A review of 2008/2009 recommended dosages of 1,000 IU cholecalciferol per 10 ng/mL required serum increase, to be given daily over two to three months. In another proposed cholecalciferol loading dose guideline for vitamin D-deficient adults, a weekly dosage is given, up to a total amount that is proportional to the required serum increase (up to the level of 75 nmL/L) and within certain body weight limits, to body weight.According to new data and practices relevant to vitamin D levels in the general population in France, to establish optimal vitamin D status and frequency of intermittent supplement dosing, patients with or at high risk for osteoporosis and vitamin D deficiency should start supplementation with a loading phase consisting of 50,000 IU weekly of vitamin D for 8 weeks in patients with levels <20 ng/mL and 50,000 IU weekly for 4 weeks in patients with levels between 20 and 30 ng/mL. Subsequently, long-term supplementation should be prescribed as 50,000 IU monthly. Should pharmaceutical forms suitable for daily supplementation become available, patients displaying good treatment adherence could take a daily dose determined based on the 25(OH)D level. Until now, there are no consistent data suggesting the ideal regimen of supplementation with vitamin D, and the question of the ideal time between doses is still of debate. Ish-Shalom et al.
Epidemiology
The estimated percentage of the population with a vitamin D deficiency varies based on the threshold used to define a deficiency. Recommendations for 25(OH)D serum levels vary across authorities, and probably vary based on factors like age; calculations for the epidemiology of vitamin D deficiency depend on the recommended level used.A 2011 Institute of Medicine (IOM) report set the sufficiency level at 20 ng/mL (50 nmol/L), while in the same year The Endocrine Society defined sufficient serum levels at 30 ng/mL and others have set the level as high as 60 ng/mL. As of 2011 most reference labs used the 30 ng/mL standard. : 435 Applying the IOM standard to NHANES data on serum levels, for the period from 1988 to 1994 22% of the US population was deficient, and 36% were deficient for the period  between 2001 and 2004; applying the Endocrine Society standard,  55% of the US population was deficient between 1988 and 1994, and 77% were deficient for the period between 2001 and 2004.In 2011 the Centers for Disease Control and Prevention applied the IOM standard to NHANES data on serum levels collected between 2001 and 2006, and determined that 32% of Americans were deficient during that period (8% at risk of deficiency, and 24% at risk of inadequacy). History
The role of diet in the development of rickets was determined by Edward Mellanby between 1918 and 1920. In 1921, Elmer McCollum identified an antirachitic substance found in certain fats that could prevent rickets.