When holiday shoppers recently went to their local liquor stores in search of some liquid spirit, many were instead greeted by the sight of increasingly barren shelves.
Although partly a result of global supply chain issues, this was also yet more evidence of the rising demand for alcohol among adults during these difficult COVID years. It's a trend that has led to concerns of an echo pandemic of alcohol-related morbidity, which has begun to play out in the form of rising rates of gastrointestinal and liver disease, hospital admissions for alcoholic hepatitis, and alcohol-related incidents of domestic violence.
Those who imbibe alcohol in low-to-moderate levels may not see themselves reflected in such stories of drinking's hefty tolls. They're instead following established health guidance that a little bit of alcohol now and then actually has robust health benefits. Yet the last couple of years have seen a notable fraying of this idea, as emerging data calls into question whether alcohol in moderation should really continue to be just what the doctor ordered.
Behind the Curve: Alcohol's Diminishing Cardioprotective Value
Perhaps the most resonant argument for the benefits of light-to-moderate alcohol consumption—usually defined as between 1 to 2 drinks a day—has been its proposed cardioprotective value. In this way, alcohol differs from tobacco, which is unsafe at any level. Alcohol's proposed cardioprotective effects are often represented as a J-shaped curve, with moderate drinking occupying the sweet spot between teetotaling and heavy/binge drinking when it comes to reduced mortality.
In reality, this association is more likely "a statistical artifact" largely derived from low-quality observational studies, according to Christopher Labos, MD, CM, MSc, an epidemiologist and cardiologist at the Queen Elizabeth Health Complex in Montreal, Canada.
"When you look at studies that correct for things like reverse causation, or the fact that some people who drink zero alcohol are former drinkers who used to drink alcohol, then you realize that the protective benefit of alcohol is either minimal or nonexistent and that alcohol does more harm than good to our society," said Labos, who detailed the reasons underpinning alcohol's unearned cardioprotective reputation in a 2020 Medscape commentary.
This statistical limitation was on display in July when BMC Medicine published results from meta-analyses suggesting that current drinkers need not stop consuming small amounts of alcohol for the secondary prevention of cardiovascular disease (CVD). The study's own investigators noted that it likely overestimated the reduced risk of CVD by including former heavy drinkers as nondrinkers.
Even if the J-shaped curve exists, its simplicity is deceiving. CVD risk increases alongside alcohol consumption owning to a complicated array of genetic and lifestyle factors. The curve also presents something of a catch-22. If you like alcohol enough to drink it every day, staying at the nadir of the curve where you'd gain the most benefits may prove challenging.
Another factor dimming alcohol's cardioprotective reputation came via recent data that atrial fibrillation episodes can be triggered by acute alcohol use. A randomized controlled trial published in the New England Journal of Medicine concluded that abstinence reduced arrhythmia recurrences in regular drinkers with atrial fibrillation.
"If we can replicate that, I think we'll find that reducing alcohol consumption might be a very effective to prevent and treat atrial fibrillation," said Labos.
However, J-curve proponents will note the publication this month of study data from the UK Biobank indicating that low levels of alcohol consumption confers the greatest reduction in atrial fibrillation risk.
An Overlooked Carcinogen No Longer
Surveys indicate that less than half of Americans realize alcohol increases cancer risk. That might have changed just a bit this year. In early 2021, an epidemiological analysis estimated that alcohol contributed to 4.8% of cancer cases and 3.2% of cancer deaths in the United States. Then this summer, Lancet Oncology published the results of a high-profile, population-based study on the global burden of cancer as a result of alcohol. Although the main take-away message was that 4% of new cancer cases worldwide in 2020 were attributable to alcohol, it was also noteworthy that moderate drinking accounted for 103,100 out of 741,300 of these projected annual cases.
"The risk of cancer increases even with low or moderate levels of drinking," said the study's lead author Harriet Rumgay, BSc, from the International Agency for Research on Cancer in Lyon, France. "Drinking less means you'll have a lower risk of cancer than if you drink heavily, but there is no safe limit of alcohol consumption."
The study linked alcohol consumption with an increased risk of at least seven different cancer types, including cancers of the oral cavity, pharynx, larynx, esophagus, colon, rectum, liver, and breast.
Although in North America men represented about two thirds of the burden of cancer due to alcohol, Rumgay added that, "low and moderate levels of drinking (one or two alcoholic drinks per day) contributed relatively more cancer cases among women than among men."
Yet more negative news for moderate alcohol drinkers arrived later in the summer, when a team of South Korean researchers published data showing that when it came to the risk of developing gastrointestinal cancers, even binge drinking may be preferrable to continuous but moderate consumption.
Perhaps the changing perception of alcohol's carcinogenic potential is best summed up by the American Cancer Society, who in updating their guidelines in 2020 after an 8-year interim offered this succinct piece of advice: "It is best not to drink alcohol."
Neurotoxic Implications
There has similarly been a reconsideration of the effects of moderate alcohol consumption on brain health.
A recent report of multi-modal MRI brain and cognitive testing data from over 25,000 participants in the UK Biobank study indicate that alcohol may have no safe dosage. Even moderate consumption reduced gray matter volume and functional connectivity, negative associations that were increased in those with higher blood pressure and body mass index.
Speaking with Medscape Medical News in May 2021, an investigator said, "The size of the effect is small, albeit greater than any other modifiable risk factor," noting that the changes have been linked to decreased memory and dementia.
Louise Mewton, PhD, from the Center for Healthy Brain Aging at the University of New South Wales in Sydney, Australia, said that these results provide an interesting comparison with others into the association between alcohol and dementia.
"A recent study of over 1 million dementia cases in France indicated that problematic alcohol use (alcohol use disorders) were one of the strongest risk factors for dementia — even more so than things like high blood pressure and diabetes," Mewton told Medscape. In comparison, "the most-recent reviews indicate that 4 drinks/week is associated with the lowest risk for dementia — so we're talking about very low levels of alcohol use in terms of maintaining brain health."
"Understanding why very small amounts of alcohol appear to be protective in terms of dementia but damaging when we look at brain scans is something that would be really interesting to unpack."
Mewton and colleagues recently published data suggesting that there are three periods when the brain might be particularly susceptible to alcohol's neurotoxic effects: gestation (from conception to birth), later adolescence (15-19 years), and older adulthood (over 65 years). Directing behavioral interventions to patients in these stages may therefore be beneficial.
And there's no time too soon to promote abstinence among those with alcohol use disorder, as brain damage is shown to still occur even in the immediate period after people cease drinking.
Although in one more argument for the J-shaped curve's relevance, data from the Massachusetts General Brigham Biobank recently indicated that moderate alcohol use, unlike low and heavy use, lowered both stress-related neurobiological activity and major adverse cardiovascular events.
Getting Patients to Reconsider Alcohol's "Benefits"
These new findings mean physicians will find themselves imparting a more nuanced message about the health impacts of moderate alcohol consumption than in prior years. To aid those efforts, cancer researcher Rumgay in France advised clinicians to consult a special issue of the journal Nutrients that features review articles of alcohol's impact on various health outcomes.
Rumgay also supports broader policy changes.
"There is some evidence that adding cancer warnings to alcohol labels, similar to those used on cigarette packages, might deter people from purchasing alcohol products and increase awareness of the causal link with cancer," she said. "But the most effective ways of reducing alcohol use in the population are through increasing the price of alcohol through higher taxes, limiting purchasing availability, and reducing marketing of alcohol brands to the public."
The neurologist Mewton recommends various interventions for patients who still find it difficult to curtail their drinking.
"For less severe, problematic use, things like cognitive behavioral therapy and motivational therapy are very effective in reducing alcohol consumption," she told Medscape.
For all the discussion about how the COVID-19 pandemic has exacerbated problematic drinking, it has also provided an opportunity for getting patients to reexamine their relationship to alcohol. A June 2021 Medscape article provided an overview of how patients are successfully incorporating alcohol alternatives into their lives.
And as the cardiologist Labos notes, emerging data on alcohol's negative effects probably won't be considered earth-shattering to most patients.
"Deep down, I think most people know that alcohol is not healthy, but it is part of our social culture and so we find ways to justify our own behavior," he told Medscape.
Labos suggests that clinicians reframe alcohol in their patients' minds for what it really is — "an indulgence that we shouldn't have too much of very often."
"Just like junk food, that doesn't mean we can't enjoy small amounts occasionally, but we have to stop presenting that it is good for us, because it isn't."
John Watson is a freelance writer in Philadelphia, Pennsylvania.
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Cite this: Last Call? Moderate Alcohol's Health Benefits Look Increasingly Doubtful - Medscape - Dec 22, 2021.
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