Effects of 100% Orange Juice on Markers of Inflammation and Oxidation in Healthy and At-Risk Adult Populations: A Scoping Review, Systematic Review, and Meta-analysis

One hundred percent orange juice (OJ) has no added sugar, naturally contains flavonoids and ascorbic acid, and can modulate the body's oxidative and inflammatory systems. This scoping review, systematic review, and meta-analysis investigated associations between 100% OJ and markers of inflammation or oxidation in healthy adults and those at risk for chronic diseases. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and scoping review extension. Literature in English was searched to July 2021 in Embase and 4 Ovid platform databases. Clinical and observational studies of any duration were eligible. Cochrane Collaboration tools were used to assess the risk of bias in controlled trials. Strength of evidence was determined using the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. The scoping review presents a qualitative synthesis of evidence in summary and results tables. Twenty-one interventional studies (16 controlled trials and 5 before-after studies) conducted in 307 healthy and 327 at-risk participants were included. Six common markers [C-reactive protein (CRP) or high-sensitivity CRP (hs-CRP), IL-6, TNF-α, malondialdehyde (MDA), oxidized LDL (oxLDL), and antioxidant capacity] measured across 16 studies were systematically reviewed, and results were synthesized narratively. Random-effects model meta-analyses were conducted on 10 studies reporting hs-CRP, IL-6, and/or MDA. After consuming 100% OJ, healthy and at-risk participants showed significantly lower IL-6 concentrations (pooled net difference: −1.51 pg/mL; 95% CI: −2.31, −0.70) and lower, but nonsignificant, hs-CRP (pooled net change: −0.58 mg/L; 95% CI: −1.22, 0.05) and MDA (crossover trials pooled net difference: −0.06 μmol/L; 95% CI: −0.19, 0.08). Findings suggest that 100% OJ may reduce inflammation, but results should be interpreted with caution due to moderate risk of bias, very low strength of evidence, and the low number of subjects. This study was registered on PROSPERO (https://www.crd.york.ac.uk/prospero/) as CRD42021235438.