Influence of Sunlight and Oral D3 Supplementation on Concentration and Exercise Performance in Elite Soccer Players
Great little study for my footballing friends on the role of vitamin D and its potential impact on performance. Vitamin D deficiency is an issue for most and as we enter the colder months this risk increases. I have included a summary below for those that don’t like to get into the sports science like me!
Highlights:
After 6 weeks of supplementing, not only did their performance improve but their testosterone levels increased.
Vitamin D plays a crucial role in both muscle strength and post-exercise recovery
Vitamin D is so critical and deficiency has been linked to cancers, high blood pressure, heart disease, diabetes, depression, fibromyalgia, chronic muscle pain, bone loss, and autoimmune diseases like multiple sclerosis
The aim of this study was to evaluate the influence of natural sun exposure and six weeks of a high dose of vitamin D supplementation on vitamin D, testosterone and cortisol serum concentrations as well as speed, power and VO2max in professional soccer players.
The research consisted of three stages. The first one, lasting 10 days, was conducted in January during a training camp in the south part of Cyprus at a latitude of 34 33°, where participants experienced natural sun exposure; it was called a winter sun exposure (WSE) period. The second stage, which was a supplementation period (SP), lasted 6 weeks, during which all subjects were randomly assigned either to an experimental group—EG (n = 15)—or a placebo group—PG (n = 13)—and were administered 6000 IU/d cholecalciferol or a placebo, respectively. The third stage took place in September, after summertime (summer sun exposure—SSE).
Vitamin D insufficiency seems to also be a prominent problem among athletes [2,6,7]. It has been estimated that during the winter season, almost 60% of outdoor athletes and 64% of indoor athletes have a level of 25(OH)D <30 ng/mL, which indicates insufficiency of vitamin D [11,12,13,14,15]. Athletes who live at latitudes of 35° degrees or below train outdoors and use sunscreen during summer and cover-up from cold during autumn, winter and spring are vulnerable to serum 25-hydroxyvitamin D (25(OH)D) insufficiency [16,17]. Therefore, optimal sport benefits occur at levels of 25(OH)D above the current definition of sufficiency [12,13].
Experimental data has proven that vitamin D plays a crucial role in both muscle strength and post-exercise recovery [1,18]. It reduces the risk of injury caused by inflammation [1,7,18,19], increases cell proliferation and differentiation [5], improves the functioning of the immune system and enhances the anti-inflammatory process [4], and improves muscle strength and power [5]. In the studies of Jastrzebska [7] and Close [14], vitamin D supplementation in a high dose of 5000 IU per day for 8 weeks improved vertical jump height, 10 m sprint times and VO2max in competitive soccer players [7,14]. A high concentration of 25(OH)D in soccer players may determine their aerobic and anaerobic performance capabilities during soccer-specific training such as small-sided games and may improve strength and explosive power [20,21]. These findings imply that athletes who have a vitamin D deficiency after supplementation, which increases its level to the recommended values, could increase their exercise performance and also contribute to faster recovery post-exercise [18].
According to the findings of the current study, although the study participants were professional soccer players, in most of them, the level of vitamin D was insufficient in the middle of the winter season, but also after the summertime. Vitamin D deficiency adversely affects the muscle, immune and hormonal systems. After 10 days of sun exposure and after 6 weeks of vitamin D supplementation, when 25(OH)D blood concentration increased, the soccer players achieved better results at the 5 m speed test and higher testosterone concentrations. This information may be valuable for sport scientists, coaches and players to enhance soccer performance and consider vitamin D supplementation. The obtained results confirm that vitamin D is very important for the muscle and hormonal system. Therefore, athletes should be constantly monitored for 25(OH)D blood levels throughout the year and should be supplemented if deficiencies or insufficient amounts occur.