Red meat intake and its influences on inflammation and immune function biomarkers in human adults: a systematic review and meta-analysis of randomized controlled trials and observational studies.

Red meat intake (RMI) is implicated in promoting inflammation and compromising immune function. We conducted a systematic review and meta-analysis assessing how RMI influences inflammation and immune function biomarkers in adults with any health status. Twenty-two randomized controlled trials (RCTs; 1152 adults) and 10 observational studies (OBS; 438,925 adults) were included from literature published through May 2024 using PubMed, Scopus, CINAHL, and Cochrane databases. Sufficient data were obtained for meta-analyses of blood C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), leptin, and adiponectin. Overall, greater total RMI led to higher CRP across 18 RCTs (weighted mean difference 0.23, 95% CI 0.08-0.39). Subgroup analyses indicated similar findings for participants diagnosed with, but not without, cardiometabolic diseases; unspecified or mixed RMI, but not unprocessed RMI; studies without, but not with, energy restriction; and RMI ≥, but not <, 0.5 servings/day (3.5 servings/week). Limited RCTs suggest total RMI did not influence IL-6, TNF-α, leptin, or adiponectin. Among 10 OBS, no associations were shown between RMI and these biomarkers. Conservatively, these results are consistent with recommendations for people who choose to consume red meat to limit or avoid consuming processed red meat, especially among individuals with cardiometabolic diseases. Registry and registry number for systematic reviews or meta-analyses: PROSPERO CRD42021256264.