Study links sulfur microbial diet to lung cancer risk and mortality

A prospective cohort study published in the Nutrition Journal investigated whether a sulfur microbial diet score correlates with lung cancer incidence and mortality among 95,612 American adults.

Dietary Patterns and Sulfur-Metabolizing Bacteria

The study analyzed data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, which enrolled U.S. adults aged 55 to 74 years between 1993 and 2001 across 10 screening centers. Researchers evaluated a food-based sulfur microbial diet score derived from a 124-item questionnaire administered at a median of three years post-randomization. This score combined 25 standardized and weighted food group components to reflect dietary patterns that shape sulfur-metabolizing gut bacteria like Bilophila wadsworthia and Desulfovibrionaceae.

Participants in the highest-scoring quintile generally consumed more red and processed meats, French fries, and high-fat dairy, alongside fewer fruits, yellow vegetables, and whole grains. Conversely, individuals in the lowest-scoring quintile followed different dietary habits. The highest quintile also showed younger mean ages, a higher proportion of males, higher body mass indices, and higher rates of smoking, diabetes, and hypertension.

Hazard Ratios for Incidence and Mortality

Over 844,773 person-years of incidence follow-up tracked through December 2009, the study recorded 1,561 lung cancer cases. Mortality tracking continued through December 2018 across 1,443,711 person-years, capturing 2,109 lung cancer deaths. Crude lung cancer incidence rates climbed from 1.20 per 1,000 person-years in the lowest quintile to 3.03 per 1,000 in the highest quintile.

After adjusting for demographic, health, lifestyle, and dietary covariates, participants in the highest scoring quintile faced a 23% higher estimated hazard of developing lung cancer and a 19% higher estimated hazard of dying from the disease compared to those in the lowest quintile. The adjusted differences were smaller than crude rates because the statistical models accounted for smoking and other characteristics.

Subgroup Interactions and Subtype Analysis

When researchers examined histologic subtypes, the association between higher sulfur microbial diet scores and lung cancer risk proved strongest for squamous cell and small cell carcinomas, while no significant association emerged for adenocarcinoma. The mortality association also appeared stronger among participants with more than 20 pack-years of smoking. However, after researchers adjusted the models for overall diet quality, the associations decreased and lost statistical significance.

Study Limitations and Unresolved Microbial Mechanisms

The authors noted that the observational design limits causal inference, and residual confounding from incompletely measured smoking exposure may have affected the results. Because the cohort lacked direct stool sequencing data, gut microbes, sulfur metabolites, or hydrogen sulfide measurements, the study could not directly test the proposed microbial pathways. Future research requires more diverse populations with repeated dietary assessments and direct microbial measurements to clarify the role of sulfur-metabolizing dietary patterns.