Can low-carb diets affect memory?

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The low-carb diet versus other diets debate rages on, this time with a new study that shows diets low in carbohydrates may affect cognitive skills.

Yes, by cutting back on carbs people could be cutting back on their mental acuity as well. Researchers in the psychology department at Tufts University in Massachusetts studied 19 women ages 22 to 55, nine of whom chose a low-carb diet, and 10 a low-calorie macronutrient balanced diet recommended by the American Dietetic Assn.

The participants were then given tests before the diets began, a week into the diets, and two and three weeks into the diet, after the low-carb group had carbohydrates put back into their diets. The tests measured attention and long- and short-term memory skills, visual attention and spatial memory.

After the first week, the low-carbers were in carb-deficient mode, and it showed — they had slower response times than the low-calorie group on two cognitive tests relating to memory. On a short-term recall test, the low-carb dieters also fared worse. They outscored the low-calorie group on an attention vigilance task, but researchers point out that in other studies, diets high in protein or fat can actually enhance short-term attention.

Hunger levels stayed the same for both groups, and all lost about the same small amount of weight (about 4.5 pounds). The low-calorie dieters also reported feeling more confused during the middle of the study.

The brain runs primarily on glucose, which it gets from the blood stream after carbs are broken down in the gastrointestinal tract.

‘Although this study only tracked dieting participants for three weeks, the data suggest that diets can affect more than just weight,’ said Holly Taylor, a psychology professor at Tufts and a co-author of the study, in a news release. The study was published in the February 2009 journal Appetite. ‘The brain needs glucose for energy and diets low in carbohydrates can be detrimental to learning, memory and thinking.’

-- Jeannine Stein