不管是沉迷已久的狂熱咖啡粉絲，還是普通的咖啡愛好者，好消息來了：一項新研究發現，喝咖啡可能有利于長壽。

該研究耗時十余年，研究結果發表在醫學期刊JAMA Internal Medicine上。通過英國的大型基因與健康數據庫Biobank，美國國家癌癥研究所（NCI）的研究人員分析了將近50萬人的數據，報告中指出：“這項研究進一步證明，咖啡可能是健康食譜的一部分，也讓咖啡愛好者感到安心。”

上述研究成果令各類咖啡愛好者感到鼓舞，包括低咖啡因粉絲、速溶咖啡愛好者，體內有與代謝咖啡相關基因的人，甚至一天能狂喝八杯咖啡的人。研究發現，喝咖啡的人死亡風險比不沾咖啡的人低，這且與喝咖啡的習慣有一定關系。

這項關于咖啡引人矚目的發現在科學角度上能否站得住？會不會又是一次高估咖啡功效卻缺乏細節的公共健康報告？讓我們來看看數據。

首先需要說明：兩件事物有相關性不代表有因果關系。單單喝咖啡未必有益健康。但是綜合分析幾十項研究，涉及數以百萬人的案例，現有研究文獻的確顯示，飲用更多咖啡有利于降低罹患心臟病和中風等心血管疾病風險（也是美國人的頭號殺手）。為《紐約時報》撰寫醫療健康相關專欄的兒科醫生、兒科教授阿倫·卡羅爾歸納了一些數字：

經過觀察長期飲用咖啡與心血管疾病風險的研究，（2014年）發表了一項系統性評估和綜合分析。研究者調查了涉及超過127萬參與者的36項研究。綜合數據顯示，如果參與者飲用適量咖啡、一天喝大概三到五杯，罹患心血管疾病風險最低，如果一天最少喝五杯咖啡，患病風險也不會超過不喝咖啡的人。

卡羅爾進而指出，雖然某些獨立的研究認為，過多飲用咖啡可能和罹患癌癥有關聯，但綜合性的分析發現未必存在相關性，咖啡對肝癌等某些癌癥治療甚至能起一定作用。

相關研究的問題在于，結論往往來自觀察，而觀察結果本身具有一些局限性。比如調查對象單方面表述信息，可能無法控制所有相關因素。假如采取隨機的對照測試，讓參與者處在受控的環境中逐個研究，對咖啡對人體健康的影響可能解釋更清楚。另外要重申一點，大量現有數據顯示，喝咖啡對大多數人至少無害，甚至可能對很多人有益（前提是不要咖啡里加入太多奶和糖）。（財富中文網）

譯者：Pessy

審稿：夏林

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Good news for coffee lovers—including those who indulge heavily: Yet another study has found a link between drinking coffee and a longer life.

“This study provides further evidence that coffee drinking can be part of a healthy diet and offers reassurance to coffee drinkers,” wrote the National Cancer Institute (NCI) researchers, who analyzed data from nearly 500,000 people through the U.K. Biobank, a large-scale genomic and health database. The study took place over 10 years and the findings were published in the journal JAMA Internal Medicine.

The results were encouraging for coffee drinkers of all stripes; decaf devotees, instant coffee lovers, those who have variants of the genes associated with metabolizing caffeine, even people who drink up to eight cups of coffee per day—drinking coffee was associated with a lower mortality risk over the study period compared to non-coffee drinkers.

So is all of the glowing research around coffee consumption scientifically sound, or yet another case of over-hyped public health reporting lacking nuance? Let’s take a look at the data.

First things first: Correlation does not imply causation. Simply drinking coffee isn’t necessarily a health panacea. But the existing literature, including meta-analyses aggregating dozens of coffee studies involving millions of people, do show some notable associations between people who report drinking more coffee and protective effects against cardiovascular disease (the number one killer of Americans) like heart disease and stroke. Aaron Carroll, a pediatrician and professor of pediatrics who writes public health-related columns for the New York Times rounds up some of the numbers:

[In 2014], a systematic review and meta-analysis of studies looking at long-term consumption of coffee and the risk of cardiovascular disease was published. The researchers found 36 studies involving more than 1,270,000 participants. The combined data showed that those who consumed a moderate amount of coffee, about three to five cups a day, were at the lowest risk for problems. Those who consumed five or more cups a day had no higher risk than those who consumed none.

Carroll goes on to note that, while individual studies have suggested a possible link between excess coffee consumption and cancer, aggregated analyses don’t necessarily find the same correlation, and coffee may even have a protective effect against certain cancers like liver cancer.

The rub with these studies is that they tend to be observational ones, and those come with limitations. For instance, they rely on self-reported information and may not control for every relevant factor. Randomized control trials pitting study participants head to head in a controlled setting could help provide more definitive answers on precisely how coffee affects your health. Then again, the data that is available overwhelmingly suggests that, at the very least, it’s not bad for the vast majority of people, and it might even be good for many (provided you’re not overloading your drink with milk and sugar).