Over the past decade vitamin D, long known as a key to bone strength, has also been linked to prevention of a host illnesses, ranging from cancer and heart disease to asthma. But during that same period, a dramatic trend to vitamin D deficiency has spread to as much as three fourths of the adult US population.
The federal government's National Health and Nutrition Examination Survey incidated that in 1994, 45 percent of the population had adequate Vitamin D levels. But in 2004 just 23 percent of US adults and teens had adequate levels. The deficiency was most pronounced in the African American population, with just three percent of that segment having adequate vitamin D levels.
Known as the sunshine vitamin because exposure triggers its manufacture in the body, vitamin D was originally best known for its role in bone health. In the 1930s the addition of Vitamin D fortification in milk was credited with all but eliminating rickets, a devastating bone-softening disease that effected thousands of children.
However over the past ten years rickets has begun to make a reappearance in the US, with incidence of the disease increasing at what doctors call "an alarming rate". In addition, incidence of bone fracture in children is on the upswing, and medical research indicates an increasing vitamin D deficiency is a key factor in these changes.
The deficiency is both puzzling and troubling, particularly in light of new research that shows Vitamin D is far more than just a strengthener of bones. Studies all over the world are showing marked correlations between vitamin D levels and a wide variety of illnesses, including many types of cancer, heart disease, diabetes, and most recently, asthma and perhaps even autism.
Some researchers point to lifestyle changes that include spending more time indoors and less time time in the sun as a major factor in the decline in Vitamin D levels, particularly in children. They note that in addition to the sun-induced manufacture of the vitamin in the body, outdoor activity generally includes exercise, which is a crucial factor in bone strength.