Efficacy of Phellinus linteus (sanghuang) extract for improving immune functions: Study protocol for a randomized, double-blinded, placebo-controlled pilot trial

BACKGROUND: With the increase in the prevalence of chronic diseases, enhancing immunity has become an important challenge. Health functional foods, such as Phellitus linteus (PL), are known to improve immune function. In previous laboratory studies, it has been reported that PL has anticancer activities. In this study, we will evaluate if PL improves immune functions in adults with reduced immunity and identify its effects on immunity factors. METHODS: This study will be a single-center, randomized, double-blinded, and placebo-controlled trial. Study participants will be randomly allocated to 3 experimental groups: those taking PL 1000 mg, PL 2000 mg, or placebo. Total duration of the clinical trial will be 8 to 10 weeks. Study participants will have follow-up visits every 4 weeks and the effect and safety will be assessed at the second and third visits. All participants will be asked to maintain a dosage schedule for this protocol. The primary outcome will be natural killer (NK) cell activity and the secondary outcomes will include peripheral white blood cell (WBC) count; levels of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin (IL)-1β, IL-2, IL-6, and IL-12 to assess autoimmune reactivity; and levels of immunoglobulin (Ig)G1, IgG2, and Immunoglobulin M (IgM) to assess allergic activity. Repeated measure analysis will be used to measure primary efficacy based on full analysis set. DISCUSSION: This study has limited inclusion and exclusion criteria and a well-controlled intervention. It will be the first randomized controlled trial to assess the efficacy and safety of PL in adults with reduced immunity. This study will provide insights into the mechanisms underlying the immune-stimulating effects of PL and lay the groundwork for further studies.