A lot of well-designed studies have found associations between moderate alcohol consumption and better health. Following large groups of people over time appears to show that those who imbibe about four to seven units – the range fluctuates across research – per week may live longer due to a lower likelihood of stroke and heart attacks and have a lower risk of developing cardiovascular disease, dementia, and diabetes.
Yet other research, like a massive review of nearly 600,000 drinkers from 19 high-income countries that was recently published in The Lancet, has yielded contradictory correlations with cardiovascular conditions, and many have established troubling links between even low levels of consumption and increased prevalence of several types of cancer.
As with any observational study on lifestyle, investigations into the benefits (or lack thereof) of modest boozing are limited by the inability of scientists to fully separate out the effects of other factors. One of the most significant hurdles is comparing drinkers to non-drinkers due to a phenomenon known as the “sick quitter”, wherein people who abstain from alcohol are doing so due to underlying health issues, so those who drink moderately seem to have better health outcomes. (The evidence on high levels of alcohol consumption are unequivocally negative.)
Hoping to finally shed some light on this perplexing issue, the US National Institutes of Health (NIH) supported and helped fund a randomized control trial – the only type of study that can show causation vs correlation – called the Moderate Alcohol and Cardiovascular Health Trial (MACH15).
MACH15 was slated to enroll 7,800 adults 50 years and older, from multiple continents, who were all at similarly high risk for cardiovascular disease and assign them to either drink roughly 15 g of ethanol – equivalent to one 5-oz glass of wine, one 12-oz beer, or one 1.5-oz shot of spirits – per day for six years, or to not touch a drop of alcohol for six years. At the endpoint, the rates of developing cardiovascular disease were going to be compared, thus confirming or refuting the theorized protective effect of alcohol.