The active form of vitamin D (calcitriol) exerts its biological effects by binding to nuclear vitamin D receptors (VDRs), which are found in most human extraskeletal cells, including skeletal muscles. Vitamin D deficiency may cause deficits in strength, and lead to fatty degeneration of type II muscle fibers, which has been found to negatively correlate with physical performance. Vitamin D supplementation has been shown to improve vitamin D status and can positively affect skeletal muscles. The purpose of this study is to summarize the current evidence of the relationship between vitamin D, skeletal muscle function and physical performance in athletes. Additionally, we will discuss the effect of vitamin D supplementation on athletic performance in players. Further studies are necessary to fully characterize the underlying mechanisms of calcitriol action in the human skeletal muscle tissue, and to understand how these actions impact the athletic performance in athletes.

A well-balanced diet is one of the main factors that may play a supportive role in enhancing acute training stimuli in optimal training adaptation. The aim of the present study was to examine the energy and macro- and micronutrient intake including and excluding supplements among top-level Polish football players during one week of the general preparatory period. In addition, the study looked at whether athletes consume carbohydrates in recommended amounts, depending on the completed training sessions. A total of 26 professional football players were included in the study. The preseason dietary intake was assessed using a 7-day estimated food record. The energy value of the diet and the amounts of the dietary ingredients were assessed using the software Dieta 6.0. The average consumption of energy, vitamin B₂, vitamin C, vitamin E, folate, and calcium was lower than recommendations, and average intake of sodium and potassium was higher than the norm in the diets of the athletes. The results of this study do not confirm the justification for adding protein preparations to diets of the studied players. Furthermore, football players dietary carbohydrate intake was relatively low in comparison to requirements based on training loads. Based on our results we conclude that further work is necessary to reinforce education about nutritional habits and adjust nutritional strategies to individual needs to enhance athletic performance.

The aim of this review was to determine whether male football players meet dietary recommendations according to a UEFA expert group statement and to identify priority areas for dietetic intervention, including training periodization and field position. A database search of PubMed, Web of Science, EBSCO and Scopus was performed. To be included within the final review, articles were required to provide a dietary intake assessment of professional and semi-professional football players. A total of 17 studies met the full eligibility criteria. Several studies showed insufficient energy and carbohydrate intake compared to the recommendations. A majority of athletes consume adequate protein and fat intakes compared to the recommendations. In addition, several studies showed the insufficient intake of vitamins and minerals. This systematic review showed that football players do not meet the nutritional recommendations according to the UEFA expert group statement. Future research should be focused on how to apply nutritional recommendations specific for athletes in accordance with training periodization and positions on the field.

Carnosine is a dipeptide formed from the amino acids β-alanine and histidine and found in large amounts in the brain and muscle, especially fast twitch muscle. Carnosine has an antioxidant role and accounts for about 10% of the muscle's ability to buffer the H+ ions produced by high intensity exercise. Due to the interesting role of carnosine, the aim of the study was observe the effects of carnosine intake on pro-antioxidant status in highly trained athletes exposed to intense exercise.Fourteen male athletes from the Polish national kayak and canoe teams participated in placebo-controlled and cross-over study. The athletes were supplemented with 4 g/d carnosine for 14 days. Blood samples were collected before and 30 min, 24 h and 48 h after 2000 m exercise trial. In blood, hydrogen peroxide (H2O2), nitric oxide (NO), markers of RO/NS activity 8-isoprostanes and 3-nitrotyrosine, total (GSHt) and oxidised glutathione (GSSG), antioxidant status (APO) and superoxide dismutase (SOD) were determined. There were not observed statistically significant differences in exercise-induced changes in H2O2 and NO concentrations and SOD activity after carnosine intake. However, carnosine prevented an increase in 8-isoprostanes, 3-nitrotyrosine and GSSG concentrations as well as elevated redox status (GSHt-2GSSG)/GSSG at post-exercise period.Although, oral supplementation with 4 g carnosine did not affect RO/NS generation, it significantly attenuated exercise-induced glutathione loss, reduced oxidation/nitration markers concentration and SOD activity. These results suggest that carnosine could provide antioxidative protection for highly trained athletes.

Exposure to intense physical exercise increases reactive oxygen and nitrogen species production. The process can be modulated by dipeptide bioavailability with antioxidant scavenger properties. The effects of dipeptide intake in combination with physical exercise on the oxi-antioxidant response were examined in a randomized and placebo-controlled trial. Blood samples were collected from 20 males aged 21.2 ± 1.8 years before and after 14-day intake of chicken breast extract (4 g/day), which is a good source of bioactive dipeptides. A significant increase in the NO/H₂O₂ ratio was observed in the 1st and 30th minute after intense incremental exercise in dipeptides compared to the placebo group. Total antioxidant and thiol redox status were significantly higher in the dipeptide group both before and after exercise; η² ≥ 0.64 showed a large effect of dipeptides on antioxidant and glutathione status. The level of 8-isoprostanes, markers of oxidative damage, did not change under the influence of dipeptides. By contrast, reduced C-reactive protein levels were found during the post-exercise period in the dipeptide group, which indicates the anti-inflammatory properties of dipeptides. High pre-exercise dipeptide intake enhances antioxidant status and thus reduces the oxi-inflammatory response to intense exercise. Therefore, the application of dipeptides seems to have favourable potential for modulating oxidative stress and inflammation in physically active individuals following a strenuous exercise schedule.

Vitamin D affects both innate and adaptive immunity. Most of the effects of vitamin D on innate immunity are anti-inflammatory. In monocytes/macrophages, vitamin D suppresses the production of the inflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-8. Therefore, the aim of our study was to investigate the relationship between 25(OH)D concentration and selected cytokines—IL-6, TNF-α, and IL-1β, which are hemogram parameters for professional football players. We enrolled 41 Polish premier league soccer players. The mean age, career duration, and VO_2max were, respectively: 22.7 ± 5.3 years, 14.7 ± 4.5 years, and 55.8 ± 4.0 mL/kg/min. Serum levels of 25(OH)D were measured by electrochemiluminescence (ECLIA) using the Elecsys system (Roche, Switzerland). Serum levels of IL-6, IL-1β, and TNF-α were measured by ELISA (R&D Systems, Minneapolis). Blood count with smear was measured on a Sysmex XT-4000i analyzer (Sysmex Corporation, Japan). Our study showed decreased serum 25(OH)D levels in 78% of the professional players. We found a significant negative correlation between 25(OH)D levels and TNF-α and LYMPH (%). The results also demonstrated a statistically significant positive correlation between vitamin D levels and NEUTH (%), NEUTH (tys/µL), and EOS (tys/µL). Based on the results of our study, we concluded that football players from Poland are not protected against vitamin D insufficiency in winter months. Moreover, vitamin D deficiency may be associated with an increased pro-inflammatory risk in well-trained athletes.