solve the CHAPTER MYSTERY

THE DEMISE OF A DISEASE

The search for the cause and a cure for rickets revealed two findings. Both cod liver oil and exposure to ultraviolet light could prevent and cure rickets.

The first finding indicated that cod liver oil contains a nutrient involved in bone health. Starting in the 1930s, many parents in the United States—including the parents of one of this textbook's authors—gave their children a daily dose of bitter cod liver oil.

The second finding indicated that exposure to the sun influences bone health. This explained why children in colder climates were more susceptible to rickets. They had little sun exposure during cold, dark winter months.

But scientists still wondered, what was the connection between cod liver oil and ultraviolet light? How could both treatments result in the same positive outcome?

Through the work of many scientists, we now know that vitamin D is the responsible nutrient in cod liver oil. And, when exposed to ultraviolet light, the skin makes compounds that can be converted to vitamin D. We've also learned that vitamin D helps the body absorb calcium and phosphorus from the digestive system.

Children today are spared cod liver oil doses because vitamin D is added to milk. Rickets is now a rare disease in the United States.

1. Explain Why were children in southern cities less likely to develop rickets?

2. Compare and Contrast Describe the structure of the bones of a healthy child in comparison to the bones of a child who developed rickets.

3. Connect to the Explain how vitamin D is related to the structure and function of the three systems you learned about in this chapter.