平時多吃紅肉 真的不健康嗎
There are people in this country eating too much red meat. They should cut back. There are people eating too many carbs. They should cut back on those. There are also people eating too much fat, and the same advice applies to them, too.
在美國，有些人食用紅肉太多，他們應該少吃點；也有些人食用碳水化合物太多，他們也應該剋制；還有些人食用脂肪太多，相同的建議也適用於他們。What’s getting harder to justify, though, is a focus on any one nutrient as a culprit for everyone.
把某一營養物質說成是危害所有人健康的罪魁禍首的說法，正變得越來越難以自圓其說。I’ve written Upshot articles on how the strong warnings against salt and cholesterol are not well supported by evidence. But it’s possible that no food has been attacked as widely or as loudly in the past few decades as red meat.
此前，我已在《紐約時報》的Upshot專欄中撰文，闡述那些關於鹽和膽固醇的強烈警告其實並沒有得到充分的證據支持。不過，在過去的幾十年裏，恐怕任何一種食物受到的攻擊都沒有紅肉這樣廣泛和強烈。
Americans are more overweight and obese than they pretty much have ever been. There’s also no question that we are eating more meat than in previous eras. But we’ve actually been reducing our red meat consumption for the last decade or so. This hasn’t led to a huge decrease in obesity rates or to arguments from experts that it is the reason for fewer deaths from cardiovascular disease.
今天美國人超重和肥胖的程度基本上都甚於以往，我們也毫無疑問是比以前吃肉多。然而，在過去十年左右的時間裏，我們的紅肉消費量實際上是在逐漸減少的。可這並沒有引起肥胖率大幅下降，也沒有專家認爲它是心血管疾病死亡人數減少的原因。The same reports also show that we eat significantly more fruits and vegetables today than we did decades ago. We also eat more grains and sweeteners.
同樣，報告還顯示，我們今天食用水果和蔬菜的量顯著多於幾十年前。我們還吃下了更多的穀物和甜味劑。This is the real problem: We eat more calories than we need. But in much of our discussion about diet, we seek a singular nutritional guilty party. We also tend to cast everyone in the same light as “eating too much.”
這纔是真正的問題：我們攝入的熱量超過了實際所需。但是，在大多數關於飲食的討論中，我們都試圖把責任歸咎於某一類營養物質。而且，我們也傾向於給所有人都套上“吃得太多”的大帽子。I have seen many people point to a study from last year that found that increased protein intake was associated with large increases in mortality rates from all diseases, with high increases in the chance of death from cancer or diabetes. A close examination of the manuscript, though, tells a different story.
我見過有很多人拿着去年的一項研究振振有詞，稱該研究發現，蛋白質攝入量的增加與因所有疾病死亡率以及因癌症或糖尿病死亡的機率大幅增加相關。然而，在仔細閱讀文獻後，我發現它說的完全是另外一回事。This was a cohort study of people followed through the National Health and Nutrition Examination Survey, or Nhanes. It found that there were no associations between protein consumption and death from all causes or cardiovascular disease or cancer individually when all participants over age 50 were considered. It did detect a statistically significant association between the consumption of protein and diabetes mortality, but the researchers cautioned that the number of people in the analysis was so small that any results should be taken with caution.
這是一項隊列研究，研究人員通過美國健康與營養調查(National Health and Nutrition Examination Survey, Nhanes)對參與者進行了隨訪。研究發現，當考慮到所有50歲以上的參與者時，蛋白質攝入量與全因死亡率、心血管疾病死亡率以及癌症死亡率中的任何一項均無相關性。研究的確發現蛋白質攝入量與糖尿病死亡率之間具有統計學顯著相關性，但研究人員提醒說，由於該分析中納入的人數過少，應謹慎對待由此得出的任何結果。The scary findings from two paragraphs up are from a subanalysis that looked at people only 50 to 65. But if you look at people over 65, the opposite was true. High protein was associated with lower levels of all-cause and cancer-specific mortality. If you truly believe that this study proves what people say, then we should advise people over the age of 65 to eat more meat. No one advises that.
而上面倒數第二段中那個可怕的結論只不過是一項僅考察50歲到65歲參與者的亞組分析的結果而已。如果你將調查的對象改爲65歲以上的參與者，就會發現情況恰恰相反。高蛋白攝入量與較低的全因死亡率和癌症特異性死亡率相關。如果你相信這項研究爲應該少吃紅肉提供了證據，那麼我們也應該建議65歲以上的人多吃些肉——顯然並沒有人這麼做。Further, this study defined people in the “high protein” group as those eating 20 percent or more of their calories from protein. When the Department of Agriculture recommends that Americans get 10 to 35 percent of their calories from protein, 20 percent should not be considered high.
此外，這項研究對“高蛋白質”組成員的定義爲：飲食總熱量中有至少20%來自蛋白質。考慮到美國農業部(United States Department of Agriculture,USDA)建議美國人從蛋白質獲得的熱量應占所需熱量的10%至35%，20%其實不能算高。If I wanted to cherry-pick studies myself, I might point you to this 2013 study that used the same Nhanes data to conclude that meat consumption is not associated with mortality at all.
如果允許我自己來挑選的話，我也能找出一項2013年的研究，它使用了相同的Nhanes數據，卻得出了相反的結論：肉類消費量與死亡率毫不相關。Let’s avoid cherry-picking, though. A 2013 meta-analysis of meat-diet studies, including those above, found that people in the highest consumption group of all red meat had a 29 percent relative increase in all-cause mortality compared with those in the lowest consumption group. But most of this was driven by processed meats, like bacon, sausage or salami.
不過，我們還是不要刻意去挑選吧。2013年的一項關於肉類膳食研究的薈萃分析納入了上述的幾類情況，分析結果發現：與紅肉消費量最低組相比，最高組成員的全因死亡率增加了29%，但這一增加主要是由加工肉類，如培根、臘腸或意大利香腸等造成的。Epidemiologic evidence can take us only so far. As I’ve written before, those types of studies can be flawed. Nothing illustrates this better than a classic 2012 systematic review that pretty much showed that everything we eat is associated with both higher and lower rates of cancer.
流行病學證據能告訴我們的也只有這麼多了。正如我之前所說，這類研究有可能存在缺陷。2012年的一項典型的系統性綜述就是最好的佐證：該綜述表明，幾乎我們的所有食物都同時與較高和較低的癌症發病率相關。We really do need randomized controlled trials to answer these questions. They do exist, but with respect to effects on lipid levels such as cholesterol and triglycerides. A meta-analysis examining eight trials found that beef versus poultry and fish consumption didn’t change cholesterol or triglyceride levels significantly.
所以，我們需要進行隨機對照試驗才能真正找到問題的答案。這樣的實驗確實是存在的，不過卻是關於膽固醇和甘油三酯等血脂水平指標的。一項薈萃分析審查了八項試驗，發現與食用禽肉和魚肉相比，食用牛肉並不會顯著改變人的膽固醇或甘油三酯水平。All of this misses the bigger point, though. It’s important to understand what “too much” really is. People in the highest consumption group of red meat had one to two servings a day. The people in the lowest group had about two servings per week. If you’re eating multiple servings of red meat a day, then, yes, you might want to cut back. I would wager that most people reading this aren’t eating that much. If you eat a couple of servings a week, then you’re most likely doing fine.
但是，所有這些都忽略了更重要的一點——“太多”的標準到底是什麼。紅肉消費量最高組的人每天食用一至兩份紅肉，而最低組的人每週才食用大約兩份。如果你每天都吃好幾份紅肉，那麼，沒錯，你是需要控制一下了。但我敢打賭，正在閱讀這篇文章的人中大多數都不會吃那麼多。如果你每週食用一兩份紅肉，那麼最有可能的情況是：你的身體一切正常。All the warnings appear to have made a difference in our eating habits. Americans are eating less red meat today than any time since the 1970s. Doctors’ recommendations haven’t been ignored. We’re also doing a bit better in our consumption of vegetables. Our consumption of carbohydrates, like grains and sugar, however, has been on the rise. This is, in part, a result of our obsession with avoiding fats and red meat.
健康警告大大改變了我們的飲食習慣。美國人今天的紅肉消費量比20世紀70年代以來的任何時候都少。人們並沒有忽略醫生的建議。我們在食用蔬菜方面也取得了一點進步。但我們對穀物和糖等碳水化合物的消費量卻一直在上升。在某種程度上，可以說這正是我們執着於不吃脂肪和紅肉的後果。We’re eating too many calories, but not necessarily in the same way. Reducing what we’re eating too much of in a balanced manner would seem like the most sensible approach.
我們仍然攝入了太多的熱量，只不過改了個途徑罷了。最明智的做法應該是以平衡的方式少吃那些我們過量食用的東西纔對。Last fall, a meta-analysis of brand-name diet programs was published in the Journal of the American Medical Association. The study compared the results from both the individual diets themselves and three classes, which included low-carbohydrate (like Atkins), moderate macronutrient (Weight Watchers) and low-fat (Ornish). All of the diets led to reduced caloric intake, and all of them led to weight loss at six months and, to a lesser extent, at 12 months. There was no clear winner, nor any clear loser.
去年秋天，《美國醫學協會雜誌》(Journal of the American Medical Association)上發表了一項對著名飲食方案的薈萃分析。該研究既比較了單個的飲食方案，也對三大類飲食方案：低碳水化合物飲食（如阿特金斯飲食法[Atkins]），中度宏量營養素飲食（如Weight Watcher）和低脂肪飲食（如Ornish飲食）進行了比較。所有的飲食方案都減少了熱量攝入，它們都能令參與者在六個月後體重減輕，並在接下來的六個月裏繼續減輕（但減重幅度較小）。它們之間並沒有表現出明顯的優劣。Where does that leave us? It’s hard to find a take-home message better than this: The best diet is the one that you’re likely to keep. What isn’t helpful is picking a nutritional culprit of bad health and proclaiming that everyone else is eating wrong. There’s remarkably little evidence that that’s true anytime anyone does it.
這給我們帶來什麼啓示？你最有可能堅持下來的飲食方案就是最好的飲食方案——世界上最棒的教益或許莫過於此。把健康狀況不佳歸咎於某一特定的營養物質，並宣稱其他人的飲食習慣都不對，這樣做沒有一點好處。很顯然，任何時候任何人這麼做都是毫無根據的。
