Vitamin D and Prostate Cancer
Prostate cancer is the most common non-skin cancer in men. Vitamin D has been examined in prevention, active surveillance progression, and androgen deprivation therapy bone side-effects. Evidence is mixed for prevention, more encouraging for active surveillance, and strong for ADT bone protection.
Ecological and observational data
Prostate cancer mortality is inversely correlated with ambient UVB exposure and serum 25(OH)D in ecological studies. Black men (who make less vitamin D at temperate latitudes) have higher prostate cancer incidence and mortality, though multiple other factors contribute. Individual-level observational studies have been inconsistent — some show reduced risk with higher 25(OH)D, others show U-shaped relationships.
Prevention trials
- SELECT (2011) — 35,000 men; selenium and vitamin E; vitamin D not directly tested but combination arm showed no benefit and slight harm in some subgroups.
- VITAL (2019) — 2,000 IU/day for 5.3 years: no reduction in prostate cancer incidence.
- No RCT supports vitamin D supplementation for primary prostate cancer prevention.
Active surveillance — the Marshall trial
Marshall 2018 randomised 44 men with low-risk prostate cancer on active surveillance to vitamin D 4,000 IU/day vs placebo × 2 years. The vitamin D arm showed a significant reduction in patients requiring reclassification to higher-risk disease at surveillance biopsy. Small trial, but generated interest in vitamin D as a possible adjunct to active surveillance. Larger trials pending.
Androgen deprivation therapy bone loss
GnRH agonists and antagonists used in advanced prostate cancer cause dramatic bone loss (~5% BMD in the first year). Vitamin D + calcium is foundational; add bisphosphonate or denosumab if osteoporosis or high fracture risk. Standard guideline: 1,000–2,000 mg calcium and 800–1,000 IU vitamin D daily for men on ADT, with baseline DEXA and follow-up.
Racial disparities
Black men in the US have ~60% higher prostate cancer incidence and ~2× the mortality of white men. Contributing factors include genetic, socioeconomic, and access-to-care disparities. Chronic vitamin D deficiency (which is substantially more common in Black men at northern latitudes) has been proposed as one contributor. See our skin color page.
Practical guide
- Test 25(OH)D at prostate cancer diagnosis; correct to ≥ 30 ng/mL.
- On ADT: 800–2,000 IU vitamin D + 1,000 mg calcium daily; DEXA at baseline and yearly.
- Active surveillance: reasonable to maintain 30–50 ng/mL; talk to your urologist about the Marshall data before initiating any high-dose regimen.
- Vitamin D is adjunctive to evidence-based care (surveillance, surgery, radiation, ADT, chemotherapy, PARP inhibitors).