October 28, 2010
Antioxidants, those cell-protecting nutrients found in foods and dietary supplements and also produced naturally in the body, have been studied extensively for their possible benefits in protecting against heart disease, cancer and other major ills. Now a new study finds that vitamin E, an antioxidant found in fats and other foods, may be associated with a lower risk of Alzheimer’s disease. The findings appeared in the American Medical Association’s Archives of Neurology.
Vitamin E and other antioxidants protect the body against highly reactive oxygen molecules called reactive oxygen species (ROS), which build up naturally in the body during the day-to-day process of living. Oxidative stress — or damage to cells from ROS — is thought to play a role in the development of Alzheimer’s disease as well.
Other studies have looked at taking high doses of dietary supplements containing vitamin E and other antioxidants. But none have shown a benefit in treating Alzheimer’s disease. And in one study involving healthy individuals, some antioxidant supplements, such as beta carotene, actually proved harmful, spurring the growth of lung cancer among smokers.
“The wider variety of antioxidants in food sources is not well studied relative to dementia risk,” wrote the authors, from Erasmus Medical Center in Rotterdam in the Netherlands. “A few studies, with varying lengths of follow-up, have yielded inconsistent results.”
For the study, the researchers looked at 5,395 men and women ages 55 and older. None had Alzheimer’s at the start of the study, which began in the early 1990s. All were given medical check-ups and extensive surveys about what they eat. The researchers focused on four antioxidants:
- Vitamin E: A fat-soluble vitamin found in margarine, sunflower oil, butter, cooking fats, soybean oil, and mayonnaise. Vitamin E is also found in wheat germ, nuts and seeds, green leafy vegetables, and whole grain.
- Vitamin C: Known since the eighteenth century, sailors carried lemons on long journeys to prevent the gum disease called scurvy. Most of the vitamin C the study participants ate came from oranges, kiwi, grapefruit juice, grapefruit, cauliflower, red bell peppers and red cabbage.
- Beta carotene: Part of the yellow-orange pigments found in carrots, beta carotene is also found in endive, tomatoes, sweet potatoes, cantaloupes. Green vegetables like spinach, broccoli, and lettuce are also high in this nutrient.
- Flavonoids: A family of plant pigments that contains over 4,000 substances, found in everything from tea and onions to apples and carrots.
In the study, patients were followed for an average of nearly 10 years. During that time, 365 study subjects developed Alzheimer’s disease, and another 100 developed other forms of dementia.
The one-third of those who got the most vitamin E in their diets were 25 percent less likely to develop Alzheimer’s than the one-third of participants who consumed the least. Dietary intake levels of vitamin C, beta carotene and flavonoids were not associated with dementia risk.
“The brain is a site of high metabolic activity, which makes it vulnerable to oxidative damage, and slow accumulation of such damage over a lifetime may contribute to the development of dementia,” the authors wrote. “In particular, when beta-amyloid, a hallmark of pathologic Alzheimer’s disease, accumulates in the brain, an inflammatory response is likely evoked that produces nitric oxide radicals and downstream neurodegenerative effects. Vitamin E is a powerful fat-soluble antioxidant that may help to inhibit the pathogenesis of dementia.”
Food studies are tricky, because people do not always report accurately what they eat. And people who tend to eat healthy foods also tend to engage in other lifestyle practices like regular exercise that may also decrease disease risk. Future studies are needed to evaluate dietary intake of antioxidants and other dietary risks.
Elizabeth E. Devore, ScD, Fraincine Grodstein, ScD, Frank J. A. van Rooij, DSc, et al: “Dietary Antioxidants and Long-term Risk of Dementia.” Archives of Neurology, Vol. 67 (No. 7), July 2010, pages 819-825.