The question

The precise cause, or causes, of dementias such as Alzheimer’s disease remain unclear, but one theory points to molecules called free radicals that can damage nerve cells. This damage, called oxidative stress, may lead to changes in the brain over time that result in dementia. Might antioxidant supplements prevent this?

This study

The study involved 7,540 men 60 and older (average age, 67) with no indications of dementia and no history of serious head injury, substance abuse or neurological conditions that affect cognition. They were randomly assigned to take vitamin E (an antioxidant, 400 International Units daily), selenium (also an antioxidant, 200 micrograms daily), both vitamin E and selenium or a placebo.

The men also had their memory assessed periodically. In just over five years, 325 of the men (about 4 percent) developed dementia, with essentially no difference in the rate of occurrence between those who took one or both supplements and those who took the placebo. The researchers concluded that the antioxidant supplements “did not forestall dementia and are not recommended as preventive agents.”

Who may be affected?

Older men. The risk for dementia increases with advanced age and is most common among the very elderly. Memory loss is the most well-known symptom, but people with dementia may also have problems thinking, speaking, controlling emotions and doing daily activities such as getting dressed and eating. Alzheimer’s disease is the most common type of dementia, affecting more than 5.5 million Americans, including more than 10 percent of those 65 and older and more women than men.

Caveats

Participants took the supplements for a relatively short time. Whether the findings would apply to women was not tested. The study did not prove that the dementia developed by the study participants was caused by oxidative stress.

(Radius Images/Alamy)
Find this study

March 20 online in JAMA Neurology (jamaneurology.com)

Learn more

Information on dementia is available at ninds.nih.gov (search for “dementia hope”). More on vitamin E and selenium can be found at ods.od.nih.gov (click on “Dietary Supplement Fact Sheets”).

The research described in Quick Study comes from credible, peer-reviewed journals.