In the 19th century, how were children treated who suffered from rickets due to a lack of vitamin D? If they were fortunate to live in New England, they were taken for long trips on Boston’s Floating Hospital. This hospital ship exposed them to prolonged periods of sun, nature’s way of producing vitamin D. Today, not many people develop rickets. But how much D do you need, when should you take it, and can it protect you from a variety of problems? Here are some facts you should know.