Diet Affects Markers of Alzheimer's Disease
Low-Fat, Low-Glycemic-Index Diets Improve Markers for Alzheimer’s Disease, Study Suggests
“We are getting closer to the day where we might give someone an anti-Alzheimer's diet prescription, but we are not there yet,” says P. Murali Doraiswamy, MD, professor of psychiatry and head of the division of biological psychiatry at the Duke University Medical Center in Durham, N.C.
Studies in animals that have been bred to develop brain changes similar to the kind that occur in Alzheimer’s show that high-fat diets can accelerate the disease, says Doraiswamy, who was not involved in the research. “This is the first randomized trial to test that in humans at risk for Alzheimer's,” he says.
But he also cautions that with just 49 participants, “the study is too small to draw any firm conclusions.”
But he said it should inspire a larger, longer-term study that could provide more definitive results.
Tracking the Influence of Diet on Alzheimer’s
For the study, researchers recruited 49 older adults. Twenty of the participants were healthy and showed no intellectual or memory declines. Twenty-nine had been diagnosed with mild cognitive impairment, a condition that’s thought to be early-stage Alzheimer’s disease.
None of the participants had histories of major mental illnesses, alcoholism, neurologic disorders, diabetes, liver or kidney disease, COPD, or unstable coronary artery disease. None was taking medications to lower cholesterol.
The average age of adults in the healthy control group was 69. Those with mild cognitive impairment were slightly younger, about 67 years old, on average.
Before the study, participants took a battery of tests designed to test how quickly their brains worked and how well they were able to remember things.
Researchers used blood tests to check insulin, glucose, and cholesterol levels.
Researchers also performed spinal taps to analyze participants’ cerebrospinal fluid -- a clear, colorless liquid that bathes the brain and spinal cord.
They measured beta-amyloid, the hormone insulin, a protein that helps in clearing out beta-amyloid called apolipoprotein E, and F2-isoprotanes, which are markers of oxidative damage caused by free radicals.
Half of each group was then randomly assigned to one of two eating patterns.
On the high-fat diet, participants got 45% of their daily calories from fat, including 25% from saturated fat, about 40% of calories came from high-glycemic-index carbohydrates, and about 20% were protein.
On the low-fat diet, 25% of calories came from fat, with less than 7% from saturated fat, 55% to 60% of calories came from low-glycemic-index carbohydrates, and about 20% from protein.
Study meals were delivered to participants twice each week.
Dietary Changes May be More Helpful for Prevention Than for Treatment
After one month on the diets, researchers repeated the original tests.
In healthy adults, the high-fat diet increased levels of beta-amyloid and other markers of inflammation and damage in the spinal fluid, suggesting that the high amounts of unhealthy fats and wide swings in blood sugar and insulin may be moving the brain toward changes associated with Alzheimer’s.