Selenium’s protective effect against colorectal cancer varies by gender and cancer location: in men, it helps prevent cancer in the lower colon and rectum; in women, it helps prevent cancer in the upper colon and rectum, but not in the upper colon of men.
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Whether selenium intake consistently reduces risk of distal colon and rectal cancer more than proximal colon cancer, and whether this pattern differs by sex across diverse populations.
A systematic review and meta-analysis of prospective cohort studies reporting selenium intake and site-specific CRC incidence (proximal colon, distal colon, rectum) stratified by sex, including at least 15 studies with individual-level data and adjustment for confounders.
Whether selenium supplementation reduces incidence of distal colon and rectal adenomas more than proximal colon adenomas in men and women.
A double-blind RCT of 2,000 adults aged 50–70 with prior adenomas, randomized to 200 μg/day selenium or placebo for 5 years, with colonoscopy at baseline and year 5, stratifying adenoma recurrence by location (proximal/distal colon, rectum) and sex.
Whether selenium intake predicts site-specific CRC incidence over time, with differential effects by sex.
A prospective cohort of 10,000 Korean adults aged 45–65, with baseline selenium intake measured by FFQ and annual health assessments, followed for 20 years with colonoscopy surveillance and cancer registry linkage, stratifying outcomes by tumor location and sex.
Whether selenium intake is lower in cases of distal colon and rectal cancer compared to proximal colon cancer, and whether this difference varies by sex.
A case-control study with 1,000 cases of proximal colon cancer, 1,000 of distal colon cancer, and 1,000 of rectal cancer, each matched to 2 controls, with selenium intake assessed via FFQ and stratified by sex, as performed in this study.
Whether selenium intake and tumor location co-occur at a single point in time, without establishing temporal sequence.
A cross-sectional survey measuring selenium intake and CRC location in 5,000 adults aged 50+ in Korea at one time point, without longitudinal follow-up.