Numerous objective research studies have shown that people who drink moderate amounts of alcohol have less risk for cardiovascular disease (CVD) compared with heavy drinkers and even nondrinkers. But, as researchers are quick to point out, association does not prove causation. That is to say, having a couple of drinks per night may not necessarily prevent a heart attack.
The only way to scientifically determine whether moderate alcohol consumption (up to 2 drinks per day for men and up to 1 drink per day for women) truly prevents or causes disease would be to perform a long-term, randomized, clinical trial. A trial of such magnitude would be difficult to accomplish—it would be very expensive and logistically complex.
Yet, such a trial began enrolling subjects in February 2018. However, the trial was suspended just three months later, in May 2018, effectively shutting it down.
The study—the Moderate Alcohol and Cardiovascular Health (MACH) trial—was designed to enroll 7,800 participants from about 20 clinical sites worldwide. Participants were to be randomized to consume one daily serving of alcohol (approximately 15 g) or to have no alcohol intake for an average of 6 years. The researchers hoped to evaluate the effects of alcohol and abstention on the rates of new cases of CVD among participants.
To fund this large undertaking, the National Institute of Alcohol Abuse and Alcoholism promised to commit $20 million. Another $67.7 million was to come from private donors. This is where the trial’s problems began. Those donors were all major alcohol beverage companies—Anheuser-Busch InBev, Carlsberg Breweries, Diageo, Heineken, and Pernod Ricard.
On March 17, 2018—St. Patrick’s Day—just a month after the study began in earnest, The New York Times reported that MACH investigators had met with and solicited donations from companies in the alcohol industry to fund the research. Within days, the director of the National Institutes of Health (NIH), Francis S. Collins, MD, PhD, called for an investigation of the funding.
On June 15, these investigators concluded: “The early and frequent engagement with industry representatives calls into question the impartiality of the process and thus, casts doubt that the scientific knowledge gained from the study would be actionable or believable.” On the same day, Dr. Collins announced the NIH’s withdrawal from the study.
But, despite the apparent conflict of interest in funding the MACH trial, a valid question remains: Does moderate alcohol intake prevent CVD?
Another large, randomized clinical trial will be needed to definitively answer that question.
In the meantime, a recent analysis of 83 prospective cohort studies found that a safe limit for alcohol consumption is no more than 100 g—about 5 or 6 drinks—per week (which is about half of the recommended limit in the United States). Drinking more was associated with lower life expectancy. For example, 10 or more drinks per week was linked with 1 to 2 years shorter life expectancy, and 18 or more drinks per week was linked with 4 to 5 years reduced life expectancy.
The analysis, published recently in The Lancet, included individual participant data on nearly 600,000 current drinkers, which was sufficiently powered to show associations for different subtypes of CVD. The researchers found that any amount of alcohol consumption was associated with a higher risk for stroke, heart failure, fatal aortic aneurysms, fatal hypertensive disease, and heart failure—there was no minimal amount that provided a benefit.
But they also found that drinking more than 100 g of alcohol per week was linked with a lower risk for nonfatal heart attacks. (The research was funded by government and research agencies in the United Kingdom, with no industry donors.)
“Alcohol consumption is associated with a slightly lower risk of nonfatal heart attacks but this must be balanced against the higher risk associated with other serious—and potentially fatal—cardiovascular diseases,” said lead author Angela Wood, PhD, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK. “If you already drink alcohol, drinking less may help you live longer and lower your risk of several cardiovascular conditions.”
These results support further lowering the limits of alcohol consumption in most current guidelines, the researchers concluded.