Fruit Smoothie Supplementation and Inflammatory Biomarkers in Individuals Receiving Opioid Agonist Therapy: A Multicenter Randomized Controlled Trial

Background/Objectives: People with opioid dependence often experience elevated inflammatory markers and poor dietary habits. Evidence from other populations suggests that higher fruit and vegetable intake may reduce inflammation. This multicenter randomized controlled trial investigates whether offering a daily supplementation of 250 mL of fruit smoothie for 16 weeks to people undergoing opioid agonist treatment (OAT) can reduce inflammation biomarkers. Methods: 319 individuals were randomized to receive either a daily supplement of 250 mL of fruit smoothie in addition to standard OAT or standard OAT alone over 16 weeks. The primary outcome was the log-transformed change in high-sensitivity C-reactive protein (hs-CRP). Secondary outcomes included changes in cytokines (IL-8, IL-1RA, and MCP-1) and leukocyte counts. Results: No between-group differences were observed in changes in hs-CRP levels (0.96 (0.77; 1.21) mg/L), leukocytes (0.99 (0.93; 1.05)109/L), IL-8 (1.10 (0.84; 1.46) pg/mL), MCP-1 (0.94 (0.80; 1.11) pg/mL), and IL-1RA (1.06 (0.91; 1.23) pg/mL). High levels of inflammatory markers were observed at baseline in both the intervention group and the control group. Conclusions: After 16 weeks of offering fruit smoothie supplementation in patients receiving OAT, we did not detect a between-group reduction in inflammation markers such as hs-CRP, IL-8, MCP-1, IL-1RA, and leukocyte counts, under the achieved level of delivery and exposure. Nonetheless, persistently high levels of inflammatory markers were observed in this study.