(NaturalNews) Vitamin D is a critically important nutrient. However, with most people spending an increasing amount of time indoors, and wearing long-sleeved tops or slapping on sunscreen lotions when they do go under the sun, levels of vitamin D in our bodies are falling to dangerously low levels. And a recent study published in the
Archives of Internal Medicine has suggested that the state of widespread deficiency in the United States population may be even more staggering than most of us realize.
Details of StudyThe study team had compared data on serum 25-hydroxyvitamin D [25(OH)D] levels from the Third National Health and Nutrition Examination Survey, or NHANES III, which had been collected from 1988 to 1994, with NHANES data which had been collected from 2001 to 2004. In total, complete data on 18,883 persons in the former survey and 13,369 persons in the latter survey was used. Data on 5,362 African Americans was used in the first exercise, while data on 3,149 of them was used in the second one.
Findings of StudyDuring the NHANES III, the researchers found that the average level of serum 25(OH)D was 30 nanogram / milliliter (ng/mL). However, for the second survey, the average level had dropped to 24 ng/mL, which represented a 20% decrease.
From the first to the second survey period, the proportion of persons who had at least 30 ng/mL of 25(OH)D fell by almost half, from 45% to 23%. On the other hand, the proportion of those who had less than 10 ng/mL of the compound rose about three-fold, from 2% to 6%.
African Americans had the worst situation to begin with, and also experienced the most marked dip in vitamin D levels. The proportion of them who had at least 30 ng/mL of 25(OH)D fell by three-quarters, from an already low figure of only 12% to an even lower figure of 3%. At the same time, the proportion of those with less than 10 ng/mL soared from 9% to a whopping 29%.
Dark-skinned people have more melanin or pigment in their skin, which means they need more exposure to sunlight for their bodies to synthesize the same amount of vitamin D as fair-skinned people. A dark-skinned person is thus more susceptible to vitamin D deficiency.
"We were anticipating that there would be some decline in overall vitamin D levels, but the magnitude of the decline in a relatively short time period was surprising," said Adit Ginde, an assistant professor at the University of Colorado Denver School of Medicine, one of the study's authors.
Does the Study Overstate Vitamin D Deficiency?Mary France Picciano, a senior nutrition scientist in the National Institutes of Health's Office of Dietary Supplements, did not believe that the situation was as dire as suggested. She noted that there was divergence of opinions on the amount of vitamin D needed, and that the Institute of Medicine (IOM) defined vitamin D insufficiency as less than 11 ng/mL. Picciano also pointed out that Ginde's study had failed to account for the fact that the two surveys had used different methods to collect 25(OH)D data. In gist, because of these two factors, she felt that Ginde's study had exaggerated the state of vitamin D insufficiency.
According to a study published in 2008 in the
American Journal of Clinical Nutrition, of which Picciano was part of the research team, a significant part of the difference between more recent and older data was due to changes made in the vitamin D measurement test used. That study had found that only about 10% of adults in the US were deficient in the vitamin.
Discussion on Vitamin D LevelsAccording to an article he wrote which was published in the
New England Journal of Medicine in 2007, Michael Holick, MD, PhD, author of
The UV Advantage, noted that there was no consensus on optimal blood 25(OH)D levels. He wrote that "vitamin D deficiency is defined by most experts as a 25-hydroxyvitamin D level of less than 20 ng/mL."
Based on factors such as parathyroid hormone levels and intestinal calcium transport, Holick added that "a level of 25-hydroxyvitamin D of 21 to 29 ng/mL can be considered to indicate a relative insufficiency of vitamin D, and a level of 30 ng/mL or greater can be considered to indicate sufficient vitamin D." Vitamin D intoxication was placed at 25(OH)D levels above 150 ng/mL.
Other statistics quoted in Holick's article also suggested that vitamin D deficiency worldwide is indeed widespread and severe. Using the abovementioned definitions, it estimated that 1 billion people throughout the world have vitamin D insufficiency or deficiency.
While experts may differ on the level of vitamin D actually needed, the reality is that rates of vitamin D insufficiency and various serious degenerative diseases are soaring side-by-side. Further, this vitamin has been continually linked to more and more health benefits. That being the case, should we be taking chances? As Ginde said, "we're just starting to scratch the surface of what the health effects of vitamin D are. There's reason to pay attention for sure."
ReferencesGinde AA, Liu MC, Camargo Jr CA. Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988-2004. Archives of Internal Medicine 2009;169(6):626-632.
Vitamin D deficiency soars in the U.S., study says (
http://www.sciam.com/article.cfm?id=vitamin-d-deficiency-united-states)
MF Holick. Vitamin D Deficiency. New England Journal of Medicine 2007;357:266-81.
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