Gut microbiota–inflammageing axis in cardiometabolic health of older adults and dietary intervention strategies
This narrative review supports the hypothesis that age-related gut dysbiosis amplifies chronic systemic inflammation and contributes to cardiometabolic deterioration in older adults, but the full causal chain has not been established in humans.
| Population | Older adults (≥65 years), with emphasis on frail individuals and those with cardiometabolic comorbidities |
|---|---|
| Intervention | Dietary patterns (Mediterranean, DASH, Green-Med, plant-forward), polyphenols, and prebiotics/probiotics modulating gut microbiota |
| Comparator | Habitual Western diet or control without specific dietary intervention |
| Outcome | Gut microbiota composition; Systemic inflammatory markers (IL-6, TNF-α, IL-1β); Intestinal barrier integrity (tight-junction proteins, circulating LPS); Cardiometabolic risk (body weight, insulin resistance, metabolic syndrome); Circulating TMAO; Preservation of cognitive, physical, and mental health at age 70; Major cardiovascular events and mortality |
Summary of findings
| Outcome | Effect | 95% CI | Certainty | Clinical relevance | Notes |
|---|---|---|---|---|---|
| Gut microbiota composition | Narrative synthesis only; in the pooled effect size reported | — | Low | — | |
| Systemic inflammatory markers (IL-6, TNF-α, IL-1β) | Narrative synthesis only; murine data: elevated colonic Il6, Tnf, Tlr4 after aged-to-young FMT — in the human numeric effect size | — | Very low | — | |
| Intestinal barrier integrity (tight-junction proteins, circulating LPS) | Narrative synthesis only; in the pooled effect size reported for humans | — | Very low | — | |
| Cardiometabolic risk (body weight, insulin resistance, metabolic syndrome) | DIRECT-PLUS RCT (n=294, 18mo): microbiota changes mediated diet-induced improvements — specific RR/MD/SMD not reproduced in this review | — | Low | — | 1 studies |
| Circulating TMAO | Narrative synthesis only; dietary polyphenols described as reducing TMAO biosynthesis — in the pooled numeric effect size | — | Low | — | |
| Preservation of cognitive, physical, and mental health at age 70 | 30-year prospective cohort: higher AHEI/aMED adherence associated with greater probability of healthy ageing — OR/RR not reproduced numerically in this review | — | Low | — | 1 studies |
| Major cardiovascular events and mortality | Not assessed as primary outcome in this review; in the effect size available | — | Very low | — |
Context
Cardiovascular disease remains the leading cause of death in adults aged 70 and over, with projections of 35.6 million absolute CVD deaths by 2050. Chronic low-grade inflammation (inflammageing) is recognised as a shared pathological substrate for CVD, metabolic syndrome, and cognitive decline. Dietary strategies targeting the microbiota–inflammageing axis have emerged as a priority non-pharmacological approach given the limited benefit of pharmacological options.
What the study showed
The review synthesises evidence that ageing-related dysbiosis — reduction of Bifidobacterium and Faecalibacterium prausnitzii, expansion of Enterobacteriaceae — impairs butyrate production and intestinal barrier integrity, facilitating LPS translocation and TLR4/NF-κB activation. In a murine model (n unspecified), transfer of intestinal contents from aged to young germ-free mice elevated colonic Il6, Tnf, Tlr4 expression and circulating LBP; these findings have not been replicated in controlled human studies. One RCT (DIRECT-PLUS, n=294, 18 months) showed the Green-Mediterranean diet remodelled the microbiota and microbial changes mediated improvements in body weight and cardiometabolic risk; specific effect sizes were not reported in this review's text. A 30-year prospective cohort associated adherence to healthy dietary patterns (AHEI, aMED) with greater odds of preserved health at age 70, without OR or RR quantified in the reviewed text.
How it was done
Narrative (non-systematic) review published in Frontiers in Nutrition (2026). No search protocol, inclusion/exclusion criteria, formal risk-of-bias assessment, or quantitative synthesis are described. Incorporates primary studies of varying designs: RCTs, prospective cohorts, observational studies, and animal experiments.
Effect magnitude
No aggregate (meta-analytic) effect size is calculated. The only RCT with a defined n cited (DIRECT-PLUS, n=294) does not have its effect data numerically reproduced in this review.
Risk of bias
No systematic search protocol or formal risk-of-bias assessment (AMSTAR-2, RoB 2, or ROBINS-I tools not applied). Most mechanistic studies rely on murine models with uncertain human generalisability. The geriatric population (≥75 years, frail, polymedicated) is under-represented in included primary studies. Selection bias and publication bias are uncontrolled. Causal inference is not possible from the dominant observational designs.
What this study does NOT prove
This review does not prove causality between gut dysbiosis and cardiometabolic disease in older humans, nor does it validate any specific dietary intervention for the frail elderly. Findings are not generalisable to the clinical setting without confirmation from controlled trials in geriatric populations.
In clinical practice
Current guidelines (ESC 2021, AHA/ACC 2023, ADA 2024) already recommend Mediterranean, DASH, and plant-forward patterns as first-line intervention for cardiometabolic risk reduction; this review reinforces the mechanistic basis of these recommendations without adding new efficacy evidence. In frail older adults, the safety of aggressive dietary interventions or high-volume supplementation lacks robust evidence. Nutritional individualisation is justified, but precision strategies still face reproducibility barriers.
Limitations
No systematic search protocol or formal risk-of-bias assessment (AMSTAR-2, RoB 2, or ROBINS-I tools not applied). Most mechanistic studies rely on murine models with uncertain human generalisability. The geriatric population (≥75 years, frail, polymedicated) is under-represented in included primary studies. Selection bias and publication bias are uncontrolled. Causal inference is not possible from the dominant observational designs.
What is still missing
Controlled RCTs in exclusively geriatric cohorts (≥75 years, frail) are needed to establish efficacy and safety of dietary interventions on the microbiota–inflammageing axis. Studies with hard clinical endpoints (cardiovascular events, mortality) as mediation outcomes are absent.
Technical appendix
Version history
- 1.0 · 2026-11-09 — Auto-generated under Evidence Standard v1.0