Dietary supplementation with rice bran fermented with Lentinus edodes increases interferon-γ activity without causing adverse effects: a randomized, double-blind, placebo-controlled, parallel-group study

BACKGROUND: The purpose of this study was to investigate the hypothesis that dietary supplementation with rice bran fermented with Lentinus edodes (rice bran exo-biopolymer, RBEP), a substance known to contain arabinoxylan, enhances natural killer (NK) cell activity and modulates cytokine production in healthy adults. METHODS: This study was designed in a randomized, double-blind, placebo-controlled, and parallel-group format. Eighty healthy participants with white blood cell counts of 4,000-8,000 cells/μL were randomly assigned to take six capsules per day of either 3 g RBEP or 3 g placebo for 8 weeks. Three participants in the placebo group were excluded after initiation of the protocol; no severe adverse effects from RBEP supplementation were reported. NK cell activity of peripheral blood mononuclear cells was measured using nonradioactive cytotoxicity assay kits and serum cytokine concentrations included interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, IL-4, IL-10, and IL-12 were measured by Bio-Plex cytokine assay kit. This study was registered with the Clinical Research Information Service (KCT0000536). RESULTS: Supplementation of RBEP significantly increased IFN-γ production compared with the placebo group (P = 0.012). However, RBEP supplementation did not affect either NK cell activity or cytokine levels, including IL-2, IL-4, IL-10, IL-12, and TNF-α, compared with the placebo group. CONCLUSIONS: The data obtained in this study indicate that RBEP supplementation increases IFN-γ secretion without causing significant adverse effects, and thus may be beneficial to healthy individuals. This new rice bran-derived product may therefore be potentially useful to include in the formulation of solid and liquid foods designed for treatment and prevention of pathological states associated with defective immune responses.