维他命饮料 究竟是好是坏

Companies are increasingly adding vitamins and minerals to juices, sports drinks and bottled water, responding to a growing consumer demand for these products. Even though the amounts of added nutrients in these drinks are typically small, some nutrition scientists are concerned that through their overall diets, many people may be ingesting levels of vitamins and other nutrients that are not only unnecessary, but potentially harmful.

饮料公司在果汁、运动饮料和瓶装水中添加了愈来愈多的维生素和矿物质，以满足顾客对这些东西日益增长的要求。尽管这些饮料中添加的营养素大多比较少，但是有些营养科学家担心，从总体饮食来看，很多人额外摄入的维生素和其他营养素不仅没必要，而且可能有害。

“You have vitamins and minerals that occur naturally in foods, and then you have people taking supplements, and then you have all these fortified foods,” said Mridul Datta, an assistant professor in the department of nutrition science at Purdue University. “It adds up to quite an excess. There’s the potential for people to get a lot more of these vitamins than they need.”

“食物中本来就含有维生素和矿物质，还有人服用补充剂，还有这些营养强化食品，”普渡大学营养科学系助理教授姆里杜尔·达塔(Mridul Datta)说，“所有这些加起来，就太多了。人们摄取的维生素可能比他们需要的多很多。”

Today more than ever, studies show, the average person is exposed to unusually high levels of vitamins and minerals. Already, more than half of all adults in the United States take a multivitamin or dietary supplement. Bread, milk and other foods are often fortified with folic acid, niacin and vitamins A and D.

很多研究表明，如今维生素和矿物质的人均摄入量明显高于以往任何时候。美国半数以上的成年人服用多种维生素片或膳食补充剂。面包、牛奶和其他食物通常都添加叶酸、烟酸，以及维生素A和D。

A study published in July found that many people are exceeding the safe limits of nutrient intakes established by the Institute of Medicine. And research shows that people who take dietary supplements are often the ones who need them the least.

7月份发表的一项研究发现，很多人摄入的营养素超出美国医学研究所确定的安全限量。研究表明，服用膳食补充剂的人往往是那些最不需要补充的人。

Particularly concerning, experts say, is the explosion of beverages marketed specifically for their high levels of antioxidants, like Vitaminwater, POM Wonderful, Naked Juice and many others. The body requires antioxidants to neutralize free radicals that can damage cells and their DNA. But it also uses free radicals to fight off infections and cancer cells, experts say, and when antioxidants are present in excess, it can throw things out of balance.

专家称，最令人忧虑的是，市场上出现了大量专门以高含量抗氧化剂为噱头的饮料，比如维他命水(Vitaminwater)、POM Wonderful石榴汁和裸汁果汁(Naked Juice)等。人体需要用抗氧化剂来中和自由基，因为自由基会破坏细胞和DNA。但是专家说，人体也用自由基来对抗传染病和癌细胞，如果抗氧化剂过多，会打破身体平衡。

A study published this month analyzed 46 beverages — both with and without sugar — sold in supermarkets alongside bottled water. It found that many of these drinks contained vitamins B6, B12, niacin and vitamin C in quantities “well in excess” of the average daily requirements for young adults.

本月发表的一项研究分析了在超市里和瓶装水一起售卖的46种（含糖或不含糖的）饮料。研究发现，其中很多饮料的维生素B6、B12、烟酸和维生素C含量“远远超过”年轻成年人的日均所需。

Eighteen of these drinks contained more than triple the daily requirement for B6. Eleven had more than three times the requirement for B12. And a half dozen had more than three times the requirement for niacin or riboflavin. Some of these products promised improvements in energy and immune function, while others promoted “performance and emotional benefits related to nutrient formulations that go beyond conventional nutritional science,” the researchers said.

其中18种饮料添加的B6含量超过日均所需的三倍。11种饮料的B12含量超过日均所需的三倍。六种饮料的烟酸或B2含量超过日均所需的三倍。研究人员说，有些产品承诺能提高活力和免疫力，还有些声称“其营养素配方超越传统饮食科学，能改善身体机能和情绪”。

The most common nutrients added were vitamins that are already plentiful in the average person’s diet, so their widespread inclusion in these drinks is almost completely unnecessary, said Valerie Tarasuk, the lead author of the study and a nutrition science professor in the faculty of medicine at the University of Toronto.

这项研究的主要作者、多伦多大学营养科学教授瓦莱丽·塔拉苏克(Valerie Tarasuk)说，饮料中最常添加的营养素是人们日常饮食中大量存在的维生素，所以在饮料中普遍添加这些营养素几乎毫无必要。

“It’s very hard to figure out the logic the manufacturers are using to do this fortification,” she said. “There’s no way that the things that are being added are things that anybody needs or stands to benefit from.”

“很难理解生产厂家进行这种营养素强化的逻辑是什么，”她说，“这些添加剂不是所有人都需要的，也不能给所有人带来益处。”

Sugary drinks were just as likely to be concentrated with vitamins as those that were sugar-free. Dr. Tarasuk said that as sugar has become the focus of public health concerns about beverage consumption, “this extreme micronutrient addition has fallen under the radar.”

和无糖饮料一样，含糖饮料中也可能添加了很多维生素。塔拉苏克说，因为人们对饮料引发的公众健康忧虑集中在糖上，所以“这种添加微量营养素的极端行为没有引起人们的注意。”

In nature, there are checks and balances that prevent overconsumption of vitamins and antioxidants, she said. It is hard to ingest too much niacin, for example, by eating whole foods like mushrooms, fish or avocados, which are natural sources of niacin that come bundled with fiber, protein and fat. But someone can easily exceed the daily recommendation for niacin with a single bottle of “formula 50” Vitaminwater, which contains 120 percent of the daily value for it (along with 120 percent of the values for vitamins C, B6, B12 and pantothenic acid).

她说，大自然会相互制衡，防止人体过量摄入维生素和抗氧化剂。比如，食用蘑菇、鱼或鳄梨等天然食物，难以让人摄取过量烟酸，因为烟酸的这些天然来源中含有大量纤维、蛋白质和脂肪。但是，一瓶“50配方”维他命水就足以让你过量摄入，因为它的烟酸含量是每日推荐摄入量的120%（同时，它添加的维生素C、B6、B12和泛酸含量也是推荐摄入量的120%）。

“You couldn’t possibly get that much from any natural foods,” Dr. Tarasuk said. “That’s concerning to me as a nutrition scientist because we don’t know what the effects of chronic exposure may be. With these products, we’ve embarked on a national experiment.”

“你从任何天然食物中都不可能摄入那么多营养素，”塔拉苏克说，“作为一名营养科学家，这让我感到忧虑，因为我们不知道长期过量摄入营养素会带来哪些危害。这些产品让我们开始了一场全国性的实验。”

A nationwide study carried out by the National Institutes of Health in 2017 found that Americans who take vitamins and supplements were already getting large amounts of nutrients from their food, and on top of that they had the lowest prevalence of vitamin deficiencies to begin with. The study found that supplement use put these people at increased risk of potentially excessive consumption of folic acid, calcium, iron, zinc, magnesium and vitamins A, C and B6.

2017年，美国国家健康研究所进行的一项全国性研究发现，服用维生素和补充剂的美国人本来已经从食物中获得了大量营养素，而且他们本来就极少患有维生素缺乏症。这项研究发现，服用补充剂增加了这些人过量摄入叶酸、钙、铁、锌、镁、维生素A、C和B6的风险。

Added vitamins may clearly aid some people, including women who are pregnant or lactating, or those with specific nutritional deficiencies. But for much of the general population today, there is no scientific justification for a high intake of vitamins and minerals, said Mara Z. Vitolins, a registered dietitian and professor of 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 2017, 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.

2017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。

But that proposal was shot down in the 1970s, and over the years Congress went on to restrict the F.D.A.’s authority over fortification and dietary supplements. This helped open the door to the eventual explosion of vitamin enhanced beverages and sports drinks, which today account for sales of more than $18 billion a year in the United States alone.

但是该提议在20世纪70年代被否决，这些年国会进一步限制食品和药物管理局对营养强化和膳食补充剂的管辖权。这最终导致维了生素强化饮料和运动饮料的激增。如今，这些饮料单在美国的年销售额就达180多亿美元。