Eating lots of fruit and vegetables will do little to reduce your risk of developing cancer, according to a review of a decade of research involving more than a million people. It concluded that maintaining a healthy weight and cutting down on smoking and drinking are far better ways to ward off the disease.
一项对过去十年总数涉及100万人的多项研究所作的综述显示，大量进食蔬菜和水果对于减轻癌症风险的效果微乎其微。这项研究表明，保持合理的体重，少吸烟喝酒更有助于让人体远离疾病。3
Vegetables and fruit are important for a healthy diet but the review says that eating increased amounts does not seem to offer much protection against cancer.
蔬菜和水果或许对于健康饮食很重要，但是研究综述表明增大其摄入量似乎并不能保护人体不受癌症的侵害。
"There's strong scientific evidence to show that, after smoking, being overweight and alcohol are two of the biggest cancer risks," said Tim Key, an epidemiologist from Oxford University, who wrote the review.
"许多科学研究都证实，吸烟，过度肥胖和酗酒是导致癌症的主要原因，"该综述的作者，牛津大学流行病学家蒂姆·基说道。
In an article published today in the British Journal of Cancer, Key summarised the epidemiological evidence from more than a million people taking part in several dozen long-term research projects looking at the amount of fruit and vegetables people eat and their overall cancer risk. He also studied specific cancers of the gastrointestinal tract, lung and breast.
1
Key在《英国癌症期刊》中的一篇文章中列举了支持这一结论的流行病学证据，这些证据是从超过100万人参加的多个长期研究项目中得出的，他们观察这些人的水果蔬菜摄入量和癌症几率。他甚至研究了一些具体的癌症，比如胃癌，肠癌，肺癌和乳腺癌。
Key found little, if any, connection between eating lots of fruits and vegetables and the likelihood of developing cancer. "The conclusion implies that, at least in relatively well-nourished westernised populations, a general increase in total fruit and vegetable intake will not have a large impact on cancer rates," he wrote. "A certain level of intake is necessary to prevent nutrient deficiencies, but intakes above that level do not make the relavant tissues 'super healthy'."
Key发现大量进食蔬菜和水果和患癌症几乎没有任何联系。"结果表明，至少在相对营养良好的西方人口中，增加蔬菜和水果的摄入量对于癌症患病率没有太大影响，"他在文中这样写道，"一定的摄入量对于避免营养不良是必须的，但是当摄入量超过这个水平时，并没有让身体变的更加健康。
The studies included data from the European Prospective Investigation into Cancer and Nutrition, the Pooling Project based at Harvard University, and the National Institutes of Health and American Association of Retired Persons Diet and Health Study.
3
研究综述中的数据来源包括欧洲对于癌症和营养的前瞻性调查数据，哈佛大学的民调系统数据，美国国立卫生研究院的数据和美国退休人员饮食与健康研究项目的数据。3
The idea that fruit and veg might help reduce cancer rates was first postulated in the 1970s, when the results of a small-scale study showed that, after controlling for smoking, people with reduced intakes of vitamin A were at increased risk of lung cancer. By the 1990s, scientists were concluding that "for most cancer sites, persons with low fruit and vegetable intake experience about twice the risk of cancer compared to those with a high intake, even after control for potentially confounding factors."
蔬菜和水果能够帮助减低癌症患病几率这一说法始于上世纪70年代，当时的一项基于少数人的研究表明，在通过对照排除了吸烟的情况下，维他命A摄入量的减少会导致癌症患病率的增加。到了上世纪90年代，科学家得出结论，"在通过对照排除了其他干扰因素的情况下，对身体大多数部位的癌症来说，蔬菜和水果摄入量低的人群的癌症患病率是摄入量高的人群的两倍。"1
But these "case-control" studies – where people with a disease are matched with controls who do not have the disease – still suffered from confounding factors. "While a lot of those [earlier] case-control studies do try and adjust for how much people smoke and how much people drink, there's always a worry that you haven't completely adjusted for that because smoking and drinking have such a massive impact on the risk of those cancers," said Ed Yong, head of health evidence and information at Cancer Research UK.
1
但是这样将患病的人与健康人进行对比的"病例对照"研究仍然总是受到其他因素的干扰。"虽然那些早期的病例对照研究曾试图将人们吸烟和饮酒量化，但是他们总是不能排除这些因素的干扰，因为吸烟和饮酒确实对癌症患病率有很大的影响，"英国癌症研究院信息数据组负责人埃德·扬说道。
Key said case-control studies can suffer from two main types of bias. "One is that people with cancer may be under treatment so it may affect how they remember what they used to eat in the years before they developed cancer. They may be feeling ill or under strong medical treatment."
3
Key表示病例对照研究有两大主要的偏向性。"一个是癌症患者可能在接受治疗，这影响到他们回忆自己患病前很多年中的饮食结构，他们可能自我感觉很虚弱或者正在接受很强烈的治疗（以至于回想不起来）。"1
A bigger problem is with the selection of the control group, which might not be entirely random. "People who come forward are those interested in health and related behaviours," said Key. "The controls may well appear to have a healthy diet because the potential controls with an unhealthy diet may have stayed in the pub eating chips and beans and not volunteered to be studied."
2
另一个更大的问题是，病例对照人群的选择或许并不完全是随机的。"参与到研究项目中的人大多都对健康和相关的东西感兴趣，"Key说道，"所以这样的对照组的研究结果显示的是饮食结构都趋于合理，而另外的一些饮食不那么健康的人，却没有参加到对照组中。"
A better way to analyse the relationship between diet and cancer is to conduct "prospective studies", which ideally follow hundreds of thousands of people who don't have cancer. "They tell you what they eat and you follow them until, inevitably, some of them do develop cancer," said Key. "But you made the measurements when they're healthy, so the biases don't apply. Those types of studies have been coming out in the last 10-15 years and have not supported the original findings [from case-control groups]."
一种更好的研究饮食与癌症关系的方法是做"前瞻性研究"，也就是说，将几十万的未患癌症的人做为研究对象。"让这些人告诉你他们的饮食结构，然后对这些人进行跟踪研究，直到他们中的一些人患上癌症为止，"Key说道，"因为你在他们健康时就做了测量，所以对照组偏向性就不会产生。这一类型的研究持续了10到15年，结果表明，通过病例对照研究而得出的结论站不住脚。"
Key's review supports work published in April in the Journal of the National Cancer Institute. Paolo Boffetta from the Tisch Cancer Institute at Mount Sinai School of Medicine in New York found that eating a lot of fruit and vegetables has only "a very modest" protective effect against cancer. That conclusion was based on a decade of research on almost 500,000 people in 10 European countries.
Key研究综述的结论和4月份发表在《国家癌症学会杂志》上的一篇文章不谋而合。纽约西奈山医学院蒂施癌症研究学院保罗·波费塔也发现大量进食水果和蔬菜只对癌症有微乎其微的抑制作用。他的这一结论是在对欧洲十国大约50万人的研究数据上做出的。
Despite the results of the studies, Yong said it was still a good idea for people get their minimum daily five portions of fruits and vegetables. "It's not a bad message because it could help people to lose weight, which is a massive cause of cancer, and it could displace other [unhealthier] things in their diet," he said. "There's no harm to eating lots of fruits and vegetables and there are benefits for other diseases as well, such as heart disease."
虽然研究结果表明水果和蔬菜并未对抑制癌症起到多大作用，但是扬认为人们每天保持一定的摄取量仍然对身体有好处。"这不是个坏消息，因为蔬菜和水果能够帮助人们减轻体重，而过度肥胖是癌症的主因之一，况且它们还能让人们少吃不健康的东西，"他说，"多吃蔬菜和水果一点害处也没有，而且它们可以防止其他疾病，比如心脏病。"
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