News 5

27 January 2009





Cutting calories 'boosts memory'


http://news.bbc.co.uk/2/hi/health/7847174.stm

Reducing what you eat by nearly a third may improve memory, according to German researchers.
They introduced the diet to 50 elderly volunteers, then gave them a memory test three months later.
The study, reported in the Proceedings of the National Academy of Sciences journal, found significant improvements.
However, a dietician said the reduction could harm health unless care was taken.

"To our knowledge, the current results provide first experimental evidence in humans that caloric restriction improves memory in the elderly "Munster University researchers.

There is growing interest in the potential benefits of calorie restricted diets, after research in animals suggested they might be able to improve lifespan and delay the onset of age-related disease.
However, it is still not certain whether this would be the case in humans - and the the levels of "caloric restriction" involved are severe.
The precise mechanism which may deliver these benefits is still being investigated, with theories ranging from a reduction in the production of "free radical" chemicals which can cause damage, to a fall in inflammation which can have the same result.
The researchers from the University of Munster carried out the human study after results in rats suggested that memory could be boosted by a diet containing 30% fewer calories than normal.
The study volunteers, who had an average age of 60, were split into three groups - the first had a balanced diet containing the normal number of calories, the second had a similar diet but with a higher proportion of unsaturated fatty acids, such as those found in olive oil and fish.
The final group were given the calorie restricted diet.
After three months, there was no difference in memory scores in the first two groups, but the 50 in the third group performed better.
Diet warning
They also showed other signs of physical improvement, with decreased levels of insulin and fewer signs of inflammation.
The researchers said that these changes could explain the better memory scores, by keeping brain cells in better health.
They wrote: "To our knowledge, the current results provide first experimental evidence in humans that caloric restriction improves memory in the elderly.
"The present findings may help to develop new prevention and treatment strategies for maintaining cognitive health into old age."
However, care was taken to make sure that the volunteers, despite eating a restricted diet in terms of calories, carried on eating the right amount of vitamins and other nutrients.
Dr Leigh Gibson, from Roehampton University, said that the drop in insulin levels were one plausible reason why mental performance might improve.
The hormone was known to act on parts of the brain related to memory, he said, and the higher levels found in people with poorly controlled type II diabetes had been directly linked to worse memory and cognitive function.
A spokesman for the British Dietetic Association said that people, particularly those already at normal or low weight, should be "extremely careful" about attempting such a diet.
She said: "There is other evidence that, far from enhancing memory, dieting or removing meals can interfere with memory and brain function.
"A drop of 30% in calories is a significant one for someone who is not overweight, and should not be undertaken lightly.
"It could even be dangerous if the person is already underweight."

Summary:
摂取カロリーを１/３減らすことで記憶力の向上が望める可能性がある、とする研究結果が発表されました。ただし、標準体型以下の人の無理なカロリー制限は悪影響も大きいようですから注意が必要です。
今回の研究では平均年齢６０歳の被験者を３つのグループに分け、グループ１には通常カロリーのバランス食を、グループ２にはカロリーは通常でもオリーブオイルや魚に多く含まれる不飽和脂肪酸を多く含む食事を、グループ３にはカロリーが通常よりも３０％少ない食事（ただしビタミンなどの栄養成分は必須量を満たすように設計）を３ヶ月間摂ってもらい、記憶テストを実施しました。
その結果、グループ１と２においてはスコアに差が見られなかったものの、グループ３では顕著な向上が確認されました。また、肉体面においても改善が見られたほか、インスリン値や炎症発現の減少も認められました。
一方で、ダイエットや食事制限が記憶力を高めるどころか脳の働きを妨げるという研究結果もあることから、注意を呼びかける専門家もいます。
「３０％のカロリー制限というのは既に標準もしくはそれ以下の体重の人にとっては非常に危険な行為で、安易にやってみるべきものではありません。」

New words/expressions I learn:

caloric:カロリーの→calorie :カロリー　plausible:（説明・陳述など）妥当と思える dietetic:栄養（学）の → dietary: 食事の、ダイエットの interfere:（人・物事が）（～を、with）妨げる