A new study by researchers from Trinity College Dublin and St James's Hospital has reported for the first time that vitamin D can be measured in human hair. The paper has been published in the international, peer-reviewed journal of human nutrition, Nutrients.
Vitamin D deficiency has reached epidemic proportions world-wide, with over 1 billion people estimated to be affected. Deficiency has been linked with bone health, but it could also be a risk factor for depression, cardiovascular disease, inflammation, diabetes and cancer. At present, the best way of assessing vitamin D is to measure the concentration of vitamin D in the blood. However, this can be painful, requires expertise and training along with hygienic conditions/equipment so getting a sample is not always workable. In addition, the blood result represents vitamin D status at a single time point, which is problematic because vitamin D changes with the seasons: it's not uncommon for someone to be sufficient in vitamin D in the summer time, and very deficient in the winter. This means that a single snapshot of vitamin D status is not able to provide information on vitamin D year-round.
The current study is the first in the world to publish that it is possible to extract and measure vitamin D in human hair. This is a major step forward in assessing vitamin D status, potentially one of the major innovations in vitamin D measurement. Traditional blood analysis captures just a moment in time; in contrast, hair, which grows at approximately 1cm per month, could reflect vitamin D status over several months capturing the large seasonal differences in vitamin D status.
This study presents the first step towards the development of a novel test for assessing vitamin D status over time. The idea is that vitamin D is being deposited continuously in the hair as it grows; more might be deposited at times when vitamin D concentration in the blood is high, and less when it's low. Therefore, test based on the hair sample might be able to give doctors a measure of vitamin D status over time if hair is long enough, this even might be over a few years!
Further research is needed to establish the exact relationship between vitamin D concentration in the blood and in hair over time. We also need to investigate different factors that might affect vitamin D levels in hair, the most obvious ones being hair colour and thickness, or use of hair products such as hair dye.
The presence of vitamin D in hair could be interpreted as a personal record of a person's vitamin D status. Having a knowledge of an individual's long-term vitamin D status through analysis of hair samples may allow for better strategies to maintain stable and adequate vitamin D concentrations over an extended period.