탄수화물 섭취 기억력에 영향 미쳐

탄수화물 섭취 기억력에 영향 미쳐

美, 시험결과 인지기능 현저히 떨어져

살찌는것을 막기위해 탄수화물을 줄이는 사람은 기억력이 저하되는것을 감수해야 할지모른다. 미국 터프츠 대학 심리학교수 홀리 테일러 박사는 탄수화물 섭취를 줄이면 기억력 등 일부 인지기능이 저하된다는 사실이 밝혀졌다고 말했다. 테일러 박사는 22-55세 여성 19명을 대상으로 9명은 저탄수화물 다이어트를, 10명에겐 저칼로리 다이어트를 1주일 계속하도록 하고 그 다음 2주일 동안은 저탄수화물 다이어트 그룹에 탄수화물 섭취량을 늘리게 했다.

이와함께 다이어트 시작 전에 한 번, 첫 주에 두 번, 그 다음 2주 동안 2번 모두 5차례에 걸쳐 단기기억, 장기기억, 주의력, 시각주의력, 공간기억 등에 관한 인지기능 테스트를 실시했다. 결과 첫 주에는 저탄수화물 그룹이 기억력과 관련된 테스트에서 저칼로리 그룹에 비해 성적이 현저히 떨어지는 것으로 나타났다. 저탄수화물 그룹은 특히 시각과 공간기억이 떨어졌다. 그러나 단기 주의력을 요구하는 테스트에서는 반응속도가 저칼로리 그룹보다 빨랐다.다이어트 실험 중 배고픔을 느끼는 정도는 두 그룹 모두 비슷한 것으로 나타났다. 탄수화물은 체내에서 포도당으로 분해돼 혈관을 통해 뇌로 전달되며 뇌세포들은 즉시 포도당을 에너지로 이용한다. 뇌가 사용하는 1차적인 연료는 포도당이며 뇌는 이를 따로 저장할 방법이 없다. 따라서 탄수화물 섭취를 줄이면 뇌의 에너지원이 줄어들어 인지기능이 떨어질 수밖에 없다는 것이 테일러 박사의 설명이다. 한편 탄수화물을 다시 섭취하면 기억력도 되돌아오는 것으로 나타났다. <기사원문> Low-carb Diets Can Affect Dieters' Cognition Skills ScienceDaily (Dec. 11, 2008)  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. 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 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. Participants were also asked about their hunger levels and mood during each session. The hunger-rating did not vary between participants on a low-carb diet and those on a low-calorie diet. The only mood difference between dieters was confusion, which was higher for low-calorie dieters during the middle of the study. "Although this study only tracked dieting participants for three weeks, the data suggest that diets can affect more than just weight," says Taylor. "The brain needs glucose for energy and diets low in carbohydrates can be detrimental to learning, memory, and thinking."

메디코파마뉴스/데일리엠디 김종필기자 (jp1122@nate.com)

기사 입력시간 : 2008-12-15 오전 11:05:45