In this study, capsaicin, a compound which gives hot peppers their heat, was found to inhibit the growth and proliferation of various breast cancer cell lines in the laboratory, including several types of estrogen receptor positive (ER+), estrogen receptor negative (ER-), and HER2 overexpressing cells. When ER-/PR- human breast cancer tumors were grown in immunodeficient mice, capsaicin was found to reduce the size of the tumors by approximately half without any evidence of harmful side effects. Capsaicin treatment was also found to inhibit the development of pre-cancerous breast lesions in mice.

Capsaicin and cancer risk

This study confirms others that have found that capsaicin has anti-cancer activities. In fact, several population studies have found an association between hot pepper consumption and lower incidence of breast cancer. However, frequent consumption of hot peppers also has been associated with higher risks of esophageal, gall bladder and stomach cancer in multiple population studies. We recommend that breast cancer survivors and those at high risk consume hot peppers and related foods such as hot sauce and red pepper flakes in moderation.