Many recent studies have shown that diets rich in vegetables, fruits, nuts and fish, such as the Mediterranean diet, are good for the brain and may delay the onset or slow the advance of Alzheimer’s disease (AD). But a new study found that high protein diets appear to lead to a smaller brain.
The average American diet is high in proteins with most Americans eating twice as much protein as their bodies need. In addition, Many Americans faithfully follow high protein diets, such as Atkins, to lose weight. These diets emphasize meats, eggs, and cheese and are often high in saturated fats. Some high protein diets restrict fruits and vegetables.
A research team comprised of members from the United States, Canada, and United Kingdom studied four different types of diets on mice which were bred to express a mutant from of human amyloid precursor protein (APP). The body uses APP to produce the amyloid plaques associated with Alzheimer’s.
Mice were fed either a regular diet, a high fat/low carbohydrate diet, a high protein/low carb diet, or a high carb/low fat diet. The researchers then studied the brains and bodies of the mice, studying the plaque buildup and differences in specific regions of the brain associated with memory deficit and Alzheimer’s. They also looked at the brain and body weight of the mice, as well as plaque build up and differences in the structure of several brain regions that are involved in the memory defect underlying AD.
Surprisingly, the mice fed the high protein/low carb diet had brains five percent smaller than mice in the other three groups, and areas of their hippocampus were less developed. The researchers speculated that the high protein diet may make the brain’s neurons—which transmit nerve impulses—more susceptible to the Alzheimer’s-associated plaques.
But what does this study mean for humans? "One wonders whether particular diets, if ingested at particular ages, might increase susceptibility to incidence or progression of AD," says lead author, Sam Gandy, a professor at The Mount Sinai School of Medicine. The only way to know for sure would be double-blind clinical tests. "This would be a challenging undertaking but potentially worthwhile,” says Gandy, “if there is a chance that the ravages of AD might be slowed or avoided through healthy eating.”
Other studies have shown that diets high in protein, especially animal protein, can raise the risk of heart disease, stroke, osteoporosis and kidney stones.
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