epidemiology and prevention at Wake Forest Baptist Medical Center.
添加维生素无疑可以帮助某些人，包括孕期或哺乳期妇女，以及那些的确缺乏营养的人。但是韦克福里斯特浸礼会医疗中心的注册营养师、传染病预防教授玛拉·Z·维托林(Mara Z. Vitolins)说，对如今的大部分普通人来说，没有科学依据证明需要摄入这么多维生素和矿物质。
When consumed in excess, some water-soluble vitamins like B and C are excreted in the urine. But fat soluble-vitamins – including A, D, E and K – accumulate in tissues, posing potential risks.
过量摄入后，有些水溶性维生素，比如维生素B和C，会随尿液排出。但是脂溶性维生素，包括维生素A、D、E和K，会积聚在组织里，带来潜在风险。
“These fat soluble vitamins are very stable,” she said. “They’re not released in the urine. If you are over-consuming them, you can raise your levels gradually over time and get into trouble with liver function. You have to be very careful with them.”
“这些脂溶性维生素非常稳定，”她说，“它们不会随尿液排出。如果过量摄入，它们在体内的含量会越来越高，导致肝功能失常。你必须对它们格外小心。”
Data from clinical trials have highlighted clear risks from excess. A large study published in JAMA in 2009, for example, looked at clinical trial data on more than 6,000 heart disease patients who were treated daily with either B vitamins or placebo over a seven year period. The study found that those who were given folic acid and B12 had higher mortality and cancer rates.
临床试验数据突显出过量服用的风险。例如，2009年发表在《美国医学会杂志》上的一项
大型研究分析了6000多名心脏病患者的临床试验数据，这些病人在七年时间里每天服用B族维生素或安慰剂。结果发现，服用叶酸和B12的研究对象死亡率和患癌比率更高。 In 2012, a review of 78 clinical trials involving 300,000 people that was published in the Cochrane Database found that antioxidant supplements like beta carotene, vitamin A and vitamin E actually increased mortality. A year later, the United States Preventive Services Task Force concluded that there was “limited evidence” that taking vitamins and minerals could prevent cancer and cardiovascular disease. 2012年发表在《科克伦数据库》(Cochrane Database)上的一项研究回顾了涉及30万人的78个临床试验。这项研究发现，β-胡萝卜素、维生素A和E等抗氧化补充剂实际上提高了死亡率。一年后，美国预防服务工作组断定，服用维生素和矿物质能预防癌症和心血管疾病的“证据有限”。
The task force noted that two clinical trials had found “small, borderline” reductions in cancer incidence in men who took multivitamins. But the group also said there was good evidence that high doses of antioxidants could cause harm. 该工作组提到，两个临床试验发现，服用多种维生素的人患癌几率的降低幅度“小而不明显”。但是这一组人也说，有明显迹象表明，高剂量抗氧化剂能造成伤害。
The federal food fortification program in the United States began in the early 1900s with the goal of addressing urgent and established nutrient deficiencies. Research showed, for example, that women in their childbearing years were not getting enough folic acid. Since bread and cereal were staples of their diets, folic acid was added to these foods – and as a result the rate of neural tube defects in infants has fallen significantly.
美国的联邦食物强化项目始于20世纪初，目标是解决紧急、明显的营养缺乏问题。比如，研究表明，当时的育龄妇女叶酸摄入不足。因为面包和谷物是她们的主食，所以在这些食物中添加了叶酸，结果，婴儿神经管缺陷的比率显著下降。
Before 1920, iodine deficiencies were common in some parts of the country. A lack of iodine can lead to goiters, miscarriage, congenital abnormalities and severe learning disabilities. So the widespread fortification of salt with iodine was started in 1924. In the 1930s, vitamin D deficiency was linked to rickets. That discovery led in 1933 to the fortification of milk with vitamin D.
1920年之前，美国有些地方普遍存在碘缺乏症。缺碘会导致甲状腺肿大、流产、先天性畸形和严重学习障碍。所以从1924年起开始普遍推广加碘盐。20世纪30年代，人们发现佝偻病与维生素D缺乏有关，所以从1933年起开始在牛奶中添加维生素D。
Other foods were enriched with additional nutrients – niacin and iron were added to flour, for example – in the decades that followed.
在之后的几十年里，其他食物也添加了营养素，比如在面粉中添加烟酸和铁。
But in most if not all of these cases, there was a compelling scientific reason for doing so.
但是，这些案例几乎都有确切的科学依据。
“The reason behind the fortification program was to bring our nutrient intake to a reasonable place, and it targeted nutrients that we were lacking,” Dr. Vitolins said. “食物强化项目的目的是把营养素摄入提高到合理水平，针对的是人们当时缺乏的营养素，”维托林博士说。
Early on, fortification was limited to a few select foods, in part so the program
would not create nutritional imbalances. In an attempt to prevent indiscriminate fortification, the Food and Drug Administration proposed restricting the number of foods that could be fortified to eight, and it specified which nutrients could be added.
在早期，营养强化仅限于几种精选的食物，部分目的在于防止该项目造成营养失衡。为了防止任意强化，美国食品和药物管理局提议将能强化营养的食物限制在八种以内，还具体指明可以添加哪些营养素。 美联英语：www.meten.com