This article originally appeared on Health.
It’s long been reported that moderate drinking—defined as one drink a day for women and two a day for men—can protect against cardiovascular disease. And according to several large studies, moderate drinkers have healthier hearts than their teetotaling peers.
But a comprehensive new review of existing research suggests that alcohol is unlikely to be responsible for these heart-health benefits. According to the review, published in the Journal of Studies on Alcohol and Drugs, it’s more plausible that people with existing health issues tend to stop drinking, while healthy older adults continue on with their daily habit—thereby skewing the results of those often-cited studies.
Meanwhile, another review published today highlights a very real downside of drinking, even in moderation: For women, just one small glass of alcohol a day increases breast cancer risk, says a new report from the American Institute for Cancer Research (AICR) and the World Cancer Research Fund (WCRF).
This report, published on AICR’s website as part of its Continuous Update Project, looked closely at how various aspects of diet and exercise affect breast cancer odds. Based on its findings, the AICR estimates that one in three breast cancer cases in the United States could be prevented “if women did not drink alcohol, were physically active, and stayed a healthy weight.”
If you enjoy a glass of wine with dinner or relaxing over happy-hour drinks after work, this news is kind of a bummer. But what does it really mean for the average American woman? We decided to take a closer look at these two reports and see what experts have to say.
Heart-health benefits may be “wishful thinking”
The new review on drinking and heart disease looked at 45 previous studies, all of which followed people for a number of years. Overall, people who identified as moderate drinkers did, in fact, have a lower rate of heart disease than non-drinkers.
But when the reviewers looked at individual studies, they found that those that began tracking people’s drinking habits at age 55 or earlier did not suggest a protective effect. Neither did studies that rigorously accounted for people’s health at the start of the tracking period.
According to the authors, these findings suggest that abstainers are less healthy than moderate drinkers—but that may be why they stopped drinking in the first place. “We know that people generally cut down on drinking as they age, especially if they have health problems,” stated co-author Tim Stockwell, PhD, director of the Centre for Addictions Research at the University of Victoria, in a press release.
“People who continue to be moderate drinkers later in life are healthier,” he added. “They’re not sick or taking medications that can interact with alcohol.”
A second study published in the same journal supported this idea, showing that most people who identified as non-drinkers at age 55 had given up alcohol at some point; very few had been lifelong abstainers. The non-drinkers in that study—which included more than 9,000 British men and women—also tended to have worse physical and mental health, compared to those who drank moderately and did not smoke.
In the press release, Stockwell said that the idea that one or two drinks a day is good for us “may just be wishful thinking,” and that no one should drink solely because they think it will help prevent disease.
Yet he doesn’t go as far as to suggest that people who enjoy alcohol in moderation should stop, and says that “the risks of low-level drinking are small.” Future studies should take prior-drinking habits and other health conditions into account, the review concludes, so that researchers can better determine the true effects of alcohol on heart disease and other health risks.
But the increased breast-cancer risk is real
One of those other health risks appears to be a higher likelihood of breast cancer. The new AICR/WCRF paper analyzed 119 previous studies, which looked at a total of 12 million women and 260,000 cases of breast cancer, in the first review of its kind since 2010.
It found “strong evidence” that drinking the equivalent of a small glass of wine or beer boosts pre-menopausal breast cancer risk by 5% and post-menopausal risk by 9%. A “small” glass has about 10 grams of alcohol; that’s even less than a standard drink, which contains 14 grams of alcohol—in other words, a 12-ounce can of beer or 5-ounce glass of wine.
Susan K. Boolbol, MD, chief of breast surgery at Mount Sinai Beth Israel Hospital in New York City, says this is “major news.” The link between alcohol and breast cancer has been long established, she says, but until now it was unclear exactly how much alcohol would raise a woman’s odds.
“Some of my patients will say to me, ‘Well, 5% is not that big; I’ll take the risk,’” says Boolbol, who was not involved in either of the new reviews. “That’s up to them, but my response is going to be, ‘If I told you that every time you crossed the street you had a 5% risk of getting hit by a car, wouldn’t you change the way you cross the street?’”
The review also found strong evidence that breastfeeding and vigorous physical activity decrease the risk of both pre- and post-menopausal breast cancers. But Boolbol says it’s important that women not think of one lifestyle factor canceling out the other.
“It’s not a tradeoff—you can’t say you’ll add risk with a glass of wine and then decrease it by going for a run,” she says. “There is no evidence that we can balance risks that way; it’s not something we have control over.”
Research on alcohol consumption and health risks is always going to have limitations, says Boolbol, since most studies in this area—including the studies in both of these reviews—are observational, rather than randomized clinical trials. “We can’t tell one group of people to drink a lot and one group of people to not drink at all, and let’s see what happens in 20 years,” she says.
Instead, studies have to rely on people’s self-reported drinking amounts, which can be over- or underestimated, and they can’t always control for outside factors that may affect drinking habits, health outcomes, or both.
But even with these limitations, Boolbol says there is a clear message in the new research: that women should strive to maintain an ideal body weight, get plenty of moderate to vigorous exercise, and, yes, drink less alcohol. “I’m not telling people to not drink at all, because I do think we need to be reality-based,” she says. “But I think this is cause to pause and look at, ‘How much am I really drinking, and where can I decrease it?”
“If you’re drinking one glass a day, cut it down to one glass every other day,” she adds. “Doing all of these things together leads to healthier living in general—not just for breast cancer risk, but for overall health.”