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Study Looks at Antioxidant Effects on Dementia Risk

An older Asian couple cooking in the kitchen; the woman is feeding the man while he holds a purple pot on the stove.
A new study examined associations between levels of antioxidants in blood and the risk of developing dementia later in life.

Photo:  Credit Tom Wang / Shutterstock

Some studies suggest that consuming high levels of antioxidants—compounds commonly found in vegetables and fruits that help protect cells from molecular damage—may help prevent the development of dementia.

In a new study, NIH researchers looked at associations between levels of certain antioxidants found in blood and the risk of developing dementia later in life. The compounds analyzed included carotenoids—antioxidant pigments found in plants—and some vitamins. The results were published in Neurology.

The team analyzed blood samples from more than 7,000 people between ages 45 and 90 who had enrolled in NHANES, an ongoing national study of nutrition, between 1988 and 1994. This data was linked with databases that tracked participants over an average of 16 years to find who later developed Alzheimer’s disease or other dementias.

Overall, the team found that people with higher blood levels of carotenoids were less likely to develop dementia. However, when the researchers expanded their analyses to include lifestyle factors such as smoking and diet, and socioeconomic factors like education and income, the benefit of higher blood carotenoid levels disappeared.

Looking at individual carotenoids, blood levels of some of them were associated with a reduced risk of developing dementia after adjusting for other health, lifestyle and social factors. However, the size of the effect was reduced by these adjustments. The potentially protective carotenoids were lutein and zeaxanthin, which are found in green, leafy vegetables, and beta-cryptoxanthin, found in some orange-colored fruits.

In contrast, blood levels of the antioxidant vitamins A, C and E weren’t individually associated with dementia risk. Additional analyses suggested that high levels of vitamin A and E might actually counteract the effects of other antioxidants. The findings suggest that protective effects of some antioxidants may depend on the presence of other molecules in the body.

Around 6 million Americans are currently living with Alzheimer’s disease or another type of dementia, a number expected to rise substantially in the coming decades as the population ages. More targeted preventive strategies are needed to help people stay cognitively healthy as they age.—adapted from NIH Research Matters

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