SAN DIEGO — A trip to almost any bookstore or a cruise around the Internet might leave the impression that avoiding cancer is mostly a matter of watching what you eat. One source after another promotes the protective powers of “superfoods,” rich in antioxidants and other phytochemicals.
幾乎隨便找一家書店逛逛，或者上網去搜尋一番之後，可能都會讓你認為，如果要避免癌症上身，最重要的就是留意飲食。許多來源強調「超級食物」（superfood）具有保護作用。超級食物含有豐富的抗氧化物與其他植物化學成分。
（編者按：所謂植物化學成分，phytochemicals，又稱植物生化素，簡稱植生素，是存在於植物內的天然化學成分。β-胡蘿蔔素就是很好的例子。 雖有許多科學家和官方建議多從蔬果攝取營養素 ，但只有少許證據證明植生素能對生理產生影響。）
But during the last two decades the connection between the foods we eat and the cellular anarchy called cancer has been unraveling.
然而在過去這20年間，我們吃下的食物與名為癌症的細胞紊亂現象之間的關係，已經逐漸拆解。
At the annual meeting of the American Association for Cancer Research in April, the latest results about diet and cancer were relegated to a single poster session and a few scattered presentations. There were new hints that coffee may lower the risk of some cancers and more about the possible benefits of vitamin D. Beyond that there wasn’t much to say.
在美國癌症研究學會（AACR）今年四月召開的年度學術會議中，有關飲食與癌症二者關係的最新研究成果，只在一項壁報發表會議與少數幾場分散的論文會議中發表。有一些新的研究顯示，咖啡可能有助於降低罹患某些癌症的風險，另外，維他命D的好處可能比已知的還要多一些。除此之外，可就乏善可陳了。
Dr. Walter C. Willett, a Harvard epidemiologist who has spent years studying cancer and nutrition, sounded almost rueful as he gave a status report. Whatever is true for other diseases, when it comes to cancer there was little evidence that fruits and vegetables are protective or that fatty foods are bad.
研究癌症與營養多年的哈佛大學流行病學家華雷特發表狀態報告時，顯得相當鬱卒。無論對其他疾病來說某些說法多麼有道理，一旦觸及癌症，幾乎沒有什麼證據顯示蔬果具有保護作用，或者高脂肪食物有害。
About all that can be said with any assurance is that controlling obesity is important, as it also is for heart disease, Type 2 diabetes, hypertension, stroke and other threats to life. Avoiding an excess of alcohol has clear benefits. But unless a person is seriously malnourished, the influence of specific foods is weak.
我們唯一有把握的是，控制肥胖很重要，這一點對心臟疾病、第2型糖尿病、高血壓、中風與其他可能致命的疾病而言亦然。避免飲酒過量顯然也有好處。然而除非一個人嚴重營養不良，特定食物的影響力其實不大。
The hypothesis that fatty foods are a direct cause of cancer has also been crumbling, along with the case for eating more fiber. The idea that red meat causes colon cancer is shrouded in ambiguity. Two meta-analyses published in 2011 reached conflicting conclusions — one finding a small effect and the other no clear link at all.
所謂高脂肪食物是引起癌症的直接因子，以及多攝取纖維有益健康的說法，也都已經開始站不住腳。紅肉會引起大腸癌的說法也並不明確。2011年發表的兩項整合分析報告歸納出兩種相互矛盾的結論，其中之一認為略有影響，另一項報告則認為二者之間完全沒有明顯關聯。
If hamburgers are carcinogenic, the effect appears to be mild. One study suggests that a 50-year-old man eating a hefty amount of red meat — about 150 grams a day — raises his chance of getting colorectal cancer to 1.71 percent during the next decade, from 1.28 percent. Spread over a population of millions, that would have an impact. From the point of view of an individual, it barely seems to matter.
就算吃漢堡真會致癌，影響似乎也還溫和。根據一項研究報告，一名50歲的男子如果食用大量紅肉（大約每天150公克），未來10年罹患大腸癌的機率，會從1.28%提高到1.71%。
如果以數百萬人口為標的來看待，這會有影響。至於對個人而言，這似乎可以說無關痛癢。
As the meeting was winding up, though, a new paper on highfat diets and breast cancer suggested there might be a connection after all.
然而根據會議即將結束之際發表的一項有關高脂肪飲食與乳癌關係的最新報告，二者之間可能真的有關。
With even the most rigorous studies, it is hard to adjust for what epidemiologists call confounding factors: Assiduous eaters of fruits and vegetables probably weigh less, exercise more and are more vigilant about their health in other ways. Some of this can be sorted out with randomized controlled trials, with two large groups of people arbitrarily assigned different diets. But such studies are expensive, and the rules are hard to enforce in the short term — and probably impossible over the many years it can take for cancer to develop.
即使研究做得再認真努力，科學家還是難以針對流行病學家所謂的困惑因素進行調整：勤吃蔬果的人很可能體重比較輕，運動量比較大，而且以其他方式注意自己的健康。其中一部分因果可以透過隨機控制實驗整理出來。在這些實驗中，兩大群人隨意分配不同飲食。然而這種實驗所費不貲，而且要落實相關的規則，即使在短期之內都不容易，要延續到癌症生成可能需要的數年之久，更是幾乎不可能。
The emphasis at the American Association for Cancer Research meeting was on other things: new immunotherapies, the role of chronic inflammation and the intricate subterfuges of cancer cells. With his focus on nutrition, Dr. Willett seemed like the odd man out.
AACR召開的前述會議重點其實另有所在：新的免疫療法、慢性發炎扮演的角色與癌細胞的複雜詭計。著重營養的華雷特顯得有如孤鳥。
“Diet and cancer has turned out to be more complex and challenging than any of us expected,” he said.
他說：「研究顯示，飲食與癌症之間的關係比我們所想像的還要複雜，也更具挑戰性。」
我們有理由可以樂觀。
There are reasons for optimism. A study last year suggested that while eating lots of produce had no effect on most breast cancers, vegetables might reduce the occurrence of a type called estrogen-negative. Cutting back on milk and other dairy products might lower the risk of prostate cancer.
根據去年發表的一項報告，雖然食用大量農產品對大多數的乳癌不會有影響，蔬菜卻可能有助於降低癌細胞對雌激素呈陰性反應乳癌的發生率。減少食用牛奶與其他乳製品或許可降低罹患攝護腺癌的機率。
During a reception at the American Association for Cancer Research convention , guests partook of thick slabs of roast beef, a variety of rich cheeses and generous servings of wine.
在AACR舉辦的一項接待餐會中，賓客享用厚片烤牛肉、多種乳酪與大量供應的葡萄酒。
The next morning the scientists were back at the meeting, rushing from session to session. In the convention dining area a display recogniz ed the 50th anniversary of the surgeon general’s report on smoking and cancer.
翌日上午，科學家返回會場，在個別會議之間趕場。會議用餐區舉辦一項展覽，用以紀念美國公共衛生署長發表吸菸與癌症關係研究報告滿50周年。
In countering this disease, the campaign against tobacco has been the closest thing to a triumph. But now that smoking is on the wane , obesity is on the rise. Being fat , Dr. Willett proposed, may now be causing more fatal cancers than cigarettes.
在對抗這種疾病的過程中，反菸運動最成功。隨著吸菸人口逐漸減少，肥胖的人卻越來越多。華雷特說，肥胖引起的致命癌症可能已經多過吸菸所引起的。
