VITAMIN E SUPPLEMENTS AS EFFECTIVE IN SLOWING LDL OXIDATION AS A COMBINATION

VITAMIN E SUPPLEMENTS AS EFFECTIVE IN SLOWING LDL OXIDATION AS A COMBINATION regimen containing vitamin E, vitamin C and beta carotene, according to a study published in the December issue of the American Heart Association journal Circulation. The study researchers, Ishwarlal Jialal, MD, and Scott Grundy, MD/PhD, University of Texas, Southwestern Medical Center, concluded that "combined supplementation with ascorbate [vitamin C], beta carotene, and alpha-tocopherol [vitamin E] is not superior to high-dose alpha-tocopherol alone in inhibiting oxidation" of low- density lipoprotein.

The study authors recommended that vitamin E therapy "be favored in future coronary prevention trials involving antioxidants."

The researchers' conclusions reflect a parallel comparison of the results of two studies: a 24-patient placebo-controlled trial designed to "ascertain both the safety and antioxidant effect of combined supplementation...on LDL," and a previous study conducted by Jialal et al. that looked at the antioxidant effect of vitamin E alone.

The combination antioxidant study was a randomized, single- blind study that measured LDL oxidation in blood samples over a three-month period. Participants in the study were divided into two groups of 12 and given either a placebo or a daily antioxidant regimen consisting of 1 g vitamin C, 800 IU of vitamin E and 30 mg beta carotene. Capsules used in the study were provided by Hoffmann-La Roche.

Jialal and Grundy reported two "significant observations" in the antioxidant combination study. First, the authors found that supplementation with high doses of vitamin E, vitamin C and beta carotene did "not appear to cause any significant side effects over the three-month study period." According to a Dec. 28 press release, the study results suggest that "vitamin E supplements are safe when taken daily in amounts more than 20 times greater than the Recommended Daily Allowance." The researchers also noted that the combination of antioxidants "does not appear to affect the absorption and plasma levels of each of these antioxidant micronutrients" that might cause a negative interaction.

Second, Jialal and Grundy found that the current study results indicate that combined antioxidant supplementation "resulted in two-fold prolongation of the lag phase," an index of the amount of antioxidants in LDL, and slowed the "oxidation rate by 40%."

The study authors also observed that neither vitamin C nor beta carotene showed an additive antioxidant effect. However, the researchers suggested that the "milder...effects" of these antioxidants "are probably lost" given the high-dose of vitamin E used in the study.

The researchers cited both in vitro and clinical trial data that suggest that beta carotene has an effect on the "oxidative modification of LDL." Noting a recent preliminary report on a study by Michael Gaziano and JoAnn Manson, MD, Harvard University, that indicates that beta carotene supplementation "reduce[s] not only major coronary events but all major vascular events," Jialal and Grundy suggested that "further investigation on the effect of beta carotene is warranted."

The study authors also discussed the possible role of vitamin C in "[preserving] the other antioxidants in LDL." They concluded that "ascorbate could indirectly protect LDL against oxidation by preventing loss of alpha-tocopherol and beta carotene."