Alcohol and coronary artery disease

Heart attack and other forms of coronary artery disease lead to nearly 500,000 deaths annually, which is 25% of the total number of deaths in the United States [2]. Study results reveal a relationship between moderate alcohol consumption1 and a lower risk of coronary artery disease. The presented issue of Alcohol Alert reviews epidemiological data on this relationship and analyzes the significance of lifestyle and physiological mechanisms that could explain the clear prophylactic effect of alcohol, and presents available data on the balance between the harmful and beneficial effects of alcohol on health.

Epidemiological data
Epidemiological data from at least 20 North American, European, Asian and Australian countries show – with a few exceptions – a 20 to 40% lower prevalence of coronary artery disease in drinkers compared to non-drinkers. Among moderate drinkers, lower coronary artery disease mortality rates are noted than for both heavy drinkers and abstainers. These types of studies include both comparisons of country-wide population data and retrospective analyzes of health status and drinking patterns in communities.

The most convincing epidemiological data on the possibility of alcohol prevention of coronary heart disease come from prospective studies, where participants provide information about their drinking habits and health behaviors before falling ill. Later health status of the respondents is assessed during a series of interviews conducted as part of further stages of the research program.

Large-scale prospective studies confirm the relationship between moderate drinking and a lower risk of coronary artery disease. The detailed studies described here were conducted on a representative sample of over a million men and women of different ethnic origin. The research programs covered an average of 11 years2; the longest – 24 years – research on coronary mortality conducted in Framingham (Framingham CHD mortality study). The two largest studies of this type were conducted by the American Cancer Society – one on a sample of 276,800 men, and the next on a sample of 490,000 men and women.

Examples of other extensive prospective studies regarding the relationship between moderate alcohol consumption and a lower risk of coronary artery disease are a series of studies analyzing cases of hospitalization in coronary artery disease and mortality rates for this disease in both men and women women; research on the prevalence of coronary artery disease and mortality among nurses; studies on the prevalence of coronary artery disease and mortality among male physicians.

The results of these American studies confirm data from similar studies conducted in England, Denmark, China and other countries. In addition, shorter studies – covering a period of 12 years – found a link between moderate drinking and a lower risk of coronary heart disease in older people (mean age 69) who had diabetes later in life – a high-risk population of coronary artery disease. However, recent prospective studies in Scotland over 21 years in a sample of 6,000 working men aged 35-64 showed no correlation between moderate drinking and a lower risk of coronary heart disease: addiction recovery guides.

Is the role of alcohol causal or accidental?
The relationship between moderate drinking and a lower risk of coronary artery disease may not necessarily mean that alcohol alone reduces the risk. For example, a review of population studies indicates that a higher risk of death among abstainers can be attributed to common features other than non-consumption of alcohol by subjects.

A significant number of collected data [1] does not take into account the fact that amongst abstainers there may be a large percentage of people who drink heavily in the past and who previously had health problems. Nevertheless, health-related lifestyle elements correlating with the level of alcohol consumption could be relevant for some relationships between alcohol and a lower risk of coronary artery disease [4]. Exercise and nutrition are among the best studied factors of this type.

Few studies took into account the level of physical activity of the subjects, despite evidence that exercises prevent coronary artery disease and death. In a full review of published papers, Berlin and Colditz concluded that the risk of coronary artery disease is proportionally lower with higher levels of physical activity. The level of activity was measured in various ways. The research assessed factors such as performing professional work, the frequency of participation in any sports activities, estimated effort put into a given type of activity, calculation of energy expenditure and tests of cardiovascular fitness.

The results of social surveys showed that regular exercise is more common among moderate and heavy drinkers than among non-drinkers. Regular physical exercise has been defined as a form of physical activity not related to work, undertaken at least three times a week. The role of physical exercise regarding the relationship between alcohol and coronary artery disease requires additional research.

Diet is one of the factors most strongly affecting mortality from coronary artery disease among men aged 50 to 70. International comparisons, laboratory data and prospective studies suggest that a diet high in saturated fat and cholesterol increases the risk of coronary artery disease. Epidemiological data suggest that moderate drinkers may consume less fat and cholesterol – potentially partially responsible for the risk of alcohol-related coronary heart disease – than heavy drinkers and abstainers. However, the results of other prospective studies show that the association of alcohol with a lower risk of coronary artery disease is independent of nutrition.

The role of choosing an alcoholic drink
The results of some studies indicate that at the same level of alcohol consumption, especially red wine, it prevents coronary heart disease more than beer or high-percentage alcohol. These data suggest that the relationship between alcohol consumption and risk of coronary artery disease may be due to the effects of beverage ingredients other than alcohol alone. Epidemiological and laboratory research on this hypothesis have yielded conflicting results.

Comparison of data from 21 highly developed countries showed that the consumption of wine is much more correlated with a lower risk of coronary heart disease than the consumption of other alcoholic beverages. However, in extensive prospective studies, no differences were found in the incidence of coronary artery disease associated with the type of drink. Red wine has been found to contain some non-alcoholic ingredients that could hypothetically impede the development of coronary artery disease. However, the study did not show a significant role of these substances in inhibiting the progression of coronary artery disease in humans.

The data indicate that the preference for wine over other alcoholic beverages is associated with a lifestyle that includes other practices that are beneficial to health. For example, people who prefer wine generally smoke less and drink less and follow a healthier diet than those who prefer beer or spirits.

How could alcohol lower the risk of coronary artery disease?
The muscular tissue, from which the heart is mainly built, needs a constant supply of oxygen-containing blood for normal functioning. Blood is delivered to the heart muscle through the arteries forming a kind of wreath. Cholesterol and other fatty substances can accumulate in them, thus hindering blood flow. This condition underlies the clinical manifestations of coronary artery disease ranging from chest pain to sudden death. The most common serious symptom of coronary artery disease is myocardial infarction. The infarction is generally caused by a blood clot forming in a narrowed artery that blocks blood flow and deprives the heart of a portion of oxygen. This weakening of the heart’s ability to pump blood can cause permanent disability or death – either immediately or as a result of progressive health complications.

Researchers have put forward several theories explaining how alcohol alone can reduce the risk of coronary artery disease. For example, alcohol can protect the heart by preventing arterial narrowing, preventing a blood clot from forming and accelerating recovery after a heart attack. Most of the data confirming the potential effect of these mechanisms comes from experiments carried out on animals or using cells isolated from the walls of the artery and grown in the laboratory. To confirm that the phenomena observed in this type of research may affect the progression of coronary artery disease in humans, controlled clinical experiments should be performed.

Laboratory results show that alcohol administration can help prevent arterial constriction in mice. This effect could result from a change in the blood concentration of certain fatty substances that affect cholesterol build-up in the arteries. However, studies in humans and animals indicate that the change in the level of fatty substances explains, at most, half the reduction in the risk of coronary artery disease resulting from alcohol consumption. Therefore, researchers are looking for an additional explanation for the clear preventive effect of alcohol.

Alcohol can help prevent a blood clot from forming in already narrowed coronary arteries. Blood clots appear partly due to the penetration of chemicals from the artery wall into the blood. Exposure of these cells to alcohol in laboratory conditions causes a decrease in the production of substances that contribute to the formation of blood clots and stimulates the production and activity of substances that stop the formation of blood clots. In addition, analysis of blood samples taken from volunteers showed that drinking alcohol increases the level of substances that prevent blood clots and lowers the “stickiness” of specialized blood cells (i.e. platelets), which form clots when grouped – online rehab services.

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