People love to latch onto studies that match their confirmation bias, so studies claiming health benefits for red wine, chocolate and organic food get a lot of attention and not much skepticism about controls. Any epidemiology claim will do when it comes to finding benefit or harm.

A new review calls into question previous studies which suggest that consuming light-to-moderate amounts of alcohol (0.6-0.8 fluid ounces/day) may have a protective effect on cardiovascular health. Instead, they find that reducing the amount of alcoholic beverages consumed, even for light-to-moderate drinkers, is more likely to improve cardiovascular health, body mass index (BMI) and blood pressure. 

The authors reviewed evidence from over 50 studies that linked drinking habits and cardiovascular health for more than 260,000 people. Researchers found that individuals who carry a specific gene which typically leads to lower alcohol consumption over time have, on average, superior cardiovascular health records.

Specifically, the results show that individuals who consume 17 percent less alcohol per week have on average a 10 percent reduced risk of coronary heart disease, lower blood pressure and a lower body mass index.

"These new results are critically important to our understanding of how alcohol affects heart disease. Contrary to what earlier reports have shown, it now appears that any exposure to alcohol has a negative impact upon heart health," says co-lead author Michael Holmes, MD, PhD, research assistant professor in the department of Transplant Surgery at the Perelman School of Medicine at the University of Pennsylvania. "For some time, observational studies have suggested that only heavy drinking was detrimental to cardiovascular health, and that light consumption may actually be beneficial. This has led some people to drink moderately based on the belief that it would lower their risk of heart disease. However, what we're seeing with this new study, which uses an investigative approach similar to a randomized clinical trial, is that reduced consumption of alcohol, even for light-to-moderate drinkers, may lead to improved cardiovascular health."

In the new study, researchers examined the cardiovascular health of individuals who carry a genetic variant of the 'alcohol dehydrogenase 1B' gene, which is known to breakdown alcohol at a quicker pace.

This rapid breakdown causes unpleasant symptoms including nausea and facial flushing, and has been found to lead to lower levels of alcohol consumption over time. By using this genetic marker as an indicator of lower alcohol consumption, the research team was able to identify links between these individuals and improved cardiovascular health.

Citation: Holmes, et al., 'Association between alcohol and cardiovascular disease: Mendelian randomisation analysis based on individual participant data', BMJ July 10 2014 DOI: 10.1136/bmj.g4164. Source: University of Pennsylvania School of Medicine