Published in:
01-02-2014 | Brief report
The association of vitamin D supplementation with the risk of cancer in postmenopausal women
Published in: Cancer Causes & Control | Issue 2/2014
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Purpose
There is inconclusive evidence on whether vitamin D therapy reduces cancer risk. We investigated the effect of vitamin D (±calcium) supplementation on the risk of breast, ovarian, uterine, colorectal, and lung cancer in women.
Methods
We conducted a case–control study using the UK Clinical Practice Research Datalink (CPRD); cases were women aged ≥55 years with a first diagnosis of either breast, colorectal, lung, ovarian, or uterine cancer between 2002 and 2009, with at least 5 years of CPRD follow-up prior to the date of diagnosis, and controls were women without cancer, frequency-matched to cases by year of birth, date of study entry, length of follow-up, and general practice. The association of vitamin D supplementation with the odds of developing each cancer was determined using multivariable logistic regression, controlling for body mass index, smoking, alcohol, and deprivation.
Results
Ninety-seven percent of women took vitamin D with a calcium supplement. Exposure to three or more prescriptions of vitamin D was associated with a 17 % reduced odds (95 % CI 0.71–0.97) of breast cancer versus 1–2 prescriptions, but this effect disappeared when omitting women first exposed within a year of diagnosis (OR 1.0, 95 % CI 0.82–1.23). Having more than 10 prescriptions of vitamin D was associated with a 17 % lower odds (95 % CI 0.65–1.06) of colorectal cancer, but the estimates are imprecise. There was little evidence of associations of supplements with lung or gynecological cancers.
Conclusion
We found little evidence that vitamin D (largely with calcium) supplementation is associated with decreased breast, lung, ovarian, and uterine cancer risk. There is a possible protective association between having more than 10 prescriptions of vitamin D supplements and colorectal cancer, but it requires further investigation.