Why take dietary supplements containing calcium and vitamin D? Besides contributing to proper nerve function and a healthy immune system, these nutrients are an integral part of good bone health.

In the U.S., inadequate levels of vitamin D are more common than you might think. About 8 percent of Americans are at risk for vitamin D deficiency, according to the National Health and Nutrition Examination Surveys conducted by the Centers for Disease Control and Prevention.

Internationally, the situation is often quite a bit worse, especially in Africa and the Middle East. In the latter, vitamin D deficiency is especially widespread, according to a recent study conducted by the International Osteoporosis Foundation.

Researchers found that in certain Middle Eastern countries, the incidence of vitamin D deficiency is between 75 and 90 percent.

“Vitamin D is an essential component of bone health,” said Dr. med Gemma Adib, the report’s lead author and the general secretary of the Pan Arab Osteoporosis Society. “It is essential that the region develops vitamin D supplementation strategies based on local data for at-risk groups.”