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Calcium plus vitamin D did not prevent fractures or colorectal cancer in postmenopausal women
  1. Lenore Riddell, RN, MSN
  1. BC Women’s Hospital and Health Centre
 Vancouver, British Columbia, Canada

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 Q In postmenopausal women, does supplementation with calcium and vitamin D reduce fractures or colorectal cancer?

    METHODS

    Embedded ImageDesign:

    randomised, placebo controlled trial (Women’s Health Initiative [WHI] calcium with vitamin D trial).

    Embedded ImageAllocation:

    {concealed}.*

    Embedded ImageBlinding:

    blinded {participants, clinicians, data collectors, outcome assessors, adjudicators, and manuscript writers}.*

    Embedded ImageFollow up period:

    mean 7 years.

    Embedded ImageSetting:

    40 centres in the US.

    Embedded ImageParticipants:

    36 282 healthy postmenopausal women 50–79 years of age (mean age 62 y).

    Embedded ImageIntervention:

    calcium carbonate, 1000 mg/day, and vitamin D3, 400 IU/day, in 2 doses (n = 18 176) or placebo (n = 18 106).

    Embedded ImageOutcomes:

    hip, wrist, vertebral, and total fractures; colorectal cancer; and death.

    Embedded ImagePatient follow up:

    99% (intention to treat analysis).

    MAIN RESULTS

    The groups did not differ for hip, wrist, vertebral, or total fractures; invasive colorectal cancer; or death (table). Calcium plus vitamin D increased kidney stones but not gastrointestinal symptoms.

    CONCLUSIONS

    In healthy postmenopausal women, supplementation with calcium and vitamin D did not prevent colorectal cancer or fractures.

    A modified version of this abstract appears in ACP Journal Club.

    Commentary

    Results from the many trials that have studied the effect of calcium supplementation, with or without vitamin D, on bone density and fractures have been inconclusive. The general belief has been that supplementation reduces the risk of fracture. Fewer studies have looked at supplementation and the risk of colorectal cancer. The WHI trial is the largest randomised trial to date on calcium and vitamin D supplementation in healthy postmenopausal women. Jackson et al concluded that although bone density increased slightly, the fracture rate was not significantly reduced, and the risk of renal calculi was increased. Wactawaski-Wende et al concluded that supplementation had no effect on the development of colorectal cancer after 7 years.

    There are several possible reasons for the negative results of the WHI trial. Participants were healthy, community living women, and both groups were allowed personal use of vitamin D, calcium, bisphosphonates, and calcitonin. 52% of women were also taking hormone therapy, which has antiresorptive properties. These variables could dilute any effect. The dose of vitamin D was lower than in other studies that supported the role of vitamin D in preventing fractures.1 The length of follow up (7 y) may not have been sufficient to account for the 10–20 year latency period for colorectal cancer. The results cannot be applied to men, housebound or institutionalised people, or women with osteoporosis or major risk factors for colorectal cancer.

    Despite these reservations, the results of the WHI trial do not support universal vitamin D and calcium supplementation. Nurses should continue to emphasise the importance of adequate calcium and vitamin D intake throughout the lifespan. Specific groups, such as older women, may benefit from vitamin D and calcium supplementation.

    Calcium plus vitamin D v placebo to prevent fractures and colorectal cancer in postmenopausal women*

    
 
 Q In postmenopausal women, does supplementation with calcium and vitamin D reduce fractures or colorectal cancer?

    View Abstract

    Footnotes

    • * Information provided by authors.

    • For correspondence: Dr R D Jackson, Ohio State University, Columbus, OH, USA. jackson.20{at}osu.edu Dr J Wactawski-Wende, University at Buffalo, Buffalo, NY, USA. jww{at}buffalo.edu

    • Sources of funding: National Heart, Lung and Blood Institute, National Center for Research Resources, and GlaxoSmithKline.

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