Vitamin D (calciferol) Deficiency

Vitamins >> Vitamin D (Calciferol) Deficiency

In vitamin D deficiency, calcium absorption cannot be increased enough to satisfy the body’s calcium needs. Consequently, PTH production by the parathyroid glands is increased and calcium is mobilized from the skeleton to maintain normal serum calcium levels—a condition known as secondary hyperparathyroidism. Although it has long been known that severe vitamin D deficiency has serious consequences for bone health, recent research suggests that less obvious states of vitamin D deficiency are common and increase the risk of osteoporosis and other health problems.

Severe Vitamin D Deficiency

Rickets

In infants and children, severe vitamin D deficiency results in the failure of bone to mineralize. Rapidly growing bones 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 delayed closure of the fontanelles (soft spots) in the skull, and the rib cage may become deformed due to the pulling action of the diaphragm. In severe cases, low serum calcium levels (hypocalcemia) may cause seizures. Although fortification of foods has led to complacency regarding vitamin D deficiency, nutritional rickets is still being reported in a number of U.S. and European cities.

Osteomalacia

Although adult bones are no longer growing, they are in a constant state of turnover. In adults with severe vitamin D deficiency, the collagenous bone matrix is preserved but bone mineral is progressively lost, resulting in bone pain and osteomalacia (soft bones).

Muscle Weakness and Pain

Vitamin D deficiency causes muscle weakness and pain in children and adults. Muscle pain and weakness was a prominent symptom of vitamin D deficiency in a study of Arab and Danish Moslem women living in Denmark. In a cross-sectional study of 150 consecutive patients referred to a clinic in Minnesota for the evaluation of persistent, nonspecific musculoskeletal pain, 93% had serum 25(OH)D levels indicative of vitamin D deficiency. A randomized controlled trial found that supplementation of elderly women with 800 IU/day of vitamin D and 1,200 mg/day of calcium for three months increased muscle strength and decreased the risk of falling by almost 50% compared to supplementation with calcium alone.

Risk Factors for Vitamin D Deficiency

Excusively breast fed infants: Infants who are exclusively breast fed and do not receive vitamin D supplementation are at high risk of vitamin D deficiency, particularly if they have dark skin and/or receive little sun exposure. Human milk generally provides 25 IU of vitamin D per liter, which is not enough for an infant if it is the sole source of vitamin D. Older infants and toddlers exclusively fed milk substitutes and weaning foods that are not vitamin D fortified are also at risk of vitamin D deficiency. The American Academy of Pediatrics recommends that all infants that are not consuming at least 500 ml (16 ounces) of vitamin D fortified formula or milk be given a vitamin D supplement of 200 IU/day.
Dark skin: People with dark skin synthesize less vitamin D on exposure to sunlight than those with light skin. The risk of vitamin D deficiency is particularly high in dark-skinned people who live far from the equator. In the U.S., 42% of African American women between 15 and 49 years of age were vitamin D deficient compared to 4% of White women.
Aging: The elderly have reduced capacity to synthesize vitamin D in the skin when exposed to UVB radiation, and are more likely to stay indoors or use sunscreen. Institutionalized adults are at extremely high risk of vitamin D deficiency without supplementation.
Covering all exposed skin or using sunscreen whenever outside: Osteomalacia has been documented in women who cover all of their skin whenever they are outside for religious or cultural regions. The application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95% (1).
Fat malabsorption syndromes: Cystic fibrosis and cholestatic liver disease impair the absorption of dietary vitamin D.
Inflammatory bowel disease: People with inflammatory bowel disease like Crohn’s disease appear to be at increased risk of vitamin D deficiency, especially those who have had small bowel resections.
Obesity: Obesity increases the risk of vitamin D deficiency. Once vitamin D is synthesized in the skin or ingested, it is deposited in body fat stores, making it less bioavailable to people with large stores of body fat.