吃什麼才健康 其實大家都是靠猜大綱

First doctor: “This morning for breakfast he requested something called ‘wheat germ, organic honey and tiger’s milk.’”

醫生甲說：“那傢伙說今天早餐想吃……某種叫做‘小麥胚芽、有機蜂蜜和Tiger's Milk有機蛋白質營養棒’的東西。”

Second doctor: “Oh, yes. Those are the charmed substances that some years ago were thought to contain life-preserving properties.”

醫生乙：“對啊。很多年前，人們對這些東西可着迷啦，他們篤信這裏面含有維持生命必備的營養成分。”

Fans of Woody Allen may recognize that snippet of dialogue from his 1973 comedy, “Sleeper.” The main character, a health-food store owner somehow frozen in 1973, has been thawed out 200 years later. He awakens to a world he can barely fathom, down to the kinds of food now said to constitute a sound diet. Everything that nutrition specialists once said was good for you, or really bad, turned out to be wrong.

如果你是伍迪·艾倫(Woody Allen)的粉絲，或許你已經認出上述對話是他1973年的喜劇電影《傻瓜大鬧科學城》(Sleeper)中的片段。影片的主角是一名健康食品商店的老闆，1973年他莫名其妙地被冷凍了起來，直到200年後才被解凍。他甦醒過來，發現自己來到了一個令他迷惑不解的新世界，就連所謂的“健康食品”也改變了——過去被營養專家宣稱是對人大有益處或害處的東西，後來發現都不是那麼回事兒。

First doctor: “You mean there was no deep fat? No steak or cream pies or hot fudge?”

醫生甲：“你是說，不包括油炸食品？也沒有牛排、奶油餡餅或熱巧克力？”

Second doctor: “Those were thought to be unhealthy — precisely the opposite of what we now know to be true.”

醫生乙：“他們覺得這些東西不健康——不過，我們現在知道，事實恰恰相反呀。”

Moviegoers laughed. They recognized how they were whipsawed by contradictory expert pronouncements about what they should or should not eat to stay healthy. On this score, not much has changed. How many times have Americans read about a study damning this or that food, only to then hear the revisionist opposite? Avoid eggs, we were told; they clog your arteries. Wait, we then heard, eggs have nutritional value. Coffee can give you cancer. Hold on, coffee can improve brain function. Butter is terrible. Well, not really. Again and again, yesterday’s verity becomes today’s punch line.

看到這裏，觀衆們紛紛大笑起來。他們意識到，關於爲了保持健康應該或不應該吃什麼，專家們一直在給他們灌輸相互矛盾的意見，讓他們莫衷一是——只有這一點似乎一直都沒有改變。多少次，一項研究言之鑿鑿，宣稱這種或那種食物“罪大惡極”，結果不久，就又有人提出相反的論斷。我們被告知不要吃雞蛋，因爲它們會堵塞你的動脈——接着我們又聽說，雞蛋頗具營養價值；咖啡會害你患癌症——等等，咖啡可以改善腦功能；黃油簡直糟透了——好吧，其實也並非如此。一次又一次，昨天被奉爲至理名言的，變成了今天的笑話。

The vagaries of nutrition claims infuse the latest episode of Retro Report, video documentaries exploring major news developments of the past and how they still resound. This installment harks back to the 1970s, when many health authorities asserted, with unshakable confidence, that a diet low in fat and cholesterol was essential for a healthful life (wheat germ and tiger’s milk presumably optional).

最近一期的“Retro Report”（回顧歷史上的重大新聞，並探討其現實意義的系列電視紀錄片）中就充斥着此類變幻莫測的營養學聲明。這期節目回顧了上世紀70年代，當時，衆多衛生部門都以堅不可摧的信心聲稱，低脂肪和低膽固醇的飲食（譬如小麥胚芽和Tiger's Milk有機蛋白質營養棒之類）是健康生活必不可少的一部分。

“Fat-free” became a mantra, not to mention a marketing tool to sell breakfast cereals and high-caloric snacks. If anyone qualified as a heretic back then, it was Dr. Robert C. Atkins, a cardiologist who died in 2003. The Atkins diet encouraged loading up on fat-laden foods like steaks and omelets, and steering clear of pasta, bread and other carbohydrates.

“脫脂”彷彿成了一個魔咒，更不用說它實際上已經化身爲推銷早餐穀物和高熱量小食品的一種營銷工具。而在當年，要說特立獨行離經叛道，當屬心臟病醫生羅伯特·C·阿特金斯(Robert C. Atkins)博士了（他在2003年去世）。阿特金斯飲食法鼓勵人們大量進食高脂肪食物，如牛排和煎蛋卷等，同時避免食用意麪、麪包等碳水化合物。

But conventional wisdom held that fat was bad, period, with relatively few Americans distinguishing between saturated fats (meat, eggs, dairy products) and healthier unsaturated fats (fish, vegetable oils, nuts). Typically, people turned to breads, cereals and potatoes — and to sugary soft drinks — for the calories they no longer got from protein-rich foods.

但傳統觀念認爲脂肪不是好東西，句號，一度只有少數美國人能對飽和脂肪（肉、蛋、乳製品）和較爲健康的不飽和脂肪（魚、植物油、堅果）區別對待。通常，人們只是直接轉而食用麪包、穀物、土豆以及含糖軟飲料，以便獲得他們原本應從富含蛋白質的食物中攝取的熱量。

“Diet is a trade-off,” Gary Taubes, a science journalist and the author of “Why We Get Fat,” told Retro Report. “If we reduce the amount of fat, you have to replace it with something.” That something tended to be carbohydrates. The result? Carbo-loading Americans grew fatter. “We put the whole country on a low-fat diet,” Mr. Taubes said, “and, lo and behold, we have an obesity epidemic.”

“膳食是個交易過程，”《我們爲什麼會發胖？》(“Why We Get Fat”)一書的作者，科學記者蓋裏·陶比斯(Gary Taubes)在接受”Retro Report”採訪時說。“如果我們減少了脂肪的攝入量，就必須用別的什麼東西來替代它。”——比如碳水化合物。結果，大量食用碳水化合物，讓美國人變得更胖了。陶比斯先生說：“在整個國家推行低脂肪飲食後，瞧啊，肥胖大肆流行了開來。”

Obesity has proved a stubborn plague, one that the Centers for Disease Control and Prevention says affects 35 percent of American adults — about 79 million people. Tens of millions more, while not technically obese, are overweight. Not coincidentally, diabetes is a big national headache, even if the C.D.C. reported last month that new cases of the disease had begun to decline.

肥胖已成爲一個頑疾，美國疾病控制和預防中心(Centers for Disease Control and Prevention，CDC)的工作人員表示，在美國的成年人中，肥胖者人數高達7900萬，佔35%。還有數以千萬計的人雖然嚴格來說算不上肥胖，至少也是超重的。無獨有偶，雖然據CDC上個月報道，糖尿病的新病例數開始下降了，但它仍是令美國頭痛的一大疾病。

As for that low-fat diet, a major federal study concluded in 2006 that its health benefits were greatly overrated. Such a diet, researchers found, had no effect on the risk of heart disease or cancer, the two biggest killers in the United States

2006年美聯邦進行的一項重大研究顯示，低脂肪飲食的健康效益被大大高估了。研究人員發現，這種飲食對美國致死率最高的兩大疾病——心臟病和癌症的風險並沒有影響

This Retro Report episode comes as the federal government is again rethinking its Dietary Guidelines for Americans. They form a nutrition template that Washington issues every five years and is a bible for millions of the diet-conscious, whose numbers undoubtedly include many who overindulged during the holidays and entered the new year with a pledge to shed pounds.

本期“Retro Report”的推出，正值聯邦政府再次反思其《美國膳食指南》(Dietary Guidelines for Americans)之際。這些每隔五年由華盛頓發佈的指南得到了數以百萬計的注重飲食者的追捧，並視其爲營養模板和飲食聖經，毫無疑問，衆多在節假日裏胡吃海喝，而後又在新年伊始許願一定要減肥的人也在其中。

The new guidelines are expected to be issued this month by the Departments of Agriculture and of Health and Human Services, which tend to follow the recommendations of an advisory committee. One likely eye-catcher is a new assessment of cholesterol, long an archvillain. It seems destined for rehabilitation to some degree. Months ago, the advisory committee concluded that the dietary intake of cholesterol (the body produces this waxy, artery-obstructing matter on its own) had no real effect on blood levels of LDL, the so-called bad cholesterol. “Cholesterol,” the committee said, “is not a nutrient of concern for overconsumption.”

預計新指南將在本月由美國衛生和公衆服務部(Department of Health and Human Service)和農業部(Department of Agriculture)發佈。這些指南通常都會遵循顧問委員會的建議。其中，一項關於膽固醇的新評估很可能將十分引人注目。長期以來，膽固醇一直被視爲洪水猛獸，而該評估可以說在一定程度上爲它平了反。幾個月前，該顧問委員會得出結論，從膳食中攝取膽固醇（人體自己也會產生這種會阻塞動脈的蠟狀物）對LDL（低密度脂蛋白膽固醇），也就是所謂的“壞膽固醇”的血液濃度沒有實質影響。該委員會稱：“我們無需擔心過度攝取膽固醇。”

There is a conspicuous American tendency to cling to a favored diet as the gateway to good health, keeping weight down, staving off cancers and banishing heart attacks. A consequence is an abundance of regimens — vegan, gluten-free, Paleolithic, fruitarian and many more — each promoted by its adherents as the one true path.

美國人中存在着一種非常明顯的傾向，總是喜歡追捧某種特殊的飲食，以爲它是能讓你身體健康、保持體重、預防癌症、避免心肌梗死的唯一制勝法寶。結果，各種各樣的膳食方案層出不窮：素食主義、無麩質飲食、舊石器時代飲食（Paleolithic，又譯，古式飲食）、果食主義等等，每一種都擁有大批忠貞不二的擁躉。

But nutrition experts, including those in this Retro Report, caution that life is complex, and that we are more than what we eat. Among them is Dr. Barbara V. Howard, who was a principal investigator in the 2006 federal study of low-fat diets.

但營養專家，包括本期“Retro Report”中的專家們都警告，生命遠比吃什麼東西複雜得多。芭芭拉·V·霍華德(Barbara V. Howard)博士也是其中之一，她是2006年美聯邦一項低脂肪飲食研究的首席研究員。

“We are not going to reverse any of the chronic diseases in this country by changing the composition of the diet,” Dr. Howard said when that report was issued. “People are always thinking it’s what they ate. They are not looking at how much they ate, or that they smoke or that they are sedentary.”

“在這個國家中，改變飲食結構是無法逆轉任何慢性疾病的，”霍華德博士在發佈上述研究報告時說道。“人們總覺得問題出在食物身上，卻從不留心自己的食量，以及吸菸與否或是否存在久坐不動的生活習慣等。”

Other explanations for why one person gains weight and someone else does not may include sleep patterns, genetic predispositions and the compositions of individual microbiomes — the trillions of microbes residing inside the human body. Some health researchers even question the significance of exercise in keeping pounds off, regardless of its other benefits. Among other things, one has to move around quite vigorously to hold the weight down. A Big Mac, for instance, has 540 calories. To burn it off, a person would need to jog or to swim laps for about 45 minutes. Not every Big Mac eater exercises that strenuously.

對於爲何有些人容易發胖而其他人則不然，還有些其他的解釋，例如睡眠模式、遺傳傾向和個人的微生物組（也就是棲息在人體內的數萬億微生物的總和）等。有些健康研究人員甚至對運動在保持體重中的重要性提出了質疑——雖然他們承認它可以帶來其他好處。別的先不說，要控制體重，一個人非積極地運動不可。例如，一個巨無霸(Big Mac)含有540卡路里的熱量。要消耗掉這些熱量，需要慢跑或游泳45分鐘。顯然，不是每個吃巨無霸的人都會這麼勤奮地鍛鍊的。

Politics, too, can enter the picture. An example is the experience of Michael R. Bloomberg, a forceful public-health advocate when he was New York’s mayor. Despite resistance from restaurant owners and their political allies, Mr. Bloomberg pushed through a ban on trans fats (almost universally deemed a health hazard), and required fast-food outlets to post calorie counts.

政治在飲食問題中也佔有一席之地。就拿邁克爾·R·布隆伯格(Michael R. Bloomberg)的經歷爲例吧，他在擔任紐約市長時是一位強有力的公衆健康倡導者。儘管遭遇了來自餐館老闆和他們的政治盟友的阻力，布隆伯格依然力促通過了對反式脂肪（普遍認爲它有害健康）的禁令，並要求快餐店公佈其產品的卡路里計數。

But he hit a political and a juridical wall when he also sought to restrict the sale of sodas and other sugary drinks of dubious nutritional value. State courts shot down his plan on procedural grounds. Mr. Bloomberg found himself widely denounced for having taken government nannyism too far.

然而，當他試圖限制汽水和其他營養價值存疑的含糖飲料的銷售時，在政治和法律兩方面都碰了壁。州法院基於程序上的原因駁回了他的議案。布隆伯格也因爲讓政府害了“奶媽主義”病（nannyism，禁止任何“可能”導致傷害的事情——譯註）而廣受批評。

Then again, no one ever said figuring out the elements of a healthy diet would be easy. Dr. Dariush Mozaffarian, a nutrition specialist at Tufts University, suggested to Retro Report that accepted wisdom was not necessarily wise. Much of what has shaped dietary guidelines, he said, are “basically best guesses.” Uncertainty abounds. “I think now we know about 50 percent of what we need to know,” Dr. Mozaffarian said.

不過話說回來，要找到健康飲食的要素絕非易事。塔夫茨大學(Tufts University)的營養學專家戴瑞什·莫薩法利安(Dariush Mozaffarian)博士向“Retro Report”表示，受到廣泛認可的觀念未必就是正確的。他說，膳食指南中的大部分內容“基本上都是些‘最佳猜測’(best guess)，”充滿了不確定性。他還說：“我認爲我們目前所知的，只佔應該和需要知道的50%左右。”

So is it possible that steaks, cream pies and hot fudge will someday be called the cornerstones of a healthy diet? Maybe if you can stick around for 200 years, you’ll find out.

既然如此，有朝一日人們會不會將牛排、奶油餡餅和熱巧克力列爲健康飲食的重要組成部分？努力再活上個200年，你就知道啦。