1. Vitamin D and calcium supplementation does not result in lower incidence of all-type cancer in post-menopausal women.
Evidence Rating Level: 1 (Excellent)
Study Rundown: With the annual number of new cancer diagnoses and cost of cancer care expected to continue rising over the next decade, cancer prevention is understandably a major public health concern. Since the 1980s, there has been considerable interest in the possible role of vitamin D supplementation in preventing cancer development and progression. The current study was designed as a randomized, placebo-controlled double-blind study to assess the effect of vitamin D3 and calcium supplementation on all-type cancer risk in healthy older women. Approximately, 2303 women (mean age 65.2 years) were randomized into treatment (2000 IU/d vitamin D3 and 1500mg/d calcium) or placebo groups. No significant difference was found between new cancer diagnoses between treatment (45 participants, 3.89%) and placebo (64 participants, 5.58%) groups. Similarly, Kaplan-Meier incidence over 4 years was not significantly between the two groups (0.042 in treatment group vs. 0.060 in placebo group).
Overall, the study suggests that dietary supplementation with vitamin D3 and calcium in post-menopausal healthy older women does not result in lower risk of cancer. The study is limited by its patient cohort consisting of non-Hispanic white women that limits generalizability to other groups and also men. Further, due to the unfeasibility and ethical concerns with asking patients to avoid their own vitamin D and calcium (participants were allowed to take doses not to exceed National Academy of Medicine recommendations) may have biased the study toward null. Future efforts may further evaluate the effect of vitamin D in cancer prevention.
Relevant Reading: The role of vitamin D in reducing cancer risk and progression
In-Depth [randomized clinical trial]: In this randomized, double-blind placebo-controlled study, post-menopausal women—55 years of age and older—were recruited from a population of independently living women in Nebraska between June 2009 and August 2011. Telephone screening was performed and eligible patients were randomized by a statistician using computerized block randomization at their first clinical visit. The treatment group received vitamin D3 (2000-IU capsule, once daily) and calcium carbonate (500-mg tablet, 3 times daily), while the control group received identical placebos. Follow-up visits occurred every 6 months. Primary outcomes comprised of the development of cancer of any type. Prespecified secondary analyses were performed for specific cancers including breast, lung, and colon, rates of cardiovascular disease, colonic adenomas and diabetes. Liaison Analyzer (Diasorin) was utilized to measure baseline serum 25(OH)D level and annual 25(OH)D levels, and annually, serum calcium levels were measured to monitor for hypercalcemia. The current study was powered to detect a 50% reduction in cancer incidence. Approximately, 2303 participants (mean age 65.2 years, 99.5% non-Hispanic white) were randomized into treatment (1156 participants, 50.2%) and placebo (1147 participants). Of all, 2064 (89.6%) completed 4 years of study. Mean adherence to intervention was 75.4% in vitamin D and calcium supplementation group, and 76.6% in the placebo group. Mean baseline 25(OH)D level was 32.8 ng/mL between the two groups, and significantly higher in the treatment group at year 1 (43.9 ng/mL in treatment vs. 31.6 ng/mL in placebo). New cancer diagnosis in treatment (45 participants, 3.89%) and placebo groups (64 participants, 5.58%) were not significantly different (p = 0.06). A similar trend was observed for Kaplan-Meier incidence over 4 years in treatment (0.042; 95%CI 0.032 to 0.056) and placebo (0.060; 95%CI 0.048 to 0.076; p = 0.06) groups. Overall, no serious supplement-related adverse effects were found during the study. Other adverse events included renal calculi (16 in treatment vs 10 in placebo) and elevated serum calcium levels (6 in treatment vs 2 in placebo).
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