Published studies show that vitamin D deficiency is widespread and it has been suggested that it increases the risk of lung, breast, colorectal and prostate cancers.
To investigate prospectively the effect of serum 25-hydroxyvitamin D (25(OH)D) level on lung, breast, colorectal and prostate cancers in people aged 30+ years.
In this nested case-control study, the data and collected serum samples from a cohort study, the Balçova Heart Study, during 2007-09, were used. Additional data were collected using a questionnaire in the follow-up. We determined incident lung, breast, colorectal and prostate cancer cases during 2008 and 2013. Serum 25(OH)D levels of 606 persons (179 cases and 427 controls) from the Balçova Heart Study were measured. Odds ratio (OR) and 95% confidence interval (CI) were calculated using logistic regression analysis.
Serum 25(OH)D levels did not show a significant association with breast, colorectal and prostate cancers. There was an inverse association between 25(OH)D level and lung cancer risk, where the OR values for the first, second and third quartiles, compared with the fourth quartile (1.00), were 2.92 (CI: 0.82-10.35), 3.76 (CI: 1.14-12.37) and 3.55 (CI: 1.04- 12.08) respectively.
It was seen that low 25(OH)D levels were associated with a greater than threefold increased risk of lung cancer; no association was detected for breast, colorectal and prostate cancers. Cohort studies with larger populations are needed to better understand the effect of vitamin D level on cancer risk.

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