English abstract
Background: Diet quality is associated with the risk of chronic diseases, including colorectal
cancer. Currently, the trend of diet and health research is shifting from focusing on individual
dietary components only to analysing gut microbial ecology (microbiome) in the host-diet
interaction systems. Studies have confirmed that microbiota can have an impact on disease
aetiology through different mechanisms, including the production of metabolites. At chronically
high physiological levels, the two major types of bacterial metabolites in the colon, Secondary
Bile Acids (SBAs) and Short Chain Fatty Acids (SCFAs), have opposite effects on colonic
inflammation. The Healthy eating Index (HEI) is one of the best diet quality indices that can
capture the effects of diet on gut microbiota. To date, no study in Oman has examined the
relationship between diet quality and microbiota metabolites.
Objective: To examine the relationship between diet quality, using the Short Healthy Eating Index
(sHEI), and microbiota-derived metabolites in patients referred for colonoscopy from outpatient
gastroenterology clinics at Sultan Qaboos University Hospital (SQUH).
Methods: This cross-sectional hospital-based study involved patients referred for colonoscopy
from the Gastroenterology Outpatient Departments (OPD) at SQUH. Patients were interviewed
to assess dietary intake using the Short Healthy Eating Index (sHEI) questionnaire, and blood
samples were collected to measure serum microbiota metabolites SCFAs, primary and secondary
bile acids using Gas Chromatography-Mass Spectrometry (GC-MS) and Liquid chromatography–
Mass Spectrometry (LC-MS), respectively. Further, colonoscopy results were retrieved from
medical records. Pearson product-moment correlations and multiple liner regression were used
for the statistical analysis of the study variables.
Results: The mean sHEI diet quality score was 42.21%, with a range of 23.42–63.55%. The
majority of participants (75.81%) had poor diets, and 24.19% had diets that needed improvement.
There was a significant correlation between the total score sHEI, age and marital status (p <0.05),
with age ≥ 57 years significantly different from the other age groups. Females had a higher mean
sHEI total diet score than males (p = 0.034). The general dietary pattern was characterized by a
low intake of adequate food components, which is recommended for inclusion in a healthy diet
(total mean <3.5). No significant association was found between the diet quality score, food
groups, and concentrations of the studied colon bacterial metabolites (p > 0.05).
Conclusion: Diet quality scores showed poor adherence to a healthy diet with a positive
association between age and diet quality. Married and female participants had higher diet quality
scores than did unmarried and male participants, respectively. None of the examined metabolites
was found to have a significant correlation with total diet quality scores.
Recommendations: The scope of this study can be broadened in the future by targeting a large
number of individuals and incorporating case-control studies to further understand the relationship
between diet quality and microbiome metabolites.
