Fatty Acids Reduce Risk of Alzheimer's Disease by 50%, Protect Brain Functions

While Cholesterol Raises Alzheimer's Risk

January 30, 2004

Middle-aged adults who eat fatty fish regularly or take supplements of marine omega-3 polyunstaurated fatty acids are less likely to experience impaired cognitive function and speed, suggests new research from the Netherlands.

Higher dietary cholesterol however was associated with an increased risk of impaired memory and flexibility.
The study is the latest to investigate the relationship between dietary fats and early symptoms of dementia such as cognitive performance in ageing people.

Researchers at Tufts University in Boston, US last year found that boosting levels of docosahexaenoic acid (DHA) in the blood and eating about three fish meals each week can almost halve the risk of Alzheimer's disease in elderly men and women. Another study, published in the British Medical Journal, found that elderly people who eat fish or seafood even once a week are at lower risk of developing dementia, including Alzheimer's disease.

The cause of Alzheimer's, a debilitating disease which affects an estimated 12 million around the world, is still not known and it is expected to increase along with the numbers of elderly.

The new study, by researchers from the University Medical Center Utrecht and the University of Maastricht, not only demonstrated the benefits of omega-3s but also the impact of high cholesterol.

The researchers used data from a cross-sectional population-based study of 1,613 subjects ranging from 45 to 70 years old. Over a five-year period they tested for memory, psychomotor speed, cognitive flexibility (i.e. higher order information processing), and overall cognition. A self-administered food-frequency questionnaire was used to assess eating habits and risk was adjusted for age, sex, education, smoking, alcohol consumption, and energy intake.

Marine omega-3 polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid) were found to reduce the risk of impaired overall cognitive function by almost 20 per cent and speed by 28 per cent, reports the team in this month's Neurology (62:275-280). Fatty fish consumption also had a similar benefit on cognition.

Meanwhile higher dietary cholesterol intake was significantly associated with an increased risk (by 27 per cent) of impaired memory and flexibility. Increase in saturated fat intake also raised the risk of impaired memory, speed, and flexibility although not significantly.

Researchers speculate that DHA levels could be a risk factor for development of the disease. It is the most abundant fatty acid in the brain, which consists mostly of fat. About a fifth of that fat cannot be formed by the body however and people have to get it from their diet.

MONDAY, Jan. 26 (HealthWire) -- Low levels of testosterone are linked with a higher risk of developing Alzheimer's disease, a new study claims.

In a large group of men, researchers looked at the levels of free testosterone, which is the amount of testosterone circulating in the blood.

The researchers found a 26 percent decrease in the risk of Alzheimer's for every 50 percent increase in the amount of free testosterone measured in the blood. While levels of testosterone do decrease with age, levels dropped significantly more in men who developed Alzheimer's.

In addition, men who developed Alzheimer's had about half the amount of testosterone compared to men who didn't get the disease. And for some men, this drop in testosterone was found 10 years before Alzheimer's was diagnosed, according to the report in the Jan. 27 issue of Neurology.

"This is one more piece that we need to understand whether testosterone will protect men from developing Alzheimer's disease," says study author Dr. Susan Resnick, an investigator with the National Institute on Aging (NIA). "The logical next step would be to see if men should be raising their levels of testosterone. We don't know the answer to that yet."

In the study, 574 men were followed for about 19 years as part of the Baltimore Longitudinal Study of Aging. Their testosterone levels were checked periodically, and none of the men had Alzheimer's at the beginning of the study. During the follow-up period, 54 of the men developed Alzheimer's disease.

In earlier studies, Resnick and her team found older men with high levels of free testosterone have better visual and verbal memory and perform spatial tasks better then men with lower levels of testosterone.

"In the current study, we found that higher levels of free testosterone were associated with a significant reduction in the risk for Alzheimer's disease," Resnick says.

However, Resnick adds it is a complicated problem, and simply raising testosterone levels might not do the trick. "There may be some optimal level of testosterone that is beneficial, but levels that are too high or too low may not be beneficial," she explains.