Studies show mixed effect of diet on Alzheimer's

CHICAGO -- Some dietary fats might help prevent Alzheimer's disease, others may increase the risk and -- contrary to some reports -- antioxidant vitamins may have no effect on the mind-robbing ailment, two studies suggest.

The study on fats adds to growing evidence that the same type of diet that protects the heart may benefit the brain.

Data are more mixed on effects on Alzheimer's of antioxidants such as vitamins C and E and beta-carotene, although recent studies have suggested a potential benefit, and scientists say a link makes biological sense.

The discrepancy may be explained by different study characteristics, say authors of the latest antioxidant research, from Columbia University. Their study, which found no effect from consuming antioxidants, involved older people who might have been less susceptible to the vitamins' purported benefits, and subjects were followed for a shorter period.

Longer-lasting earlier research may "have allowed for a better opportunity to find an association," said Columbia's Dr. Jose Luchsinger, the lead author.

It's possible that there truly is no association, although more research is needed to determine that, Luchsinger said.

The fats study, led by researcher Martha Clare Morris at Chicago's Rush-Presbyterian-St.Luke's Medical Center, involved 815 Chicago residents ages 65 and older who were asked about their eating habits. Followup tests nearly four years later found that 131 participants had developed Alzheimer's.

People who reported consuming relatively large quantities of saturated fats, found in many animal-based products including meat and butter, faced double the risk of having Alzheimer's compared with people who ate very small amounts. That risk was found for people who ate on average 25 grams of saturated fats daily; one tablespoon of butter has about 7 grams. Lower but still elevated risks were linked with smaller amounts of saturated fat.

Those who consumed large quantities of polyunsaturated fats (14.5 grams daily), found in vegetables and nuts, faced a 70 percent reduction in Alzheimer's risk, compared to those who ate small amounts of these fats.

Morris said the benefits could be gained from regularly eating foods like toast with polyunsaturated margarine, peanut butter, nuts and safflower-oil salad dressing.

The findings are "really consistent with other data that has been developing that suggests anything that raises your risk of vascular disease is associated with more Alzheimer's disease," said William Thies, vice president of medical and scientific affairs for the Alzheimer's Association.

Eating unhealthy fats promotes the buildup of "bad" cholesterol, which can narrow arteries. Researchers think it may also promote the formation of protein deposits called beta amyloid in the brain -- a hallmark of Alzheimer's.

The study of antioxidants involved 980 Medicare patients in New York, averaging age 75, who were asked about their food intake during the first year of the four-year study.

Alzheimer's was diagnosed during the study in 242 people.

Participants reported eating varying amounts of foods rich in antioxidants, such as oranges, corn-oil margarine and carrots. Some also took supplements, but no amount of antioxidants was associated with a decreased risk of Alzheimer's.

Antioxidants can block the effects of oxygen molecules called free radicals, which can damage cells and promote the accumulation of beta amyloid, the authors said.

Thies said the results don't rule out the possibility of an Alzheimer's-related benefit from antioxidants.

Previous evidence suggests "that it is not what you're doing in your late 70s that's going to affect your risk of dementia, it's what you're doing in your 50s and 60s," Thies said.

"I do think this suggests that antioxidants' effects are perhaps not huge," and that "vitamin E or C are never going to be a perfect preventative," Thies said.

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On the Net:

Archives of Neurology: http://archneurol.com

Alzheimer's Association: http://www.alz.org