Fig. 2: Impact of diet on the gut microbiome, immune function, and biological aging.

A A healthy diet promotes beneficial microbiota shifts that enhance short-chain fatty acid (SCFA) production, modulate immune responses, and reduce chronic low-grade inflammation (“inflammaging”). These effects collectively contribute to a delay in biological aging. B Schematic overview of the age-related trajectories of immune competence and NCD incidence in relation to dietary quality. Early-life adherence to a healthy diet supports eubiosis and robust immune function (green curve), whereas an unhealthy diet is associated with dysbiosis, increased inflammation, and rising NCD burden over time (red curve). The transition zone reflects midlife vulnerability, where dietary choices critically shape aging trajectories. Illustrative icons depict examples of healthy (e.g., fiber-rich plant foods, fermented items) versus unhealthy (e.g., processed meats, sugary snacks) dietary patterns.