As our scientific understanding of the fundamental importance of vitamin D for broad-spectrum health protection has dramatically risen over the past two decades, unfortunately our blood levels have gone in the opposite direction.  Researchers reported in the March issue of the Archives of Internal Medicine that 3 of every 4 Americans have insufficient blood levels and for blacks and Hispanics, almost all do.  This is a dramatic change from the previous period of measurement and translated to a 50% drop in the prevalence of healthy vitamin D levels (30 ng/ml or >) and a 3-fold increase in the prevalence of overt vitamin D deficiency (10ng/ml or <). 

 For the study, the researchers compared vitamin D levels taken on 18,333 people between 1988 and 1994 with measurements in 13,369 people taken between 2001 and 2004.  The investigators contribute the drop to rising rates of obesity, a decrease in outdoor activities, and broader use of sunscreen and sun avoidance.  For my best advice on maintaining a healthy vitamin D level, click here.