Which is healthier? Dry January or year-round moderation? A new study out of Harvard University's T.H. Chan School of Public Health has found that adherence to a healthy lifestyle, including moderate alcohol consumption, exercising, eating a healthy diet and not smoking, is associated with a longer life expectancy.
For the study, published in The BMJ, Harvard professor of nutrition and epidemiology Dr. Frank Hu and a team of researchers from Chicago, Switzerland, the Netherlands and China analyzed data from the 34-year Nurses' Health Study (NHS) and 28-year Health Professionals Follow-Up Study (HPFS), which together collected health information on nearly 112,000 participants, specifically health professionals.
The NHS cohort consisted of female nurses ages 30 to 55, while the HPFS group was male health professionals ages 40 to 75. Questionnaires were sent out every two years to gather health information. The researchers looked at rates of three chronic diseases—diabetes, cardiovascular disease and cancer—and also tracked five lifestyle factors—smoking, body mass index (BMI), regular moderate to vigorous physical activity, moderate alcohol intake and quality of diet.
"Based on human data and long-term studies, moderate drinking as a practice has a lower risk of developing heart disease, diabetes and can enhance cognitive function," Harvard associate professor of nutrition and study co-author Dr. Qi Sun told Wine Spectator. "That's why we consider moderate drinking one of the five low-risk factors in the study."
The results were promising for moderate drinkers. "When we included only four lifestyle factors without alcohol, women who adhered to all four low-risk lifestyle factors had 9.5 years' (men: 8.8 years) longer life expectancy free of the major chronic diseases than those with none of these factors," the authors write. "After further inclusion of moderate alcohol consumption, women who adhered to all five low-risk factors had 12.5 years' (men: 9.6 years) longer life expectancy free of the major chronic diseases than those with none of these factors."
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Additionally, the study found a significant correlation between alcohol intake and serum high-density lipoprotein cholesterol (HDL). "It's fair to say HDL is good cholesterol and moderate drinking is associated with higher levels of it," said Dr. Sun. As expected, heavy smokers and obese men and women had the lowest life expectancy free of cancer, cardiovascular disease or diabetes.
Every study that relies on self reporting and questionnaires has limitations. Dr. Sun is cautious about the study's ability to be generalized and emphasizes being conservative with the results. Also, the data comes almost entirely from white professionals, but Dr. Sun argues that the data suggests this would be a healthy lifestyle for other populations as well.
The team defined moderate alcohol intake by U.S. guidelines as one drink a day for women and two for men. But one co-author, Harvard epidemiology and nutrition professor Dr. Eric Rimm, says he believes the "greatest evidence shows moderate drinking three to five days a week or every other day to be most beneficial."
While the researchers did not establish whether moderate drinkers lived longer because of alcohol consumption or because of other factors, their findings add to the growing evidence supporting moderate alcohol consumption's positive impact on longevity.
The study comes at a time when some Americans are taking a break from their usual tipple for Dry January. Dr. Sun argues that science has not determined yet whether going sober for a month has any negative or positive effects on health, but suggests it may be a good choice for heavy drinkers. Both Dr. Sun and Dr. Rimm firmly agree that there is a link between moderate alcohol consumption and greater life expectancy, when it is part of a healthy lifestyle.