MEDFORD/SOMERVILLE, Mass. -- A new study from the psychology department at Tufts University shows that when dieters eliminate carbohydrates from their meals, they performed more poorly on memory-based tasks than when they reduce calories, but maintain carbohydrates. When carbohydrates were reintroduced, cognition skills returned to normal.
"This study demonstrates that the food you eat can have an immediate impact on cognitive behavior," explains Holly A. Taylor, professor of psychology at Tufts and corresponding author of the study. "The popular low-carb, no-carb diets have the strongest potential for negative impact on thinking and cognition."
Taylor collaborated with Professor Robin Kanarek, former undergraduate Kara Watts and research associate Kristen D'Anci. The study, "Low-carbohydrate weight-loss diets. Effects on cognition and mood," appears in the February 2009 edition of the journal "Appetite."
While the brain uses glucose as its primary fuel, it has no way of storing it. Rather, the body breaks down carbohydrates into glucose, which is carried to the brain through the blood stream and used immediately by nerve cells for energy. Reduced carbohydrate intake should thus reduce the brain's source of energy. Therefore, researchers hypothesized that diets low in carbohydrates would affect cognitive skills.
Study participants included 19 women ages 22 to 55 who were allowed to select the diet plan they preferred -- either a low-carbohydrate diet or a low-calorie, macronutrient balanced diet recommended by the American Dietetic Association. Nine women chose a low-carbohydrate diet and 10 selected the low-calorie diet.
"Although the study had a modest sample size, the results showed a clear difference in cognitive performance as a function of diet," says Taylor.
The 19 dieters completed five testing sessions that assessed cognitive skills, including attention, long-term and short-term memory, and
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