A summary paper on the effects of alcohol consumption on biologic mechanisms associated with coronary heart disease provides an excellent review of a large number of intervention studies in humans. Appropriate analyses were done and the results are presented in a very clear fashion, although there was little discussion of the separate, independent effects of alcohol and polyphenols on risk factors.
The trials the authors reviewed have demonstrated that the moderate intake of alcoholic beverages leads to increases in HDL-cholesterol (good cholesterol), apolipoprotein A1, and adiponectin and decreases in fibrinogen, all factors associated with a lower risk of heart disease. The findings described in this paper strengthen the case for a causal link between alcohol intake and a reduced risk of coronary heart disease, suggesting that the lower risk of heart disease observed among moderate drinkers is caused by the alcoholic beverage itself, and not by other associated lifestyle factors.
The reviewers independently selected studies that examined adults without known cardiovascular disease and that compared fasting levels of specific biological markers associated with coronary heart disease after alcohol use with those after a period of no alcohol use (controls). A total of 4,690 articles were screened for eligibility, the full texts of 124 studies reviewed, and 63 relevant articles selected. Of 63 eligible studies, 44 on 13 biomarkers were meta-analysed in fixed or random effects models. Quality was assessed by sensitivity analysis of studies grouped by design. Analyses were stratified by type of beverage (wine, beer, spirits).
The authors concluded that favourable changes in several cardiovascular biomarkers (higher levels of high density lipoprotein cholesterol and adiponectin and lower levels of fibrinogen) provide indirect pathophysiological support for a protective effect of moderate alcohol use on coronary heart disease.
There have been thousands of basic science studies showing that administering alcohol or wine to laboratory animals results in beneficial effects on the risk of atherosclerosis and heart disease. The present excellent paper summarizes what are now a large number of human trials testing whether wine and/or alcohol have the same effects on reducing risk factors for CVD. There have not yet been randomized clinical trials to evaluate the effects of alcohol administration on cardiovascular outcomes such as myocardial infarction, cardiac death, or other cardiovascular diseases (CVD) in humans. It is unlikely that such studies will be done because of the long time of follow up required, the huge cost, and the difficulties in getting a very large number of people randomly assigned to agree to consume a specified amount of alcohol, or agree to avoid all alcohol, for many years. For these lifestyle habits, we must use our best judgment based on carefully done observational studies, research into potential mechanisms of effect, and studies of intermediate outcomes that are in pathways and processes in the development of the disease.
The second paper (Reference: Ronksley PE, Brien SE, Turner BJ, Mukamal KJ, Ghali WA. Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis. BMJ 2011;342:d671; doi:10.1136/bmj.d671 ) looked at cohort studies on the association between alcohol consumption and overall mortality from cardiovascular disease, incidence of and mortality from coronary heart disease, and incidence of and mortality from stroke. 4,235 studies were reviewed for eligibility, quality and data extraction, 84 were included in the final analysis.
Dose-response analysis revealed that the lowest risk of coronary heart disease mortality occurred with 1