2640
The first valid reports correlating the importance of an adequate vitamin D status to optimal human health originate from the early part of the 20th century , when vitamin D was described to prevent and treat the bone disease rickets .
 Chemical: vitamin D; Chemical: vitamin D
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: vitamin D; Chemical: vitamin D