Breast Cancer Risk Not Higher with Limited Caffeine Use

Drinking coffee or consuming other caffeine-laden foods does not appear to boost overall breast cancer risk, says a study in the Archives of Internal Medicine.

Caffeine "does not appear to be associated with overall risk of breast cancer," says study co-author Dr. Shumin M. Zhang at Harvard Medical School.

"However," cautions Dr. Zhang, "when consuming a high amount of caffeine or four cups or more daily of coffee, there is a possibility of increased risk of breast cancer for women with benign breast disease."

In addition, there could be an increased risk for developing certain subtypes of breast tumors that have less favorable prognoses, says Dr. Zhang.

Caffeine Linked to Benign Breast Problems

The authors note that caffeine - found in coffee, chocolate, tea, soft drinks, and various medications - is thought to be the world's most commonly ingested drug.

That said, recent research focused on women diagnosed with non-cancerous breast disease revealed that cutting caffeine from the diet could improve symptoms among such patients.

Because benign breast disease is considered to be a risk factor for developing the malignant form of the disease, this finding had raised concerns that caffeine might also elevate the risk for breast cancer.

To explore this possibility, Dr. Zhang looked at the diets of almost 39,000 women over the age of 45 over a period of four years, between 1992 and 1995.

All the women were part of The Women's Health Study, a cohort of US health professionals, and 75 percent were registered nurses.

All the women worked as health-care professionals - three-quarters as registered nurses.

The research team observed that nearly one-quarter never drank coffee, and about another quarter drank either one cup or less per day. Almost a third consumed two to three cups per day, while just over 15 percent downed four or more cups on a daily basis.

Within a decade following the collection of dietary information nearly 1,190 of the women developed invasive breast cancer.

Yet, consuming caffeine in any of its forms was not found to be significantly associated with breast cancer risk.

However, among those with a history of benign breast cancer disease, those consuming caffeine at the highest end of the scale did have a "borderline significantly increased risk" for malignant disease.

A similar positive link was found between caffeine consumption and the risk for developing tumors larger than two centimeters.

Caffeine raised the risk for such tumors by 79 percent, says Dr. Zhang.

The risk for developing certain forms of breast cancer - known as estrogen and/or progesterone receptor-negative breast cancer - also rose with caffeine consumption by 68 percent, the researcher notes.

Complex Findings, Moderate Use Best

Since breast cancers and tumors in excess of two centimeters are associated with poorer outcomes, it is important to continue investigating whether or not caffeine truly has a negative impact on the development of specific kinds of breast cancer - even if the general risk remains insignificant.

Dr. Alan Astrow, at Maimonides Medical Center in New York City, suggests the findings are both comforting and preliminary.

"Overall, the results of this study should be reassuring to women who are concerned about their risk of breast cancer and who also like to drink coffee moderately," he says.

"However, the field of diet and breast cancer risk remains one of active research, and the results of these kinds of investigations are not always easy to interpret. It is possible that future studies will show a different result,” explains Dr. Astrow.

Dr. Larry Norton at Memorial Sloan-Kettering Cancer Center in New York City, agrees.

The findings "might motivate further studies [which the authors propose], but are not definitive in themselves," he says. "Hence, there is nothing in this paper to suggest that at this time someone should not consume caffeine for fear of increasing her risk of developing breast cancer."

Always consult your physician for more information.