According to a study conducted by researchers at Sweden’s Lund University, patients who took the pill Tamoxifen along with two or more cups of coffee daily, reported less than half the rate of cancer recurrence compared to those who took the pill but drank only one cup or less.
 
In all, the team followed over 600 breast cancer patients from southern Sweden for an average of five years, approximately half of which took Tamoxifen.

And while it's known that the drug reduces the risk of new tumors by blocking estrogen receptors, researchers are not sure how coffee is interacting with the treatment in a way that would produce the results they have seen.

“One theory we are working with is that coffee ‘activates’ Tamoxifen and makes it more efficient,” Maria Simonsson, a doctoral student in oncology at the university, said in a press release.

This is not the first time the team has found a link between coffee and breast cancer: previous studies have exhibited a link between consumption of the beverage and a decreased risk in developing certain kinds of breast cancer.

Ultimately, the team feels the observational study, while preliminary, underlines the need for more research in coffee’s role in breast cancer prevention.

“We would like to know more about how lifestyle can interact with breast cancer,” Associate Professor of Experimental Oncology at Lund University Helena Jernstrom said.

The idea that coffee may stave off breast cancer does not go totally unchallenged, however.

Mayo Clinic’s Dr. Sandhya Pruthi has warned, for example, that women consuming several cups of coffee a day might want to cut back based on the results of two "large, long-term women’s health studies," which revealed a possible link between high caffeine intake and precancerous, or high-risk, breast lesions.