Saturated Fat May Make the Brain Vulnerable to Alzheimer's

Researchers say a small, new study shows that fat cut the body's level of a chemical that keeps Alzheimer's at bay

By Dennis Thompson

HealthDay Reporter

MONDAY, June 17 (HealthDay News) -- A diet high in saturated fat can quickly rob the brain of a key chemical that helps protect against Alzheimer's disease, according to new research.

In a small study published online Monday in the journal JAMA Neurology, researchers found that dietary saturated fat cut the body's levels of the chemical apolipoprotein E, also called ApoE, which helps "chaperone" amyloid beta proteins out of the brain.

"People who received a high-saturated-fat, high-sugar diet showed a change in their ApoE, such that the ApoE would be less able to help clear the amyloid," said research team member Suzanne Craft, a professor of medicine at Wake Forest School of Medicine.

Amyloid beta proteins left loose in the brain are more likely to form plaques that interfere with neuron function, the kind of plaques found in the brains of people with Alzheimer's disease.

Diet also directly affected the amount of loose amyloid beta found in cerebrospinal fluid, Craft said. Those on a high-saturated-fat diet had higher levels of amyloid beta in their spinal fluid, while people on a low-saturated-fat diet actually saw a decline in such levels, she said.

"An amyloid that is not cleared -- or attached to ApoE to get cleared -- has a greater likelihood of becoming this toxic form," Craft said.

The clinical trial, led by Dr. Angela Hanson of the Veterans Affairs Puget Sound Health Care System in Seattle, involved 20 seniors with normal cognition and 27 with mild thinking impairment, a precursor to Alzheimer's disease.

The patients, all in their late 60s, were randomly assigned to diets that contained the same amount of calories but were either high or low in saturated fat. The high-saturated-fat diets had 45 percent of total energy coming from fat, and more than a quarter of the total fat came from saturated fats. The low-saturated-fat diets had 25 percent of energy coming from fat, with saturated fat contributing less than 7 percent to total fat.

After just a month, the diets caused changes in the amounts of amyloid beta and ApoE in the study participants' cerebrospinal fluid, researchers said.

"Diet can really change levels of these toxic proteins and of these mediators that help clear these amyloids," Craft said. "Diets that are very high in bad cholesterol seem to interfere with ApoE's ability to clear amyloid."

One gerontology expert, who wrote an editorial accompanying the study in the journal, didn't think the link was quite that clear.

Although the study shows that diet can affect brain chemistry, it does not definitely tie diet to a person's risk for Alzheimer's disease, said Dr. Deborah Blacker, director of the Gerontology Research Unit at Massachusetts General Hospital in Boston.

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