Colorectal cancer deaths 26-32% lower with higher Vitamin D – meta-analysis

Circulating vitamin D status and prognosis in colorectal cancer: a systematic review and meta-analysis with exploratory evidence on vitamin D receptor polymorphisms

BMC Cancer, 16 April 2026, https://doi.org/10.1186/s12885-026-16026-x

Daylia Thet, Nutthada Areepium, Chidchanok Rungruang, Nattawut Leelakanok, Tippawan Siritientong

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Summary by Claude - June, 2026

Colorectal cancer (CRC) patients with higher blood vitamin D lived longer in this 2026 meta-analysis — a strong and consistent signal, though because the data are observational it is not proof that vitamin D itself extends survival.

This was a systematic review of 61 studies (55,176 CRC patients), with 35 pooled in the meta-analysis. Importantly, studies using oral vitamin D supplementation were deliberately excluded: this looks only at naturally circulating 25(OH)D as a prognostic marker, not at the effect of taking vitamin D.

Comparing high vs. low 25(OH)D, higher levels were associated with:

  • 26% lower CRC-specific death (HR 0.74; 95% CI 0.69–0.80)
  • 32% lower overall death (HR 0.68; 95% CI 0.64–0.72)
  • Better disease-free survival (HR 0.71), recurrence-free survival (HR 0.81), and longer time to recurrence (HR 0.67)
  • Even larger effects in metastatic CRC (OS HR 0.61) and stage III CRC (OS HR 0.54)

Heterogeneity was low for the main outcomes, and results held in a sensitivity analysis restricted to studies using comparable clinical cutoffs (≥20 ng/mL vs. <12 ng/mL). The vitamin D receptor (VDR) polymorphisms (ApaI, BsmI, FokI, TaqI, Cdx2) were too inconsistent across 18 studies to pool, and remain inconclusive.

What this does NOT show / limitations:

This is observational and cannot establish causation. The authors emphasize reverse causality — advanced or aggressive cancer drives inflammation and cachexia that lower 25(OH)D, so low vitamin D may partly be a marker of worse disease rather than its cause. "High" and "low" cutoffs varied widely between studies, so no dose-response curve could be drawn. GRADE certainty was rated low (CRC-specific survival) to very low (overall survival), and most patients were European/North American. The authors themselves frame the findings as "hypothesis-generating rather than indicative of direct practice-oriented implications" — whether raising vitamin D improves survival needs randomized trials.

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