KLEAN-D™ by Klean Athlete® contains 5,000 I.U. of natural vitamin D3 per tablet. Vitamin D supplementation may help support immunity, musculoskeletal strength and physical performance in athletes.KLEAN-D™ is tested and certified by the NSF Certified for Sport® Program, which was created to meet the growing demands of athletes, coaches and healthcare professionals to certify that sports supplements are safe and completely free from banned substances. Every product that carries the NSF® for Sport mark has undergone stringent laboratory testing to confirm content, purity and compliance.Functions:Vitamin D, also known as the “sunshine vitamin” is an essential vitamin that plays many important roles in the proper functioning of the body. Though classified as a vitamin, vitamin D is actually a key regulatory hormone for multiple physiological processes. It is estimated that 1 billion people, including the elderly, young adults, athletes and children, are vitamin D deficient or insufficient. The main cause of vitamin D deficiency in the athletic population is the direct result of decreased ultraviolet B (UVB) radiation absorption into the skin, which especially affects indoor athletes and those who live and train in northern latitudes. Adequate vitamin D status is essential for ensuring normal calcium absorption and maintenance of healthy plasma calcium levels. Besides bone support, vitamin D has many other roles in the body, including modulation of cell growth, neuromuscular and immune function, and inflammatory support. Clinical research has shown there is a positive association between Vitamin D 25(OH)D serum concentrations, lower extremity function, proximal muscle strength and physical performance. Vitamin D deficiency is associated with diffuse muscle pain, muscle weakness predominantly in the proximal muscle groups, and a reduction in performance speed. A serum 25-hydroxyvitamin D level below 50 nmol/l has been associated with