Older men who take vitamin E and selenium supplements have the same risk of dementia as people who don't use these products, according to a new study from University of Kentucky in Lexington. The finding quashes hopes these antioxidants might prevent cognitive decline.
Previous research has linked antioxidants to the prevention of cellular damage that can occur with aging as well as in cancer and other diseases.
The role of antioxidants
Antioxidants may achieve this by halting or slowing oxidative stress, which has also been linked to the progression of dementia.
As the body uses oxygen, it produces by-products called free radicals. Damage to cells and tissues by oxygen free radicals is known as oxidative stress.
Antioxidants, either through food or supplements, are believed to reduce oxidative stress throughout the body.
For the study, researchers examined data on 7,540 older men who took part in a larger trial of the effects of selenium and vitamin E on cancer risk. Participants were randomly assigned to one of four groups that received either vitamin E or selenium supplements, both supplements or placebo pills.
About half the men were followed for five years and half for an additional six years. The study found no differences in dementia risk between any of the groups.
At the start of the study, the men were 68 years old on average and had no history of cognitive or neurological problems. During the study, 325 of them developed dementia, or roughly 4.4 percent of the men in each treatment group.
Limitations of the research
One limitations of the study is that many participants dropped out early. During the study, other research emerged linking vitamin E to an increased risk of prostate cancer and linking selenium to higher odds of diabetes; these findings may have prompted at least some men to leave the antioxidant study.
Based on the results, however, people without dementia should not be taking antioxidant supplements just to prevent cognitive decline, the researchers conclude.
It's possible that the study participants got enough antioxidants from their diets so that the supplements didn't appear beneficial. The dose of supplements or the formulation might have also contributed to the lack of benefit found in the study.
Get your antioxidants from food
A Mediterranean diet rich in fruits, vegetables, legumes, whole grains, fish and healthy fats may help ward off dementia even if supplements do not, and exercise may also help prevent cognitive decline, Schmitt said.
Related: Mediterranean diet may have lasting effects on brain health
Foods rich in antioxidants include berries like blueberries, cranberries, goji berries and elderberries as well as dark chocolate, pecans, artichokes and kidney beans.
The antioxidant vitamin E can be found in nuts, seeds, vegetables and fish oil but the body may need supplements to get enough of this nutrient. Brazil nuts, tuna and certain other fish, as well as red meat and poultry can contain selenium, but supplements may also be needed to boost supplies of this nutrient.
Source: JAMA Neurology, online March 20, 2017.
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