Influence of 6-weeks Supplementation With Vitamin D Portobello Mushroom Powder on Muscle Function and Performance, Innate Immune Function, and Exercise-induced Muscle Damage and DOMS in NASCAR Pit Crew Members

Vitamin D2 is found naturally in sun-exposed mushrooms, and vitamin D3 is synthesized in the skin when exposed to sunlight and is present in oil-rich fish such as salmon, mackerel, and herring. Mushrooms contain very little or any vitamin D2 but are abundant in ergosterol, which can be converted into vitamin D2 by ultraviolet (UV) illumination (Eur J Clin Nutr. 2011;65:965-71). In recent decades, there has been increased awareness of the impact of vitamin D on muscle function (Scand J Med Sci Sports. 2010;20:182-90). In the early 20th century, athletes and coaches felt that ultraviolet rays had a positive impact on athletic performance, and evidence is accumulating to support this view. Both cross-sectional and longitudinal studies support a functional role for vitamin D in muscle, and the discovery of the vitamin D receptor in muscle tissue provides a mechanistic pathway for understanding the role of vitamin D within muscle. Studies in athletes have found that vitamin D status is variable and is dependent on outdoor training time (during peak sunlight), skin color, and geographic location (Pediatr Clin North Am. 2010;57:849-61). 25(OH)D is the best indicator and major form of vitamin D in the blood, with a circulating half-life of 2-3 weeks. Vitamin D deficiency is defined as a plasma vitamin D [25(OH)D] level of less than 20 ng/ml, with vitamin D insufficiency defined as 21-29 ng/ml. Estimates are that 20-100% of children, young and middle-aged adults, and community-dwelling elderly men and women are vitamin D deficient (J Clin Endocrinol Metab. 2011;96:1911-30). Purpose: To determine if 6 weeks supplementation with Dole Vitamin D Portobello Mushroom Powder (4,000 IU/day) can, 1) increase winter serum vitamin D levels, and measure whether vitamin D supplementation 2) has a chronic influence on muscle function and strength, and innate immune function, and 3) can attenuate exercise-induced muscle damage and delayed onset of muscle soreness (DOMS) in athletes.