Abstract
: Vitamin D can influence athletic performance and infection risk. This study aimed to investigate vitamin D status, hematochemical factors, anthropometric and performance parameters, and dietary habits in runners (n = 23) and sedentary healthy individuals (non-runners, n = 22) during the autumn season. Methods: Both groups had their serum 25-Hydroxyvitamin D (ng/mL) levels, blood and performance parameters, and dietary habits measured. Results: Serum 25-Hydroxyvitamin D levels were significantly lower in non-runners (runners: males 30.0±5.6, females 31.2±5.2 vs. non-runners: males, 22.8±6.5, females 24.7±6.5 ng/mL,p<
and dietary habits in runners (n = 23) and sedentary healthy individuals (non-runners, n = 22) during the autumn season. Methods: Both groups had their serum 25-Hydroxyvitamin D (ng/mL) levels, blood and performance parameters, and dietary habits measured. Results: Serum 25-Hydroxyvitamin D levels were significantly lower in non-runners (runners: males 30.0±5.6, females 31.2±5.2 vs. non-runners: males, 22.8±6.5, females 24.7±6.5 ng/mL,p< 0.001). White blood cells, monocyte, and neutrophil levels were higher in non-runners for both males and females. Among the subjects, 23 had optimal vitamin D levels (>29 ng/mL), while 22 had insufficient/deficient levels (<29 ng/mL), with a higher prevalence of insufficiency in non-runners compared to runners (63.6% vs. 34.8%;p= 0.053). Maximal isometric force and jump height were equal in both groups, but VO 2max was higher in runners. Linear regression analysis identified monocyte count as the only predictor of vitamin D levels for both males (y =−24.452 x + 40.520; R 2 = 0.200;p= 0.015) and females (y =−33.409 x + 45.240; R 2 = 0.368;p= 0.003). Conclusions: This study highlights significant differences in vitamin D status between runners and non-runners, with runners exhibiting higher serum 25-Hydroxyvitamin D levels, although this finding is likely due to the increased sun exposure that runners receive. It also provides valuable insights into the vitamin D status of healthy young sedentary individuals and runners, enhancing the understanding of how physical activity influences vitamin D levels. Keywords:vitamin D; leucocyte; endurance; runners; healthy people; vo 2max; maximal isometric force; monocyte 1. Introduction Vitamin D is a fat-soluble secosteroid hormone primarily obtained by exposure to ultraviolet B rays and secondarily by nutrition. UVB radiation may produce around 80% of this vitamin by converting 7-dehydrocholesterol to previtamin D. Ergocalciferol or cholecal- ciferol can be obtained by food. These levels might vary based on season, sun exposure du- Nutrients2024,16, 3912.
Nutrients2024,16, 3912 2 of 15 ration, and ethnicity, among other things [1]. In addition to effects linked to calcium home- ostasis and bone metabolism, vitamin D has been linked to other pleiotropic effects. It is widely believed that the interaction between 1–25 dihydroxy cholecalciferol (1,25(OH)2D3) and a nuclear vitamin D receptor (VDRn), which when liganded forms a heterodimeric complex with the retinoid-X receptor (RXR), mediates the actions of 1,25(OH)2D3. By attaching to target gene promoter sequences known as the vitamin D response element, this complex has the ability to either up- or down-regulate the transcription of many target genes [2]. Alongside the genomic pathway, a non-genomic pathway has also been proposed. These activities, which may include both VDRn and a membrane VDR, show up as the activation of signaling cascades or pathways that cause cells to react right away. They may also have an influence on general physiological processes by influencing epigenetic regulation [3]. Although some of the proposed mechanisms for non-genomic actions have only been describedin vitro, and the actual rolein vivohas yet to be demonstrated, they could help elucidate the potential of vitamin D as a regulator. Vitamin D is essential for the immune system, cardiovascular health, and musculoskele- tal health [4,5]. Furthermore, endothelial dysfunction, dyslipidemia, type 2 diabetes, and cardiovascular illnesses have all been linked to its lack [6]. Poor diet reduced cutaneous vitamin D synthesis (e.g., decreased sun exposure), altered expression of vitamin D metabolic enzymes, and decreased expression of the VDR in skeletal muscle are associated with an increased risk of insufficiency and abnormal vitamin D activity [7]. The degree to which VDR is expressed varies among tissues, determining the vitamin D’s degree of effect [ Vitamin D plays a crucial role in the formation and upkeep of robust bone structure, with the underlying mechanisms governing its effects well elucidated. Specifically, the active form of vitamin D, 1,25(OH)2D3, facilitates the absorption of calcium and phosphate through diverse pathways, thereby enhancing bone mineralization and serving as a pro- tective measure against bone deterioration and fractures. VDR was also found in skeletal muscle tissue [9], indicating that
and upkeep of robust bone structure, with the underlying mechanisms governing its effects well elucidated. Specifically, the active form of vitamin D, 1,25(OH)2D3, facilitates the absorption of calcium and phosphate through diverse pathways, thereby enhancing bone mineralization and serving as a pro- tective measure against bone deterioration and fractures. VDR was also found in skeletal muscle tissue [9], indicating that vitamin D may affect muscle in both physiological and pathological conditions [10,11]. Skeletal muscle oxidative stress, which impacts mitochon- drial activity and contributes to the development of skeletal muscular atrophy, is linked to vitamin D deficiency (low serum of 25-Hydroxyvitamin D: 25(OH)D), and the activation of VDR may be associated with these detrimental effects. Furthermore, vitamin D deficiency may exacerbate muscular atrophy [12], and it is also associated with a lower level of muscle function, as well as an increased risk of sarcopenia and other illnesses [13]. Conditions involving VDR knockout and vitamin D deficiency appear to imply detri- mental effects on the homeostasis of skeletal muscle. In C2C12, until the cells fully mature into myotubes, VDR expression is gradually lowered from a high level at the start of the differentiation process. Intracellular VDR concentration is higher in undifferentiated cells than in differentiated cells, according to a prior study by Kong et al. [14]. Given that several studies conducted on humans have linked inadequate levels of vitamin D to a decrease in muscular function [13], sports science is becoming increasingly interested in the potentiality of vitamin D in maximizing athletic performance [15]. Despite not much research on vitamin D in endurance athletes, a positive correlation between serum 25(OH)D concentration and maximum oxygen consumption (VO2max) (r = 0.29,p= 0.0001) has been demonstrated. Additionally, a significant interaction (p< 0.02) was discovered between self-reported hours of moderate to intense physical activity and 25(OH)D level [16]. The predominant focus of the existing literature on vitamin D and sports performance has centered on exploring the association between its levels and muscular strength and power. Supplementation with vitamin D has been shown to notably enhance muscle strength and power in athletes, with a pronounced impact observed
self-reported hours of moderate to intense physical activity and 25(OH)D level [16]. The predominant focus of the existing literature on vitamin D and sports performance has centered on exploring the association between its levels and muscular strength and power. Supplementation with vitamin D has been shown to notably enhance muscle strength and power in athletes, with a pronounced impact observed on lower-body muscular strength as opposed to upper-body muscle strength [17]. Conversely, insufficient vitamin D levels have been associated with a lower physical performance in indoor athletes [18–20]. However, the impact of vitamin D levels on athletic performance remains unclear across various populations, including outdoor athletes and healthy individuals, due to the significant variability in study outcomes.
Nutrients2024,16, 3912 3 of 15 One billion people are thought to be deficient in vitamin D globally [21]. A serum 25(OH) D concentration of less than 20, 20 to 29, and more than 29 ng/mL has been proposed to characterize vitamin D deficiency, insufficiency, and sufficiency, respectively [21]. Even while supplementation with vitamin D is often advantageous, there is no agreement on the suggested daily amount of vitamin D, and little information is presently available regarding vitamin D intake among young adult demographic groups, including university students. Although data on individuals with adequate vitamin D levels is limited, the advantages of supplementation in enhancing energy metabolism, muscle mass, and strength among those deficient in vitamin D are extensively acknowledged [1]. An examination of the resting metabolic rate, strength, and body composition of physically active young people who were sufficient in vitamin D and took a 12-week supplement found no further physiological advantages, with blood total 25(OH)D concentrations reaching supraphysiological levels [22]. In addition, vitamin D is crucial for the control of inflammatory response and immune system. According to recent research, immune cells, including monocytes, macrophages, dendritic cells, and lymphocytes, express VDR and enzymes that activate vitamin D and respond to vitamin D lowering the levels of pro-inflammatory cytokines [ According to Jones et al., vitamin D status modulates exercise-induced alterations in innate immune defense parameters and metabolomic signatures, including indicators of inflammation and metabolic stress [25]. It has been discovered that low vitamin D status has detrimental impacts on immunological health in athletic populations, which supports the advice that athletes’ circulatory 25(OH)D concentrations should be closely monitored [ It may be possible to obtain insight into the effects of various lifestyle choices on vitamin D status and its link to the immune system by comparing the experiences of athletes and non-athletes. This exploratory study aimed to investigate vitamin D levels, blood markers associated with immunological function, nutritional status, cardiorespiratory fit-ness, strength performance, and the correlation between these parameters in runners and non-runner healthy subjects. Our hypothesis is that an endurance sport such as running can help improve vitamin D status
the immune system by comparing the experiences of athletes and non-athletes. This exploratory study aimed to investigate vitamin D levels, blood markers associated with immunological function, nutritional status, cardiorespiratory fit-ness, strength performance, and the correlation between these parameters in runners and non-runner healthy subjects. Our hypothesis is that an endurance sport such as running can help improve vitamin D status in healthy subjects, and that vitamin D levels can influence performance and the immune system. 2. Materials and Methods 2.1. Participants Five local running associations were contacted and informed about the research project and inclusion/exclusion criteria. Out of thirty-two responses, seven runners were excluded for not meeting the criteria (four due to age and three due to insufficient weekly training volume). Additionally, two runners were excluded: one due to insufficient training caused by work commitments, and the other because they had the flu in the days leading up to the blood test. non-runners were also contacted through social media and local cultural associations. From the 25 responses received, three individuals were excluded for exceeding the maximum age limit. Ultimately, a cohort comprising forty-five individuals consisting of twenty-three amateur runners (fifteen males, eight females) and twenty-two sedentary healthy subjects (ten males, twelve females) completed this study. All participants were Caucasian and lived and trained at a latitude between 43.6 ◦ N and 43.9 ◦ N. The inclusion criteria were being healthy at the time of the study and aged between 25 and 45 years for all participants. For athletes, the eligibility criteria required at least three years of continuous training in endurance running prior to the start of the study.; a training frequency of at least three times/week; minimum average mileage outdoors of at least 50 km/week for men and 40 km/week for women. Exclusion criteria included being a smoker; consuming more than three alcoholic drinks per day; acute or chronic disease or treatment with drugs affecting muscle recovery and musculoskeletal performance; use of supplements such as vitamin D, calcium, iron or immune-stimulating complexes containing zinc or echinacea; and, for female subjects, early menopause. All participants provided written informed consent to
km/week for women. Exclusion criteria included being a smoker; consuming more than three alcoholic drinks per day; acute or chronic disease or treatment with drugs affecting muscle recovery and musculoskeletal performance; use of supplements such as vitamin D, calcium, iron or immune-stimulating complexes containing zinc or echinacea; and, for female subjects, early menopause. All participants provided written informed consent to participate in this study, following a medical health screening. The protocol was approved by the Ethics Committee of the University of Urbino “Carlo Bo”, Italy (54_24gennaio2023_running D+)
Nutrients2024,16, 3912 4 of 15 and was conducted in accordance with the Declaration of Helsinki for research with human volunteers. All data were collected during the 2023 autumn season (third week of October). Data about temperature, average daily solar radiation, and daily sunshine duration were obtained from the Osservatorio Metereologico “Alessandro Serpieri”, Department of Applied and Pure Sciences of the University of Urbino (Italy). 2.2. Experimental Design and Procedures After the recruitment phase, all participants were invited to the laboratories of the research center and followed the same routine: (i) compilation of the Physical activity rat- ing (PA-R) 0–15 scale questionnaire [26]; (ii) anthropometric assessments (weight, height); (iii) warm-up phase consisting of 5 min of walking/running treadmill followed by 5 min of mobilization exercises; (iv) a maximal isometric strength test using a sensor-controlled leg press; (v) after a 5 min rest, a countermovement jump test by using a force platform. Partic- ipants underwent serum analysis to measure vitamin D levels, blood count, leukocytes, high-sensitivity C-reactive protein (hs-CRP), calcium, and iron serum levels one week after the physical tests to avoid any acute influence on blood values. 2.3. Jump Test Vertical peak force (N) produced during vertical countermovement jumps (CMJ) performed with both legs and without any arm movement was measured using a force platform (MuscleLabTM system, type PFMA 3010e, Ergotest Innovation, AS, Stathelle, Norway) at a sampling rate of 100 Hz. Each participant started from a stationary erect position with knees fully extended. The participants then squatted down to about 90- of knee flexion before starting the upward motion. Subjects were instructed to keep their hands on their hips to prevent the influence of arm movements. The position of the feet was standardized during all tests at shoulder width. Participants were carefully observed before and during the jumps to ensure that the proper placement and jumping technique were used, and only correct trials were accepted. Subjects performed three to five warm-up jumps and then started a total of three maximal jumps. The highest jump determined by the impulse-momentum method was collected [27]. 2.4. Isometric Leg Press Test Peak force (in
were carefully observed before and during the jumps to ensure that the proper placement and jumping technique were used, and only correct trials were accepted. Subjects performed three to five warm-up jumps and then started a total of three maximal jumps. The highest jump determined by the impulse-momentum method was collected [27]. 2.4. Isometric Leg Press Test Peak force (in N) developed during closed-chain maximal isometric contractions was measured using a load cell (AIP, Varese, Italy) connected to an A/D converter (Muscle- LabTM system) mounted on a horizontal leg press (Technogym, S.p.A, Cesena, Italy) at a sampling rate of 100 Hz. The load cell was positioned in series with the sliding axis of the leg press so that the direct line of force was registered. Before each trial, the two chains fixing the load cell to the leg press were tensed to obtain a rigid system. Then, the load cell was reset to zero to negate the force produced on it by the two chains. The dynamometer was routinely calibrated using ISO-certified weights. The backrest of the leg press, on which the subjects were lying, was inclined 30 ◦ from the horizontal plane. The knee angle was set at about 100- and was controlled using an electronic goniometer (MuscleLabTM system). Before the maximal isometric contractions, subjects performed two to three submaximal isometric contractions as specific warm-up and practice. The participants then performed three maximal isometric contractions, with 2–3 min of recovery in between. Subjects were asked to exert force as hard and fast as possible for 5 s. During isometric leg-press tests, participants were verbally encouraged. The maximal of the peak forces measured during the three maximal trials was used as maximal isometric force [28]. 2.5. Maximal Oxygen Consumption Estimation Maximal oxygen consumption was estimated for all participants following the equa- tion proposed by Jamnick et al. (2016) [26]: Estimated VO2max (mL/kg/min) = 56.363 + (1.921×PA-R) – (0.381×Age) – (0.754×BMI) + (10.987×Gender)
Maximal oxygen consumption was estimated for all participants following the equa- tion proposed by Jamnick et al. (2016) [26]: Estimated VO2max (mL/kg/min) = 56.363 + (1.921×PA-R) – (0.381×Age) – (0.754×BMI) + (10.987×Gender)
Nutrients2024,16, 3912 5 of 15 where PA-R is the Physical activity rating (PA-R) questionnaire assessed on a scalefrom 0 to 15; Age is participants’ age in years; BMI is the Body Mass Index in kg/m 2 ; and Gender is 0 for females and 1 for males. 2.6. Dietary and Training Monitoring The participants’ diet and training was monitored for the two weeks prior to serum analysis. They were asked to keep a food and training diary, and an experienced nutrition researcher performed a daily 24-hour recall to remind them to fill in the diary and ensure it was done correctly. The participants were instructed on how to properly complete the food diaries, including methods for measuring their food. Subjects were encouraged to include all food and beverages consumed over the course of the fourteen-day period in their food diary as detailed and accurate as possible. In fact, the food diary must contain date, time and weight (grams) of all the meals consumed. The missing data from the questionnaire and clarifications on food consumed/portions were followed up via email or phone call. Food diary information was collected and then processed using WinFood nutritional analysis software version Pro 3.37.3 (Medimatica S.u.r.l., Teramo, Italy), and macro- and micronutrients, particularly average calcium and vitamin D intakes, were included in the analyses. The daily intake of macronutrients (proteins, lipids, and glucides) was reported in grams (g), percentage (%), and grams per kilogram of body weight (g/kg/day). Regarding micronutrients, they are expressed in milligrams (mg) and micrograms (µg). Training diary was completed with information about training type (continuous running or interval training), volume (in km), and rate of perceived exertion (RPE) for each session (CR-10). 2.7. Blood Analysis One week after the anthropometric and performance tests, all participants were in- vited to a blood testing center (Biolab s.r.l., Pesaro, Italy) to undergo blood sampling. All participants were asked to present themselves by 8.30 a.m. with an empty stom- ach for at least 8 h. The laboratory analyses were performed blind, i.e., the operator was unaware of the group to which the subject belonged (runners and
Description
The study highlights differences in vitamin D status between runners and non-runners.