Dual-emission X-ray absorptiometry (DEXA) is a means of measuring bone mineral density (BMD). Two X-ray beams with differing energy levels are aimed at the patient's bones. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption of each beam by bone. Dual-energy X-ray absorptiometry is the most widely used and most thoroughly studied bone density measurement technology.

The DEXA scan is typically used to diagnose and follow osteoporosis. Most studies show that low calcium intake is associated with low bone mass, bone loss and higher fracture rates (broken bones).

Getting enough calcium is one of the many things people can do to help reduce bone loss. People who get plenty of calcium during their lifetime may still be at risk for bone loss and osteoporosis due to a variety of factors. These factors include Vitamin D deficiency, genetics (family history), physical inactivity, smoking, alcohol abuse and certain medication and medical disorders known to cause bone loss.