Efficacy of Phellinus linteus extract on immunity enhancement: A CONSORT-randomized, double-blind, placebo-controlled pilot trial

Immunity is a major system that defends the human body from the outside. Recently, interest in foods related to immunity has been increasing. METHODS: The purpose of this clinical trial was to determine the safety and efficacy of Phellinus linteus (PL) extract in improving immune function. A total of 30 participants were randomly assigned to 3 groups: the PL1000 group (n = 10) took 1000 mg of PL extract and 1000 mg of dextrin per day; the PL2000 group (n = 10) took 2000 mg of PL extract per day; and the placebo group (n = 10) took 2000 mg of dextrin per day. All participants took 2 capsules twice a day for 8 weeks. We measured their natural killer cell activity and cytokine levels in blood before and after consuming the clinical trial food. Variables were also investigated to evaluate safety, such as adverse reactions, vital signs, and abnormal findings. Student t test or the Mann–Whitney U test, a paired t test or the Wilcoxon signed-rank test, a chi-square test, analysis of variance, and Kruskal–Wallis test were conducted according to the characteristics of the data to compare the differences between each group before and after participants ate the clinical trial food. RESULTS: The natural killer cell activity and interleukin-6 levels of the PL1000 group tended to improve compared to those of the placebo group. Immunoglobulin G1, immunoglobulin G2, and immunoglobulin M levels did not show significant changes, but tended to improve in the PL1000 and PL2000 groups compared to those of the placebo group. Both the Per Protocol and Intention to Treat populations had improved validation parameters. It is safe because no hazards were found in the safety assessment. CONCLUSION: PL extract can help improve immunity. Evidences to conduct the main clinical trial is secured through this pilot study. A future large-scale main trial will be conducted based on this pilot study results.