This large 18-year study of 77,688 postmenopausal women found that drinking coffee showed no link to breast cancer risk. However, higher caffeine intake was mildly associated with increased breast cancer risk overall, and more notably with a specific hormone-sensitive type (ER+/PR+). The difference between coffee and caffeine suggests it's not just the caffeine—other compounds in coffee may have protective effects.

Researchers tracked postmenopausal women from the Women's Health Initiative, recording their coffee and caffeine consumption at the start and monitoring breast cancer diagnoses over 18+ years. They analyzed results by cancer type and hormone receptor status to see if caffeine affected risk differently.

Funding not disclosed in abstract