Vitamin D Status of US Population-Even Worse
A study published in the Archives of Internal Medicine has revealed that there is widespread Vitamin D deficiency in the US population and that the extent of the deficiency is far worse than many realize.
Two studies, NHANES III and NHANES collected data on patients between 1988-1994 and 2001-2004 respectively. These were large studies with over 18,000 patients in the former and 13,000 in the later. The two groups also contained significant number of African Americans with data on over 5,000 in the former study and over 3000 in the later. Vitamin D levels were compared in the two study groups.
The average serum level of 25(0H)D during the first study period was 30nanogram/milliliter (ng/ml) and this dropped to 24ng/ml during the second.
Of more concern was the fact that the proportion of people who had levels of at least 30ng/ml had fallen by almost 50%, from 45% to 23%. A level of 30ng/ml is where many experts think levels need to be to take advantage of the anticancer effect of Vitamin D.
In addition the proportion of people with levels less than 10ng/ml which is gross deficiency had increased from 2 to 6%, a threefold increase.
African Americans who consistently have the lowest levels in the general population showed an even greater decline between the two study periods. During the first study period only 12% had levels of at least 30ng/ml and this fell to 3% during the second study period. The proportion of those with less than 10ng/ml went from 9% to a massive 29%.
National Institutes Office of Dietary Supplements Criticizes the Study.
The National Institutes Office of Dietary Supplements took the position that the study had overstated the severity of the situation. The institute still defines deficiency as less than 11ng/ml which according to most experts on Vitamin D is considered to be way too low. Many think a level of less than 15ng/ml is deficiency and some would put the hurdle at even higher, at 20ng/ml.
The Institute also pointed out that the two studies had used different methods to measure 25(OH)D levels and that the main difference between the two study periods could be accounted for by the difference methods used.
However the fact remains that even if the levels are no different from the first study period the vast majority of the population certainly have levels that less than considered optimal by those knowledgeable in the area.
What is the appropriate Vitamin D level?
Michael Holick MD, PhD who conducted much of the original research on Vitamin D and who authored The UV Advantage published an article in the New England Journal of Medicine in 2007 in which he noted that there was no general consensus on what is an optimal level but that deficiency is defined by most experts as less than 20ng/ml. Levels of 21-29ng/ml are considered relative insufficiency and levels above 30ng/ml are sufficient.
Many now think that optimal levels are between 50-70ng/ml which is the range of levels seen in workers who spend most of their time out of doors in sunny parts of the world. Intoxication does not occur until level exceed 150ng/m/. It is impossible to reach toxic levels by sun exposure alone as the body starts to break down Vitamin D as levels climb into this region.
The fact remains that many conditions that are associated with Vitamin D deficiency such as cancer, diabetes and other degenerative diseases continue to increase which would suggest that Vitamin D levels are in fact falling. As there is no known down side to maintaining a sufficient or even optimal level of Vitamin D everyone should take steps to ensure that they are getting enough of this essential nutrient.
Ginde 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.
MF Holick. Vitamin D Deficiency. New England Journal of Medicine 2007;357:266-81.