I. General information:1. The history of the nutrient: Since ancient times, vitamin D has been the leading cause of bone deficiencies.1 However, it was not until the 17th century that both Dr. Daniel Whistler and Professor Francis Glisson made the first scientific description of a nutrient. deficiency.2 During the mid-17th century there was an increase in the number of children diagnosed with the bone disease called rickets.2 The cause of rickets was determined to be associated with lack of sunlight. German researcher Kurt Huldschinsky came to the conclusion that when children were exposed to ultraviolet light they were cured of rickets2. He claimed that a substance present in the skin was the potential source of the cure.2 In 1922, American scientist Elmer McCollum demonstrated that when cod liver oil was heated; the beneficial effects of vitamin A in the oil were reduced.2 However, the oil remained effective in treating rickets, leading McCollum to conclude that a nutrient other than vitamin A was present in the oil. Consequently, he called this nutrient vitamin D , which became the fourth vitamin to be discovered and named.2 Furthermore, shortly after 1918, vitamin D was also discovered by an accidental experiment that included a group of scientists treating dogs suffering from rickets. feed them cod liver oil.12. The chemical characteristics and qualities of the nutrient• Vitamin D2 (cholecalciferol) originates from yeast and the plant sterol, ergosterol.3• Vitamin D3 (ergocalciferol) originates from 7-dehydrocholesterol, a precursor of cholesterol when synthesized in skin.3• Vitamin D is derived from a steroid; the structure maintains the numbering of the original compound cholesterol.3• Name or...... in the center of the sheet ......a casein-free diet was 19.9 ng⁄mL, for participants who were not following a casein-free diet was 19.6 ng/mL and for controls it was 17 ng/mL. There were no differences in 25(OH)D measurements across all groups. Approximately sixty-one percent, fifty-four children, had concentrations less than 20 ng/mL. This is the minimum concentration recommended by the American Academy of Pediatrics to ensure good bone health. These children may be at risk for problems associated with vitamin D deficiency. This includes concerns about bone health and calcium and phosphorus metabolism. Children with autism spectrum disorder are limited in the activities they can do and are usually not exposed to much sunlight, which puts them at greater risk. Understanding the needs and taking preventative measures for children with autism will help reduce the risk of health problems as they enter adulthood.