Supplementation with Citrus Low-Methoxy Pectin Reduces Levels of Inflammation and Anxiety in Healthy Volunteers: A Pilot Controlled Dietary Intervention Study

Background/Objective: Although low-methoxy (LM) pectin (polysaccharides extracted from citrus peels) can reduce inflammation by binding to and inhibiting the TLR-2 pathway in animal models and in vitro studies, the anti-inflammatory effects of LM pectin in humans and mood have not been explored to date. The purpose of this study is to assess the role of dietary supplementation with LM pectin in healthy volunteers on inflammatory markers and on mood, specifically anxiety and depression. Methods: We carried out a 4-week dietary intervention with LM citrus pectin on healthy volunteers (N = 14, age 40 ± 16 y, BMI 24.7 ± 3.0 kg/m², sex F 57%) comparing the effects of daily supplementation with 20 g of LM citrus pectin versus 10 g of maltodextrin as the control (N = 15 age 43.2 ± 11 y, BMI 25.18 ± 2.0 kg/m², sex F 66%). The effects on mood and inflammation were also tested with LM pectin at 5 g, 10 g and 15 g (2 weeks each) in an independent cohort of n = 15 healthy volunteers (age 36 ± 21 y, BMI 23.5 ± 2.4 kg/m², sex F 80%). We assessed serum levels of TNF-alpha (downstream from TLR-2 activation), IL-1 beta, IL-6, IL-10, INF-gamma, CRP, zonulin and TLR-2 concentration which were measured using ELISA in blood samples collected at both the baseline and follow-up visits. Validated measures of anxiety and depression were collected at baseline and follow-up. Results: Supplementation with 20 g of LM pectin resulted in decreases in the pro-inflammatory markers TNF-alpha, IL-1 beta, IL-6 and INF-gamma (all p < 0.05) and an increase in anti-inflammatory marker IL-10 (p = 0.01) at the end of the 4 weeks. No such effects were observed in the control group. In addition, a significant drop in anxiety scores (from 8.38 to 4.46, p < 0.006) was found with the 20 g/day intervention but not in the control arm. In the dose-response study, anti-inflammatory effects were seen only at 15 g for TNFα (p < 0.003) and a suggestive increase in IL-10 (p = 0.08), alongside a drop in TLR-2 (p < 0.027). No significant anti-inflammatory effects were observed at 5 g and 10 g doses of LM pectin supplementation. Significant dose-dependent drops in both anxiety and depression scores were found with 10 g (p < 0.001) and 15 g per day (p < 0.0002). Conclusions: The current study identifies anxiety-reducing and anti-inflammatory effects of supplementation with 15 g/day LM pectin in healthy humans. Further research is needed to elucidate the precise mechanism and to validate the efficient dose and minimum duration of supplementation.