jyuan说得对,维生素在这边是保健品不是药品,Walmart就卖的。
至于维生素常年是是否会有害,这两年讨论还是很有一些的。我引的那篇cnn昨天的新闻就是又讨论这个话题,里面提到了对一篇说服用复合维生素对身体有害的文章的置疑。
另外(ABC News http://abcnews.go.com/WNT/SpecialSeriesCoverage/story?id=1911337&page=1):
... ...
Instead of improving heart health, vitamin E was shown in one study to increase rates of congestive heart failure. According to the Medical Letter, a nonprofit research group, one study found that long-term use of vitamin E supplements did nothing to prevent cancer or major cardiovascular events -- and may have even increased the risk of heart failure for patients with vascular disease or diabetes. And a cancer study found that patients taking vitamin E while undergoing radiation therapy had a higher rate of cancer recurrence than patients taking a placebo.
Instead of reducing the risk of lung cancer, beta carotene was found to increase the rate of lung cancer in one study of smokers. Another study found that smokers and asbestos-exposed workers, when given doses of beta carotene and vitamin A, had an increased risk of lung cancer, death from cardiovascular disease and overall mortality. The rate of death was so high that the study was stopped early.
And another study showed that too much vitamin A from supplements and food increased postmenopausal women's risk of hip fractures. Another study found that a high intake of vitamin A was associated with birth defects when taken during early pregnancy.
Even calcium, which is encouraged in large amounts as women get older, can be dangerous. The Women's Health Initiative, though it found calcium and vitamin D can lower the risk of hip fractures in women over 60, also found that women taking calcium were at a higher risk for kidney stones.
... ...
"As calcium goes very high, it can interfere with your brain's ability to think and is actually one of the causes of dementia."
乍一看还真挺吓人,不过回头想,什么东西太多了也都不好,所以说什么维生素矿物质过多有害都是意料之中的。
我还是相信大部分复合维生素没有太多这个那个的过量,对饮食结构不好的人应该是利大于弊的。我就常备着,平均一个月能想起来吃两三回
但想起来吃了就觉得自己对自己好了一回。 
中国人的饮食一般的蔬菜还是不少,所以我觉得大部分维生素应该不太缺。要我说必要的就是孕妇要补叶酸,女人和老人要补钙,容易贫血的补点儿铁。
Jianjun Zhang wrote:
这些维生素产品在美国市场上算保健品还是药品呢?在大陆地区,多维片一般算药品,市场上比较常见的是施贵宝的金施尔康。我怀疑长期补充多种维生素会不会造成副作用?有些维生素过量后会有毒性,我们都知道,但常年吃多维片如何呢?