Summary: In an observational analysis nested in the PREDIMED-Plus trial, older adults with metabolic syndrome whose diets had lower inflammatory potential showed greater gut microbiota diversity and distinct microbial and metabolite profiles; this is an associational finding, not a randomised comparison.
PICO Summary
| Element | Detail |
|---|---|
| Population | 648 older adults (mean age 65, 47% women) with overweight/obesity and metabolic syndrome; longitudinal sub-study and secondary analysis of the PREDIMED-Plus trial, Spain. |
| Intervention | An anti-inflammatory dietary pattern (lower energy-adjusted Dietary Inflammatory Index, by food frequency questionnaire), examined as an exposure rather than an assigned treatment. |
| Comparison | A more pro-inflammatory dietary pattern (higher index score) over the same period. |
| Outcome | Lower inflammatory dietary potential was associated with greater microbial alpha diversity (Chao1, Inverse Simpson, Shannon; all p<0.05) and distinct beta-diversity profiles (PERMANOVA p=0.047 at baseline, p=0.003 at 1 year), and with 24 microbial genera, 4 faecal metabolites, and one metabolomic network (all FDR<0.05). Associations persisted when examining change over time. |
Expert Commentary
This is a substantial and carefully analysed microbiome study drawing on a large, well-characterised cohort, and its strengths are real: 648 participants, two timepoints with longitudinal modelling, 16S sequencing paired with faecal metabolomics, and false-discovery-rate correction across many comparisons. The consistent association between a less inflammatory diet and greater microbial diversity, a feature generally regarded as favourable, is biologically coherent and adds depth to why anti-inflammatory eating patterns might benefit metabolic health. The crucial caveat is causal direction: although nested in a randomised trial, this analysis treats the dietary inflammatory index as an observed exposure rather than a randomised intervention, so it is associational and cannot establish that anti-inflammatory eating causes the microbiome changes, with confounding and reverse causation remaining possible. The effect sizes for diversity, while significant, are modest, and the clinical meaning of these compositional and metabolite shifts for hard outcomes is not addressed. Can I use this with my patients? Yes, as supportive context rather than proof. It reinforces encouraging anti-inflammatory dietary patterns such as the Mediterranean diet in older adults with metabolic syndrome, while I would frame the gut-health benefits as a plausible association under active study rather than an established cause-and-effect outcome.
References
Vázquez-Lorente H, Hernández-Cacho A, García-Gavilán JF, et al. Inflammatory dietary potential and gut microbiota in older adults with overweight or obesity and metabolic syndrome. Food Res Int. 2025;221(Pt 1):117263. doi:10.1016/j.foodres.2025.117263