The pros and cons of alcohol

The pros and cons of alcohol

Updated August 27, 2018

Even though alcohol has been a daily part of human existence for millennia, this substance is far from innocuous and in fact has very complex effects on health. This complexity is clearly evidenced by the J-shaped relationship between the quantity of alcohol consumed and the risk of premature death (Figure 1). Indeed, a meta-analysis of numerous studies conducted on this topic shows that daily consumption of small quantities of alcohol (2 glasses for men and 1 glass for women) is associated with a significant reduction (about 20%) of the risk of premature death compared to non-drinkers. However, this window of protection is very narrow: for example, a daily alcohol intake of about 30 g of alcohol by women, which corresponds to two glasses, is sufficient to cancel out almost all positive effects associated with alcohol. In higher quantities, the protective effect of alcohol disappears completely and gives way to a rapid increase of the risk of premature death. A more recent study conducted among 333,247 Americans yielded similar results, with a 20% decrease of the risk of all-cause mortality in light to moderate drinkers compared to people who have never had a drink.

Figure 1. Relationship between alcohol consumption and the risk of premature death. Adapted from Béliveau and Gingras, Les aliments contre le cancer (2nd edition), 2015.

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

Table 1. Standard alcoholic beverages and their alcohol content. Adapted from Educ’alcool

Type of alcoholic beverageOne standard drink equals:
Beer (5% alc/vol)340 mL (12 oz.)
Wine (12% alc/vol)140 mL (5 oz.)
Fortified wine (e.g. Port) (20% alc/vol)85 mL (3 oz.)
Spirits (40% alc/vol) 45 mL (1.5 oz.)

However, the protective effect of low levels 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 levels of alcohol, but rather a significant increase of the risk of premature death starting at 100 g of alcohol per week, which only equals one glass per day (Figure 2). According to the authors, these results suggest that the alcohol quantities that are currently recommended (1 glass per day for women, two for men) are too high and 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 a higher risk of developing any one of the 23 diseases associated with alcohol consumption, and, according to the authors, that there does not appear to be a safe level of alcohol consumption. Nevertheless, as some specialists have pointed out, this approach is a bit “absolutist”, since the increased risk observed at low levels of alcohol was extremely low, going from 0.914 per cent in non-drinkers to 0.918 in those that consumed one glass a day and to 0.977 in those who drank two glasses. 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 death, based on an analysis of 83 epidemiological studies among 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 studies and that moderate alcohol consumption is indeed devoid of any beneficial effects on mortality.  Each epidemiological study has its strengths and weaknesses, and the only true method to resolve this ambiguity is 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 quantities of alcohol considered to be associated with health benefits are 1 to 3 glasses per day for men and 1 to 2 glasses per day for women. At these low levels, alcohol increases levels of HDL cholesterol, improves glycemic control, and has anticoagulant and anti-inflammatory properties, all of which contribute to reducing the risk of a cardiovascular event, 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 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, oesophageal, 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 increases the risk of cardiovascular mortality. It should also be noted that binge drinking, where large quantities of alcohol are 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). 

Type of consumptionPure alcohol (g)Standard drinksEffect on health
< 20 g per day (men)
< 10 g per day (women)
1 glass
¾ glass
Moderate20-45 g per day (men)
10-30 g per day (women)
1-3 glasses
1-2 glasses
> 45 g per day (men)
> 30 g per day (women)
More than 3 glasses
More than 2 glasses
Binge drinking
> 60 g in one sitting4 glasses or moreNegative

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 a day for men and 1 glass for women, and more than 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 aDanish 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 thus 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 of mortality, which is much lower than that observed in those who drink beer and spirits (Figure 3).

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

Overall, these observations confirm the results of the INTERHEART study and those of the Akesson 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, eat healthy, 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.

Dark chocolate is good for the heart!

Dark chocolate is good for the heart!

Updated on February 11, 2019

Not only are plants important sources of vitamins, fibres and minerals but they also contain phytochemicals such as polyphenols that play a very important role in the positive effects of these foods on cardiovascular health. Among the thousands of distinct polyphenols found in nature, the family of flavonoids has received special attention in recent years because of its presence in a large number of plants (fruits, vegetables, nuts, legumes) and beverages (tea, coffee, red wine) that are part of our daily diet. The impact of these molecules on health appears to be particularly important, as population studies indicate that people with the highest flavonoid intake have a lower risk of stroke or coronary artery disease, effects that are accompanied by a decrease in cardiovascular mortality and overall mortality.

Cocoa and its by-products, especially dark chocolate, are exceptional sources of polyphenols (Table 1), in particular flavonoids, suggesting that regular consumption of cocoa products could be very positive for cardiovascular health.

Table 1. Polyphenol content of some foods and beverages. Adapted from Pérez-Jiménez et al. (2010).

FoodPolyphenol content
(mg/100 g or 100 mL)
Cocoa powder3448
Dark chocolate1664
Flax seeds1528
Black olives569
Coffee (filter)214
Red wine101
Green tea89

The first clue to this positive effect comes from Marjorie McCullough’s observations on the Kuna Indians of the San Blass Islands, an archipelago off Panama. These people are very large consumers of cocoa, which they use to prepare a beverage according to the traditional method of pre-Colombian civilizations. The Kuna drink about five cups of cocoa a day, which translates into a polyphenol intake of around 1800 mg per day, almost 10 times more than North Americans. These people are also distinguished for their very low blood pressure  (110/70 mmHg even at over 60 years old), despite a very high salt diet, and their low incidence of myocardial infarction and stroke. These characteristics are not of genetic origin, because the individuals who have left the island to live on the mainland see their blood pressure quickly increase. Among the lifestyle factors that may explain this difference, the most plausible is the drastic decrease in continental cocoa consumption, which is 10 times lower than among islanders. Therefore, it seems that cocoa polyphenols can have a real impact on cardiovascular health by lowering blood pressure and, at the same time, the risk of ischemic events such as heart attack or stroke that result from hypertension.

Several epidemiological studies have confirmed that high cocoa intake is indeed associated with a decrease in blood pressure and a reduction in the risk of cardiovascular disease and premature mortality. For example, a 15-year Dutch study of 500 people over the age of 65 found that those who consumed the most cocoa-based products had an average systolic pressure of 3.7 mm Hg and a marked reduction (50%) in the risk of cardiovascular mortality. These results have been confirmed by several randomized clinical trials where the consumption of dark chocolate, cocoa or cocoa-derived polyphenols is associated with a decrease in blood pressure and an improvement in endothelial function and insulin sensitivity. These vascular effects are largely due to an increase in the formation of nitric oxide (NO), a powerful vasodilator, by some cocoa flavonoids. A beneficial effect of cocoa consumption on the lipid profile (triglycerides, LDL and HDL cholesterol) and on the reduction of chronic inflammation has also been reported and could contribute to the benefits of dark chocolate for cardiovascular health.

These beneficial effects are also suggested by the results of a meta-analysis of 14 prospective studies conducted with a total of 508,705 participants, followed for a period of 5 to 16 years. The authors observed that people who consumed the most cocoa had a lower risk of coronary heart disease (10% decrease), stroke (16% decrease), and diabetes (18% decrease).

The most recent meta-analysis, which included 23 prospective studies with 405,304 participants, indicates that chocolate consumption is associated with a reduced risk of cardiovascular disease (CVD), if consumption is limited to less than 100 g/week. Those who consumed more chocolate had a 12% lower risk of CVD in general (stroke: -16.3%, myocardial infarction: -16.2%) than those who consumed little. However, the dose-response analysis (Figure 1) shows that at more than 100 g/week there is no longer any protective effect and that the risk of CVD increases at higher doses, which could be attributable to the harmful effect of consuming too much sugar. According to the authors of this meta-analysis, the best dose of chocolate to reduce the risk of CVD is 45 g/week (about half of a 100 g chocolate bar, a common size sold in grocery stores).

Figure 1. Dose-effect association between the consumption of chocolate and the risks of cardiovascular events. From Ren et al., Heart, 2019.

It is now clearly established that several risk factors for cardiovascular disease (hypertension, inflammation, insulin resistance, metabolic syndrome) also increase the risk of cognitive decline and dementia. Conversely, recognized factors to protect cardiovascular health, such as physical exercise or the Mediterranean diet, are associated with a significant decrease in the risk of cognitive disorders. In other words, what is good for the heart is also good for the brain, which raises the interesting possibility that the regular consumption of cocoa-based products can also result in benefits for cognitive function. Studies conducted to date support this, as a high intake of flavonoid-rich foods such as tea, red wine and chocolate is associated with reduced risk of cognitive decline and improved brain performance. In a study of people aged 65 to 82 who showed clinical signs of early cognitive decline, daily consumption of a beverage made with chocolate high in polyphenols was associated with significant improvement of cognitive functions.

More recently, a randomized clinical study showed that dark chocolate consumption was associated with a significant improvement in visual acuity and contrast sensitivity a few hours after intake, a positive impact possibly related to an improvement in blood circulation in the richly vascularized retina. Milk chocolate, which contains less polyphenols, has no effect, suggesting that flavonoids in cocoa are responsible for this improvement in vision.