
The study was sponsored by the Natural Source Vitamin E Association, the National Foundation for Cancer Research, and the Association for International Cancer Research. Other collaborating institutions included the University of California, Berkeley; East Tennessee State University, Johnson City; and New York University Medical Center.
In an earlier study (Am J Clin Nutr 1998;67;459-64), researchers found 3 1/2 times higher levels of natural vitamin E in the placental cords of pregnant women than synthetic, after the women took supplements containing both natural and synthetic forms of the vitamin. This is significant because it suggests the placenta can deliver natural vitamin E to the fetus much more efficiently than synthetic, suggesting that women should take prenatal supplements that contain the natural form of the vitamin.
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