Vitamin D is not really a vitamin in the classic sense because it can be produced in the body from the action of sunlight on the skin. If you have read some of my previous articles, you will already be aware that vitamin D plays an important role in the modulation of the immune system and that deficiency can result in autoimmune disorders, cancer or diabetes. Insufficiency is a term applied to vitamin D status whereby the plasma levels drop below 40 nmol / L (16 µg/L). While these levels are not low enough to cause rickets or osteomalacia (classic vitamin D deficiency diseases) they are low enough to lead to chronic disease over decades, and increase the chance of infections. The amount of people with serum levels below 40 nmol/L in Western populations is currently unknown, but research has attempted to estimate the number.
For example, a paper published in the Journal of Nutrition in 20051 reviewed the literature regarding the vitamin D levels in a variety of populations in North America. Evidence suggests that vulnerable and infirm groups were more likely to show low levels of vitamin D. In a nursing home 38 % of resident had vitamin D levels below 25 nmol/L, and in sheltered accommodation the figure was as high as 54 %. Below 25 nmol/L would be considered the range of severe deficiency. In Massachusetts general hospital, 57 % of patients had vitamin D levels below 40 nmol/L with 27 % of these below 20 nmol/L. The vitamin D levels of healthy, non pregnant African American and Caucasian women has also been measured. The results of this research are shown in table 1.
Table 1. Vitamin D levels in young adult African American and Caucasian women.
Other data shows that high proportions of young health individual adults have vitamin D levels below 50 nmol/L (table 2). This data clearly shows that after the winter period, the levels of vitamin D in plasma decreases so that more individuals fall into the < 50 nmol/L range. Other studies have also looked at the vitamin D levels in winter in various populations. For example in Boston, 21 % of elderly black subjects and 11 % of elderly white subjects had plasma vitamin D levels below 25 nmol/L in the summer, and 73 % of elderly black subjects and 35 % of elderly white subjects has plasma levels below 50 nmol/L during the winter. In Toronto, the vitamin D plasma levels were higher in elderly care residents in the summer (44 nmol/L) than in the winter (39.9 nmol/L).
Table 2. Percentage of young adults with vitamin D insufficiency1
Evidence also suggests that large numbers of children living in North America might be deficient in vitamin D. In Alaska, researchers found that 11 % of the children had vitamin D levels below 37.5 nmol/L and 20 % has levels in the 37.5 to 50 nmol/L. In another study vitamin D levels were below the normal range in 43 % of mothers and 76 % of children. Between 1988 and 1992 there were 17 cases of clinical rickets recorded in Toronto in children of 7 to 33 months of age. In a period between 1972 and 1984, 48 cases of rickets were recorded in the Winnipeg Children’s Hospital and of those, 38 were native Canadians and 2 were Inuit. This supports evidence that persons with darker skin are more likely to develop vitamin D insufficiency or deficiency because their increased level of pigment in the skin increases the intensity of the sunlight required to synthesis adequate vitamin D.
Research has shown that there is serious cause for concern regarding the vitamin D status of large portions of North American population. Although it is often dangerous to make assumptions, it would be hard to argue that a similar pattern of vitamin D insufficiency were not seen throughout other countries in the Western World. In fact data supports this viewpoint. Importantly, these insufficiencies are based on decades old vitamin D values, that were created at a time when the importance of vitamin D did not stretch beyond its role in the development of rickets in children and osteomalacia in adults. Many scientists have produced compelling evidence that argues these plasma values for vitamin D are too low and that the vitamin plasma levels and intake recommendations should be increased. Vitamin D supplements are safe and effective at raising plasma levels, and should be taken by anyone at danger of vitamin D insufficiency.
RdB
1Hanley, D. A. and Davidson, K. S. 2005. Vitamin D insufficiency in North America. Journal of Nutrition. 135: 332-337
