How antioxidants work

Oxidation is the primary cause of damage to the body's cells, organs, and tissues. As the body ages, its ability to repair oxidative damage slows down, and the results are the changes we generally associate with aging: wrinkles, gray hair, the need for reading glasses, and so on. Slow diminishment of brain (cognitive) function, which sometimes leads to dementia, is also caused by oxidative damage.

Antioxidants are special nutrients that prevent and repair oxidation's damaging effects. Beta-carotene; vitamins A, C, and E; and the minerals zinc and selenium are the best-known of the antioxidant nutrients, and a countless array of plant chemicals known as bioflavonoids appear to be even stronger.

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The Physician's Health Study of men over 65 showed that those who had been using 50 mg of beta-carotene every other day for an average of 18 years showed better cognitive function than those who took a placebo. A follow-up study including new recruits showed that using beta-carotene for three years or less had no impact on cognitive performance, but using beta-carotene for 15 years or more seemed to prevent age-related cognitive decline. They estimated that the difference in brain function between the men who used long-term beta-carotene and those who did not was similar to the cognitive decline that elderly men can expect over 1 to 1.5 years.

Best bets for beta-carotene

Food and supplements are both good ways to ensure you're getting enough beta-carotene. To add more beta-carotene to your diet, look to the following food sources:

• Orange, red, and yellow vegetables and fruits such as carrots, sweet potatoes, squash, tomatoes, and apricots.

• Greens, such as spinach, broccoli, and kale.

"This information helps us to understand how eating a good diet-lots of fruits and vegetables-protects the brain," said Erika Kellerhalls, MD, who practices family medicine in British Columbia, Canada. "There are a number of studies showing that we can prevent, or at least slow, age-related changes in cognition. The results from this study suggest that beta-carotene might be one reason for this effect. Most likely the combination of antioxidants that occur naturally in plant foods has the best effect, but it clearly requires a lot of time."

(Arch Intern Med 2007;167:2184-90)