Vitamin D Deficiency: An Epidemic?

There has been a lot of blame thrown around for this recent, troublesome discovery. Vitamin D deficiency or insufficiency is the new hot topic in osteoporosis. Some have even gone as far as blamed the dermatologists for making us avoid the sun and making us apply sunscreen with extremely high SPF’s.

Let us see if we can clarify what vitamin D is, does, and figure out how we can help ourselves in getting the appropriate amounts.

What is it?
Vitamin D is a fat-soluble substance (it dissolves in and can be stored by fat deposits in the body). It is present in salmon, mackerel, sardines, and cod liver oil; fortified foods including milk, breakfast cereals, and some juices; and vitamin supplements. It can also be produced in the skin during sun exposure. Vitamin D (in its active form, which is created after several modifications by the body) functions as a hormone which means it binds to receptors in various tissues to influence the expression of genes, thereby affecting a range of processes, especially the regulation of calcium.

It has long been known that vitamin D is crucial for healthy bones. The presence of vitamin D in the small intestine aids in the absorption of dietary calcium—people with vitamin D deficiency are able to absorb only a third to half as much calcium as those with sufficient levels—and calcium is vital to the hardness of bone. The two diseases traditionally associated with severe vitamin D deficiency—rickets in children and osteomalacia in adults—are characterized by deformation or softening of bone. Chronic vitamin D deficiency is strongly linked to osteoporosis.

Deficiency
The common assumption has been that with the fortification of milk, instituted in the United States in the 1930s, and casual exposure to sunshine, most people get all the vitamin D they need. However, a recent resurgence of rickets has brought new studies. It has become clear that vitamin D deficiency (usually defined as blood levels of less than 15 ng/mL [or nanograms/milliliter]) and insufficiency (less than 20 or according to most experts probably less than 30 ng/mL) are far more widespread than researchers had expected. The elderly, who often receive little sun, are at particular risk, as are African Americans and other dark-skinned people, since skin pigmentation, which protects against damage by UV rays, also interferes with vitamin D production.

Perhaps the biggest surprise, though, has been the prevalence of vitamin D deficiency among women of childbearing age and among healthy children and adolescents. It is possible that chronic insufficiency early in life may prevent proper bone development and increase the risk of disorders, such as osteoporosis, later in life.

Benefits of Vitamin D
Laboratory, animal, and epidemiologic evidence suggests that vitamin D may be protective against some cancers. These include colon, breast, and prostate cancers. Deficiency has also possibly been found to be a source of chronic, non-specific musculoskeletal pain (2003 in the Mayo Clinic Proceedings). It is also been studied in autoimmune diseases to possibly prevent the occurrence of various diseases.