How a High-Protein Eating Regimen Can Hurt Your Brain

Not only can the foods you eat affect the size of your body, they also can affect the size of your brain. That’s what researchers discovered when searching for a connection between food and Alzheimer’s disease. Researchers in the US, Canada, Australia and the UK recently conducted a mouse study investigating four types of diet to see if any of them triggered brain plaque formation, the hallmark sign of Alzheimer’s that also leads to brain shrinkage. What they discovered came as quite a surprise.

The mice, which had been bred with a vulnerability for developing Alzheimer’s, were divided into four groups, and each fed one of the following four diets…

  • Standard commercial mouse chow (58% carbs, 29% protein, 13% fat)
  • A high-fat/low-carb version of the chow that was standardized at 60% fat, 30% protein, 10% carbs
  • High-protein/low-carb chow (60% protein, 30% fat, 10% carbs)
  • High-carb/low-fat chow (60% carbs, 30% protein, 10% fat)

Brain Food

After 14 weeks, researchers studied the brains of the mice. Previous research had shown that a high-fat diet increases the amount of amyloid beta protein (the main constituent of Alzheimer’s plaques) in the brain, and this study found that, too — but interestingly, this did not translate to an increase in plaque itself. Another finding was that the high-protein/low-carb diet was associated with a tendency to lose nerve cells from the hippocampus, the area of the brain where memory resides. That’s interesting in itself — but what really astonished the scientists was that in the course of the 14-week study, the brains of the same high-protein/low-carb group of mice had shrunk. They weighed 5% less than the brains in all other groups. 

The lead author on this study is Sam Gandy, MD, professor at Mount Sinai School of Medicine in New York City and a neurologist at the James J. Peters VA Medical Center in the Bronx. Dr. Gandy told me that it isn’t unusual for people’s brains to shrink very slightly (less than 1%) as they age, but the 5% brain shrinkage as seen in this group of mice is a considerable decrease. Dr. Gandy told me that how problematic this is depends on what part of the brain was diminished. He said that his team plans to study these findings further — including whether the type of protein eaten makes a difference. In the meaintime, keep your diet properly balanced. Weight loss at the cost of brain volume is not a good trade-off.