3. Discussion
inflammation, skeletal muscle damage
INFLAMMATION, OXIDATIVE STRESS
In the current study, we tested the hypothesis that a 90-day (7 times per week) supplementation program with 6 g of lyophilized black chokeberry extract affects the adaptation process and exercise-induced inflammation and exerts beneficial effects on the selected parameters of iron metabolism. We focused mainly on the interaction between the supplementation and changes in the serum levels of LA, and selected markers of inflammation (IL-6 and IL-10), oxidative stress (8-OHdG), antioxidant potential (TAC), iron metabolism (iron, ferritin, hepcidin), and skeletal muscle damage (myoglobin). We show that administration of a lyophilized black chokeberry extract leads to an increase in the serum TAC and IL-10 levels, and a decrease in IL-6 levels during the recovery period after maximal aerobic testingThe effectiveness of the tested supplementation program was reflected by a significant post-supplementation increase in the resting serum TAC and a decrease in 8-OHdG levels (In the supplemented group, lactate levels after MAE were significantly higher than those in the placebo group, which may suggest an improvement of anaerobic metabolism as a result of training and supplementation. Higher post-exercise lactate concentrations after the supplementation period indicate that athletes’ exercise tolerance increased. Similar results were found by Pilaczynska-SzczesniakIn the current study, the effect of MAE on young football players was reflected by a post-exercise decrease in the serum TAC, which was observed both prior to and after the supplementation (While TAC increased after the supplementation, we also observed a decrease in resting 8-OHdG levels, which remained low after MAE in the supplemented group compared to placebo. 8-OHdG is one of the predominant forms of ROS-induced DNA lesions and, thus, is a commonly used biomarker of oxidative stress [It is notable that flavonoid extracts, such as black chokeberry lyophilizate, are rich in flavonoids, α-tocopherol, and ascorbic acid. These substances protect against increased oxidative stress and suppress free radical generation. Furthermore, they interact with each other. On the one hand, high flavonoid concentrations have a protective effect on oxidative changes facilitated by ascorbic acid. On the other hand, high concentrations of ascorbic acid positively interact with flavonoid activity [In the current study, we also showed that the favorable changes observed during the supplementation period are associated not only with the changes in TAC but also with changes in many inflammatory markers, such as IL-6 and IL-10. IL-6 plays an important role in the regulation of inflammation. Typically, physical exercise is accompanied by an increase in IL-6 levels. We observed this effect in the current study in both the supplemented and control groups. Importantly, supplementation with the lyophilized black chokeberry extract reduced the increase in IL-6 levels for up to 24 h after exercise. To date, this effect has been reported only rarely [In the current study, supplementation with the lyophilized black chokeberry extract affected the resting levels of IL-6. Unlike Skarpańska–Stejnborn et al., who reported that there is no effect of proposed supplementation on IL-6 [Flavonoids maintain the balance between oxidized, reduced, and radical forms of antioxidants, which is an important element of protection against increased ROS levels. In the current study, in addition to affecting IL-6 levels, the tested supplementation protocol rich in flavonoids affected serum levels of IL-10, another inflammatory marker. IL-10 is an anti-inflammatory cytokine whose blood levels increase after exercise. Accordingly, we here observed a significant increase in IL-10 levels after MAE. The effect was more pronounced in football players in the supplemented group than in those in the control group. Notably, in the supplemented group, the IL-6 level increase was smaller than that in the control population. IL-6 release from the exercising muscle is accompanied by the appearance of IL-10 and other anti-inflammatory cytokines in the circulation. The presented observations indicate that the lyophilized chokeberry extract induces an anti-inflammatory response independent from IL-6 [According to Aaseth and Stoa Birketvedt [The current study has some potential limitations. The first limitation is the relatively small sample size. Further studies should be performed, with an increased sample size and/or implementing a crossover study design. Second, the football players’ field position or volume of competition play (starter vs. non-starter) was not considered during randomization. Third, the study did not include a control of the dietary regime, and potential changes in the amount of consumed fruits and/or vegetables rich in flavonoids might have interfered with the applied intervention. In addition, we used an indirect VO