Short-term animal product dietary restriction alters metabolic profiles and modulates immune function

Background Dietary interventions are powerful tools for disease prevention and health promotion, yet the molecular mechanisms by which diet influences health remain incompletely understood. Investigating the effects of diet in healthy individuals enables characterization of molecular and physiological responses in the absence of disease-related confounders and facilitates the identification of diet-responsive pathways underlying physiological regulation. Methods We investigated the immunometabolic effects of short-term dietary restriction of animal products in a unique group of apparently healthy individuals (N = 200) who alternate between omnivory and animal product restriction for religious reasons. We profiled clinical biomarkers and immune parameters during both dietary states, alongside a control group of continuously omnivorous individuals (N = 211). Results Short-term restriction was associated with reductions in total and non-high-density lipoprotein cholesterol, urea, creatinine, alanine aminotransferase, and gamma-glutamyltransferase, and a concurrent 73% reduction of normal-range C-reactive protein levels. Immune profiling revealed reductions in frequencies of non-classical monocytes, CD56⁺ natural killer cells, and CD8⁺ memory T cells, accompanied by an increased response of anti-inflammatory cytokine IL-10, suggesting a shift toward a less inflammatory immune state. Although most changes were in a direction suggesting beneficial health effects, levels of alkaline phosphatase increased upon restriction, implying possible negative effects on bone turnover or liver function. Conclusions Short-term animal product restriction mostly improves immunometabolic health markers and may lower chronic inflammatory disease risk. Our findings highlight the value of studying diet in the absence of disease to reveal adaptive molecular changes and emphasize the translational potential of short-term dietary interventions in altering health-related risks.