Following last week's Has the WHO lost its way regarding alcohol?, we're pleased to republish another helpful commentary on the scientific evidence regarding alcohol and health. Written by Kenneth Mukamal and Eric B Rimm, this article originally appeared in Harvard Public Health magazine. Subscribe to their newsletter.
It's all more nuanced than headlines (including this one) suggest
It’s hard to escape the message these days that every sip of wine, every swig of beer is bad for your health. The truth, however, is far more nuanced.
We have been researching the health effects of alcohol for a combined 60 years. Our work, and that of others, has shown that even modest alcohol consumption likely raises the risk for certain diseases, such as breast and esophageal cancer. And heavy drinking is unequivocally harmful to health. But after countless studies, the data do not justify sweeping statements about the effects of moderate alcohol consumption on human health.
Yet we continue to see reductive narratives, in the media and even in science journals, that alcohol in any amount is dangerous. Earlier this month, for instance, the media reported on a new study that found even small amounts of alcohol might be harmful. But the stories failed to give enough context or probe deeply enough to understand the study’s limitations – including that it cherry-picked subgroups of a larger study previously used by researchers, including one of us, who concluded that limited drinking in a recommended pattern correlated with lower mortality risk.
Those who try to correct this simplistic view are disparaged as pawns of the industry, even when no financial conflicts of interest exist. Meanwhile, some authors of studies suggesting alcohol is unhealthy have received money from anti-alcohol organisations.
We believe it’s worth trying, again, to set the record straight. We need more high-quality evidence to assess the health impacts of moderate alcohol consumption. And we need the media to treat the subject with the nuance it requires. Newer studies are not necessarily better than older research.
It’s important to keep in mind that alcohol affects many body systems – not just the liver and the brain, as many people imagine. That means how alcohol affects health is not a single question but the sum of many individual questions: how does it affect the heart? The immune system? The gut? The bones?
As an example, a highly cited study of one million women in the United Kingdom found that moderate alcohol consumption – calculated as no more than one drink a day for a woman – increased overall cancer rates. That was an important finding. But the increase was driven nearly entirely by breast cancer. The same study showed that greater alcohol consumption was associated with lower rates of thyroid cancer, non-Hodgkin lymphoma, and renal cell carcinoma. That doesn’t mean drinking a lot of alcohol is good for you – but it does suggest that the science around alcohol and health is complex.
One major challenge in this field is the lack of large, long-term, high-quality studies. Moderate alcohol consumption has been studied in dozens of randomised controlled trials, but those trials have never tracked more than about 200 people for more than two years. Longer and larger experimental trials have been used to test full diets, like the Mediterranean diet, and are routinely conducted to test new pharmaceuticals (or new uses for existing medications), but they’ve never been done to analyse alcohol consumption.
Instead, much alcohol research is observational, meaning it follows large groups of drinkers and abstainers over time. But observational studies cannot prove cause-and-effect because moderate drinkers differ in many ways from non-drinkers and heavy drinkers – in diet, exercise and smoking habits, for instance. Observational studies can still yield useful information, but they also require researchers to gather data about when and how the alcohol is consumed, since alcohol’s effect on health depends heavily on drinking patterns.
For example, in an analysis of over 300,000 drinkers in the UK, one of us found that the same total amount of alcohol appeared to increase the chances of dying prematurely if consumed on fewer occasions during the week and outside of meals, but to decrease mortality if spaced out across the week and consumed with meals. Such nuance is rarely captured in broader conversations about alcohol research – or even in observational studies, as researchers don’t always ask about drinking patterns, focusing instead on total consumption. To get a clearer picture of the health effects of alcohol, researchers and journalists must be far more attuned to the nuances of this highly complex issue.
One way to improve our collective understanding of the issue is to look at both observational and experimental data together whenever possible. When the data from both types of studies point in the same direction, we can have more confidence in the conclusion. For example, randomised controlled trials show that alcohol consumption raises levels of sex steroid hormones in the blood. Observational trials suggest that alcohol consumption also raises the risk of specific subtypes of breast cancer that respond to these hormones. Together, that evidence is highly persuasive that alcohol increases the chances of breast cancer.
Similarly, in randomised trials, alcohol consumption lowers average blood sugar levels. In observational trials, it also appears to lower the risk of diabetes. Again, that evidence is persuasive in combination.
As these examples illustrate, drinking alcohol may raise the risk of some conditions but not others. What does that mean for individuals? Patients should work with their clinicians to understand their personal risks and make informed decisions about drinking.
Medicine and public health would benefit greatly if better data were available to offer more conclusive guidance about alcohol. But that would require a major investment. Large, long-term, gold-standard studies are expensive. To date, federal agencies like the National Institutes of Health have shown no interest in exclusively funding these studies on alcohol.
Alcohol manufacturers have previously expressed some willingness to finance the studies – similar to the way pharmaceutical companies finance most drug testing – but that has often led to criticism. This happened to us, even though external experts found our proposal scientifically sound. In 2018, the National Institutes of Health ended our trial to study the health effects of alcohol. The NIH found that officials at one of its institutes had solicited funding from alcohol manufacturers, violating federal policy.
It’s tempting to assume that because heavy alcohol consumption is very bad, lesser amounts must be at least a little bad. But the science isn’t there, in part because critics of the alcohol industry have deliberately engineered a state of ignorance. They have preemptively discredited any research, even indirectly, by the alcohol industry – even though medicine relies on industry financing to support the large, gold-standard studies that provide conclusive data about drugs and devices that hundreds of millions of Americans take or use daily.
Scientific evidence about drinking alcohol goes back nearly 100 years – and includes plenty of variability in alcohol’s health effects. In the 1980s and 1990s, for instance, alcohol in moderation, and especially red wine, was touted as healthful. Now the pendulum has swung so far in the opposite direction that contemporary narratives suggest every ounce of alcohol is dangerous. Until gold-standard experiments are performed, we won’t truly know. In the meantime, we must acknowledge the complexity of existing evidence – and take care not to reduce it to a single, misleading conclusion.