Fish oil is now the third most widely used dietary supplement in the United States, after vitamins and minerals, according to a recent report from the National Institutes of Health. At least 10 percent of Americans take fish oil regularly, most believing that the omega-3 fatty acids in the supplements will protect their cardiovascular health.
最近，一份来自美国国立卫生研究院(National Institutes of Health)的报告称，在美国应用最广泛的若干膳食补充剂中，鱼油位列第三，仅次于维生素和矿质元素。至少10%的美国人定期服用鱼油，其中大多数人都相信鱼油中的ω-3脂肪酸会促进心血管健康。

But there is one big problem: The vast majority of clinical trials involving fish oil have found no evidence that it lowers the risk of heart attack and stroke.
不过一个明显的问题是：绝大多数有关鱼油的临床试验都未发现任何证据足以证明鱼油的确可以降低心肌梗死和中风的风险。
From 2005 to 2012, at least two dozen rigorous studies of fish oil were published in leading medical journals, most of which looked at whether fish oil could prevent cardiovascular events in high-risk populations. These were people who had a history of heart disease or strong risk factors for it, like high cholesterol, hypertension or Type 2 diabetes.
2005年至2012年，顶尖医学期刊上至少登载了二十多篇有关鱼油的严谨研究，其中大部分研究都探讨了鱼油能否预防高危人群患心血管疾病的问题。这里的高危人群是指：具有心脏病史或者具有强风险因素，如高胆固醇、高血压或患2型糖尿病的病人。
All but two of these studies found that compared with a placebo, fish oil showed no benefit.
这些研究中，除了两项外研究，其他所有研究都发现与安慰剂相比，鱼油未显示任何效果。
And yet during this time, sales of fish oil more than doubled, not just in the United States but worldwide, said Andrew Grey, an associate professor of medicine at the University of Auckland in New Zealand and the author of a 2014 study on fish oil in JAMA Internal Medicine.
然而，在此期间，不只美国，全球的鱼油销售量都翻了一倍以上，2014年在《美国医学会期刊：内科学》杂志上(JAMA Internal Medicine)发表了一项研究的作者，新西兰的奥克兰大学(University of Auckland)的医学副教授安德鲁·格雷(Andrew Grey)说道。
“There’s a major disconnect,” Dr. Grey said. “The sales are going up despite the progressive accumulation of trials that show no effect.”
“脱节相当严重，”格雷博士说。“尽管越来越多的试验都证明（鱼油）无效，但其销售量在节节攀升。”
In theory at least, there are good reasons that fish oil should improve cardiovascular health. Most fish oil supplements are rich in two omega-3 fatty acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — that can have a blood-thinning effect, much like aspirin, that may reduce the likelihood of clots. Omega-3s can also reduce inflammation, which plays a role in atherosclerosis. And the Food and Drug Administration has approved at least three prescription types of fish oil — Vascepa, Lovaza and a generic form — for the treatment of very high triglycerides, a risk factor for heart disease.
至少在理论上，有很多理由使人觉得鱼油应该可以改善心血管健康。大多数鱼油补充剂都富含两种ω-3脂肪酸——二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)，这两种物质都像阿司匹林那样对血液有稀释效果，从而降低发生血栓的可能性。ω-3脂肪酸还可以减少炎症，而炎症在动脉粥样硬化中有一定的作用。美国食品和药品监督管理局(Food and Drug Administration)现已批准了至少三种鱼油产品——Vascepa、Lovaza（ω-3脂肪酸乙酯胶囊）和一种仿制药——作为治疗甘油三酯过高（心脏病的一个风险因素）的处方药。
But these properties of omega-3 fatty acids have not translated into notable benefits in most large clinical trials.
但在大多数大型临床试验中，脂肪酸的这些特性未能转化为显著的效益。
Some of the earliest enthusiasm for fish oil goes back to research carried out in the 1970s by the Danish scientists Dr. Hans Olaf Bang and Dr. Jorn Dyerberg, who determined that Inuits living in northern Greenland had remarkably low rates of cardiovascular disease, which they attributed to an omega-3-rich diet consisting mainly of fish, seal and whale blubber. Dr. George Fodor, a cardiologist at the University of Ottawa, outlined flaws in much of this early research, and he concluded that the rate of heart disease among the Inuit was vastly underestimated. But the halo effect around fish oils persists.
对鱼油最早的追捧可以追溯到丹麦科学家汉斯·奥拉夫·邦(Hans Olaf Bang)博士和约恩·戴尔伯格(Jorn Dyerberg)博士在20世纪70年代进行的一项研究。他们认为生活在格陵兰北部的因纽特人患心血管疾病比率非常低的原因是，因纽特人的膳食以鱼类、海豹和鲸脂为主，这些食品富含ω-3脂肪酸。渥太华大学(University of Ottawa)的心脏病专家乔治·福多尔(George Fodor)博士列举了这一研究中的诸多破绽，并断定因纽特人中的心脏病率被大大低估了。不过，萦绕在鱼油之上的光环仍然闪耀不息。
The case for fish oil was bolstered by several studies from the 1990s, including an Italian study that found that heart attack survivors who were treated with a gram of fish oil daily had a drop in mortality, compared with patients taking vitamin E. These findings prompted groups like the American Heart Association to endorse fish oil about a decade ago as a way for heart patients to get more omega-3s in their diets.
该项关于鱼油的研究得到了从20世纪90年代起的若干项研究的支持，其中一项来自意大利的研究发现，每日服用一克鱼油的心肌梗死幸存者的死亡率较服用维生素E的患者有所降低。这些研究结果促使美国心脏协会(American Heart Association)等组织在大约十年前大力推崇心脏病患者服用鱼油来补充膳食ω-3脂肪酸。
“But since then, there has been a spate of studies showing no benefit,” said Dr. James Stein, the director of preventive cardiology at University of Wisconsin Hospital and Clinics. Among them was a clinical trial of 12,000 people, published in The New England Journal of Medicine in 2013, that found that a gram of fish oil daily did not reduce the rate of death from heart attacks and strokes in people with evidence of atherosclerosis.
“但此后的大量研究却显示鱼油没什么功效，”威斯康星大学医院和诊所(University of Wisconsin Hospital and Clinics)的预防心脏病学主任詹姆斯·斯坦(James Stein)博士说。其中2013年发表在《新英格兰医学杂志》(The New England Journal of Medicine)上的一项涉及12000人的临床试验发现，在存在动脉粥样硬化证据的人群中，每日服用一克鱼油并未降低因心肌梗死和中风死亡率。
“I think that the era of fish oil as medication could be considered over now,” said the study’s lead author, Dr. Gianni Tognoni of the Institute for Pharmacological Research in Milan.
该研究的作者之一，米兰药理研究所(Institute for Pharmacological Research in Milan)的詹尼·托尼奥尼(Gianni Tognoni)博士说：“我认为，现在是该考虑结束将鱼油当做药物的时代了。”
Dr. Stein said the early fish oil studies took place in an era when cardiovascular disease was treated very differently than it is today, with far less use of statins, beta blockers, blood thinners and other intensive therapies. So the effect of fish oil, even if it were minor, he said, would have been more noticeable.
斯坦博士说，有关鱼油的早期研究出现在心血管疾病的治疗还十分困难的时代，那时，他汀类药物、β受体阻滞剂、血液稀释剂和其他强化治疗的使用都比现在少得多。因此，鱼油的作用——哪怕十分轻微——也会较为显而易见。
“The standard of care is so good today that adding something as small as a fish oil capsule doesn’t move the needle of difference,” he said. “It’s hard to improve it with an intervention that’s not very strong.”
“如今的医护水平已经非常高，多吃一颗小小的鱼油胶囊不会带来多大改观，”他说。“要改善本来就已经十分强效的干预措施是非常困难的。”
Dr. Stein also cautions that fish oil can be hazardous when combined with aspirin or other blood thinners. “Very frequently we find people taking aspirin or a ‘super aspirin’ and they’re taking fish oil, too, and they’re bruising very easily and having nosebleeds,” he said. “And then when we stop the fish oil, it gets better.”
斯坦博士还提醒说，当与阿司匹林或其他血液稀释剂合起用时，鱼油可能会带来危险。“我们经常发现人们在服用阿司匹林或‘超级阿司匹林’的同时服用鱼油，这些人身上很容易出现青紫的瘀伤，也容易流鼻血，”他说。“当他们停止服用鱼油后，情况就好转了。”
Like many cardiologists, Dr. Stein encourages his patients to avoid fish oil supplements and focus instead on eating fatty fish at least twice a week, in line with federal guidelines on safe fish intake, because fish contains a variety of healthful nutrients other than just EPA and DHA. “We don’t recommend fish oil unless someone gets absolutely no fish in their diets,” Dr. Stein said.
像许多心脏病专家一样，斯坦博士也鼓励他的患者尽量不要服用鱼油补充剂，而是注意每周至少食用两次富含脂肪的鱼类（遵循联邦指南中鱼肉的安全摄入量），因为除了EPA和DHA，鱼肉中还含有多种其他有益健康的营养成分。斯坦博士说：“除非饮食中完全没有鱼类，否则我们不建议服用鱼油。”
But some experts say the case for fish oil remains open. Dr. JoAnn Manson, the chief of preventive medicine at Brigham and Women’s Hospital in Boston, said the large clinical trials of fish oil focused only on people who already had heart disease or were at very high risk. Fish oil has also been promoted for the prevention of a variety of other conditions, including cancer, Alzheimer’s and depression.
但一些专家称，有关鱼油的这段公案仍未了结。位于波士顿的布莱根妇女医院(Brigham and Women’s Hospital)的预防医学主任乔安·曼森(JoAnn Manson)博士表示，针对鱼油的大型临床试验只侧重于那些已患有心脏病或风险非常高的人。鱼油还被一些人称作可预防多种其他疾病，如癌症、阿尔茨海默氏症和抑郁症。
Dr. Manson is leading a five-year clinical trial, called the Vital study, of 26,000 people who are more representative of the general population. Set to be completed next year, it will determine whether fish oil and vitamin D, separately or combined, have any effect on the long-term prevention of heart disease, Type 2 diabetes, and other diseases in people who do not have many strong risk factors.
目前，曼森博士正领导开展着一项名为“Vital”的临床试验，该实验选取2.6万个更能代表普通人情况的人作为研究对象，为期五年，计划明年完成。它将确定在无强风险因素的人群中，鱼油和维生素D（无论是单独使用还是联用）对于心脏病、2型糖尿病和其他疾病是否具有长期效果。
Dr. Manson says that although she recommends eating fatty fish first, she usually does not stop people from taking fish oil, in part because it does not seem to have major side effects in generally healthy people.
曼森博士说，她虽然建议优先食用富含脂肪的鱼类，但一般不会阻止人们服用鱼油，一部分原因是鱼油对于健康的普通人似乎没有什么严重的副作用。
“But I do think people should realize that the jury is still out,” she said, “and that they may be spending a lot of money on these supplements without getting any benefit.”
“不过我认为人们应该意识到事情没有最后定论，”她说，“他们很可能花了很多冤枉钱买这些补充剂，却没能获得任何帮助。”