An adequate calcium intake and adequate amounts of vitamin D are important foundations for maintaining bone density and strength. However, vitamin D and calcium alone are not sufficient treatment for osteoporosis and are given in conjunction with other treatments. Vitamin D is important in several respects:
Vitamin D helps the absorption of calcium from the intestines.
A lack of vitamin D causes calcium-depleted bone (osteomalacia), which further weakens the bones and increases the risk of fractures.
Vitamin D, along with adequate calcium (1200 mg of elemental calcium), has been shown in some studies to increase bone density and decrease fractures in older postmenopausal, but not in premenopausal or perimenopausal women.
Vitamin D comes from the diet and the skin. Vitamin D production by the skin is dependent on exposure to sunlight. Active people living in sunny regions can produce most of the vitamin D they need from their skin. Conversely, lack of exposure to sunlight, due to location or physical limitations, causes vitamin D deficiency. In less temperate regions such as Minnesota, Michigan, and New York, skin production of vitamin D is markedly diminished in the winter months, especially among the elderly. In that population, dietary vitamin D becomes important.
Unfortunately, vitamin D deficiency is quite common in the U.S. In a study of hospitalized patients in a general medical ward, vitamin D deficiency was detected in 57% of the patients. An estimated 50% of elderly women consume far less vitamin D in their diet than is recommended.
The Food and Nutrition Board of the Institute of Medicine has recommended the following as an as adequate vitamin intake:
600 IU daily for men and women 19 to 70 years old
800 IU daily for men and women 71 years and older
But if a person already has osteoporosis, the recommended intake may be different.
Vitamin D can be found in multivitamins and also in combination with many calcium supplements. Adequate calcium and vitamin D are critical for bone health.
Adequate levels of calcium and vitamin D must be assured along with any prescription osteoporosis medication. Chronic excessive use of vitamin D, especially above 4,000 units/day, can lead to toxic levels of vitamin D, elevated calcium levels in blood and urine, and may also cause kidney stones. Since various dietary supplements may also contain vitamin D, it is important to review vitamin D content in dietary supplements before taking additional vitamin D.