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Online Clinical Calculator |
Calcium/vitamin D do not prevent
colon cancer (WHI)
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Clinical Question:
Does supplementation with 1000 mg calcium and 400 IU vitamin D reduce the
risk of colorectal cancer in healthy women?
Bottom Line:
Daily supplementation of calcium with vitamin D for seven years had no
effect on the incidence of colorectal cancer among postmenopausal women. The
long latency associated with the development of colorectal cancer, along
with the seven-year duration of the trial, may have contributed to this null
finding.
Reference:
Wactawski-Wende J, Kotchen JM, Anderson GL, et al, for the Women's Health
Initiative Investigators. Calcium plus vitamin D supplementation and the
risk of colorectal cancer. N Engl J Med 2006;354:684-96. |
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Study Design:
Randomized controlled trial (double-blinded)
Synopsis:
Higher intake of calcium and vitamin D has been associated with a reduced
risk of colorectal cancer in epidemiologic studies and polyp recurrence in
polyp-prevention trials. However, randomized-trial evidence that calcium
with vitamin D supplementation is beneficial in the primary prevention of
colorectal cancer is lacking. We conducted a randomized, double-blind,
placebo-controlled trial involving 36,282 postmenopausal women from 40
Women's Health Initiative centers: 18,176 women received 500 mg of elemental
calcium as calcium carbonate with 200 IU of vitamin D3 [corrected] twice
daily (1000 mg of elemental calcium and 400 IU of vitamin D3) and 18,106
received a matching placebo for an average of 7.0 years. The incidence of
pathologically confirmed colorectal cancer was the designated secondary
outcome. Baseline levels of serum 25-hydroxyvitamin D were assessed in a
nested case-control study. The incidence of invasive colorectal cancer did
not differ significantly between women assigned to calcium plus vitamin D
supplementation and those assigned to placebo (168 and 154 cases; hazard
ratio, 1.08; 95 percent confidence interval, 0.86 to 1.34; P=0.51), and the
tumor characteristics were similar in the two groups. The frequency of
colorectal-cancer screening and abdominal symptoms was similar in the two
groups. There were no significant treatment interactions with baseline
characteristics. |
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