Diet Affects Markers of Alzheimer's Disease

June 13, 2011 -- Diets that are low in saturated fat and rich in carbohydrates that steady blood sugar and insulin can beneficially change levels of substances associated with the development of Alzheimer’s disease, a new study shows. Such diets may also improve some measures of memory.

“Diet can have a very significant impact on some of the pathological markers of Alzheimer’s disease,” says study researcher Suzanne Craft, PhD, associate director of the Geriatric Research and Clinical Education Center at the Veterans Affairs Puget Sound Health Care System in Seattle.

“I think we’re starting to see in epidemiologic studies a connection between diet and brain aging, but I think our study is the first that has really shown, in an experimental fashion, that by creating a very carefully controlled diet you could show these very significant effects,” she says.

If further research bears the findings out, experts say the study may point to a way that people can reduce their risk of developing this kind of dementia, which erodes thinking and memory and alters behavior.

The study compared the effects of two different eating patterns on biomarkers in the spinal fluid of healthy older adults and those who had memory loss consistent with early Alzheimer’s.

Half of study participants ate foods high in saturated fat, like red meat and butter, with high-glycemic-index carbohydrates like french fries and sugar-sweetened sodas.

The other half ate a low-fat diet that also had plenty of low-glycemic-index carbohydrates from whole grains, fruits, vegetables, and beans.

The glycemic index  measures how quickly carbohydrates raise blood sugar. Foods that score over 70 cause rapid spikes in blood sugar and are said to be high-glycemic-index foods. Foods that rank under 55 allow blood sugar to rise more gradually and are low on the glycemic index.

Both groups ate the same amount of protein, and the diets were individually balanced so they did not cause weight loss or weight gain.

Healthy people who ate high-fat, high-glycemic-index diets for one month saw increases in spinal fluid levels of beta-amyloid, a fibrous protein that clogs the brains of people who have Alzheimer’s disease.

Eating a low-fat, low-glycemic-index diet, on the other hand, lowered levels of beta-amyloid in healthy adults and improved other markers of inflammation and damage in both groups.

What’s more, people who were already showing signs of Alzheimer’s appeared to be even more sensitive to the diets. They saw blood levels of total cholesterol rise nearly twice as much as those of healthy adults on a high-fat, high-glycemic-index diet.

For both groups, the low-fat, low-glycemic-index diet also improved delayed visual memory, which is the ability to remember and recognize complex patterns.

The study is published in the Archives of Neurology.