Effect of anti-inflammatory diets on health-related quality of life in adults with chronic disease: a systematic review and meta-analysis.

Objective: To evaluate the effectiveness of anti-inflammatory diets on health-related quality of life (HRQOL) in adults with at least one chronic disease. Design: Systematic review and meta-analysis of randomised controlled trials (RCTs). Data sources: MEDLINE, EMBASE, CINAHL, Web of Science and the Cochrane Centre Register of Controlled Trials from inception to 6 May 2024. Eligibility criteria for selecting studies: Full-text RCTs published in English assessing the effectiveness of any anti-inflammatory dietary intervention (ie, a diet that emphasises the intake of nutrient-rich, minimally processed foods rich in polyphenols, carotenoids and omega-3 polyunsaturated fatty acids and limits highly-processed, pro-inflammatory foods) on HRQOL in adults with at least one chronic disease were included. Methods: Data extraction, risk-of-bias assessments and strength-of-evidence assessments were done by two independent reviewers. Pooled effects (standardised mean difference (SMD)) for HRQOL (separated into mental and physical component scores wherever possible) were calculated using random effects models with restricted maximum likelihood estimations. Subgroup analyses and meta-regressions were performed to assess the influence of study-level characteristics on HRQOL outcomes. Results: 23 studies reporting HRQOL for 3294 participants were included. The most common chronic diseases were type two diabetes, musculoskeletal conditions and cardiovascular conditions. Anti-inflammatory diets were associated with small improvements in HRQOL physical component scores compared with usual care/other dietary interventions (18 trials, SMD=0.17, 95% CI 0.06 to 0.27) but not in mental component scores (18 trials, SMD=0.09, 95% CI -0.02 to 0.20) or general HRQOL scores (four trials, SMD=0.27, 95% CI -0.22 to 0.77). Pooled effects did not differ by available study-level characteristics; however, diet-only interventions (compared with multi-component interventions) had a greater effect on mental component scores. No study met the Cochrane criteria for low risk of bias. Certainty of evidence was low for physical and mental HRQOL scores and very low for general HRQOL scores. Conclusions: In adults with at least one chronic disease, anti-inflammatory diets lead to small improvements in physical component HRQOL, which may not be clinically relevant. No effect was found on the mental component or general HRQOL. Further high-quality RCTs may change this conclusion.