Vitamin D, a fat-soluble vitamin, exists naturally in only a few foods, such as cod liver oil, salmon, mackerel, tuna fish and beef liver. Many foods contain added vitamin D, including fortified orange juice, milk, yogurt, margarine and cereals. Along with calcium, vitamin D plays an important role in bone health and the prevention of osteoporosis.
Boosting Calcium Absorption
Vitamin D assists in bone growth and bone remodeling, and serves as a transcriptional regulator of bone matrix proteins, according to Colorado State University. Vitamin D's assistance with calcium absorption represents its most important role in bone health, however. Vitamin D improves calcium absorption in the intestinal tract, and helps the body maintain adequate serum calcium, phosphate and magnesium concentrations. The body needs adequate levels of these nutrients for proper bone mineralization.
Osteoporosis Prevention
Vitamin D and calcium can help protect against osteoporosis, a disease common in older adults. Osteoporosis causes reduced bone density, deterioration of bone tissue and an increased risk of fractures. While vitamin D supplementation alone does not seem to reduce the risk for fractures, studies have shown that vitamin D supplementation along with calcium can reduce fractures and falls, according to the National Institutes of Health Office of Dietary Supplements.
Bone Problems Associated with Deficiency
Insufficient vitamin D in children can cause rickets, a disease characterized by inadequate bone mineralization. Rickets can cause soft bones and skeletal deformities. Insufficient vitamin D in adults can cause osteomalacia, a condition causing weak bones and bone pain. Without sufficient vitamin D, bones can become brittle or mis-shapen. Inadequate vitamin D can hinder calcium absorption and increase the risk for osteoporosis. Serum levels below 30 nmol/L or 12 ng/mL have been associated with vitamin D deficiency, causing rickets and osteomalacia, and levels between 30 and 50 nmol/L and 12 to 20 ng/mL are generally considered inadequate for bone health, notes the National Institutes of Health Office of Dietary Supplements.
Vitamin D Intake
Sufficient intake of vitamin D can do more than just promote bone health, recent research shows. Evidence suggests that vitamin D may also reduce the risk of heart disease, multiple sclerosis, infectious diseases and some cancers, according to the Harvard School of Public Health. Optimal daily intake of vitamin D may exceed the Institute of Medicine's recommended intake of 600 IU for people ages 1 to 70. Evidence shows that intakes of 800 to 1,000 IU may be better, according to the Harvard School of Public Health. Intakes higher than 4,000 IU may not be safe for adults, however, warns the Harvard School of Public Health.
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