Association between daily caffeine intake and uterine fibroids: Results from NHANES 1999–2006

Abstract Objective To investigate associations between daily caffeine intake and uterine fibroids (UF) among US women of reproductive age. Methods This cross‐sectional analysis used NHANES data from 1999 to 2006. The sample included 4712 women aged 20–50 years. Daily caffeine intake was assessed through 24‐h dietary recalls. Caffeine consumption was categorized using the FDA‐recommended threshold of 400 mg per day. UF diagnosis was based on physician confirmation. Multivariable logistic regression was used to explore relationships. Restricted cubic spline (RCS) analysis was also performed. Results The mean age was 34.04 ± 8.90 years. UF were reported by 12% of participants ( n = 524). High caffeine consumers (>400 mg/day) showed elevated UF risk. This elevated risk disappeared after age adjustment. RCS analysis revealed a biphasic relationship. Protective effects occurred at low doses (<71.5 mg/day). Risk elevation appeared beyond this threshold, which was much lower than FDA guidelines. Conclusion This study demonstrates a dose‐dependent relationship between caffeine and UF. Risk elevation occurs above 71.5 mg per day. These findings suggest a need to reconsider caffeine guidelines for hormone‐dependent conditions. The results support personalized dietary counseling for UF prevention.