Reducing chronic stress contributes to the positive effects of moderate alcohol consumption on the risk of cardiovascular disease

• Several studies have reported a significant reduction in the incidence of cardiovascular disease and premature mortality among people who consume low amounts of alcohol.
• A study using positron emission tomography (PET) brain imaging shows that this positive effect of light/moderate alcohol consumption is correlated with a decrease in activity in the amygdala, the region of the brain associated with stress responses.
• Since chronic stress is a well-documented risk factor for cardiovascular disease, reducing the activity of neurological pathways involved in the stress response could therefore contribute to the cardioprotective effects of low amounts of alcohol observed in epidemiological studies.

As we mentioned before, a very large number of epidemiological studies have reported a significant reduction in the risk of cardiovascular disease in people who drink alcohol moderately, i.e., 14 drinks or less per week. Compared to abstainers, a J-curve is typically observed, with a reduction in the risk of cardiovascular events and premature mortality at low alcohol consumption (≤ 1 drink per day for women, ≤ 2 drinks for men), followed by an increase in risk at higher consumption levels.

This cardioprotective effect of moderate alcohol consumption is systematically observed in the vast majority of studies, even those that report an increase in the risk of overall mortality at very low amounts of alcohol consumed. For example, a synthesis of 83 epidemiological studies involving 600,000 participants showed that consumption of 150 g per week of alcohol, which corresponds to approximately 10 drinks (i.e., a very moderate consumption), is associated with a slight but significant increase (approximately 4%) of the overall mortality risk. However, when the authors examine the causes of mortality separately, there was a decrease of about 5% in mortality from cardiovascular disease for the same quantities of alcohol. A similar phenomenon has been reported in other studies (see here, for example), and it therefore seems increasingly clear that alcohol, in low doses, has positive effects on the heart, different from those on the body in general. The J-curve where there is a decrease in mortality at low amounts of alcohol is therefore essentially attributable to the positive effect of these amounts of alcohol on cardiovascular mortality, since there is no protective effect on cancer and even, on the contrary, an increase in the risk of these diseases.

Anxiolytic effect
The cardioprotective effect of low doses of alcohol is generally attributed to a series of physiological changes favourable to cardiovascular health. The increase in HDL cholesterol, the reduction in the potential for thrombosis (formation of clots), the improvement in the effectiveness of the response to insulin, and the reduction in chronic inflammation caused by alcohol are all phenomena that may contribute to the reduction in the incidence of cardiovascular events observed in epidemiological studies.

Another facet of alcohol’s mode of action that could contribute to its positive effects on heart health is its relaxing action on the central nervous system. We have known for several years that psychosocial stress represents an important risk factor for cardiovascular disease, of a magnitude comparable to that associated with abdominal excess weight and hypertension, and it is therefore possible that the well-documented anxiolytic effect of alcohol can help reduce the cardiovascular risks of stress. In this sense, it should be noted that alcohol consumption is associated with a reduction in the activity of the amygdala, the area of the brain involved in the response to stressors. This effect is interesting because it was observed that the degree of amygdala activation is strongly associated with the risk of cardiovascular events.

To further explore this link between the relaxing effect of alcohol and cardiovascular health, a team of researchers from Yale and Harvard Universities used data collected by the Mass General Brigham Biobank, a database containing health information from 53,064 participants. The analysis first revealed that moderate alcohol consumption (1-14 drinks per week) was associated with an approximately 25% reduction in the risk of different types of cardiovascular disease (Figure 1), consistent with the cardioprotective effect of these relatively small amounts of alcohol documented by several studies. However, even at these doses, alcohol consumption has been observed to be associated with a significant increase in the risk of cancer (all types combined), again highlighting the difference between the effects of alcohol on the heart and the rest of the body.

Figure 1. Association between moderate alcohol consumption and risk of major cardiovascular events and cancer. The data represent the risk ratio observed for low-to-moderate alcohol consumption (1-14 drinks/week) vs. infrequent or no consumption (<1 drink/week). Note the significant drop in the risk of all cardiovascular events among moderate drinkers, including those affecting the coronary arteries (myocardial infarction, unstable angina, angioplasty), but also the notable increase in the overall risk of cancer. Adapted from Mezue et al. (2023).

The researchers then studied a subgroup of 754 people who had previously undergone brain imaging (positron emission tomography (PET)) to determine the effect of light/moderate alcohol consumption on stress-related neural network activity. Imaging results showed reduced activity in the amygdala (the region of the brain associated with stress responses) in people who drank moderately compared to those who never or very rarely drank or those who drank significantly more (>15 drinks per week) (Figure 2). Examination of the history of cardiovascular events affecting these individuals indicates that this reduction in stress observed in light to moderate drinkers is correlated with a reduction in the incidence of heart attacks and strokes in this population. This positive impact of reducing stress caused by moderate alcohol consumption is also suggested by the twofold reduction in the risk of cardiovascular events in people with a history of anxiety.

Figure 2. Variation in the activity of brain areas involved in stress according to the frequency of alcohol consumption. Stress-related neural network activity was determined by positron emission tomography (PET) by measuring ¹⁸ F-fluorodeoxyglucose uptake in the amygdala and ventromedial prefrontal cortex (a region influencing amygdala activity). The results represent the Z-score, i.e., the deviation of the values from the mean standard deviation. Note that the stress-related decrease in neural network activity is observed only in moderate drinkers. From Mezue et al. (2023).

Consumption patterns
These results suggest that, in addition to being moderate, alcohol consumption should ideally take place in a social context that promotes its anxiolytic effects. A good example is the Mediterranean consumption pattern, characterized by a moderate alcohol intake, preferably in the form of wine consumed with meals, and spread over the entire week, without episodes of excessive consumption. The conviviality of meals, as well as the pleasure of taking the time to cook and eat food, are also essential elements of the Mediterranean diet and ensure that meals are privileged moments of sociability and relaxation. Studies indicate that moderate alcohol consumption in this context represents one of the main elements involved in reducing the risk of mortality associated with the Mediterranean diet, which can reach almost 50% in people who adhere most strongly to this mode of alcohol consumption. In light of the results of the study discussed earlier, it is possible that this protective effect comes from the combination of physiological and psychological benefits (reduction of chronic stress) provided by moderate alcohol consumption on cardiovascular health (Figure 3).

Figure 3. Physiological and psychological factors involved in reducing the risk of cardiovascular events associated with moderate alcohol consumption. In addition to the well-documented positive effects of low-dose alcohol on several physiological parameters involved in the development of atherosclerosis and plaque rupture (left panel), Mezue et al. (2023) propose that the inhibitory action of alcohol on the amygdala simultaneously reduces chronic stress, which would contribute to its cardioprotective effect observed in epidemiological studies.

One of the most important aspects of the Mediterranean consumption pattern is certainly the distribution of consumption in small quantities throughout the week. Most studies on alcohol (including the most recent ones, which advocate almost total abstinence from alcohol) generally take into account the quantity of alcohol consumed per week, regardless of how it is ingested; however, drinking 7 drinks on Saturday evening and drinking nothing the rest of the week is clearly not equivalent to having one drink every day, even if the total quantity of alcohol consumed is the same. Studies show that this type of binge-drinking is associated with a marked increase in the risk of cardiovascular events (heart attack and stroke), while conversely, regular consumption of moderate quantities of alcohol three or more days per week substantially reduces the risk of heart attack and overall mortality.

Few substances exert such complex effects on the human body as alcohol, and this complexity is well reflected by the conflicting messages surrounding the dangers and benefits associated with the consumption of alcoholic beverages. However, an unbiased analysis of the data accumulated over the last few years provides a clearer picture. On the one hand, it is indisputable that in large quantities, alcohol is harmful to health, both physical and psychological, and it is important to raise awareness about the dangers posed by excessive alcohol consumption. On the other hand, these dangers should not obscure the fact that a very large number of studies have also clearly shown that moderate alcohol consumption offers significant cardiovascular benefits, associated with a substantial reduction in the risk of premature mortality. For people who drink, it is therefore possible to take advantage of these benefits, while avoiding most of the bad sides of alcohol, by adopting a moderate drinking pattern, which optimizes its positive physiological and psychological effects on cardiovascular health. Based on current knowledge, the consumption of 1-2 glasses per day, ideally in the form of wine with meals, combined with a diet rich in plants, regular physical activity, maintaining a normal body weight, and not smoking represents the best combination known to date for increasing healthy life expectancy.