維他命飲料，究竟是好是壞?

Are Vitamin Drinks a Bad Idea?

維他命飲料，究竟是好是壞?

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.

飲料公司在果汁、運動飲料和瓶裝水中添加了愈來愈多的維生素和礦物質(zhì)，以滿足顧客對這些東西日益增長的要求。盡管這些飲料中添加的營養(yǎng)素大多比較少，但是有些營養(yǎng)科學(xué)家擔(dān)心，從總體飲食來看，很多人額外攝入的維生素和其他營養(yǎng)素不僅沒必要，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.”

“食物中本來就含有維生素和礦物質(zhì)，還有人服用補充劑，還有這些營養(yǎng)強化食品，”普渡大學(xué)營養(yǎng)科學(xué)系助理教授姆里杜爾·達塔(Mridul Datta)說，“所有這些加起來，就太多了。人們攝取的維生素可能比他們需要的多很多。”

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，如今維生素和礦物質(zhì)的人均攝入量明顯高于以往任何時候。美國半數(shù)以上的成年人服用多種維生素片或膳食補充劑。面包、牛奶和其他食物通常都添加葉酸、煙酸，以及維生素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月份發(fā)表的一項研究發(fā)現(xiàn)，很多人攝入的營養(yǎng)素超出美國醫(yī)學(xué)研究所確定的安全限量。研究表明，服用膳食補充劑的人往往是那些最不需要補充的人。

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.

專家稱，最令人憂慮的是，市場上出現(xiàn)了大量專門以高含量抗氧化劑為噱頭的飲料，比如維他命水(Vitaminwater)、POM Wonderful石榴汁和裸汁果汁(Naked Juice)等。人體需要用抗氧化劑來中和自由基，因為自由基會破壞細胞和DNA。但是專家說，人體也用自由基來對抗傳染病和癌細胞，如果抗氧化劑過多，會打破身體平衡。

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.

本月發(fā)表的一項研究分析了在超市里和瓶裝水一起售賣的46種(含糖或不含糖的)飲料。研究發(fā)現(xiàn)，其中很多飲料的維生素B6、B12、煙酸和維生素C含量“遠遠超過”年輕成年人的日均所需。

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種飲料添加的B6含量超過日均所需的三倍。11種飲料的B12含量超過日均所需的三倍。六種飲料的煙酸或B2含量超過日均所需的三倍。研究人員說，有些產(chǎn)品承諾能提高活力和免疫力，還有些聲稱“其營養(yǎng)素配方超越傳統(tǒng)飲食科學(xué)，能改善身體機能和情緒”。

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.

這項研究的主要作者、多倫多大學(xué)營養(yǎng)科學(xué)教授瓦萊麗·塔拉蘇克(Valerie Tarasuk)說，飲料中最常添加的營養(yǎng)素是人們?nèi)粘ｏ嬍持写罅看嬖诘木S生素，所以在飲料中普遍添加這些營養(yǎng)素幾乎毫無必要。

“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.”

“很難理解生產(chǎn)廠家進行這種營養(yǎng)素強化的邏輯是什么，”她說，“這些添加劑不是所有人都需要的，也不能給所有人帶來益處。”

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.”

和無糖飲料一樣，含糖飲料中也可能添加了很多維生素。塔拉蘇克說，因為人們對飲料引發(fā)的公眾健康憂慮集中在糖上，所以“這種添加微量營養(yǎng)素的極端行為沒有引起人們的注意。”

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).

她說，大自然會相互制衡，防止人體過量攝入維生素和抗氧化劑。比如，食用蘑菇、魚或鱷梨等天然食物，難以讓人攝取過量煙酸，因為煙酸的這些天然來源中含有大量纖維、蛋白質(zhì)和脂肪。但是，一瓶“50配方”維他命水就足以讓你過量攝入，因為它的煙酸含量是每日推薦攝入量的120%(同時，它添加的維生素 C、B6、B12和泛酸含量也是推薦攝入量的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.”

“你從任何天然食物中都不可能攝入那么多營養(yǎng)素，”塔拉蘇克說，“作為一名營養(yǎng)科學(xué)家，這讓我感到憂慮，因為我們不知道長期過量攝入營養(yǎng)素會帶來哪些危害。這些產(chǎn)品讓我們開始了一場全國性的實驗。”

A nationwide study carried out by the National Institutes of Health in 2012 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.

2012年，美國國家健康研究所進行的一項全國性研究發(fā)現(xiàn)，服用維生素和補充劑的美國人本來已經(jīng)從食物中獲得了大量營養(yǎng)素，而且他們本來就極少患有維生素缺乏癥。這項研究發(fā)現(xiàn)，服用補充劑增加了這些人過量攝入葉酸、鈣、鐵、鋅、鎂、維生素A、C和B6的風(fēng)險。

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.

添加維生素?zé)o疑可以幫助某些人，包括孕期或哺乳期婦女，以及那些的確缺乏營養(yǎng)的人。但是韋克福里斯特浸禮會醫(yī)療中心的注冊營養(yǎng)師、傳染病預(yù)防教授瑪拉·Z·維托林(Mara Z. Vitolins)說，對如今的大部分普通人來說，沒有科學(xué)依據(jù)證明需要攝入這么多維生素和礦物質(zhì)。

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.

過量攝入后，有些水溶性維生素，比如維生素B和C，會隨尿液排出。但是脂溶性維生素，包括維生素A、D、E和K，會積聚在組織里，帶來潛在風(fēng)險。

“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.”

“這些脂溶性維生素非常穩(wěn)定，”她說，“它們不會隨尿液排出。如果過量攝入，它們在體內(nèi)的含量會越來越高，導(dǎo)致肝功能失常。你必須對它們格外小心。”

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.

臨床試驗數(shù)據(jù)突顯出過量服用的風(fēng)險。例如，2009年發(fā)表在《美國醫(yī)學(xué)會雜志》上的一項大型研究分析了6000多名心臟病患者的臨床試驗數(shù)據(jù)，這些病人在七年時間里每天服用B族維生素或安慰劑。結(jié)果發(fā)現(xiàn)，服用葉酸和B12的研究對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年發(fā)表在《科克倫數(shù)據(jù)庫》(Cochrane Database)上的一項研究回顧了涉及30萬人的78個臨床試驗。這項研究發(fā)現(xiàn)，β-胡蘿卜素、維生素A和E等抗氧化補充劑實際上提高了死亡率。一年后，美國預(yù)防服務(wù)工作組斷定，服用維生素和礦物質(zhì)能預(yù)防癌癥和心血管疾病的“證據(jù)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.

該工作組提到，兩個臨床試驗發(fā)現(xiàn)，服用多種維生素的人患癌幾率的降低幅度“小而不明顯”。但是這一組人也說，有明顯跡象表明，高劑量抗氧化劑能造成傷害。

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.

美國的聯(lián)邦食物強化項目始于20世紀初，目標是解決緊急、明顯的營養(yǎng)缺乏問題。比如，研究表明，當(dāng)時的育齡婦女葉酸攝入不足。因為面包和谷物是她們的主食，所以在這些食物中添加了葉酸，結(jié)果，嬰兒神經(jīng)管缺陷的比率顯著下降。

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，美國有些地方普遍存在碘缺乏癥。缺碘會導(dǎo)致甲狀腺腫大、流產(chǎn)、先天性畸形和嚴重學(xué)習(xí)障礙。所以從1924年起開始普遍推廣加碘鹽。20世紀30年代，人們發(fā)現(xiàn)佝僂病與維生素D缺乏有關(guān)，所以從1933年起開始在牛奶中添加維生素D。

Other foods were enriched with additional nutrients – niacin and iron were added to flour, for example – in the decades that followed.

在之后的幾十年里，其他食物也添加了營養(yǎng)素，比如在面粉中添加煙酸和鐵。

But in most if not all of these cases, there was a compelling scientific reason for doing so.

但是，這些案例幾乎都有確切的科學(xué)依據(jù)。

“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.

“食物強化項目的目的是把營養(yǎng)素攝入提高到合理水平，針對的是人們當(dāng)時缺乏的營養(yǎng)素，”維托林博士說。

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，營養(yǎng)強化僅限于幾種精選的食物，部分目的在于防止該項目造成營養(yǎng)失衡。為了防止任意強化，美國食品和藥物管理局提議將能強化營養(yǎng)的食物限制在八種以內(nèi)，還具體指明可以添加哪些營養(yǎng)素。