You may develop broken bones or a weakened immune system prone to disease, when you do not get enough vitamin D or have invisible deficiency of vitamin D – that’s what the US study released on Monday articulated.

The study at Children's Hospital Boston involving 380 people, found that 2 out of 5 U.S. children aged 8 months to 2 years had less-than-optimal blood levels of vitamin D. According to the report published in the Archives of Pediatric and Adolescent Medicine, the main risk factors were not drinking enough fortified milk, not taking vitamins and being overweight

Catherine Gordon of Children's Hospital Boston, the lead researcher of the study asserted that the 40 percent deficiency rate "is higher than expected in a country that has vitamin D fortified milk." The study concluded that vitamin D, made when sunlight hits the skin and used to fortify many foods, is important for preventing chronic diseases. It is key player in maintaining strong bones but has also been linked with a lower risk of cancer, artery disease and even kidney disease.

The lack of symptoms, at least initially, led Gordon calling ‘vitamin D deficiency’ as "silent disease." Gordon said, “What was striking to us was how many infants were vitamin D deficient but they were asymptomatic. The silence of what we saw worries me more," The researchers theorized that children with vitamin D deficiency sometimes have bowed legs or easily fractured bones. They can also appear tired, or shaky, or suffer seizures in severe cases.