A new research in the journal Nutrients has found that your hair can hold the clue for vitamin D deficiency. This means that you can actually measure the level of Vitamin D in your body by examining hair. Vitamin D deficiency is fairly common with over a billion people estimated to be affected by it reports IANS. According to the report while traditional blood analysis captures the levels at a single time point in contrast hair which grows at approximately one centimetre per month could reflect vitamin D status over several months capturing the large seasonal differences in the levels.