Harvard Health Letters: Can cutting calories help your memory?

Q: I'm 65, and I don't think my memory is as good as it once was. I read about a study that says you can improve your memory by eating less. Is there any truth to it? It sounds too good to be true.

A: It's not as crazy as it might sound.

The study you're referring to was published in the prestigious Proceedings of the National Academy of Sciences (PNAS), and it came after literally thousands of other studies of calorie restriction. In all animals that have been studied, from the simplest creatures to complicated mammals like us, cutting daily calorie consumption by about 30 percent improves vitality and lengthens life.

In the PNAS study, 50 people whose average age was about 60 were randomly assigned to one of three diets: one that reduced daily calorie intake by 30 percent; another that included a large amount of unsaturated fat (the type of fat found in plant-based oils like olive oil and in fish), an eating pattern that some studies suggest might be a memory booster; and a third that involved people just following their usual diets.

All the people in the study scored similarly on a memory test when the three-month study started. But at its conclusion, the study volunteers assigned to the restricted-calorie diet had scores on the test that were 20 percent better than at the beginning of the study, while those in the other two groups showed no improvement. The improved memory scores correlated with metabolic changes (decreases in levels of insulin and C-reactive protein, an inflammatory marker) that might strengthen the connections among the brain cells that are responsible for memory.

This was a small, relatively short study, so it's not even close to being definitive. And even if larger and longer studies were to confirm the results, it's fair to ask about the practical application. How many of us could manage a diet that cut our calories back by 30 percent? However, scientists are working on drugs that mimic the effects of calorie restriction, and those drugs already have shown benefits in mice - although the impact on memory has yet to be evaluated.

In my view, severe calorie restriction isn't likely to be realistic for most people, although I know some who have adopted it and are sticking with it. But I think it is possible that someday there will be medications that help with memory loss and many other problems associated with aging.

Anthony Komaroff is the Steven P. Simcox/Patrick A. Clifford/James H. Higby Professor of Medicine at Harvard Medical School, Senior Physician at Brigham and Women's Hospital in Boston, and Editor-in-Chief of Harvard Health Publications.

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