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Fall/Winter 2009

Research Shows that High Protein Diet May Shrink Brain

A high protein diet may help with weight loss, but according to a new study by Mount Sinai researchers, it may also increase the risk of brain shrinkage and the susceptibility to Alzheimer’s disease.

The study, published in the journal Molecular Neurodegeneration, tested the impact of several diets for their effects on Alzheimer’s disease pathology in mice. “Given the previously reported association of high-protein diet with aging-related neurotoxicity, one wonders whether particular diets, if ingested at particular ages, might increase susceptibility to incidence or progression of Alzheimer’s disease,” says lead study author Samuel E. Gandy, M.D., Ph.D., Mount Sinai Professor in Alzheimer’s Disease Research.

Dr. Gandy led an international team that included researchers from the United States and Canada.

The researchers tested four different diets on mice that had been genetically altered to be susceptible to Alzheimer’s disease. The mice were fed either the standard commercial diet that all mice in the facility receive; a custom-made high-fat, low-carbohydrate diet; a high protein, low carbohydrate diet; or a diet high in carbohydrates, but low in fat. The mice consumed these diets beginning at age four weeks until they were 18 weeks old. The researchers then looked at the brains and body weights of the mice, as well as plaque build-up and differences in the structure of the hippocampus, a brain region involved in memory.

They found that mice fed a high-protein, low-carbohydrate diet had brains 5 percent lighter than all the other mice, and regions of their hippocampus were less developed. Surprisingly, mice on a high-fat diet had raised levels of plaque proteins, but no loss of brain mass. This dovetails well with the knowledge that some fats, such as cholesterol, raise plaque levels, while other fats, such as those found in fish oil, protect from plaque.

One theory, says Dr. Gandy, is that a high-protein diet may leave neurons more vulnerable to Alzheimer’s disease plaque, but more research must be done to weed out the neurological impact of consuming different diets.

“At the end of the day, these are mouse experiments,” says Dr. Gandy. “Next, we want to see whether this is important for humans. There is enormous interest in identifying high-risk dietary components, but studying diets as though they were drugs is very challenging and, as with drugs, randomized double-blind clinical trials will be required if we are ever to be able to prescribe a diet that lowers the risk for Alzheimer’s.”

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