Osteomalacia is a disease in which insufficient mineralization leads to a softening of the bones. Usually, this is caused by a deficiency of vitamin D, which reduces bone formation by altering calcium and phosphorus metabolism. Osteomalacia can occur because of reduced exposure to sunlight (which, after touching the skin, causes the body to make vitamin D), insufficient intake of vitamin D–enriched foods (like vitamin D–fortified milk), or improper digestion and absorption of food with vitamin D (as in bowel disorders such as lactose intolerance or celiac disease).
This disease causes the bending and misshaping of bones, such as bow-legging of the lower limbs, and is called rickets when it occurs in children. Affected children are usually listless and irritable. Symptoms in adults are often delayed until the disorder has advanced. These include easy fatigability, malaise, diffuse bone pain, and spasms. Muscular weakness occurs in severe cases. Osteomalacia should not be confused with osteoporosis, which is a disease of normal mineralization but decreased amounts of bone.
Osteomalacia can be diagnosed by blood and urine tests and confirmed by bone biopsy and X-rays. Treatment consists of oral doses of vitamin D, calcium, and phosphorus as well as increased exposure to ultraviolet light.
The easy availability of vitamin D–fortified milk has reduced the incidence of osteomalacia in developed countries to 0.1 percent. In areas with high levels of vegetarianism, such as in Asia, the incidence has been reported to be nearly 15 percent. Vitamin D, a fat-soluble vitamin, while not readily found in vegetables, is available in cheese, butter, cream, fish, oysters, fortified milk, and fortified cereals.