Gut Microbiota and Nutritional Profiles of Colon Cancer Patients Undergoing Chemotherapy: A Longitudinal Pilot Study.

Diet quality declined during chemotherapy in colon cancer patients over 6 months.

• 48 adults with stage II-III colon cancer receiving 5-fluorouracil-based chemotherapy were assessed at baseline and 6 months post-initiation.
• Diet quality was measured using 3-day dietary recalls to calculate Healthy Eating Index (HEI) scores.
• Reduced intake of fiber, fruits and vegetables, and whole grains was observed during the chemotherapy period.

Gut microbial alpha diversity decreased over the 6-month chemotherapy period.

• Alpha diversity was assessed using Shannon diversity index from 16S rRNA sequencing of stool samples.
• Pre-post changes were analyzed using paired tests.
• Beta diversity composition also shifted over the course of chemotherapy.

Chemotherapy was associated with phylum-level shifts in gut microbiota composition.

• Actinobacteriota decreased over the 6-month period.
• Bacteroidota and Proteobacteria increased over the same period.
• These changes were identified through 16S rRNA sequencing and taxonomic composition analysis.

At the genus level, Streptococcus decreased and Escherichia increased significantly after multiple testing correction.

• These were the only two genera to remain statistically significant after multiple testing correction.
• Other genus-level changes were observed but did not survive correction for multiple comparisons.
• Analyses were performed using multivariable linear regression adjusting for demographic and clinical covariates.

Higher baseline diet quality and improvements in diet quality over time were associated with greater microbial diversity and lower Proteobacteria abundance.

• Associations were evaluated using multivariable linear regression adjusting for demographic and clinical covariates.
• Diet quality was inversely associated with Proteobacteria abundance.
• Higher diet quality was also inversely associated with Streptococcus and Escherichia abundances.

Diet quality was positively associated with short-chain fatty acid-producing, fiber-responsive genera.

• The genera positively associated with diet quality included Faecalibacterium, Mediterraneibacter, Ruminococcus_E, and Fusicatenibacter.
• These genera are characterized as short-chain fatty acid-producing and fiber-responsive.
• Associations were determined via multivariable linear regression with adjustment for demographic and clinical covariates.

Baseline gut microbiota did not significantly associate with changes in diet quality over the study period.

• This finding was assessed as part of the bidirectional analysis between diet and gut microbiota.
• While diet quality was associated with microbiota measures, the reverse direction (microbiota predicting diet change) was not statistically significant.
• This suggests the relationship may be directionally asymmetric within this study context.