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Of the references you provided, this one is relevant & quite interesting - greater bowel motility appears to be associated to some extent with reduced risk of breast cancer:
A Prospective Study of Bowel Motility and Related Factors on Breast Cancer Risk
Sonia S. Maruti,1,2 Johanna W. Lampe,1,2 John D. Potter,1,2 Ann Ready,2,3 and Emily White
Abstract
Background
Estrogen is an established risk factor for breast cancer. Greater bowel motility has been associated with increased estrogen excretion and lower serum estrogen levels, suggesting it may influence breast cancer risk. However, only one other epidemiologic study thus far, to our knowledge, has examined the relation between bowel motility and breast cancer risk.
Methods
We prospectively examined whether bowel motility, measured by self-reported frequency of bowel movements, and related factors (constipation, laxative use, water consumption, and dietary fiber intake) were associated with incidence of breast cancer among 28,586 postmenopausal women, aged 50–76, in the Vitamins And Lifestyle (VITAL) study. Cox proportional hazards models were used to estimate multivariate-adjusted relative risks (RR) and 95% confidence intervals (CI). From 2000–2005, 507 incident invasive breast cancers among the cohort were identified.
Results
Women with very frequent (≥ 3/day) bowel movements had a 46% decreased risk compared to 1/day women (RR = 0.54, 95% CI = 0.31 to 0.92), but the test for linear trend was not significant (Ptrend=0.41). Constipation was nonsigificantly associated with increased risk (RR = 1.30 for ≥1/week versus <1/year, 95% CI = 0.87 to 1.95). No statistically significant associations were observed for the other study exposures: 10-year chemical laxative use, 10-year use of fiber laxatives, water consumption, and dietary fiber intake.
Conclusion
This study adds limited support to the hypothesis that increased bowel motility lowers breast cancer risk.
Keywords: bowel function, breast cancer, epidemiology
The proposed mechanism is a reduction in estrogen levels:
Experimental studies suggest that greater bowel motility lowers estrogen levels (4, 5) potentially enough to reduce risk...
Edited by blood, 31 August 2014 - 06:15 AM.