Vitamin D Measured in Human Hair

Vitamin D deficiency has reached epidemic proportions worldwide, with over one 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.

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.

A team of scientists collaborating with Trinity College Dublin (Dublin, Ireland) in a proof-of-concept study set out to provide evidence that 25-hydroxyvitamin D (25(OH)D3) can be extracted from hair samples in a similar fashion to steroid hormones. Two of the authors provided hair samples harvested from the crown area of the scalp and the third author provided beard samples. These samples were cut into 1 cm lengths, weighed, washed and dried. 25(OH)D was extracted using a previously published steroid hormones extraction procedure. Blood samples were taken from the subjects at the same time all samples were analyzed using the API 4000 liquid-chromatography mass spectrometry system.

The team reported that the hair samples showed presence of quantifiable 25(OH)D3 with concentrations ranging from 11.9–911 pg/mg. The beard sample had a concentration of 231 pg/mg. Serum levels of 25(OH)D3 ranged from 72 to 78 nmol/L. The results confirmed the feasibility of measuring 25(OH)D3 in hair samples. They noted that 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.

Lina Zgaga, PhD, an Associate Professor and lead author of the study, said, “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!” The study was published on February 18, 2019, in the journal Nutrients.

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