多喝咖啡当真有益延年益寿？看看科研结果怎么说

不管是沉迷已久的狂热咖啡粉丝，还是普通的咖啡爱好者，好消息来了：一项新研究发现，喝咖啡可能有利于长寿。

该研究耗时十余年，研究结果发表在医学期刊JAMA Internal Medicine上。通过英国的大型基因与健康数据库Biobank，美国国家癌症研究所（NCI）的研究人员分析了将近50万人的数据，报告中指出：“这项研究进一步证明，咖啡可能是健康食谱的一部分，也让咖啡爱好者感到安心。”

上述研究成果令各类咖啡爱好者感到鼓舞，包括低咖啡因粉丝、速溶咖啡爱好者，体内有与代谢咖啡相关基因的人，甚至一天能狂喝八杯咖啡的人。研究发现，喝咖啡的人死亡风险比不沾咖啡的人低，这且与喝咖啡的习惯有一定关系。

这项关于咖啡引人瞩目的发现在科学角度上能否站得住？会不会又是一次高估咖啡功效却缺乏细节的公共健康报告？让我们来看看数据。

首先需要说明：两件事物有相关性不代表有因果关系。单单喝咖啡未必有益健康。但是综合分析几十项研究，涉及数以百万人的案例，现有研究文献的确显示，饮用更多咖啡有利于降低罹患心脏病和中风等心血管疾病风险（也是美国人的头号杀手）。为《纽约时报》撰写医疗健康相关专栏的儿科医生、儿科教授阿伦·卡罗尔归纳了一些数字：

经过观察长期饮用咖啡与心血管疾病风险的研究，（2014年）发表了一项系统性评估和综合分析。研究者调查了涉及超过127万参与者的36项研究。综合数据显示，如果参与者饮用适量咖啡、一天喝大概三到五杯，罹患心血管疾病风险最低，如果一天最少喝五杯咖啡，患病风险也不会超过不喝咖啡的人。

卡罗尔进而指出，虽然某些独立的研究认为，过多饮用咖啡可能和罹患癌症有关联，但综合性的分析发现未必存在相关性，咖啡对肝癌等某些癌症治疗甚至能起一定作用。

相关研究的问题在于，结论往往来自观察，而观察结果本身具有一些局限性。比如调查对象单方面表述信息，可能无法控制所有相关因素。假如采取随机的对照测试，让参与者处在受控的环境中逐个研究，对咖啡对人体健康的影响可能解释更清楚。另外要重申一点，大量现有数据显示，喝咖啡对大多数人至少无害，甚至可能对很多人有益（前提是不要咖啡里加入太多奶和糖）。（财富中文网）

译者：Pessy

审稿：夏林

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).