Vitamin D : Deficiency...

Vitamin D deficiency can result from:

• inadequate intake coupled with inadequate sunlight exposure
• disorders that limit its absorption
• conditions that impair conversion of vitamin D into active metabolites, such as liver or kidney disorders
  
• rarely, by a number of hereditary disorders.

Deficiency results in impaired bone mineralization, and leads to bone softening diseases, rickets in children and osteomalacia in adults, and possibly contributes to osteoporosis.

Diseases caused by deficiency

Vitamin D deficiency is known to cause several bone diseases including:

• Rickets, a childhood disease characterized by impeded growth, and deformity, of the long bones
• Osteomalacia, a bone-thinning disorder that occurs exclusively in adults and is characterised by proximal muscle weakness and bone fragility.
• Osteoporosis, a condition characterized by reduced bone mineral density and increased bone fragility.

Prior to the fortification of milk products with vitamin D, rickets was a major public health problem. In the United States, milk has been fortified with 10 micrograms (400 IU) of vitamin D per quart since the 1930s, leading to a dramatic decline in the number of rickets cases.

Vitamin D malnutrition may also be linked to an increased susceptibility to several chronic diseases such as high blood pressure, tuberculosis, cancer, periodontal disease, multiple sclerosis, chronic pain, depression, schizophrenia, seasonal affective disorder and several autoimmune diseases.

Vitamin D and the Sun

The use of sunscreen with a sun protection factor (SPF) of 8 inhibits more than 95% of vitamin D production in the skin.[10][19] Recent studies showed that, following the successful "Slip-Slop-Slap" health campaign encouraging Australians to cover up when exposed to sunlight to prevent skin cancer, an increased number of Australians and New Zealanders became vitamin D deficient.

Ironically, there are indications that vitamin D deficiency may lead to skin cancer. To avoid vitamin D deficiency dermatologists recommend supplementation along with sunscreen use.