Last week the NY Times wrote about whether Vitamin D could improve athletic performance:
However, getting Vitamin D by way of sunshine is not so easy in these skin-cancer conscious days, and the normal diet is not so helpful either:
So, my guess - although we may be OK at establishing a minimal level of Vitamin D to avoid rickets we have no idea what the optimal level is. However, I will tell you right now that although most of us are at risk for Vitamin D deficiency, an obvious high-risk group for Vitamin D deficiency is dark-skinned city dwellers in the North living on a poor person's diet [More below - see DEFICIENT}. What are the health implications? I don't know, but I would start with the list of childhood diseases whose incidence is rising - hypertension, diabetes and obesity spring to mind.
The next part of the guess - a major effort to promote Vitamin D could be as powerful as the campaign to get the lead out of paint, gasoline, and households.
DEFICIENT: From this article:
Although no minimum vitamin D level ideal for health has been established, there is a general consensus that people ought to have at least 30 nanograms per milliliter of blood — sometimes described as about 80 nanomoles per liter (SN: 10/16/04, p. 248). In this NHANES data set, only about 45 percent of the population had that minimum. So the researchers separated the NHANES participants into three groups: those with 30 or more ng/ml, those with gross deficiency (less than 10 ng/ml of vitamin D) and those in between.
Also disturbing, Ginde points out that the NHANES data he analyzed had been collected about 15 years ago, when almost twice as many people as today had vitamin D levels above 30 ng/ml.
So if 45% of us were above the minimal threshold 15 years ago, roughly 22% are above the threshold today. I claim the impact of that is widely misunderestimated.
And let me throw this stray thought out - what if the most important part of the "Mediterranean diet" is the sunshine?
CONTINUING TO SCRATCH THE SURFACE: Vitamin D is the "It" vitamin as of June 2009 (I am soo like, last quarter); 40% of Boston toddlers had "sub-optimal" levels in June 2008 (I'll bet "optimal" is sub-optimal, too; time will tell); As of June 2009, global deficiency is widespread. And apparently some of my guesses have already been researched:
ScienceDaily (July 10, 2007) — Many otherwise healthy children and adolescents have low vitamin D levels, which may put them at risk for bone diseases such as rickets. African American children, children above age nine and with low dietary vitamin D intake were the most likely to have low levels of vitamin D in their blood, according to researchers from The Children's Hospital of Philadelphia.
A study in the current issue of the American Journal of Clinical Nutrition measured blood levels of vitamin D in 382 healthy children between six years and 21 years of age living in the northeastern U.S. Researchers assessed dietary and supplemental vitamin D intake, as well as body mass, and found that more than half of the children had low blood levels of vitamin D. Of the subjects, 55 percent of the children had inadequate vitamin D blood levels and 68 percent overall had low blood levels of the vitamin in the wintertime.
...In addition to musculoskeletal effects, vitamin D is important for immune function, and low blood levels of the vitamin may contribute to diseases such as hypertension, cancer, multiple sclerosis and type 1 diabetes. Decreased blood levels of vitamin D have also been linked to obesity.
Further study is needed to determine the appropriate blood levels of vitamin D in children, said Dr. Zemel, who added that a review of the current recommendations for vitamin D intake is needed.
Hmm - common sense triumphant! Later I will air my theories about the earth - flat or round?!?