Drs. Brooks and Zakhari are correct that understanding the molecular mechanisms and time courses of the relationship between alcohol consumption and breast cancer is important for making the “best public health recommendations,” said Wendy Y. Chen, MD, MPH, assistant professor of medicine at Harvard Medical School.

“I also agree with the authors that misreporting of alcohol consumption may occur, although this is more common with heavier users of alcohol, rather than the more moderate levels that we have studied,” she told The Advisor Blog.

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“Low levels of alcohol consumption were associated with a small increase in breast cancer risk, with the most consistent measure being cumulative alcohol intake throughout adult life,” her team reported in JAMA in 2011. “Alcohol intake both earlier and later in adult life was independently associated with risk.”

Most of the available literature is composed of association cohort studies, notes Cynthia A. Thomson, PhD, RD, professor of health promotion sciences and director of the Canyon Ranch for Prevention & Health Promotion at Arizona State University.

“We do not have nor will we ever have a randomized controlled trial to test the hypothesis that alcohol modifies breast cancer risk,” she told The Advisor Blog, citing the potential harm to individuals from regular alcohol consumption. (There is no evidence alcohol might prevent any type of cancer, she explained.)

“Although data are limited, most cancer researchers would recommend to clinicians that alcohol intake be restricted in at-risk individuals, including breast cancer survivors,” Dr. Thomson said.

Breast cancer risk from alcohol might be greatest among the elderly, she noted.

“Risk may be greatest with advancing age – simply because alcohol is thought to promote cancer rather than to initiate cancer,” Dr. Thomson said.

Some “intriguing” research suggests red wine contains aromatase inhibitors, Dr. Thomson points out.

“But how this translates to risk has not been sufficiently evaluated,” she cautioned.

(Resveratrol is one such aromatase inhibitor. The University of Connecticut Health Center announced earlier this year that it had contacted the journals that had published 11 research papers by a leading resveratrol researcher, who the university concluded had fabricated study data while he served as director of the university’s Cardiovascular Research Center.)

“People metabolize alcohol differently,” Dr. Thomson notes. “We may at some time be in a position to identify subgroups of women at greater or lesser risk of breast cancer in relation to alcohol intake and how they metabolize it.”

Until then, Dr. Seitz believes, we should err on the side of caution.

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