LINUS PAULING INSTITUTE RESEARCH REPORT

Maret Traber

2004 LPI Public Lecture

Maret Traber, Ph.D.
Professor of Nutrition and Food Management
LPI Principal Investigator

Dr. Maret Traber of LPI delivered the LPI Public Lecture on January 14th to a large audience from the community. The LPI Public Lecture series is designed to allow internationally renowned scientific and medical authorities to present reviews of important health subjects for the lay public. It was inaugurated in 1998 by Dr. Bruce Ames of the University of California-Berkeley. Other speakers have included Drs. Paul Talalay of Johns Hopkins, Norman Krinsky and Jeffrey Blumberg of Tufts, and Connie Weaver of Purdue. Dr. Meir Stampfer of Harvard is scheduled to speak on May 3, 2004.

Dr. Traber's presentation, "A Fair and Balanced Look at Vitamin E", addressed questions concerning the nature of vitamin E, its antioxidant function, and its role in health and chronic disease. The full spectrum of the biological activity in humans of the eight members of the vitamin E family remains unknown, but its deficiency, due to fat malabsorption or genetic defects, causes peripheral neuropathy (loss of sensation in hands and feet) and ataxia, an inability to walk. The alpha-tocopherol form of vitamin E has the greatest biological activity in humans. The alpha-tocopherol transfer protein, synthesized in the liver, specifically selects alpha- tocopherol to package into lipoproteins that distribute the vitamin to tissues. Dr. Traber presented her recent data demonstrating that natural vitamin E, or d-alpha-tocopherol (also called RRR-alpha-tocopherol), which is about twice as potent as synthetic vitamin E (labeled as dl-alpha-tocopherol or all rac-alpha-tocopherol), remains in the plasma about four times longer than gamma-tocopherol. Gamma-tocopherol is the form consumed at the highest levels in the American diet.

Dr. Traber discussed results from studies in her laboratory showing that vitamin E supplements protected marathon runners from oxidative stress and was also depleted rapidly from the blood of smokers. Another study demonstrated that the absorption, or bioavailability, of vitamin E was tremendously increased when the vitamin was consumed as fortified cereal. Although the RDA for vitamin E is 15 mg of alpha-tocopherol/day for adult men and women, nearly 75% of American women did not consume as much as 8 mg/day in 1994-1996.

Dr. Traber reviewed several of the intervention studies in which supplemental vitamin E was given to patients. A few studies, such as the CHAOS and GISSI trials, found some benefit, while the HOPE trial did not. A 1993 Harvard epidemiological study found that the intake of vitamin E supplements for more than two years reduced the risk of heart disease in women by 40%. A recent meta-analysis of the published clinical trials showed no effect of supplemental vitamin E on all-cause mortality. The form of vitamin E and the manner in which it was consumed may have influenced these outcomes. Additionally, vitamin E may have different effects, depending on its usefulness in the prevention of disease or in the treatment of disease.

In response to questions at the conclusion of her lecture, Dr. Traber suggested that many factors influence the decision to take supplemental vitamin E, including diet, disease risk, and level of oxidative stress. Based on the accumulated research, LPI recommends a daily supplement of 200 IU of natural vitamin E (d-alpha-tocopherol). Very high intakes of vitamin E may enhance bleeding, so the tolerable upper intake level set by the U.S. Food and Nutrition Board is 1,500 IU/day of natural vitamin E, or 1,100 IU/day of synthetic vitamin E (figures derived from conversion factors for mg to IU and from natural to synthetic forms). Dr. Traber advised the audience to visit the LPI website for detailed information.

Last updated May, 2004


Micronutrient Research for Optimum Health


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