The Link Between Vitamin D Deficiency and Cancer: What You Need to Know

Vitamin D Deficiency and Cancer Risk

The idea that vitamin D deficiency might increase the risk of developing cancer arose from observations that incidence and mortality from cancer are generally higher in regions of low sunlight. There has long been speculation that such an association was with Frank and Cedric Garland in the 1980s, who proposed that a greater incidence of colon cancer in regions furthest from the equator is due to lesser exposure to sunlight, eventually causing lesser synthesis of vitamin D.

In addition, many more studies have been conducted about the vitamin D and cancer association:

Biological Mechanisms

The anticancer effects of vitamin D are likely to be mediated through additional pathways:

Regulation of Cell Proliferation and Differentiation: Calcitriol, a biologically active form of vitamin D, inhibits the proliferation of cells and induces differentiation, thus further lowering the risk of malignant transformation.

Induction of Apoptosis: Vitamin D might trigger the programmed death of malignant cells and might suppress their progression as tumors.

Prevention of Angiogenesis: Vitamin D exerts its effects by inhibiting the vessel formation that supply nutrients to the tumor and eventually limit tumor size.

Immune Modulation: Vitamin D modulates the immune system to improve the body's ability to detect and destroy inevitable cancer cells.

Clinical Trials and Supplementation 

Until now, observational studies have associated vitamin D deficiency with the augmented risk for cancer. RCTs have tested vitamin D for the prevention of cancer, producing yet other mixed results.

VITAL Study: The study enrolled over 25000 participants and tested vitamin D supplementation (2000 IU/day) and cancer incidence. The conclusion was, in general, no significant association with reducing risk of cancer was seen.  

Meta-Analyses: Some meta-analyses have stated that vitamin D supplementation decreases cancer death, indicating that the beneficial effects of supplementation are rather in improving prognosis than in preventing any cancer incidence.

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