Sports Health Benefits of Vitamin D

Vitamin D is a necessary nutrient that must be obtained from the diet when sufficient quantities cannot be synthesized. Vitamin D3 is primarily produced following incidental skin exposure to ultraviolet B irradiation, with very little derived from dietary sources.Cutaneous production can be absent or dramatically reduced due to skin coloration and sunblock use.Melanin in the skin of Africans or African Americans blocks nearly 99% of vitamin D production, with similar decreases in cutaneous synthesis achieved following application of SPF 15 sunblock.Indoor activities, pollution, time of day, increasing age, latitude, and seasonal changes all affect cutaneous vitamin D production.

As mentioned, very little vitamin D is obtained from dietary sources, including D2   (ergocalciferol, plant) and D3 (cholecalciferol, human) forms. Of note, vitamin D3 is more potent than D2 and should be used for supplementation.Unfortunately, the average American diet supplies very little of the 4000 to 5000 IU of vitamin D3 used per day,even diets with significant amounts of wild-caught fatty fish.The accepted definition of vitamin D sufficiency is 25-hydroxyvitamin D3, (25(OH)D) above 30 ng/mL.

Based on this definition, vitamin D deficiency affects all age groups and demographics. Fifty to seventy percent of children and adolescents are vitamin D deficient.Over 75% of whites and 90% of African Americans and Latinos are vitamin D deficient, with increasing age increasing the likelihood of deficiency.In addition, deficiency rates have doubled from 1994 to 2004 with multiple factors responsible, including sun avoidance, sunblock use, and increasing obesity rates causing sequestration of this fat-soluble vitamin.Vitamin D deficiency is associated with numerous health effects, with the musculoskeletal system affected by both genomic and nongenomic mechanisms.

Vitamin D is a secosteroid hormone. Upon activation to1,25 hydroxyvitamin D3—1,25(OH)D, or calcitriol—vitamin D–responsive gene expression is altered, with over 1000

vitamin D–responsive genes identified.These genes affect muscle protein synthesis, muscle strength, muscle size,reaction time,balance,coordination, endurance,inflammation,and immunity—all important to sports health and athletic.