Average vitamin D levels declining

March 30, 2009

Researchers from the University of Colorado School of Medicine, Johns Hopkins University and Harvard report a decline in levels of vitamin D among Americans over a ten year period. The researchers compared the active level of vitamin D (25-hydroxyvitamin D) in the serum of 18,883 participants in the Third National Health and Nutrition Examination Survey (NHANES), conducted from 1988 to 1994. The results were compared with levels from 13,369 participants in NHANES 2001-2004. They found that the average vitamin D level, which was 30 nanograms per milliliter (observed in the Third NHANES) dropped to 24 nanograms per milliliter in the NHANES 2001-2004. The percentage of those with levels below 10 nanograms per milliliter increased from 2% to 6%, and those with levels above 30 nanograms per milliliter, an amount that is considered by some authorities to be the minimum for optimal health, decreased from 45% to 23%.
“Vitamin D insufficiency has been associated with increases in cardiovascular disease, cancer, and infection,” the authors observe in their introduction to the article. “Vitamin D supplementation appears to mitigate the incidence and adverse outcomes of these diseases and may reduce all-cause mortality.” The study is published in the March 23, 2009 issue of Archives of Internal Medicine.

Even low dosage vitamin D (400 IU a day) may cut the risk of fractures by up to 20% according to a new analysis of multiple studies

A daily dose of Vitamin D even at just 400IU may reduce hip fractures by 18%, and non-vertebral fractures by 20%, according to pooled data from double-blind randomised controlled trials involving 42,279 participants.

The researchers performed a meta-analysis of 12 published clinical trials involving oral vitamin D supplements in 42,279 adults aged 65 or older. Eight trials specifically studied hip fractures. When the researchers considered only data from nine studies using doses of vitamin D over 400 IU per day, the supplements were associated with a 20% and 18% reduction in non-vertebral and hip fractures, respectively. The authors published their study in the March 23rd, 2009 issue of the journal Archives of Internal Medicine.