Vitamin D deficiency is widespread in the UK due to limited sun exposure, particularly in the winter months, and research has identified a plausible link between low vitamin D levels and certain forms of hair loss — particularly alopecia areata and diffuse telogen effluvium.
Vitamin D receptors (VDRs) are expressed in hair follicle cells, and animal studies have shown that disruption of VDR signalling impairs the hair cycle. In humans, low vitamin D levels have been associated with increased hair loss in several cross-sectional studies. Patients with alopecia areata consistently show lower vitamin D levels than controls, though whether this is causative or a consequence of the same immune dysregulation is not fully established.
For androgenetic alopecia — male and female pattern baldness — the evidence for a direct relationship with vitamin D is weaker. However, optimising vitamin D levels in deficient patients is low-risk and may provide benefit as part of a comprehensive approach to hair health.
Supplementation with 1,000 to 2,000 IU of vitamin D3 daily is appropriate for most UK adults, particularly in the autumn and winter months. A blood test measuring 25-hydroxyvitamin D will confirm whether you are deficient. Levels above 75 nmol/L are considered optimal for general health, and this appears to be the threshold below which hair-related effects become more likely.
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