牛奶雖好可別貪杯 研究稱一天3杯奶死的快大綱

Drinking more than three glasses of milk a day may not protect bones against breaking - and may even lead to higher rates of death, say researchers. A new study suggests certain types of sugars found in milk may increase inflammation and oxidative stress, which can damage body cells. But Swedish researchers said their study could not prove ‘cause and effect’ and much more research was needed before anyone would be advised to limit their milk consumption.

調研者稱，每天喝三杯以上牛奶非但不會幫你預防骨折，還可能導致更高的致死率。一項最新的研究表明，牛奶中包含的特定糖類會增加炎症和氧化壓力，損壞身體細胞組織。然而在確定這一調查結果之前，瑞典調查者認爲還需要進行更多的調查。

Milk is recommended for cutting the risk of fractures because it contains calcium and vitamin D, which are vital for bone strength. However, there have been conflicting results from studies into the health benefits of milk in recent decades, with some showing it prevents heart attacks and strokes and others the opposite. Professor Karl Michaëlsson, Sweden, led a team to investigate whether the mechanism for potential harm was consumption of the sugars lactose and galactose found in high levels in milk, compared with much lower levels in other dairy products.

牛奶因其還有鈣質和維生素D、可以預防骨折而被推薦飲用。然而近年來，牛奶的功效一直備受爭議。有人認爲牛奶可以預防心臟病和中風，而又有人對此持反對意見。瑞典烏普薩拉大學卡爾教授帶領一個小組調查的內容就是：和其他乳製品相比，牛奶中乳糖和半乳糖含量較高，而這是否會對人體造成潛在危害。

Two large groups of 61,433 women and 45,339 men in Sweden completed food frequency questionnaires for 96 common foods including milk, yoghurt and cheese. Women were tracked for an average of 20 years, during which time 15,541 died and 17,252 had a fracture, of whom 4,259 had a hip fracture. In women, drinking more milk did not cut the risk of broken bones, says the study published in The BMJ. Men were tracked for an average of 11 years, during which time 10,112 died and 5,066 had a fracture, with 1,166 hip fracture cases. Men who drank more milk also had a higher risk of death, although much lower than in contrast, eating more dairy products such as yoghurt and cheese - with a low lactose content – led to lower death rates and fewer fractures, particularly in women.

瑞典，共有61433名女性和45339名男性接受了關於攝入牛奶、優格和乳酪頻率的問卷調查。關於女性的追蹤調查歷時20年，期間15541名女性過世，17252名女性曾骨折，其中4259名女性髖骨骨折。飲用牛奶並沒有降低女性骨折的風險。而男性的調查則持續了11年，期間10112名男性過世，5066名男性骨折，其中1166名髖骨骨折。飲用更多牛奶的男性死亡率雖與女性相比較低，但仍舊高於牛奶攝入少的人羣。相反，攝入乳糖含量較低的優格或乳酪之類的乳製品死亡率更低，而且骨折風險更小。

Prof Sue, Head of the Department of Nutritional Sciences, University of Surrey, said the study had limitations, such as weak methods to assess lifestyle habits including bodyweight. She said: ‘Also key is that all milk in Sweden is fortified with vitamin A. This may well be an important confounding factor. Milk and dairy products in the UK provide 50-60 percent of the calcium in our diet. We know that low calcium intakes is a risk factor for osteoporosis.’

薩里大學營養科學系主任蘇教授認爲這些調研都有其侷限性，並不能準確地評估包括體重等生活習慣。她說，“瑞典的牛奶中有加強補充維生素A，這可能也是關鍵因素之一。英國的牛奶和乳製品提供了日常營養攝入中50%~60%的鈣質。而我們知道，低鈣攝入會導致骨質疏鬆。”

Prof Brian Ratcliffe, Professor of Nutrition, Robert Gordon University, Aberdeen, said the possible role of alcohol intake was understated given that most of the extra deaths in milk drinkers were from heart disease. Lowest milk consumption was associated with the highest consumption of alcohol, and ‘there is considerable evidence for a cardio-protective effect of alcohol at modest intakes’ he said.

羅伯特戈登大學營養學布萊恩·雷德克里夫教授認爲，酒精攝入也應劃入考慮範圍內，因爲研究中很多牛奶飲用者死於心臟疾病。低牛奶攝入和高酒精攝入是分不開的，而且“有可觀的證據表明，適量飲酒會保護心臟”。