the best way to get vitamins is through food, not vitamin pills, according to susan taylor mayne, a professor at the yale school of public health's division of chronic disease epidemiology. a major problem with supplements is that they deliver vitamins out of context, she says. the vitamins found in fruit, vegetables and other foods come with thousands of other phytochemicals, or plant nutrients that are not essential for life but may protect against cancer, cardiovascular （心脏血管的）disease, alzheimer's disease and other chronic ailments. carotenoids（类胡萝卜素） in carrots and tomatoes, isothiocyanates in broccoli and cabbage, and flavonoids（类黄酮）in soy, cocoa and red wine are just a few examples. the combined effect of all these vitamins and phytochemicals seems to have much greater power than one nutrient taken alone.
a healthy diet is paramount, but is there ever a time for supplements? meir stampfer, professor of nutrition and epidemiology at the harvard school of public health in boston, recommends that healthy adults take a multivitamin and extra vitamin d, if they don't get a lot of sun. taking more than the institute of medicine's recommended daily allowance (rda) of certain vitamins may lower one's risk for certain chronic diseases, he says.
mayne disagrees, pointing to a recent meta-analysis suggesting that vitamin e supplementation increases mortality of all causes. "we can debate" whether this analysis shows that vitamin e supplements are harmful, she says, but "there certainly wasn't any benefit shown." with the possible exception of vitamin d, there is no need to consume more than the rda of vitamins, mayne contends. in fact, there is increasing evidence that excessive intake of certain micronutrients is deleterious.
stampfer acknowledges that overdosing on certain vitamins can be dangerous. "the most common one to look out for is preformed… vitamin a. it does not take too much to get too much," he says. try to avoid retinol, retinyl palmitate and retinyl acetate, which may increase the risk of hip fracture and certain birth defects when taken at levels exceeding 10,000 ius.
but mayne and stampfer both agree that more randomized clinical trials are needed to determine the health effects of vitamin supplements—and that such supplements are critical for certain people. ironically, "the people who are most likely to take vitamin supplements are the people who least need them," mayne says. the affluent and health conscious are popping supplements faster than anyone. it may not be doing any good, and it could be harming them, she says. anding concurs: "if you eat well, you probably don't need a multivitamin."
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“摄取维他命的最好办法是通过饮食，而不是通过服用维他命片”，一个在耶鲁大学公共健康慢性流行病部门的教授susan taylor mayne 说。她还说，需要“补充维他命”这种现象的主要问题是：人们已经舍本逐末了。在水果和蔬菜当中我们就可以发现维他命。而在其他许多食物当中，我们则可以发现几千种的植化物和植物营养素。他们虽然不是生命的必需品，但是它们可以预防癌症，心脏血管疾病，老年前期痴呆还有其他慢性疾病。胡萝卜和西红柿中含有胡萝卜素，异硫氰酸酯存在于花椰菜和大白菜当中，类黄酮则能在大豆，可口可豆和红酒当中发现。这些都仅仅是其中的一些例子。和单一的摄取一种维他命来比较，这种能够联合维他命和植化物一起摄取的方式似乎会有更强大的功效。
最主要的是要有一个健康的日常饮食。那么还有需要采取片剂的方式来补充维他命吗？波士顿哈弗大学公共健康中心，研究营养与流行病学的教授meir stampfer 说，我建议健康的成人们摄取多种维生素和额外地补充维他命d，如果他们不能得到很多光照的话。当摄取维他命的量比每日药物推荐机构所规定的量还多时，可能会降低一个人患某种慢性病的危险，他说。
但是mayne 并不同意，他指出近来的一个“元分析”表明，比起其他原因来说，维他命e的补充会增加死亡率。 我们可以讨论：是否这个分析报告真的表明维他命e的补充会对人体有害，她说，“但是真的没有表明有任何好处。”除了维他命d有可能是例外之外，完全没有必要摄取比每日药物推荐机构所规定的量还多，mayne说。实际上，有越来越多的证据表明，过量的摄取某种微量营养素会对人体有害。
stampfer知道过量的摄取某种营养素的确是有害的。搜寻最普遍的一种维生素是可以预见这种情况的，例如维他命a。不用花费很多时间就可以摄取很多的这种维生素”他说，但是也要尽量避免过量摄取视黄醇，视黄酯，维生素a乙酸酯。因为当摄入量超过10,000 ius.这个水平的时候。这些维生素都会增加大腿骨骨折，某种先天性缺陷的风险。
不过mayne and stampfer都同意的是：如果想要知道补充维他命对身体健康的影响，更多的不定期的到医院去检查是必要的。类似的这种补充对于某类人群来说是很有必要的。具有讽刺意味的是，“那些最可能补充维他命的人尽然是最不需要的人。” mayne说。富裕和健康的意识比起其他因素来说，更能够激起补充维他命这种方式快速发展。但是这种方式可能并没有什么好处，还可能对人们的身体产生伤害，她说。意见相同的是“如果你吃的合理，那么你并不需要摄取多种维生素。”