It is common for athletes to experience times of an unexpected loss of stamina or a plateau in performance gains. There are many factors that could be contributing to this confounding condition. Often, after all the usual culprits are ruled out, there is no reasonable explanation for this frustrating roadblock. 

The possibility of vitamin D deficiency is often overlooked. Vitamins and minerals are necessary in minute amounts for maintaining good health. They are organic components found in foods and some beverages. Vitamin D is absorbed into the skin through exposure to sunlight, specifically UVB rays. It can also be ingested by the consumption of certain foods or beverages. This important vitamin is necessary for the proper absorption of calcium by the body. Once ingested through food consumption or absorbed through sun exposure, it is converted to the metabolically active form called dihydroxyvitamin D, commonly known as calcitrol. 

Maintaining consistent optimal levels of vitamin D can be very beneficial to the intense athlete. Proper amounts of calcitrol have been shown to produce an antimicrobial peptide. These peptides, or proteins, fight infections such as influenza virus and the common cold. Seasonal fluctuations in vitamin D levels in the population may explain why winter months result in increased incidences of these illnesses even in healthy athletic individuals. An athlete that maintains the optimal levels of vitamin D will have a stronger immune system due to these peptides; therefore, he or she will have less downtime in the training schedule than an athlete of similar caliber who is deficient in vitamin D. 

Intense exercise increases the body’s production of pro-inflammatory cytokines. Production of these cytokines has been long associated with training related injury as well as over training. Sufficient physiologically active vitamin D is associated with the increased production of anti-inflammatory cytokines which aid in a quicker recover for the athlete and protect against over training injuries. 

A stronger immune system coupled with the ability to recover from intense training more quickly and with less chance of sports related injuries can be two factors that give an athlete the edge over a competitor.