VIT D, IS THERE A J-CURVE.

The Nov 13th online edition of Circulation - CV quality and outcomes, carries an article by Dr Lu Wang, to revive this topic. This article deals with the threshold effects of vitamin D, and not directly with Calcium. Dr Wang and group from the Bringham's and Women's hospital, Boston, did a meta-analysis of 19 clinical trials on Vit D levels and the risk of CV events. They included about 66,000 patients with no known CVD. These studies had follow-up till 10 years, giving us data over a very large cohort of patient days. They found that low levels of Vit D were associated with increase CV risk. As Vit D levels rise, the CV risk got lower. This was true till a Vit D level of 60 nmols/L After the Vit D level of 60 nmols/L, the data were conflicting. Between 20-60 nmols/L, the data wee all in agreement. This suggest that there may be a threshold for Vit D levels and CV risk. Any Vit D levels up in excess of 60 nmols/L may not do any good, but we are not sure if they do harm.
To make it more interesting, we even have a problem defining normal serum Vit D levels. I suppose that it is generally accepted that normal serum 25 hydroxy vit D is between 25-137 nmols/L.