High saturated fat diet may raise Alzheimer's risk

Diets high in saturated fat and sugar may increase the risk of Alzheimer's disease, a new research shows.

In a small study published online Monday in the journal JAMA Neurology, researchers found that saturated fat cuts the body's levels of 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 researcher Suzanne Craft, a professor of medicine at Wake Forest School of Medicine, north Carolina, US.

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.

Fat diet also directly affects 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 study involved 20 seniors with normal cognition and 27 with mild thinking impairment, a precursor to Alzheimer's disease.

The participants, 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 a month, the diets caused changes in the amounts of amyloid beta and ApoE in their 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."