The effects of coffee on cardiovascular disease

The effects of coffee on cardiovascular disease

Updated on July 13, 2018

A recent study published in Nature Medicine suggests that coffee consumption may protect the heart and blood vessels due to the anti-inflammatory effect of caffeine. As we age, a slowing metabolism, combined with increased oxidative stress, causes the body to accumulate several inactive metabolites that are considered toxic to the immune system and activate the inflammatory response. Chronic inflammation is very harmful to the cardiovascular system, as it promotes the progression of several phenomena that damage the heart and blood vessels, such as atherosclerosis, hypertension and insulin resistance. Researchers have observed that people who regularly consume caffeinated drinks, particularly coffee, produce less of these inflammatory metabolites, have more elastic blood vessels, and are on average healthier.

These results are in line with several epidemiological studies showing that regular coffee consumption is associated with the reduced risk of cardiovascular disease and mortality in general. For example, a meta-analysis of studies involving 1,279,804 participants found that people who consumed a moderate amount of coffee (3 to 5 cups per day) were about 15% less likely to be affected by cardiovascular disease (coronary heart disease and stroke) than people who never drank coffee.

Several studies have also shown that coffee consumption is safe for people with established coronary heart disease. For example, a randomized clinical trial involving patients who had suffered a heart attack with acute ST-segment elevation (STEMI) showed that coffee consumption (4 to 5 cups per day, for a caffeine intake of 353 mg) did not cause arrhythmia and was not associated with any cardiovascular disorder. These observations are consistent with other studies showing that coffee consumption is not associated with the development of arrhythmias such as atrial fibrillation, and may even be associated with a decreased risk of such events.

Coffee also does not seem to have any major effects on blood pressure, although caffeine is known to stimulate the sympathetic nervous system. Studies show that, in individuals who never drink coffee, caffeine can indeed cause a short-term increase in blood pressure (by about 10 mm Hg), but the effect is transient and disappears completely in regular drinkers due to the phenomenon of tolerance. The absence of the long-term hypertensive effect of coffee was confirmed by a study involving 155,594 women showing that the regular consumption of coffee, even in high amounts (6 cups per day), is not associated with an increased risk of hypertension. However, the same study reported that the consumption of other sources of caffeine such as soft drinks (regular and diet) is associated with an increased risk of high blood pressure, suggesting that there are other compounds in coffee that may offset the effect of caffeine on blood pressure. Indeed, it is interesting to note that the intravenous administration of caffeine increases blood pressure even among regular coffee drinkers, while the consumption of the beverage itself has no impact. Overall, this data suggests that the neutral effect of coffee on blood pressure is due to the presence of molecules that reduce caffeine’s stimulation of the sympathetic nervous system. This is not surprising considering that coffee is not merely a source of caffeine, but rather a highly complex beverage containing more than a thousand distinct compounds, including several antioxidant and anti-inflammatory molecules.

Studies show that some of these molecules, such as chlorogenic acids and lignans, may also contribute to improving sugar metabolism and thus prevent type 2 diabetes. For example, an analysis of a dozen studies on the relationship between coffee consumption and the risk of type 2 diabetes shows that people who drank 4–6 cups a day were about 30% less likely to develop the disease compared to those who drank it very little or never. A prospective study involving 88,000 women aged 26 to 46 suggests that the protective effect of coffee may be even greater, and can be observed for smaller amounts of coffee, with a 13% and 42% reduction in risk for a daily consumption of 1 cup and 2–3 cups, respectively. These reductions are also observed for decaffeinated coffee, suggesting that, beyond caffeine, the molecules contained in this beverage can help maintain normal blood sugar levels.

Several recent studies also indicate that regular coffee consumption is associated with a decreased risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease, several types of cancer, particularly liver cancer, a decreased risk of recurrence in people who have been affected by hormone-dependent breast and colon cancer, a decreased risk of end-stage renal disease, and a decreased risk of premature death. Coffee’s long-standing reputation as unhealthy is therefore irrelevant. While it is notably appreciated for its stimulating properties, coffee is a drink that has many positive effects, not only for preventing cardiovascular disease but also on health in general.

Social isolation: An important risk factor for premature death

Social isolation: An important risk factor for premature death

Several studies have clearly shown that some psychological factors, such as stress anxiety, depression and the lack of adequate social relationships, have a negative impact on health and significantly reduce life expectancy. This close relationship between psychology and physiology is particularly well documented with regard to social relationships. Indeed, a large number of studies have shown that people who are more socially engaged are in overall better health and have a decreased risk of depression and a reduced rate of cognitive decline. Conversely, social isolation and solitude (see box below for the distinction between the two) increase the risk of premature death, an impact comparable to that of well-established risk factors such as obesity, physical inactivity, and even tobacco use.  For example, the data collected during studies conducted among a total of 308,849 subjects indicated that those who have adequate social relationships have a 50% lower risk of premature mortality compared to those who have unsatisfying social relationships, an impact comparable to smoking cessation. These results are in line with the data collected during the Harvard Study of Adult Development, which has been studying the factors involved in healthy aging, from both the physical and psychological point of view, since 1939. The main conclusion of this study, which has been ongoing for 75 years, is simple: quality personal relationships, whether with family or friends, are one of the most important predictive factors of a person’s happiness and good health throughout their life.

Social isolation and solitude: two distinct realities
Social isolation refers to a lack of interpersonal relationships. It is an objective parameter that can be measured by examining whether a person lives alone, their conjugal status, the size of their social network, and their participation in group activities. Social isolation is a particularly frequent problem in elderly people, when a decrease in economic resources, invalidity, or the death of family and friends contribute to reducing social contacts. Studies show that socially isolated individuals are at greater risk of heart diseaseinfectious diseases (such as colds), cognitive decline, and premature mortality. These increased risks are a result of the negative impact of social isolation on several physiological parameters, in particular an increase in blood pressure and fibrinogen levels (higher risk of developing blood clots) as well as the activation of inflammatory processes.

As for solitude, it can be viewed as the psychological counterpart of social isolation, i.e., it is not only the number of contacts that come into play, but mainly dissatisfaction regarding the quality of the social relationships a person maintains (frequency, intimacy). Thus, a person can suffer from solitude even when surrounded by people, and, conversely, someone can feel not alone even if they live in an isolated way. Studies show that solitude is associated with a disruption of several physiological processes, including increased blood pressurecortisol levels in the blood and inflammatory processes, as well as a higher risk of heart disease and premature mortality.

One of the main health problems resulting from social isolation and solitude is the increased risk of heart disease.  Epidemiological studies show that low social support is associated with an approximately two-fold increase of the risk of cardiovascular events and is a predictive factor for hypertensioncoronary heart disease and heart failure. In patients who have already suffered a myocardial infarction, studies show that low emotional and social support triples the risk of cardiovascular events and mortality, impacts comparable to those of other well-documented risk factors such as hypercholesterolemia, type 2 diabetes, and tobacco use.

Two main reasons explain this enormous influence of the social network on the risk of heart disease. First, social relationships can act as “stress buffers” that alleviate the negative impacts associated with difficult times in life (disease, bereavement, divorce, etc.). An adequate social network can offer structural and emotional support to the people affected by these ordeals, helping them better deal with the shock, and thus reducing the harmful physiological consequences resulting from chronic stress, in particular on the risk of heart disease.  Studies also show that individuals with a developed social network tend to be more physically active and adopt better lifestyle habits, which contributes to reducing the risk of heart disease and improving life expectancy. Socially active people are also more likely to receive better advice from their family and friends in the event of health problems and to quickly consult following an anomaly (chest pain, for example). Isolated people cannot count on this type of support due to the absence of someone they can trust in their circle, which contributes to a higher rate of premature death, in particular in those who present certain risk factors for heart disease.

However, the impact of the social network is not only psychological: it is now clearly proven that isolation is perceived by the body as a form of “aggression” and provokes the activation of physiological mechanisms involved in the stress response, such as the secretion of cortisol and adrenaline. For example, studies show that inadequate social relationships are associated with an increase in adrenaline levels in urine, a higher resting heart rate and an exaggerated increase in blood pressure and heart rate in response to stress, followed by a slower recovery. Socially isolated individuals are also more at risk of presenting lower heart rate variability (the interval between two heartbeats) and left ventricular hypertrophy, two risk factors of cardiovascular mortality.  Over time, all these effects of chronic stress damage the heart and blood vessels and would explain the marked increase in cardiovascular events observed in socially isolated people.

Studies suggest that social isolation could also foster the development of atherosclerosis, the process responsible for the formation of plaque on the artery walls. Studies conducted in the 50s on animals at the Philadelphia zoo showed that isolation of birds and mammals was associated with a ten-fold increase of atherosclerotic lesions in these animals. In humans, a study showed that some markers of a diminished social network (widowhood, celibacy) were associated with an increase of the degree of coronary artery calcification, a marker of atherosclerosis. It was also observed that low social support, combined with a tendency toward anger, greatly accelerates the progression of atherosclerosis plaques, which could contribute to a higher risk of cardiovascular events observed in people exhibiting hostile behaviour.

When we discuss the prevention of heart disease, what generally comes to mind is the importance of quitting smoking, adopting a healthy diet high in plant-based foods, exercising regularly, and maintaining a healthy body weight. These lifestyle changes are of course crucial, but the disastrous impact of inadequate social relationships on the risk of developing and dying from these diseases is a reminder that we cannot overlook the importance of psychosocial factors in any strategy intended to reduce their incidence. Especially since several current trends such as the aging of the population, high divorce rates, and the increasing number of people living alone (in Quebec, 1 out of 3 households were one person in 2011) can exacerbate social isolation and the feeling of solitude. The impending mass retirement of baby-boomers is another factor to consider, since several new retirees see their health rapidly decline following their departure from the workplace.  However, studies show that this risk can be considerably reduced by replacing the loss of work relationships by joining other groups (sports, cultural, political or other).  Several people turn to social media, in particular Facebook, to maintain a network of contacts, and a recent study suggests that this “virtual” social life can provide the same benefits as a “real” social life in terms of reducing the risk of premature death. Whatever shape it takes, it is certain that a dynamic, diversified social network is a major asset to living longer in good health and should be a basic element of life hygiene.  Indeed, in all the regions of the world recognized for the longevity of their inhabitants (Blue Zones), establishing a close-knit social fabric is part of the “secret” to a long life, on par with a healthy diet, regular physical activity, moderate alcohol consumption, and stress management.