“Alcohol is related to both premenopausal and postmenopausal breast cancer,” says Walter Willett, chair of the nutrition department at the Harvard School of Public Health. “And the more you drink, the higher your risk.”
Drinking over more of your life also matters. “Women who started drinking earlier in life and then stopped, their risk goes down,” Willett explains. “The highest risk is in women who started consuming alcohol early and continued.”
And it’s not just women who overdo it.
“We now see a 17 percent increased risk with only one drink every other day,” notes Willett. “What’s remarkable is how modest that amount is. With colorectal cancer, you don’t see much increase in risk until you get to over two drinks a day.”
Alcohol’s ability to raise blood estrogen levels appears to explain at least part of the increased risk. “But we’re still not entirely sure whether it’s limited to the increase in estrogen or whether there’s more to it than that,” adds Willett.
Could teenage drinking pose a particularly potent threat?
“That’s been a worry from the beginning, because the breast is more sensitive then,” says Willett.
When he and others tracked nearly 6,900 teens aged 13 to 20 for five years, each daily serving of alcohol they consumed was linked to a 50 percent higher risk of benign breast disease. (Some types of benign breast disease are risk factors for cancer.)
“So far we haven’t seen a massive time bomb due to teenage drinking,” says Willett. “But it deserves some more looking.”
Sources: JAMA 306: 1884, 2011; J. Natl. Cancer Inst. 93: 710, 2001; Pediatrics 125: e1081, 2010.