Low carb diet impairs thinking

I never jumped on the low carb bandwagon (the diet would be pretty difficult to pull of as a vegetarian) but I have rethought my relationship to carbs over the past five years or so. What it boils down to is that I try to eat less bread. Well, according to the latest research from Tufts, maybe I should eat the bread after all. In the results of the small study, women on low carb diets actually showed decreased cognitive abilities. Less mental clarity is NOT something I need considering I am yanked from sleep at 4:30 most mornings by my 20 month old! Because the study was rather small I wondered about the value of passing on the results to you, but the researchers highlight some compelling info about why carbohydrates may help your brain function better during the course of a day.

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.

"Although the study had a modest sample size, the results showed a clear difference in cognitive performance as a function of diet," says Holly A. Taylor, professor of psychology at Tufts and corresponding author of the study.

The 19 dieters completed five testing sessions that assessed cognitive skills, including attention, long-term and short-term memory, and visual attention, and spatial memory. The first session was held before participants began their diets, the next two sessions occurred during the first week of the diet, which corresponded to the week when low-carb dieters eliminated carbohydrates. The final two sessions occurred in week two and week three of the diets, after carbohydrates had been reintroduced for those on the low-carb diet.

"The data suggest that after a week of severe carbohydrate restriction, memory performance, particularly on difficult tasks, is impaired," Taylor explains.

Low-carb dieters showed a gradual decrease on the memory-related tasks compared with the low-calorie dieters. Reaction time for those on the low-carb diet was slower and their visuospatial memory was not as good as those on the low-calorie diet. However, low-carb dieters actually responded better than low-calorie dieters during the attention vigilance task. Researchers note that past studies have shown that diets high in protein or fat can improve a person's attention in the short-term, which is consistent with the results in this study.

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