饮酒对健康究竟有害还是有利？
BBC比安卡·诺格拉迪 (Bianca Nogrady) (2023年9月9日)
酒吧里耀眼的酒杯（图片来源： Thinkstock)
喜欢偶尔喝点啤酒或葡萄酒的人们深信这样的习惯对身体是有益的。
而那些宣称“一天一两杯、不用看医生”的研究，也受到了媒体和公众的极度追捧。 但确定适量饮酒对健康是否有益，是一项很复杂的工作。
一项由已故杰出循证医学教父阿奇·科克伦 (Archie Cochrane) 主持的早期研究发现，饮酒与健康之间存在关联。1979 年，科克伦和两个同事又试图在包括美国、英国和澳大利亚在内的18个发达国家中找出心脏病致死率不同的原因。
他们的分析显示：增加饮酒量（尤其是葡萄酒）和降低缺血性心脏病发病率（因供应心脏血液的血管内脂肪沉积引起的心脏病）之间存在明显的重要关联。
科克伦及其同事援引此前证实饮酒与心脏病致死率降低之间存在关联的研究，提出有益于这一现象的可能是酒精中的芳香剂和其他化合物（最近假定为诸如植物多酚的抗氧化剂），而非酒精本身。 本着循证医学的精神，他们呼吁对这一问题进行实验性的探讨。
用实验对象来做酒精实验，虽然会挺有趣，但不大可能揭示酒精是否像人们猜测的那样具有涉及慢性病的益处。 因此，多数有关酒精及其对健康的利弊研究均以长期的、基于人口的研究形式展开。
1986 年关于男性医生饮酒习惯的一项研究发现，他们喝的越多，冠状动脉疾病的发病率就越低，但这真是一份精确的描述吗？ （图片来源： iStock)
1986 年，研究人员对逾5万名美国男性医生过去两年内的饮酒和饮食习惯、病史及健康状况进行了调查。他们发现，尽管受访医生的饮食习惯不同，但他们报告的饮酒量越多，患有冠状动脉疾病的几率就越低。
发表于 2000 年的另一项关于男性医生的大型研究发现，适量饮酒和死亡（而非冠状动脉疾病）之间存在一种“U”形的关系。 即在为期5年半的研究期间，每天标准饮酒量一杯的男性医生死亡的几率小于那些每周饮酒少于一杯，或每天饮酒多于一杯的人。
这表明饮酒存在一种“最佳状态”、一种介于过多和过少之间的的中间地带，此时其有益于心血管健康的一面抵消了因各种原因导致的死亡的风险。
但这些益处是否源自酒精本身？还是说酒精只是其他健康行为的一个标记呢？比如，适量饮酒的人是否也经常运动、饮食平衡并且在通常情况下都会照顾好自己呢？
2005 年，针对医务人员的另一项研究（此次的研究对象是32000名女性和18000名男性）试图通过观察他们的饮酒习惯对心脏病发作风险以及生理机能的影响来回答这一问题。
那些每周喝三、四次酒，每次一到两杯的医务人员，其心脏病发作的风险较低；研究人员推测这可能是由于酒精对高密度脂蛋白胆固醇（所谓的“好”的胆固醇）以及糖化血红蛋白（糖尿病风险的指标）和纤维蛋白原（帮助血液凝结的组织）产生了有益的效果。这三个因素都在“代谢综合症”方面发挥着重要作用。作为一组复杂的代谢紊乱症候群，“代谢综合症”是心血管疾病和糖尿病的先兆。
另外一些研究也发现酒精可以改变上述因素之间的平衡，使之向好的方向发展，这就使得适度饮酒增强健康的机制变成了可能。
其他研究还证实了酒精对缺血性中风（大脑血凝块引起的中风）和死亡也存在“最佳状态”的作用。但在你匆匆行动、要在一周内给自己开几瓶酒作医病良方之前 — 当然是出于健康的考虑 — 你可能还需要读下去。
不饮酒者比那些一天喝上一两杯的风险会更高吗？ （图片来源： Getty Images)
不饮酒者的死亡风险实际上比那些每天喝上一两杯的人更高？ 这一问题似乎并没有表面上看起来那么简单。
2006 年，一组研究人员仔细观察了这些研究的设计方式。 他们的整合分析表明饮酒者（或者是不饮酒者）的分类方法存在漏洞：许多研究中的不饮酒者包含了那些因生病或年老已经减少或停止饮酒的人群。这就可能导致不饮酒者的健康状况看起来远低于一般人群。
重要的是，那些没有这种错误分类的研究却并未发现适量饮酒人群的心脏疾病和死亡率有所降低。
目前，其他研究人员已经深入探索了这种“误分类假设”，其中包括今年发布的一项基于英国人口的大型研究结果。
该研究表明，如果你只是简单对饮酒量和健康结果进行比较，便会发现适度饮酒明显对人体有益。 但如果你将以前的饮酒者从不饮酒者群体中中拎出来再看，那么相应益处看起来就不那么乐观了 — 事实上，它们全都荡然无存。
与此同时，另一组研究人员对酒精过敏（因此，他们一般根本不喝酒）的人群进行了研究，结果发现带有这种遗传标记的人相比那些没有的人心血管健康状况更好，患冠心病的风险也更低。
许多大型的研究都在对酒精和心脏病之间的联系进行研究，得出的结果也各有不同（图片来源： Thinkstock)
真正的坏消息是， 无论酒精对心脏病的发病风险是否存在任何影响，它都能够以各种各样的其他方式加速死亡。
世界卫生组织去年的报告显示，饮酒可以增加抑郁和焦虑、肝硬化、胰腺炎、自杀、暴力和意外伤害的风险。
酒精也可导致女性患口腔癌、鼻癌、喉癌、食道癌、结肠癌、肝癌和乳腺癌。 全世界 4% 至 30% 的癌症死亡都可归因于饮酒（对于最常见的乳腺癌，这一数字为 8%）。
重要的是，即便是适量饮酒也会增加风险： 每天饮用一杯就会增加 4% 的乳腺癌患病风险，而过量饮酒则会增加 40% 至 50% 的风险。
大量饮酒会削弱免疫系统的功能，从而导致肺炎和肺结核。 它还会导致危险性行为，增加获得性传播感染（如艾滋病毒）的机会。 而且怀孕期间饮酒可造成胎儿损伤以及胎儿酒精综合症。
总数超过 200 种疾病及伤害均与饮酒有关，其中有 30 种更是完全由酒精所造成的。
但是认为适度饮酒可能对身体有益的观点并没有完全消失，甚至连一些专门解决酒精问题的组织也不得不承认，少量饮酒可能对预防心脏病和某些类型的中风具有积极作用。
(责编：郱书)
Is alcohol actually bad for you?
Any study suggesting a glass or two a day can keep the doctor away is greeted with disproportionate enthusiasm by the media and general public. But it is a complex task to determine whether or not alcohol in moderation has health benefits.
One of the earlier studies drawing a link between alcohol consumption and health was performed by the late, great Archie Cochrane; the godfather of evidence-based medicine. In 1979, Cochrane and two colleagues tried to work out what exactly was responsible for the differing rates of death from heart disease across 18 developed countries, including the US, UK and Australia.
Their analysis came up with a clear and significant link between increasing alcohol consumption – specifically of wine – and decreasing rates of ischaemic heart disease (heart disease caused by the build-up of fatty deposits inside the blood vessels supplying the heart).
Citing earlier studies that had found an association between alcohol consumption and lower rates of deaths from heart attack, Cochrane and colleagues suggested that the aromatic and other compounds in alcohol – recently hypothesised to be antioxidants such as plant-based polyphenols – were likely responsible for the benefits, rather than the alcohol itself. In the spirit of evidence-based medicine, they called for an experimental approach to the question.
Plying experimental subjects with alcohol, while amusing, is unlikely to reveal the kind of chronic disease benefits that alcohol is speculated to deliver. So instead, much of the research around alcohol and its health costs and benefits has been in the form of long-term, population-based studies.
In 1986, researchers surveyed a group of more than 50,000 male doctors in the US about their drinking and eating habits, their medical history and state of health over two years. They found that the more alcohol the doctors reported drinking, the lower their chance of developing coronary artery disease, despite their dietary habits.
Another large study published in 2000, also in male doctors, found a ‘U’ shaped relationship between moderate alcohol consumption and – in this case – death, rather than coronary artery disease. Subjects who drank one standard drink a day were less likely to die within the 5.5-year-long study than those who drank less than one a week, or those who drank more than one a day.
This suggested there was a ‘sweet spot’ for alcohol consumption; a healthy middle ground between too little or too much, where the benefit for cardiovascular health balanced the risk of death from all causes.
But was the alcohol itself providing the benefits, or is it just a marker for other healthy behaviours? Are people who drink in moderation also the kind of people who exercise regularly, eat a balanced diet, and generally look after themselves?
In 2005, yet another study in medical professionals – this time 32,000 women and 18,000 men – attempted to answer this question by looking at how their drinking habits affected not only their risk of heart attack, but also their physiology.
The people who drank one to two glasses of alcohol, three to four times a week, had a lower risk of heart attack, which the researchers hypothesised could be due to beneficial effects of alcohol on HDL cholesterol – the so-called ‘good’ cholesterol – as well as haemoglobin A1c (a marker of diabetes risk) and fibrinogen, an agent that helps the blood to clot. These three factors all play an important role in ‘metabolic syndrome’; the cluster of abnormalities that often heralds cardiovascular disease and diabetes. Other studies have found hints that alcohol might alter the balance of these factors for the better, which pointed to a possible mechanism by which alcohol in moderation could improve health.
Other studies have replicated this sweet-spot effect of alcohol for ischaemic stroke (strokes caused by a blood clot in the brain) and death in general. But before you dive out and prescribe yourself a couple of bottles a week – for your health, of course – you might want to read on.
Do abstainers actually have a higher risk of death than people who have one or two alcoholic drinks a day? It isn’t as straightforward as it looks.
In 2006, a team of researchers took a closer look at how these studies were designed. Their meta-analysis showed a major flaw in the way drinkers – or rather abstainers – were classified: the abstainers in many of these studies included people who had cut back or stopped drinking because of ill health or old age. This could potentially make non-drinkers look like a far less healthy group than the general population.
Importantly, the studies without this misclassification didn’t find a reduction in heart disease or death among moderate drinkers.
Other researchers have now explored this ‘misclassification hypothesis’ more closely, including a huge UK-based population study published this year.
It showed that when you simply compare alcohol consumption and health outcomes, you find a clear beneficial effect of moderate alcohol consumption. But if you take former drinkers out of the abstainers group, then the benefits don’t look so rosy – in fact, they all but disappear.
Meanwhile, another team of researchers studied people whose bodies cannot process alcohol properly – and therefore who generally don’t drink alcohol at all – and found those with this genetic marker had better cardiovascular health and a lower risk of coronary heart disease than those without it.
And then there’s the really bad news. Whatever the effects that alcohol does or doesn’t have on your heart disease risk, it can still hasten your death in a myriad of other colourful ways.
The World Health Organization reported last year that drinking can increase your risk of depression and anxiety, liver cirrhosis, pancreatitis, suicide, violence, and accidental injury.
Alcohol is also linked to cancer of the mouth, nose, larynx, oesophagus, colon, liver, and breast cancer in women. Between 4% and 30% of cancer deaths worldwide could be attributed to alcohol use (for breast cancer, the most common, the figure was 8%). Importantly, even moderate drinking confers some increased risk: just one glass a day increases the risk of breast cancer by 4%, while heavy drinking can increase the risk by 40-50%.
Heavy drinking weakens the immune system and is therefore linked with pneumonia and tuberculosis. It also encourages risky sexual behaviour which increases the chance of acquiring sexually transmitted infections such as HIV. And drinking during pregnancy can cause damage to the foetus, leading to Foetal Alcohol Syndrome.
In total, there are more than 200 diseases and injuries that can be linked to alcohol consumption, including 30 that are caused only by alcohol.
But the idea that moderate alcohol consumption might be beneficial has not entirely gone away, and even organisations dedicated to combating the problem of alcohol grudgingly say that small amounts of alcohol may have a protective effect against heart disease and some types of stroke.
Confused? You’re not the only one. Perhaps the best summation of how alcohol affects our health comes from a critical analysis published in early 2013. Its author concluded that, while the evidence of alcohol’s harmful effects was solid, there were plenty of reasons to take evidence of alcohol’s health benefits with a grain of salt – but not, perhaps, a slice of lemon.