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Vitamin D and skin cancer

Cholecalciferol; vitamin D3; 25-hydroxyvitamin D

The vitamin D paradox is a frequent question in skin-oncology clinic — can a patient who must avoid UV exposure maintain adequate vitamin D status? The simple answer is yes, through dietary intake and supplementation. The UK Scientific Advisory Committee on Nutrition (SACN 2016) recommends 10 µg (400 IU) vitamin D daily during autumn and winter for the whole UK population, and year-round for at-risk groups including those who avoid the sun, the elderly, residents of care homes, and Fitzpatrick V–VI skin (where cutaneous synthesis is slower). For skin-cancer survivors and immunosuppressed patients, supplementation is preferable to deliberate sun exposure.

CurrentLast reviewed 15 May 2026

UK requirements

  • SACN 2016 / NICE — 10 µg (400 IU) per day from October to March for the general UK population; insufficient UVB for cutaneous synthesis at UK latitudes in those months.
  • Year-round 10 µg/day for at-risk groups:
    • Those who consistently cover skin or avoid the sun.
    • Fitzpatrick V–VI skin (slower cutaneous synthesis).
    • Older adults, particularly in care homes.
    • Pregnant and breastfeeding women.
    • Children aged 1–4 years.
  • Vitamin D status — SACN defines serum 25-hydroxyvitamin D < 25 nmol/L as deficiency (the population protective threshold); ≥ 50 nmol/L is a commonly used clinical adequacy target (IOM / Endocrine Society convention, not a SACN cut-off).

In skin-cancer patients

  • Skin-cancer survivors, particularly those with multiple primaries, OTRs, Gorlin, XP — should photoprotect strictly.
  • Supplement vitamin D at standard 10 µg/day or higher if deficient.
  • Sun exposure for vitamin D production is not recommended — the additional UV exposure required is small but the cancer risk outweighs the benefit when supplementation is freely available.
  • Check 25-hydroxyvitamin D in those at risk of deficiency or on therapy that affects bone (corticosteroids, mTOR inhibitors).

Observational data and skin cancer

  • Observational studies have variously suggested higher 25-OH-D is associated with better melanoma outcomes — but residual confounding (sun-exposure status of survivors, performance status, body composition) prevents causal inference.
  • Randomised trials of vitamin D supplementation in melanoma (e.g. ViDMe) are ongoing — current evidence does not support pharmacological vitamin D as anti-cancer therapy.
  • Counsel patients pragmatically — maintain replete vitamin D status, but do not use this as a justification for sun exposure.

Practical advice

  • Over-the-counter 10 µg (400 IU) cholecalciferol — affordable and widely available.
  • Higher doses (1000–2000 IU/day) acceptable for at-risk patients without checking levels; toxicity threshold typically > 10 000 IU/day.
  • Check 25-OH-D in newly diagnosed advanced melanoma, OTRs, suspected deficiency, on bone-affecting medication.
  • Replace deficiency — colecalciferol 50 000 IU weekly for 6 weeks, then maintenance.
  • Dietary sources — oily fish, fortified foods, eggs — supplement contributions limited.

References

  1. SACN. Vitamin D and Health Report. 2016.
  2. NICE PH56. Vitamin D: supplement use in specific population groups. London: NICE; 2014 (last updated 30 August 2017; reviewed 9 December 2025).
  3. NICE NG34. Sunlight exposure: risks and benefits. London: NICE; 2016.
  4. Scientific Advisory Committee on Nutrition. Vitamin D and Health. Public Health England; 2016 (updated online 2023).

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