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Does dietary supplementation with vitamin D3 and calcium reduce the risk of cancer among older women?
In this randomized clinical trial of 2303 healthy postmenopausal women with a mean baseline serum 25-hydroxyvitamin D level of 32.8 ng/mL, supplementation with vitamin D3 and calcium compared with placebo did not significantly reduce the incidence of all-type cancer over 4 years of follow-up.
Supplementation with vitamin D3 and calcium did not result in a significantly lower risk of cancer among healthy older women.
Evidence suggests that low vitamin D status may increase the risk of cancer.
To determine if dietary supplementation with vitamin D3 and calcium reduces the risk of cancer among older women.
Design, Setting, and Participants
A 4-year, double-blind, placebo-controlled, population-based randomized clinical trial in 31 rural counties (June 24, 2009, to August 26, 2015—the final date of follow-up). A total of 2303 healthy postmenopausal women 55 years or older were randomized, 1156 to the treatment group and 1147 to the placebo group. Duration of treatment was 4 years.
The treatment group (vitamin D3 + calcium group) received 2000 IU/d of vitamin D3 and 1500 mg/d of calcium; the placebo group received identical placebos.
Main Outcomes and Measures
The primary outcome was the incidence of all-type cancer (excluding nonmelanoma skin cancers), which was evaluated using Kaplan-Meier survival analysis and proportional hazards modeling.
Among 2303 randomized women (mean age, 65.2 years [SD, 7.0]; mean baseline serum 25-hydroxyvitamin D level, 32.8 ng/mL [SD, 10.5]), 2064 (90%) completed the study. At year 1, serum 25-hydroxyvitamin D levels were 43.9 ng/mL in the vitamin D3 + calcium group and 31.6 ng/mL in the placebo group. A new diagnosis of cancer was confirmed in 109 participants, 45 (3.89%) in the vitamin D3 + calcium group and 64 (5.58%) in the placebo group (difference, 1.69% [95% CI, −0.06% to 3.46%]; P = .06). Kaplan-Meier incidence over 4 years was 0.042 (95% CI, 0.032 to 0.056) in the vitamin D3 + calcium group and 0.060 (95% CI, 0.048 to 0.076) in the placebo group; P = .06. In unadjusted Cox proportional hazards regression, the hazard ratio was 0.70 (95% CI, 0.47 to 1.02). Adverse events potentially related to the study included renal calculi (16 participants in the vitamin D3 + calcium group and 10 in the placebo group), and elevated serum calcium levels (6 in the vitamin D3 + calcium group and 2 in the placebo group).
Conclusions and Relevance
Among healthy postmenopausal older women with a mean baseline serum 25-hydroxyvitamin D level of 32.8 ng/mL, supplementation with vitamin D3 and calcium compared with placebo did not result in a significantly lower risk of all-type cancer at 4 years. Further research is necessary to assess the possible role of vitamin D in cancer prevention.
clinicaltrials.gov Identifier: NCT01052051
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Corresponding Author: Joan Lappe, PhD, RN, Creighton University Schools of Nursing and Medicine, Ste 4820, 601 N 30th St, Omaha, NE 68131 (firstname.lastname@example.org).
Author Contributions: Drs Lappe and Watson had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Lappe, Travers-Gustafson, Recker, Garland.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Lappe, Watson, Garland, Gorham, Baggerly.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Watson, Baggerly, McDonnell.
Obtained funding: Lappe.
Administrative, technical, or material support: Lappe.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Lappe reports having joined the scientific panel for GrassrootsHealth after this study was under way. GrassrootsHealth is a nonprofit 501(c)(3) organization based in San Diego, California, with public health promotion as its primary endeavor. The focus is on vitamin D testing and education. Dr Lappe has advised GrassrootsHealth on research design and data interpretation, but she is not employed by them, and has never received any funding from them. She has shared data from a previous study for Drs Garland, Gorham, and Baggerly and Ms McConnell to combine with data collected by GrassrootsHealth for analysis and publication. Drs Garland and Gorham both serve on the scientific advisory board for GrassrootsHealth, but they are not employed by GrassrootsHealth and have not received funding from them. Dr Baggerly reports that he is the son of Carole Baggerly, director of GrassrootsHealth. Dr Baggerly has no direct affiliation with GrassrootsHealth—he is not employed by them, nor does he receive any funding from them. Ms McDonnell reports that she is employed by GrassrootsHealth. She was paid by Creighton funds for her analysis work for this article. No other disclosures were reported.
Funding/Support: The study was funded by National Cancer Institute (NCI) and Creighton University internal funding. Diasorin lent a Liaison Analyzer for analysis of serum 25(OH)D and provided analytic kits free of charge.
Role of the Funder/Sponsor: NCI provided oversight. The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: We thank the Creighton University project team members who collected the study data: Julie Aken; Margaret Begley, BSN, BA, RN; June Bierman, BSMT, ASCP; Susan Dowell, PhD, RN; Colleen Dummer, RT, CDT; Carmen Fraher, BSN, RN; Barbara George; Jenny Larsen, R, BD, ARRT, CDT; Karla Malesker, BS, BA; Melissa Meyer, BSN, RN; Joan Sawtelle; Julie Stubby, BSN, RN; Jamie Vanek, BSN, RN; and Bethanie West. All were compensated for their work. We also thank the contributions of study participants, and the organizations that rented space for study sites—Fremont Area Medical Center, Fremont NE, Concordia College, Seward NE, and Northeast Community College, Norfolk NE, and the members of the data and safety monitoring board. This article is dedicated to the memory of Robert P. Heaney, MD, John A. Creighton Professor of Medicine, Creighton University. He was a co-investigator in this study and participated in the design and consulted on the project until his death on August 6, 2016.
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