The impact of tangeretin combined with whey protein on exercise-induced bronchoconstriction in professional athletes: a placebo-controlled trial.

Background: Exercise-induced bronchoconstriction (EIB) is highly prevalent in athletes. The objective of this study was to assess the therapeutic efficacy of daily tangeretin combined with whey protein supplementation over a period of 4 weeks in professional athletes with EIB.

Methods: Using a placebo-controlled, double-blind, paired, randomized trial design, a cohort of 30 professional athletes with EIB, consisting of 14 females and 16 males, was divided into two groups: the tangeretin combined with whey protein intervention group (TIG), and the placebo control group (PCG). Both the TIG and PCG underwent exercise challenge tests (ECT) and VO_2max tests before (ECT₁, V1) and after (ECT₂, V2) the intervention. Blood (eosinophils, neutrophils, and basophils) and serum (interleukin-5, IL-5; interleukin-8, IL-8; Clara cell secretory protein-16, CC16; immunoglobulin E, IgE) levels were measured early in the morning of ECT₁ and ECT₂, respectively. Lung function was assessed immediately before and post-ECT immediately.

Results: Tangeretin combined with whey protein use for 4 weeks attenuated the decrease in forced expiratory volume in 1 s (FEV₁) post trials (∆FEV₁(ECT1-ECT2): mean (SD) TIG -7.51(6.9)% vs. PCG -2.33(11.49)%, p = 0.013). Tangeretin also substantially attenuated IL-5 concentration (∆IL-5(T₁-T₅): Tangeretin -19.4% vs Placebo + 8.37%, p = 0.022); IL-8 concentration (∆IL-8(T₁-T₅): Tangeretin -17.28% vs Placebo + 6.1%, p = 0.012); CC16 concentration (∆CC16(T₁-T₅): Tangeretin -11.77% vs Placebo + 24.19%); and IgE concentration in the serum (∆IgE(T₁-T₅): Tangeretin -24.1% vs Placebo -3.9%), and significantly decreased neutrophil count (∆N(T₁-T₅): Tangeretin -11.34% vs Placebo + 0.3%) and eosinophil count in blood (∆N(T₁-T₅): Tangeretin -38.5% vs Placebo + 4.35%). Compared with V1, VO_2max (p = 0.042) and TLim (p = 0.05) of V2 were significantly increased in the TIG, and there was no significant change in the PCG. Meanwhile, six athletes in the TIG and 0 athletes in the PCG became EIB-negative at ECT₂; the overall negative conversion rate of EIB was 40.00% in TCG. Additionally, the number of cough symptoms decreased from 9 to 3 and dyspnea from 4 to 2 in the TIG.

Conclusion: After high-intensity exercise, athletes with EIB achieved significant improvements in lung function and blood inflammatory factors by combining tangeretin and whey protein supplementation. EIB athletes also showed longer exercise endurance and VO_2max at 4 weeks after TI. In addition, some patient symptoms disappeared after combination supplementation. The effect of this treatment on professional athletes with EIB was beneficial.