In our research we hypothesized, that vitamin C could increase antioxidant capacity and reduce oxidative stress and in this way lead to decrease in expression of genes induced by oxidative stress, such genes associated with inflammation. Unfortunately, our hypothesis have not been confirmed by research. In order to examine changes caused by vitamin C supplementation we selected women similar in body mass. As a result, the dose of vitamin C per kg of body weight was similar within supplemented group. Although we not assumed the differences in body composition at baseline and after 6 weeks of 1000 mg vitamin supplementation, our participants differed significantly in muscle mass and fat mass at baseline, despite no significant differences in total body mass and body mass index (BMI.) Moreover, a significant decrease in body mass and fat mass was observed in CON group after 6 weeks of training without supplementation (strong effect for total body mass). Thus, in the best case vitamin C did not influence body mass and fat loss. Opposite data was reported by Johnston et al. . The authors postulated that plasma vitamin C concentration inversely related to body mass and markers of obesity, however 500 mg of vitamin C supplementation did not influence the circulating concentration of adiponectin (necessary for lipolysis) in adult participants. The hindered reduction of fat mass observed in our participants receiving supplementation could be associated with the high dose of vitamin C supplementation (1000 mg/day). It is possible, that this supplementation affects IL-6 expression in adipose tissue, leading to a decrease in IL-6 expression. In the literature there are some studies in which IL-6 is considered an important factor to induce fat loss by promoting white adipose tissue and browning lipolysis . However, Wong et al.  postulated the negative relationship between intake of vitamin C and risk of developing metabolic syndrome, associated with obesity.
The concentration of vitamin C in the serum of our subject at baseline was average, and a significant increase was noted in SUP group after 6 weeks 1000 mg vitamin C supplementation (strong effect size). The final concentration was close to the upper limit of normal in supplemented group. Unfortunately, increase in vitamin C concentration was associated with a tendency to increase prooxidative and antioxidative status (strong effect size) and finally we observed tendency to increase pro/antioxidative balance. Generally, in both groups, six weeks of training supported or unsupported by vitamin C supplementation proved to be too short for any significant changes in pro or antioxidative status. Similar data after 6 weeks of supplementation during 12 weeks of training was observed in previously published data . It seems, that 6 weeks of vitamin C supplementation in a dose of 1000 mg/day does not influence pro and antiinflammatory status, independently of body mass and BMI. Similar reports can be found in the literature. No changes in pro/antioxidative balance were reported by Bunpo and Antony , although their participants were healthy young men who received 250–500 mg vitamin C per day during 12 weeks of exercise. Moreover, the cited authors reported a decrease in antioxidative enzyme activity in erythrocytes. Assuming no influence of this supplementation on pro/antioxidative balance it is probable that vitamin C could show oxidative action, which is often indicated by other various authors [3, 33, 34]. It is possible, that vitamin C could promote generation of reactive oxygen species i.e., OH, O2−, H2O2 or ferryl ion [3, 8].
In terms of the obtained results, changes in genes associated with immune response may not be consistent with our assumptions. Our hypothesis, that vitamin C supplementation in a dose of 1000 mg/day will cause a decrease in proinflammatory and an increase in anti-inflammatory gene expression was not confirmed. First of all, no significant changes in gene expression of all studied genes were noted in the SUP group. Only in the CON group, CCL2 mRNA significantly decreased after the training period. This gene is not often investigated under exercising conditions, despite its important functions in inflammation. Overexpression of IL-6 and CCL2 could be a reason for the development of acute inflammation and inflammatory pain . The most common changes in the CCL2 expression in humans are indicated in peripheral blood mononuclear cells (PBMC) or leukocytes. According to Strömberg et al.  its expression in muscle cells was marginal. CCL2 mRNA and CCL2 protein are responsible for macrophage induction. It is well documented, that CCL2 released by astrocytes has an impact on cognitive dysfunction and brain inflammation [37, 38]. It means that a decrease in expression may have a positive impact on cognitive function and decrease brain inflammation. Thus, obtained results showed positive changes affected by training in those not supported by vitamin C supplementation.
In the literature there is data regarding the influence of vitamin C supplementation mainly on plasma CRP. Bianias et al.  reported that vitamin C supplementation is associated with a decrease in CRP in patients undergoing hemodialysis. Ellulu et al.  reported that vitamin C (500 mg twice daily) has potential effects in alleviating inflammatory status by reducing high-sensitivity C-reactive protein (hs-CRP) and IL-6in hypertensive and/or diabetic obese patients . Unfortunately, their research was conducted on sick people, for which vitamin C supplementation may have different effects than in healthy people, when subjected to effort. Results of ultramarathon runners showed that vitamin C caused an increase in CRP by reducing the secretion of cortisol . Our results (no changes in CRP mRNA in both groups) are consistent with the data published by Righi et al. . The authors observed no changes in CRP following single both of acute exercise.
It is well documented that changes in IL-1 caused by exercise are less than another in cytokines, e.g. IL-6. The available data shows that the increase in IL-1 is dependent on training load. Significant increase in this cytokine was observed after ultramarathon, but only in people supplemented by 1500 mg of vitamin C (at a dose of 500 mg of vitamin C there was no such effect). This increase was small in comparison to IL-6. No changes in IL-1 mRNA were observed in our study which confirms lower induction of this cytokine gene expression by effort and no effect of six weeks of 1000 mg/day vitamin C supplementation.
In both groups the same tendency to decrease in IL-6 mRNA was observed. Thus, this effect is mainly associated with training. Our results are compatible with data from other literature studying the influence of aerobic exercise on the modulation of the cytokine profile. Although available data is mainly associated with changes in inflammatory (IL-6 or IL-1) protein measurement in plasma or serum. According to ElKader and All Jiffri , significant decrease in IL-6 and increase in IL-10 was observed following 6 months of aerobic exercise in elderly subjects. Thus, 6 weeks of training may be too little to obtain significant differences.
Moreover, Canali et al.  suggested a small effect of vitamin C supplementation on gene expression, especially those associated with immune response. In the cited research the authors investigated changes in gene expression in five volunteers supplemented high dose of vitamin C (1 g/day) over 5 days. They suggested that vitamin C plays important role in the modulation of IL-10 mRNA during an inflammatory stimulus. We agree with these authors that in healthy, well nourished participants, supplementation of vitamin C is “buffered” within a homeostatic physiological equilibrium. However, tendency to increase IL-10 with a simultaneous decrease in IL-6 is important in terms of adaptation to training . This was clear in the supplemented group, however, 6 weeks of supplementation did not significantly influence this change.