Oranges, grapefruits and other vitamin C-loaded foods have many health benefits. But study after study has shown that the vitamin does little to cure, prevent or even shorten the duration of the common cold. 

    The most recent roundup of vitamin C research, published this spring in the Cochrane Database of Systematic Reviews, evaluated several decades of studies that included more than 11,000 subjects taking 200 or more milligrams of vitamin C each day. (The government's recommended daily allowance is 60 milligrams.) The research found that vitamin C did little to reduce either the length or severity of colds among the general population. However, studies have found that it may lower the risk of catching a cold among people whose bodies are under high physical stress—think marathon runners or soldiers on subarctic exercises. They were 50 percent less likely to catch a cold if they took a daily dose of vitamin C. 
 
    橙子、葡萄和其他含維生素C的食物對(duì)健康有很多益處。但是不斷地研究表明，維生素對(duì)于感冒幾乎沒(méi)有治療、預(yù)防作用，甚至也不能縮短感冒持續(xù)的時(shí)間。

    今年春季發(fā)表在“庫(kù)切拉內(nèi)系統(tǒng)評(píng)審數(shù)據(jù)庫(kù)”的維生素C研究方面的最新摘要評(píng)估了幾十年來(lái)的研究，包括11000名每天食用維生素C 200毫克或以上的實(shí)驗(yàn)對(duì)象。(政府建議每天定量60毫克。)研究發(fā)現(xiàn)，維生素C在普通人群中對(duì)于縮短感冒的時(shí)間或者降低感冒的嚴(yán)重程度幾乎沒(méi)有作用。然而研究發(fā)現(xiàn)，對(duì)于身體承受高強(qiáng)度體力消耗的人如馬拉松運(yùn)動(dòng)員和在亞北極地區(qū)訓(xùn)練的士兵來(lái)說(shuō)，服用維生素C可能降低得感冒的風(fēng)險(xiǎn)。如果這些人每天食用一定劑量的維生素，他們得感冒的幾率會(huì)降低50%。