Can vitamin D deficiency cause alopecia?

Vitamin D Deficiency and Alopecia: Evidence and Implications

Vitamin D deficiency is strongly associated with alopecia areata (AA) and may play a causal role in its pathogenesis, with multiple studies showing significantly lower vitamin D levels in AA patients compared to healthy controls. 1

Relationship Between Vitamin D and Hair Loss

Evidence of Association

• Multiple case-control studies have consistently demonstrated that serum 25(OH)D levels are significantly lower in patients with alopecia areata compared to healthy controls 1, 2, 3, 4
• The prevalence of vitamin D deficiency is markedly higher in AA patients:
  • 96.7% of AA patients vs. 73.3% of controls in one study 3
  • 83.3% of AA patients vs. 23.3% of controls in another study 1
  • 64% of AA patients vs. 38% of controls in a third study 2

Severity Correlation

• There is a significant inverse correlation between vitamin D levels and disease severity:
  • Patients with more severe alopecia have lower vitamin D levels 1, 2, 4
  • SALT (Severity of Alopecia Tool) scores show negative correlation with vitamin D levels (r = -0.298) 2
  • Patients with alopecia totalis/universalis have significantly lower vitamin D levels than those with patchy AA 5

Duration Relationship

• Longer disease duration is associated with lower vitamin D levels:
  • Old cases show significantly lower vitamin D levels (15.11 ± 4.75 ng/mL) compared to new cases (20.85 ± 9.09 ng/mL) 2
  • The proportion of subjects with vitamin D deficiency is higher among old cases (84.3%) compared to new cases (53.1%) 2

Biological Mechanisms

Vitamin D Receptor (VDR) Connection

• VDR expression is reduced in AA patients compared to healthy controls 3
• VDR plays a crucial role in hair follicle cycling:
  • Mice with VDR knockout mutations develop hair loss 1
  • Humans with vitamin D-dependent rickets type II (who have VDR gene mutations) often develop total scalp and body alopecia 1
• VDR expression inversely correlates with inflammation in hair follicles 3

Immune Regulation

• Vitamin D has important roles in immune regulation that may impact AA development:
  • Inhibits T-cell proliferation and reduces inflammatory mediator production 1
  • AA patients show elevated inflammatory markers (high-sensitivity C-reactive protein) alongside low vitamin D levels 4

Treatment Implications

Vitamin D Supplementation

• British Journal of Dermatology recommends checking vitamin D levels and supplementing if deficient (<30 ng/mL for adults, <20-30 ng/mL for children) 6
• Vitamin D supplementation may promote hair regrowth in cases of nonscarring alopecia associated with vitamin D deficiency 7
• Patients with the lowest baseline vitamin D levels experienced the greatest improvement in SALT scores when treated with topical vitamin D analogs 1

Topical Vitamin D Analogs

• Topical calcipotriol (0.005%) applied twice daily has shown promising results:
  • 59.1% of patients had hair regrowth with onset at 4.21 ± 2.13 weeks in one study 1
  • 75% of patients had ≥50% hair regrowth after 12 weeks in another study 1
  • Complete regrowth was observed in 27.1% of patients 1

Clinical Approach to Vitamin D Deficiency in Alopecia

1. Screen for vitamin D deficiency in all patients presenting with alopecia areata
2. Supplement if deficient:
   • Adults: target levels >30 ng/mL
   • Children: target levels >20-30 ng/mL
   • Monitor calcium and phosphorus levels if severely deficient (<10 ng/mL) 6
3. Consider topical vitamin D analogs (calcipotriol 0.005%) as an adjunctive treatment, especially in patients with patchy AA
4. Monitor response using SALT scores and adjust treatment accordingly

Important Caveats

• One prospective cohort study found no significant association between vitamin D intake or surrogate vitamin D scores and incident AA, suggesting the relationship may be more complex 1
• It remains unclear whether vitamin D deficiency is a cause or consequence of AA, as psychosocial stress from AA might lead to sun avoidance 1
• VDR upregulation after treatment was seen in only 13% of patients and did not correlate with treatment response 3
• Spontaneous recovery occurs in 34-80% of AA patients, making it difficult to attribute improvement solely to vitamin D interventions 1

In conclusion, while the evidence strongly supports an association between vitamin D deficiency and alopecia areata, with a potential causal relationship, more research is needed to definitively establish vitamin D supplementation as a primary treatment for AA.