(P30-006-23) Randomized, Double-Blind, Placebo-Controlled Trial of Onion Peel Extract on Immune Enhancement

Objectives: The purpose of the present study was to investigate the hypothesis that supplementation of onion peel extract modulated natural killer (NK) cell activity and serum levels of cytokine in Korean adults.

Methods: In randomized, double-blind, placebo-controlled, and parallel-group trial, 80 participants aged between 19 and 75 with white blood cell counts of 4,000-8,000 cells/uL, symptoms of upper respiratory infection at least once within the previous 12 month, and perceived stress scale over 14 were recruited. Participants were randomly assigned to take four capsules per day containing either 1000 mg onion peel extract produced by hot water (OPE) or placebo for 8 weeks. Seven participants withdrew their consent, and three participants were excluded per protocol analysis for taking prohibited medication during the study, and outlier with measurements. Activity of NK cell isolated from PMBCs, serum levels of cytokines, such as interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, IL-6, IL-12, and IL-1β, and safety measures such as complete blood test, blood chemistry, and urine analysis were measured at baseline and week 8. Wisconsin upper respiratory symptom survey (WURSS)-21 was measured at baseline, week 4, and week 8. This study was approved by the Hanyang University Institutional Review Board (HYUIRB-202210-001-1) and registered with the Clinical.Trials.gov (NCT05666752).

Results: Supplementation of OPE had no significantly effect on NK cell activity, levels of IL-2, IL-6, IL-12, IL-1 β, INF-γ, and TNF-α, safety measures, and adverse events compared to the placebo. However, participants supplemented with OPE had significantly (P=0.015) higher WURSS-21 symptom score than those with placebo at baseline. Supplementation of OPE significantly (P = 0.038) increased NK cell activity compared to placebo in participants with higher than median of WURSS-21 symptom score.

Conclusions: The present study suggested that supplementation of OPE could improve NK cell activity in participants with higher WURSS-21 symptom score without causing any adverse effects.

Funding Sources: This study was supported by the R&D grant from the Rural Development Administration, Republic of Korea.