Dietary fiber intake and risk of breast cancer in postmenopausal women: the National Institutes of Health-AARP Diet and Health Study.
BACKGROUND
Although dietary fiber has been hypothesized to lower risk of breast cancer by modulating estrogen metabolism, the association between dietary fiber intake and risk of breast cancer by hormone receptor status is unclear.


OBJECTIVE
The objective was to examine the relation of dietary fiber intake to breast cancer by hormone receptor status and histologic type among postmenopausal women in the National Institutes of Health-AARP Diet and Health Study (n = 185,598; mean age: 62 y).


METHODS
Dietary intakes were assessed with a food-frequency questionnaire. Incident breast cancer cases were identified through linkage with state cancer registries. Cox proportional hazard models were used to estimate relative risks (RRs) and 2-sided 95% CIs.


RESULTS
During an average of 7 y of follow-up, 5461 breast cancer cases were identified, of which 3341 cases had estrogen receptor (ER) and progesterone receptor (PR) status. Dietary fiber intake was inversely associated with breast cancer risk [RR for the highest quintile (Q5) compared with the lowest quintile (Q1): 0.87; 95% CI: 0.77, 0.98; P for trend: 0.02]. The inverse association appeared to be stronger for ER(-)/PR(-) tumors (RR(Q5vsQ1): 0.56; 95% CI: 0.35, 0.90; P for trend: 0.008; 366 cases) than for ER(+)/PR(+) tumors (RR(Q5vsQ1): 0.95; 95% CI: 0.76, 1.20; P for trend: 0.47; 1641 cases). The RR(Q5vsQ1) of lobular tumors was 0.66 (95% CI: 0.44, 0.97; P for trend: 0.04), and the RR(Q5vsQ1) of ductal tumors was 0.90 (95% CI: 0.77, 1.04; P for trend: 0.10). Fiber from grains, fruit, vegetables, and beans was not related to breast cancer.


CONCLUSIONS
Our findings suggest that dietary fiber can play a role in preventing breast cancer through nonestrogen pathways among postmenopausal women.
Park
Yikyung
Y
Divisions of Cancer Epidemiology and Genetics and Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD, USA. parkyik@mail.nih.gov
Brinton
Louise A
LA
Subar
Amy F
AF
Hollenbeck
Albert
A
Schatzkin
Arthur
A
D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D044584:Carcinoma, Ductal / Q000453:epidemiology / Q000517:prevention & control; D018275:Carcinoma, Lobular / Q000453:epidemiology / Q000517:prevention & control; D004032:Diet; D004034:Diet Surveys; D004043:Dietary Fiber / Q000008:administration & dosage*; D002523:Edible Grain; D007887:Fabaceae; D005260:Female; D005500:Follow-Up Studies; D005638:Fruit; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D016016:Proportional Hazards Models; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology; D014675:Vegetables
D004043:Dietary Fiber; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone