維他命飲料 究竟是好是壞大綱

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，以滿足顧客對這些東西日益增長的要求。儘管這些飲料中添加的營養素大多比較少，但是有些營養科學家擔心，從總體飲食來看，很多人額外攝入的維生素和其他營養素不僅沒必要，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，還有人服用補充劑，還有這些營養強化食品，”普渡大學營養科學系助理教授姆裏杜爾·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的人均攝入量明顯高於以往任何時候。美國半數以上的成年人服用多種維生素片或膳食補充劑。麪包、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月份發表的一項研究發現，很多人攝入的營養素超出美國醫學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，市場上出現了大量專門以高含量抗氧化劑爲噱頭的飲料，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，因爲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.

本月發表的一項研究分析了在超市裏和瓶裝水一起售賣的46種（含糖或不含糖的）飲料。研究發現，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，有些產品承諾能提高活力和免疫力，還有些聲稱“其營養素配方超越傳統飲食科學，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、多倫多大學營養科學教授瓦萊麗·塔拉蘇克(Valerie Tarasuk)說，飲料中最常添加的營養素是人們日常飲食中大量存在的維生素，所以在飲料中普遍添加這些營養素幾乎毫無必要。

“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.”

“很難理解生產廠家進行這種營養素強化的邏輯是什麼，”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，因爲人們對飲料引發的公衆健康憂慮集中在糖上，所以“這種添加微量營養素的極端行爲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，因爲煙酸的這些天然來源中含有大量纖維、蛋白質和脂肪。但是，一瓶“50配方”維他命水就足以讓你過量攝入，因爲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麼多營養素，”塔拉蘇克說，“作爲一名營養科學家，這讓我感到憂慮，因爲我們不知道長期過量攝入營養素會帶來哪些危害。這些產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現，服用維生素和補充劑的美國人本來已經從食物中獲得了大量營養素，而且他們本來就極少患有維生素缺乏症。這項研究發現，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.

添加維生素無疑可以幫助某些人，包括孕期或哺乳期婦女，以及那些的確缺乏營養的人。但是韋克福里斯特浸禮會醫療中心的註冊營養師、傳染病預防教授瑪拉·Z·維託林(Mara Z. Vitolins)說，對如今的大部分普通人來說，沒有科學依據證明需要攝入這麼多維生素和礦物質。

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.

過量攝入後，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，會積聚在組織裏，帶來潛在風險。

“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定，”她說，“它們不會隨尿液排出。如果過量攝入，它們在體內的含量會越來越高，導致肝功能失常。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.

臨牀試驗數據突顯出過量服用的風險。例如，2009年發表在《美國醫學會雜誌》上的一項大型研究分析了6000多名心臟病患者的臨牀試驗數據，這些病人在七年時間裏每天服用B族維生素或安慰劑。結果發現，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年發表在《科克倫數據庫》(Cochrane Database)上的一項研究回顧了涉及30萬人的78個臨牀試驗。這項研究發現，β-胡蘿蔔素、維生素A和E等抗氧化補充劑實際上提高了死亡率。一年後，美國預防服務工作組斷定，服用維生素和礦物質能預防癌症和心血管疾病的“證據有限”。

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，兩個臨牀試驗發現，服用多種維生素的人患癌機率的降低幅度“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.

美國的聯邦食物強化項目始於20世紀初，目標是解決緊急、明顯的營養缺乏問題。比如，研究表明，當時的育齡婦女葉酸攝入不足。因爲麪包和穀物是她們的主食，所以在這些食物中添加了葉酸，結果，嬰兒神經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症。缺碘會導致甲狀腺腫大、流產、先天性畸形和嚴重學習障礙。所以從1924年起開始普遍推廣加碘鹽。20世紀30年代，人們發現佝僂病與維生素D缺乏有關，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.

在之後的幾十年裏，其他食物也添加了營養素，比如在麪粉中添加煙酸和鐵。

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依據。

“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素攝入提高到合理水平，針對的是人們當時缺乏的營養素，”維託林博士說。

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，營養強化僅限於幾種精選的食物，部分目的在於防止該項目造成營養失衡。爲了防止任意強化，美國食品和藥物管理局提議將能強化營養的食物限制在八種以內，還具體指明可以添加哪些營養素。

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.

但是該提議在20世紀70年代被否決，這些年國會進一步限制食品和藥物管理局對營養強化和膳食補充劑的管轄權。這最終導致維了生素強化飲料和運動飲料的激增。如今，這些飲料單在美國的年銷售額就達180多億美元。