May 26, 2022
A very large number of studies suggest that antioxidants, the natural compounds found in fruits, vegetables and other foods, may be good for the health of the brain and other organs. The list of potentially beneficial compounds is long and can be confusing, and the benefits are difficult to prove. But a new study identified three antioxidants that may be particularly effective for brain health, helping to ward off Alzheimer’s disease and other forms of dementia in old age.
The three antioxidants were lutein, zeaxanthin and beta-cryptoxanthin. The study, published in the journal Neurology, found that people with the highest blood levels of these substances were less likely to develop Alzheimer’s disease decades later than people who had low levels of these antioxidants.
Lutein and zeaxanthin commonly occur together in foods. They are found in dark leafy greens like kale, spinach and chard, peas, Brussels sprouts, broccoli, asparagus and lettuce. These potent antioxidants belong to the family of compounds known as carotenoids, which are known to give foods such as cantaloupe, corn, carrots, and bell peppers their yellow or orange color. Salmon and eggs are also high in these antioxidants. Numerous studies have shown that lutein and zeaxanthin may be particularly effective for helping to preserve vision and eye health. This study suggests they are also good for the brain.
Beta-cryptoxanthin is found in fruits such as oranges, papaya, tangerines, peaches and persimmons.
“Antioxidants may help protect the brain from oxidative stress, which can cause cell damage,” said the study’s first author May A. Beydoun, of the National Institute on Aging, part of the National Institutes of Health.
For the study, researchers looked at 7,283 people who were part of the National health and Nutrition Examination Surveys, a nationally representative sample of men and women. They ranged in age from 45 to 90 at the study’s start, when they had a physical exam and blood tests to check for antioxidant levels. They were then followed for an average of more than 16 years, and up to 26 years, to see who developed Alzheimer’s disease or other forms of dementia.
The researchers found that people with the highest levels of lutein, zeaxanthin and beta-cryptoxanthin in their blood were at the lowest risk of developing dementia many years later. The higher the levels of these antioxidants, the lower the dementia risk.
The researchers considered other risk factors for Alzheimer’s disease, such as lack of physical activity and few years of formal education. These factors also affected dementia risk and were corrected for, but antioxidants continued to have an impact on risk.
The study did not find a significant effect of other antioxidants, including vitamins A, C and E and lycopene, on brain health.
In an editorial accompanying the study, doctors at the Karolinska Institute in Sweden noted that while some earlier studies suggest that antioxidants may lower dementia risk, findings have been “inconsistent.” They also noted that one recent review found that taking dietary supplements high in antioxidants had no effect on preserving memory and thinking skills or preventing dementia.
It is important to note that over-the-counter antioxidants, like other dietary supplements, are not regulated as drugs are. Therefore, the preparations, including the dose, of such supplements can vary from batch to batch, as well as from company to company. This inconsistency makes studies more difficult and is probably an important factor explaining the mixed findings. In addition, some of those compounds have been found to contain toxic impurities.
Nutrition experts point out that unlike supplements, fruits and vegetables contain a rich and varied blend of antioxidants and other healthful compounds. Numerous studies suggest that eating a varied diet containing a bounty of colorful and heart-healthy foods may help to preserve brain health.
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: May A. Beydoun, PhD, MPH; Hind A Beydoun, PhD, MPH; Marie T. Fanelli-Kuczmarski, PhD; et al: “Association of Serum Antioxidant Vitamins and Carotenoids With Incident Alzheimer Disease and All Cause Dementia Among US Adults.” Neurology, May 4, 2022.