- In a new study from Tufts University, 19 overweight women
followed either a “low-carbohydrate” or a “low-calorie” diet, based
on American Dietetic Association guidelines, for three weeks. After
the first week, people in the low-carbohydrate group, who
were told to completely eliminate carbohydrates from their diets,
did worse on tests of working memory (i.e., why did I walk into
this room?) and visuospatial memory (remembering locations on a
map) than people in the low-calorie group. (Find
25+ delicious low-calorie recipes here.) Fortunately
for the study subjects, “memory performance returned to normal when
we re-introduced carbohydrates in the second week of the study,”
says Holly Taylor, Ph.D., cognitive psychologist at Tufts and
co-lead investigator on the study. A piece of fruit or one-quarter
of a slice of bread seemed to be enough.
- Another study, published in The American Journal of
Clinical Nutrition in 2007, showed that people on a
higher-carbohydrate diet processed information more quickly than
those on a low-carbohydrate diet.
- Why? “The brain’s primary fuel is glucose,”
says Taylor. Eating carbohydrate-rich foods—grains, fruits,
vegetables—is by far the most efficient way of keeping the brain’s
glucose supply on “full.”
Try these recipes for a healthy mind—and
memory. But the body can only store one to two days’
worth of glucose, and when these stores are gone, glucose levels in
the blood (also known as “blood sugar”) drop. Fats and proteins can
be backup fuel sources, but they don’t provide the glucose needed
to sustain peak brain power.
- The good news: All diets don’t dampen brain power. A balanced, low-calorie diet, like the EatingWell Diet, may, in fact, boost it. A study in the Proceedings of the National Academy of Sciences earlier this year showed that restricting total calories by up to 30 percent for three months actually increased verbal memory scores (i.e., how many words were remembered 30 minutes after seeing them) in a group of elderly people. Researchers suspect that losing weight improved the body’s ability to use glucose, and that this allowed the brain to work more smoothly.
Bottom Line: Be cautious about striking carbohydrates from your diet: you may lose more than just a few pounds. The Recommended Dietary Allowance for carbohydrates is 130 grams per day, a number based on the amount of glucose the brain needs to function optimally. What does 130 grams look like? A cup of oatmeal, plus an apple, two slices of whole-wheat bread and 3/4 cup of cooked pasta.
By Brierley Wright, M.S., R.D.
Brierley’s interest in nutrition and food come together in her position as an associate editor at EatingWell. Brierley holds a master’s degree in Nutrition Communication from the Friedman School of Nutrition Science and Policy at Tufts University. A Registered Dietitian, she completed her undergraduate degree at the University of Vermont.
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