Diet may contribute to the increasing incidence of colorectal cancer (CRC) before age 50 (early-onset CRC). Microbial metabolism of dietary sulfur produces hydrogen sulfide (H2S), a gastrointestinal carcinogen that cannot be easily measured at scale. As a result, evidence supporting its role in early neoplasia is lacking.
We evaluated long-term adherence to the sulfur microbial diet, a dietary index defined a priori based on increased abundance of 43 bacterial species involved with sulfur metabolism, with risk of CRC precursors among 59,013 individuals who underwent lower endoscopy in the Nurses’ Health Study II (NHSII, 1991-2015), a prospective cohort study with dietary assessment every four years through validated food frequency questionnaires and an assessment of dietary intake during adolescence in 1998. The sulfur microbial diet was characterized by intake high in processed meats and low in mixed vegetables and legumes, foods previously linked to CRC development. Multivariable logistic regression for clustered data was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).
We documented 2,911 cases of early-onset adenoma. After adjusting for established risk factors, higher sulfur microbial diet scores were associated with increased risk for early-onset adenomas (ORQ4vs.Q1=1.31, 95% CI: 1.10 to 1.56, Ptrend=0.02), but not serrated lesions. Compared to the lowest, women in the highest quartile of sulfur microbial diet scores had significantly increased risk of early-onset adenomas with greater malignant potential (ORQ4vs.Q1=1.65 for villous/tubulovillous histology, 95% CI: 1.12 to 2.43; Ptrend=0.04). Similar trends for early onset-adenoma were observed based on diet consumed during adolescence. In contrast, there was no clear association for adenomas identified after age 50.
Our findings in a cohort of young women support a role for dietary interactions with gut sulfur-metabolizing bacteria in early-onset colorectal carcinogenesis, possibly beginning in adolescence.