Lots of people have taken to heart reports that moderate drinking lowers the risk of cardiovascular disease, especially because a glass of wine or a beer with a meal is often viewed as one of life's small pleasures.
Lately, though, there has been a veritable tsunami of bad news.
In February, it was reported that even moderate drinking was associated with higher rates of breast, liver and rectal cancer among women. Then came a study showing that alcohol use correlates with an increased risk for pancreatic cancer. And yet another research team found that alcohol use was associated with higher rates of prostate cancer in men.
So drinking is bad for you, right? Not necessarily. Another recent study showed that men and post-menopausal women who consumed alcohol in moderation had higher bone mineral density than non-drinkers, suggesting there is a protective effect against osteoporosis.
Perhaps the most troubling of the new reports was based on Britain's Million Women Study, which followed nearly 1.3 million women over the age of 50. In a paper titled "Moderate Alcohol Intake and Cancer Incidence in Women," published in the Journal of the National Cancer Institute, researchers found "regular consumption of low to moderate amounts of alcohol by women increases the risk of cancers of the upper aerodigestive tract, rectum, liver, and breast."
Whether women drank red or white wine made no difference, according to the report, which also found that about 11 percent of all breast cancer in women in the United Kingdom is attributable to alcohol.
"It's not what people wanted to hear; let's put it that way," said lead researcher Dr. Naomi E. Allen, an epidemiologist at the University of Oxford. Although prior studies had shown a link between drinking and breast cancer, "What's novel about this study is we found even moderate alcohol use is connected to other cancer sites, such as liver cancer."
All told, the study included about one-quarter of all U.K. women over 50, Allen said. "It's the largest cohort study in the world, certainly of women," she says. "The cancer risk associated with alcohol can be generalized to the whole population."
The women who drank averaged one drink per day, which matches the definitions of moderate drinking set forth by the U.S. dietary guidelines. Even at those levels, "We see a significant increase in cancer risk," Allen said. "In this analysis we found no suggestion there is a minimum threshold below which there is no increase in risk."
Meanwhile, Jeanine Genkinger, an epidemiologist at Georgetown University's Lombardi Cancer Center, led a pooled analysis of 14 prospective cohort studies encompassing nearly 863,000 people. "Our findings are consistent with a modest increase in risk of pancreatic cancer with consumption of 30 or more grams of alcohol per day," she said of her study, published in the journal of the American Association for Cancer Research.
The researchers identified several possible biological pathways by which alcohol could promote cancer in the pancreas, Genkinger said. One is the presence of acetaldehyde, which is produced when alcohol is metabolized and may serve as a co-carcinogen. Another possibility is that alcohol increases immuno-suppression or inflammation in the body, or it may activate enzymes that promote liver cancer. Alcohol is also known to deplete folate in the body, which may alter DNA synthesis and transcription.
Part of the study's significance is that there are only a few known risk factors for pancreatic cancer. "We think it's a modest association," Genkinger said, "but we think that because there are only a few known risk factors for pancreatic cancer, understanding even modest risk factors is important."
If that weren't enough gloom and doom, Tim Stockwell, a scientist at the University of Victoria in British Columbia, and a team of colleagues reported that men who average two or more drinks a day have about a 20 percent higher risk of prostate cancer. The study, titled "Alcohol Use and Prostate Cancer: A Meta-Analysis," was published in Molecular Nutrition & Food Research. It reviewed 35 previous studies, some of which had found no alcohol-prostate cancer risk and others that had found a weak association. After accounting for methodological weaknesses in some of the studies, a pattern emerged.
"It's a small increase in the big picture of things, but it's there," Stockwell said. "This adds to a growing body of knowledge. There's a growing consensus around the idea of lowering drinking guidelines."
On the other side of the equation, nutritional scientist Katherine L. Tucker of Tufts University led a group that examined data from the Framingham Offspring osteoporosis study regarding bone mineral density. Bone density was higher among men and post-menopausal women who consumed one to two drinks per day than among non-drinkers, according to the study published in the American Journal of Clinical Nutrition.
"We were able to show that it's not altogether linear," Tucker said. Although some drinking was more protective than none, heavy drinkers actually had the highest rates of osteoporosis, she said.
"Nutrition is like this," Tucker said. "Moderation is important."
A possible explanation for the study results is that alcohol has a hormone-stimulating action, which might benefit women. In addition, both wine and beer, which were preferred by the moderate drinkers, have significant amounts of bio-available silicon, an important micronutrient in the formation of bone, she said.
Is there a take-home message?
"For people who are drinking moderately and regularly, it generally does have health benefits, and you shouldn't stop because you're worried about osteoporosis," Tucker said. "It's a very individual choice, and it's good to know your family risks."
Meanwhile, Rosalind Breslow, an epidemiologist at the National Institute on Alcohol Abuse and Alcoholism, and statistician Barry Graubard stepped back to look at the relative effects of drinking frequency versus alcohol quantity.
"We found that how much and how often people drink — not just the average amount of alcohol they consume over time —independently influence the risk of death from several causes," said Breslow of the study, which focused on nearly 44,000 drinkers included in the 1988 National Health Interview Survey and was published last year in Alcoholism: Clinical and Experimental Research.
"In men, alcohol frequency and quantity had opposite effects on cardiovascular mortality," Breslow said. "The greater the amount of alcohol that men consumed on drinking days, the greater was th
eir risk for death from cardiovascular disease.
"On the other hand, frequency of drinking was associated with decreased risk for death from cardiovascular disease among men — those who reported drinking 120 to 365 days per year had about 20 percent lower cardiovascular mortality than men who drank just one to 36 days per year." Women did not see a similar cardiovascular benefit, she said.
Breslow added that among women, frequent drinking was linked to a significantly higher risk of cancer, while increased quantity was associated with risk for mortality from all causes.
What are the implications of this study? Should people modify their behavior? Should women, for example, avoid drinking altogether?
"I think the clear message for ordinary people is, if you are going to drink, do so in moderation," Breslow said.
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