This finding is yet another blow to the idea that vitamin and mineral supplements can help protect against major age-related chronic diseases.
Indeed, the participants in this study were among 7,540 men aged 60 and older who took part in a clinical trial that was designed to examine whether vitamin E and selenium reduced the risk of developing another age-related disease, prostrate cancer. That study (the Selenium and Vitamin E Cancer Prevention Trial, or SELECT) was halted prematurely in 2009 (after six years) when researchers became concerned that the supplements were doing more harm than good — that they might actually raise the risk of prostate cancer.
More than half of the men in that study — 3,786 — agreed to be followed for another six years after they went off the supplements as part of the dementia study.
But the findings for that study — known as the Prevention of Alzheimer’s Disease by Vitamin E and Selenium, or PREADViSE — were equally disappointing. The men who took supplements of vitamin E (400 IU daily), selenium (200 μg daily) or both developed dementia at the same rate — 4.4 percent — as those who took a placebo.
No progress in search for treatment
More than 5 million Americans have Alzheimer’s disease, a number that is expected to grow substantially in coming years as the U.S. population ages.
There’s been no progress so far in finding a treatment for this devastating illness, so researchers have been trying to identify successful approaches to prevention. Antioxidants, such as vitamin E and selenium, have been considered a possibility because some research has suggested that cell-damaging oxidative stress — a process that accelerates with age — may be involved in the formation of the disease.
Previous research — mostly observational studies — that investigated the effects of vitamin E and selenium on Alzheimer’s disease and other forms of dementia have produced mixed results. The current study — a randomized clinical trial, considered the gold standard of research studies — was designed to provide more definitive answers.
Limitations and implications
The study has several limitations. The researchers lost about half of their participants when the SELECT study ended. Furthermore, most of the participants were in their 60s, a decade when the incidence of dementia is quite low. Also, the screening test used to identify dementia may have missed individuals in the early stages of the disease, say the researchers.
Still, the study’s authors are clear about their findings: “The supplemental use of vitamin E and selenium did not forestall dementia and are not recommended as preventive agents.”
“For consumers specifically concerned about brain health and cognition, they should be aware that no scientifically rigorous studies have identified any supplement as an effective treatment or prevention for dementia,” said study co-author Frederick Schmitt, a professor of neurology at the University of Kentucky, in an interview with HealthDay reporter Alan Mozes.
For people who want to do something, he added, “regular physical activity, such as walking, and a heart-healthy diet have much more evidence supporting their effectiveness for reducing dementia risk.”
The study was supported by a grant from the National Institute of Aging.
FMI: You can read the study on the JAMA Neurology website.