A deficiency of vitamin D can occur when dietary intake of vitamin D is inadequate, when there is limited exposure to sunlight, when the kidney cannot convert vitamin D to its active form, or when someone cannot adequately absorb vitamin D from the gastrointestinal tract .
The classic vitamin D deficiency diseases are rickets and osteomalacia. In children, vitamin D deficiency causes rickets, which results in skeletal deformities. Rickets results in the failure of bone to mineralize. Children have rapidly growing bones which are most severely affected by rickets. The growth plates of bones continue to enlarge, but in the absence of adequate mineralization, weight-bearing limbs (arms and legs) become bowed. In infants, rickets may result in soft spots in the skull, and the rib cage may become deformed due to the pulling action of the diaphragm.
The treatment of rickets includes vitamin D or calcitriol supplementation, a diet that provides adequate calcium and phosphorus, and a plan for the prevention of future vitamin D deficiency.
What Causes Vitamin D Deficiency in Adults
In adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones. Although adult bones are no longer growing, they are in a constant state of turnover. Bone is a dynamic tissue that is continually remodeling in response to stress. The remodeling process involves the demineralization and remineralization of bone through the action of bone cells called osteoclasts and osteoblasts. In adults with prolonged vitamin D deficiency, the collagenous bone matrix is preserved but bone mineral is progressively lost as a result of normal bone turnover, resulting in bone pain (in ribs, lower spine, pelvis and legs), muscle weakness and osteomalacia (soft bones).
Vtiamin D and Your Health
Vitamin D and osteoporosis
It is estimated that over 25 million adults in the United States have, or are at risk of developing osteoporosis. Osteoporosis is a disease characterized by fragile bones. It results in increased risk of bone fractures. Having normal storage levels of vitamin D in your body helps keep your bones strong and may help prevent osteoporosis in elderly, non-ambulatory individuals, in post-menopausal women, and in individuals on chronic steroid therapy.
Researchers know that normal bone is constantly being remodeled (broken down and rebuilt). During menopause, the balance between these two systems is upset, resulting in more bone being broken down (resorbed) than rebuilt. Estrogen replacement, which limits symptoms of menopause, can help slow down the development of osteoporosis by stimulating the activity of cells that rebuild bone.
Vitamin D deficiency, which occurs more often in post-menopausal women and older Americans, has been associated with greater incidence of hip fractures. A greater vitamin D intake from diet and supplements has been associated with less bone loss in older women. Since bone loss increases the risk of fractures, vitamin D supplementation may help prevent fractures resulting from osteoporosis.
In a group of women with osteoporosis hospitalized for hip fractures, 50 percent were found to have signs of vitamin D deficiency. Treatment of vitamin D deficiency can result in decreased incidence of hip fractures, and daily supplementation with 20 mcg (800 IU) of vitamin D may reduce the risk of osteoporotic fractures in elderly populations with low blood levels of vitamin D. Your physician will discuss your need for vitamin D supplementation as part of an overall plan to prevent and/or treat osteoporosis when indicated.
Vitamin D and cancer
Laboratory, animal, and epidemiologic evidence suggest that vitamin D may be protective against some cancers. Some dietary surveys have associated increased intake of dairy foods with decreased incidence of colon cancer. Another dietary survey associated a higher calcium and vitamin D intake with a lower incidence of colon cancer. Well-designed clinical trials need to be conducted to determine whether vitamin D deficiency increases cancer risk, or if an increased intake of vitamin D is protective against some cancers. Until such trials are conducted, it is premature to advise anyone to take vitamin D supplements to prevent cancer.
Vitamin D and Alzheimer’s Disease
Adults with Alzheimer’s disease have increased risk of hip fractures. This maybe because many Alzheimer’s patients are homebound, and frequently sunlight deprived. Alzheimer’s disease is more prevalent in older populations, so the fact that the ability of skin to convert vitamin D to its active form decreases as we age also may contribute to increased risk of hip fractures in this group. One study of women with Alzheimer’s disease found that decreased bone mineral density was associated with a low intake of vitamin D and inadequate sunlight exposure. Physicians evaluate the need for vitamin D supplementation as part of an overall treatment plan for adults with Alzheimer’s disease.
Vitamin D is a fat-soluble vitamin. You may have it either from dietary or from sunlight absorbtion through skin. It absorbs and uses calcium and phosphorus to make bone. It is essential for normal growth and development. Finally, older individuals are at higher risk of being deficient in vitamin D.
