The pros and cons of alcohol

This is an updated version of an article originally published in 2018

Even though alcohol has been a daily part of human existence for millennia, the substance is far from innocuous and in fact has very complex effects on health. This complexity is well illustrated by the J-shaped relationship between the quantity of alcohol consumed and the risk of premature death observed in a large number of epidemiological studies. One large-scale study, carried out among more than 300,000 people followed for nearly 10 years, shows that moderate alcohol consumption (3 to 14 glasses per week for men and 3 to 7 glasses for women) is associated with an approximately 20% lower risk of all-cause mortality compared to non-drinkers (Figure 1). This protective window is very narrow, however, with a rapid increase in mortality risk observed at higher quantities.

Figure 1. Relationship between alcohol consumption and the risk of premature death. The maximum risk reduction observed in the study (– 0.1 log) corresponds to a reduction of approximately 20% in risk. Adapted from Xi et al. (2017).

As a reminder, what is commonly considered a “glass” or a “standard drink” refers to the quantity of alcoholic drink that leads to the absorption of approximately 12 to 15 grams of pure alcohol (Table 1). The size of a glass therefore directly depends on the alcohol content of the drink consumed.

Table 1. Alcohol content of the main types of alcoholic beverages. Adapted from Educ’alcool.

However, the protective effect of low doses of alcohol on mortality has been called into question by a major study recently published in The Lancet. In this study, which analyzed the alcohol consumption habits of about 600,000 drinkers, the authors did not observe a decrease in mortality, even at low amounts of alcohol, but rather a significant increase in the risk of premature death starting at 100 g of alcohol per week, which only equals one drink per day (Figure 2A). In contrast, analysis of the same data revealed a lower risk of cardiovascular mortality, consistent with hundreds of studies that have observed a cardioprotective effect resulting from moderate alcohol consumption (Figure 2B). Nevertheless, the authors suggest that the amounts of alcohol that are currently recommended (1 drink daily for women, two for men) are too high and that these limits should be lowered. Another study, also published in The Lancet, draws similar conclusions, specifically that intake as low as only one glass per day is associated with an increased risk of developing one of the 23 pathologies associated with alcohol consumption, and, according to the authors, that there does not appear to be a safe level of alcohol consumption. Yet, as some experts have pointed out, this approach is a bit “absolutist”, since the increased risk observed at low amounts of alcohol was extremely low, going from 0.914 percent in non-drinkers to 0.918 in those who consumed one glass a day and to 0.977 for those who drank two glasses a day. Therefore, for moderate drinkers, the actual risk associated with alcohol consumption is for all intents and purposes negligible.

Figure 2. Relationship between alcohol consumption (in g per week) and the risk of premature all-cause mortality (A) or cardiovascular mortality (B) calculated from a synthesis of 83 epidemiological studies involving 600,000 participants. Adapted from Wood et al. (2018).

At this stage, it is difficult to say whether these recent studies are superior to previous ones and if moderate alcohol consumption is indeed devoid of any beneficial effects on mortality (see box). Each epidemiological study has its strengths and weaknesses, and the only true method to resolve this ambiguity would be to conduct a randomized clinical study where the health of moderate drinkers could be compared to that of non-drinkers, but such a study is not feasible due to ethical considerations. In any event, a cautious interpretation of all these studies is to state that the negative effects of alcohol should certainly not be trivialized, and that it is important to drink very moderately to take advantage of its potential benefits while avoiding its well-documented harmful effects (Table 2). Historically, the maximum amounts of alcohol considered to be associated with health benefits are 1-3 glasses per day for men and 1-2 glasses per day for women. At these low levels, alcohol increases HDL cholesterol levels, improves glycemic control, and has anticoagulant and anti-inflammatory properties, all of which contributes to reducing the risk of cardiovascular events, notably myocardial infarction. In light of the results of the two studies published in The Lancet, it would seem advisable to slightly lower these limits to 2 glasses a day for men and 1 glass a day for women.

Above these levels, however, consumption is clearly abusive, since it is associated with an increased risk of several cancers, in particular oral, laryngeal, esophageal, colon, liver and breast cancer. Chronic consumption of large quantities of alcohol is also associated with several cardiovascular diseases, including atherosclerosis, hypertension, some cardiomyopathies as well as arrhythmias, which considerably increase the risk of cardiovascular mortality. It should also be noted that binge drinking, where large amounts of alcohol can be consumed in a short amount of time, is also associated with several harmful effects, in particular a much higher risk of stroke.

Table 2. The different types of alcohol consumption. Adapted from Fernandez-Sola (2015). 

Alcohol is thus a formidable double-edged sword, and it is important to limit daily alcohol consumption to low levels, ideally a maximum of 2 glasses per day for men and 1 glass for women, and most likely a bit less.

Opt for red wine
Red wine is a complex beverage containing several milligrams of phenolic compounds (specifically resveratrol), which are extracted from grape skin during the fermentation process. These molecules have antioxidant, anti-inflammatory, antiplatelet, and vasodilator properties, which suggests that red wine could have more significant positive effects than those associated simply with the presence of alcohol.

One of the foremost examples of these benefits is the famous “French paradox”, where regularly drinking red wine would be responsible for the low incidence of coronary heart disease observed in France compared to other Western countries, despite a diet high in saturated fats. This beneficial effect is supported by a Danish study, which showed that the risk of premature death was three times lower in moderate red wine drinkers than in those who drink beer or spirits, and also by the results of other studies conducted in Northern California and in Eastern France.

Another argument in favour of choosing red wine is its lower impact on the risk of cancer, possibly due to its resveratrol content. In laboratories, this molecule has one of the most powerful anticancer effects in the plant world and could thus counteract the carcinogenic effect of alcohol. For example, a study showed that whereas the moderate consumption of alcoholic beverages other than wine increases the risk of oral cancer by 38%, this increased risk lowers to only 7% in red wine drinkers. A similar phenomenon is observed for lung cancer, where moderate wine consumption is associated with a reduced risk of this cancer, whereas consumption of beer and spirits increases the risk. It would therefore appear that the greatest decrease in mortality associated with red wine consumption observed in several studies is not only associated with a more pronounced protective effect on the risk of heart disease but also with a less harmful effect on the risk of cancer than other types of alcohol. This phenomenon was also observed in the study published in The Lancet mentioned above. When the authors examined mortality according to the type of alcohol consumed, they observed an enormous difference in risk between wine and other types of alcohol, with red wine consumption (up to 300 g per week) being associated with a slight 10% increase in mortality, which is much lower than that observed in beer and spirit drinkers (Figure 3).

Figure 3. Relationship between the type of alcohol consumed (in grams per week) and the risk of premature death. Adapted from Wood et al. (2018).

The superiority of red wine over other types of alcohol is also suggested by a recent study on the association between alcohol consumption and the risk of atrial fibrillation (AF), an arrhythmia that significantly increases the risk of stroke. In this study, the researchers observed that moderate alcohol consumption in general (7 glasses per week or less) was associated with a small decrease in the risk of AF, but that this risk increased significantly at higher amounts (14 glasses and more per week). However, when the same analysis was carried out taking into account the type of alcohol consumed, it was observed that the risk of AF did not increase in people who drank up to 14 glasses of red wine per week (Figure 4). White wine also seems to minimize the risk of AF, but to a lesser degree (increased risk starting at 10 glasses per week), while beer and spirits increase this risk very quickly, starting from about 3 glasses per week.

Figure 4. Relationship between the type of alcohol consumed (in standard drinks per week) and the risk of atrial fibrillation. Note that one drink is the British standard unit of 8 g (10 mL) of alcohol. The gray areas represent the 95% confidence intervals. Adapted from Tu et al. (2021).

Overall, these observations confirm the results of the INTERHEART study and those of the Åkesson group, which show that moderate consumption of alcohol represents one of the lifestyle factors that can contribute to a lower risk of coronary heart disease and early death. A recent study demonstrates to what extent the impact of lifestyle habits can be extraordinary: 50-year-olds who don’t smoke, have a healthy diet, do 30 minutes or more of daily physical activity, maintain a healthy weight (BMI between 19 and 25), and drink moderately (5-15 g/day for women, 5-30 g/day for men) have 82% less risk of dying from heart disease and 65% less risk of dying of cancer. In practice, this translates to a 14-year increase in life expectancy for women and 12 years for men! Thus, to truly be beneficial, alcohol consumption should be part of an overall healthy lifestyle, including a diet high in plant-based foods, regular physical activity, maintaining a normal body weight, and, of course, not smoking.