Vitamin E and Selenium Fail to Prevent Dementia

September 27, 2017

Vitamin E and selenium, taken alone or together, did not prevent Alzheimer’s disease in healthy older men who took the supplements over a nearly eight year period. The results highlight the difficulty of finding effective treatments that may ward off Alzheimer’s disease or other forms of dementia in older people.

The two nutrients were studied because they showed some promise in initial studies for a variety of health benefits, including protecting the brain. Vitamin E is a vitamin found in vegetable oils, nuts and seeds, leafy green vegetables and whole grains; selenium is a mineral found in Brazil nuts, seafood and meats.

Both vitamin E and selenium are powerful antioxidants, which are known to protect cells throughout the body, including the cells of the blood vessels and the brain. Antioxidants exert their protective effect by sopping up free radicals, which are hyper-reactive molecules that can damage cells. Some antioxidants are produced naturally in the body. Others, including vitamin E and selenium, are found in foods and sold as dietary supplements.

In an initial study, from 2002 to 2009, vitamin E and selenium were tested to see whether these potent antioxidants might help to prevent the onset of prostate cancer. Vitamin E was given at a dose of 400 IU daily, and selenium at a dose of 200 micrograms daily. Some men got vitamin E, others got selenium, others got a lookalike pill containing both supplements, and a control group got lookalike inactive dummy pills. That study, carried out on 35,000 healthy men aged 55 and older, did not show any benefits in preventing prostate cancer onset.

The current study was a follow-up study from that earlier report. Known as the Prevention of Alzheimer’s Disease by Vitamin E and Selenium, or PREADViSE, trial, it looked at nearly 3,800 of the men who, after the prostate study ended, agreed to continue in the study over the next six years, from 2009 to 2015. They did not continue to take the vitamin E or selenium supplements, but they all underwent regular tests of memory and thinking skills to look for signs of impending Alzheimer’s disease.

Over the follow-up period, there were no differences in Alzheimer’s onset among the men who had taken a vitamin or mineral, or both, and those who had taken a placebo. Just over 4 percent of the men in each group developed Alzheimer’s or another form of dementia, about what would be expected for men that age, most of whom were in their 60s.The findings appeared in JAMA Neurology.

“The supplemental use of vitamin E and selenium did not forestall dementia and are not recommended as preventive agents,” the authors concluded.

Antioxidants have long been regarded as good potential treatments for Alzheimer’s and dementia, since they are known to protect blood vessels and cells throughout the body. But so far there has been little success in identifying supplements that may benefit the aging brain – or the conditions under which such effects would be measurable. It is plausible,for example,that the duration of the present study was not long enough to observe beneficial effects.

Ginkgo biloba, for example, a plant extract with potent antioxidant properties and derived from an ancient Chinese tree, has been commonly promoted for brain health. But earlier studies trying to address the efficacy of ginkgo have been disappointing. The Ginkgo Evaluation of Memory study, from 2008, for example, looked at more than 3,000 older men and women over seven years, but showed no benefit for ginkgo biloba extract. The GuidAge study in France, from 2012, recruited people with mild memory complaints, but similarly found no benefits from ginkgo.

The authors of the latest PREADViSE trial noted that the study had shortcomings. It looked only at men, many of whom dropped out during the follow-up periods. Supplements were given over a relatively short time period of seven to eight years, not decades. And it looked only at certain dosages of each nutrient.

So it’s possible that taking supplements for longer periods, starting earlier in life, or getting a rich array of supplements from foods, may still have benefits in the context of Alzheimer’s. Indeed, other studies have shown that a heart-healthy Mediterranean style diet, rich in fruits, vegetables and other foods high in antioxidants, may help to ward off Alzheimer’s or slow its progression. Other studies have found that exercise and other activities that are good for the heart are likewise good for the brain.

Alzheimer’s is a complex disease that likely takes many years to unfold. While genetics and advancing age play an important role in who develops the disease, a healthy diet is no doubt a good bet.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Richard J. Kryscio, PhD; Erin L. Abner, PhD; Alison Caban-Holt, PhD; et al: “Association of Antioxidant Supplement Use and Dementia in the Prevention of Alzheimer’s Disease by Vitamin E and Selenium Trial (PREADViSE). JAMA Neurology, March 20, 2017

Editorial: “Preventing Dementia: Many Issues and Not Enough Time,”by Steven T. DeKosky, M.D., of the University of Florida, Gainesville, and Lon S. Schneider, M.D., of the Keck School of Medicine of the University of Southern California, Los Angeles. JAMA Neurology, March 20, 2017


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