Concerns About Vitamin D Deficiency
~ June 1998 No.44 ~
In a recent article published in the New England Journal of Medicine, a team of medical researchers at Harvard Medical School and two Australian hospitals reported that 57% of the subjects in their study were considered to be vitamin D deficient. Even more disturbing findings were that 46% of the people studied, reported that they took vitamin supplements but were still classified as vitamin D deficient and over a third of the subjects who reported that they consumed the recommended amounts of vitamin D daily were found to be deficient.
Vitamin D is termed a fat soluble vitamin along with vitamins E and A. We have two sources of Vitamin D - diet and sunlight. When the skin is exposed to sunlight, the ultraviolet radiation converts 7-dehydrocholesterol in the skin to previtamin D. The previtamin D is then quickly converted to the metabolically active 1,25-dihydroxyvitamin D. Dietary sources of Vitamin D include dairy products, fish and eggs. In addition, in many countries milk and some cereals are fortified with vitamin D.
Vitamin D is most often associated with calcium metabolism and bone formation. Rickets, a disease characterized by softening of the long bones, results from vitamin D deficiency in children. In older people, bone fractures result from inadequate Vitamin D. Recently there have been reports that Vitamin D may be involved in immune response, muscle function and may be useful in the prevention of certain cancers.
The Harvard study took blood samples from 290 patients in a general medical ward to assess their Vitamin D status. Serum levels of less than 8 ng/ per millilitre of blood were classified as deficient. Because of the unexpected large number of patients who were found to be deficient by this test, the researchers concluded that perhaps it was necessary to revise the current dietary recommendations for Vitamin D. This conclusion was enforced in an editorial written by Robert Utiger M.D. in the same issue of the New England Journal of Medicine. Dr. Utiger predicted that increased intake of Vitamin D would likely result in lower incidences of osteoporosis and bone fractures.
Food composition tables very often do not include Vitamin D values which makes it difficult to calculate daily intakes.
|Food||Vitamin D (ug per 100 g)|
|cod liver oil:||210|
|Source: Fat-soluble Vitamin Assays in Food Analysis, G.F.M. Ball, 1988|
Note : 1 ug = 0.000001 gram Vitamin D concentrations are often expressed in international units (IUs)1 IU = 0.025 ug vitamin D
New England Journal of Medicine