High folate intake is associated with lower breast cancer incidence in postmenopausal women in the Malmo Diet and Cancer cohort

Background: Epidemiologic studies of associations between folate intake and breast cancer are inconclusive, but folate and other plant food nutrients appear protective in women at elevated risk. Objective: The objective was to examine the association between folate intake and the incidence of postmenopausal breast cancer. Design: This prospective study included all women aged >= 50 y (n = 11699) from the Malmo Diet and Cancer cohort. The mean follow-up time was 9.5 y. We used a modified diet-history method to collect nutrient intake data. At the end of follow-up, 392 incident invasive breast cancer cases were verified. We used proportional hazard regression to calculate hazard ratios (HRs). Results: Compared with the lowest quintile, the incidence of invasive breast cancer was reduced in the highest quintile of dietary folate intake (HR: 0.56; 95% CI: 0.35, 0.90; Pfor trend = 0.02); total folate intake, including supplements (HR: 0.56; 95% CI: 0.34, 0.91; P for trend = 0.006); and dietary folate equivalents (HR: 0.59; 95% CI: 0.36, 0.97; P for trend = 0.01). Conclusion: A high folate intake was associated with a lower incidence of postmenopausal breast cancer in this cohort.