1. Daily consumption of neither vitamin D3 nor calcium, alone or in combination, reduced the risk of recurrent colorectal adenomas.
2. The study draws strengths from its large number of participants, high adherence, low exogenous vitamin intake but is limited due to selecting a lower dose than the current vitamin D intake level guidelines.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Previous studies have shown that vitamin D and high calcium intake are associated with antineoplastic and lower risks of colorectal neoplasia respectively. This study investigated the chemopreventive potential of vitamin D and calcium for the prevention of new colorectal adenomas in persons with a recent history of adenomas. A total of 2259 participants with recently diagnosed adenomas were randomly assigned to receive either daily vitamin D3 (1000 IU), calcium as carbonate (1200 mg), both or neither in a partial 2×2 factorial design. The study found that daily supplementation did not result in any significant reduction in risk of recurrent colorectal adenomas over the 3-5 year follow-up period. The trial was sufficiently large enough to detect modest chemopreventive effects. Adherence to the study treatment was high and the number of participants that dropped out, were lost to follow-up, or died were minimal (4.6%).
In-Depth [randomized controlled trial]: This was a randomized, multicenter, double-blind, placebo-controlled trial. A total of 2259 participants underwent randomization and received either 1000 IU of vitamin D3, 1200mg of calcium as carbonate, both agents, or placebo. Participants were expected to continue on with the study treatment until the anticipated 3-year or 5-year colonoscopic examination. Primary end points included all adenomas that were diagnosed in any colorectal endoscopic or surgical procedure at least 1 year after randomization and up to 6 months after the anticipated 3 or 5 year colonoscopic examination. Only 4.6% of the participants dropped out of the study, were lost to follow-up, or died. The adjusted RR for any adenoma among patients taking vitamin D vs. those not taking vitamin D was 0.99 (95%[CI] 0.89-1.09). Adjusted RR among patients taking calcium compared to those not taking calcium was 0.95 (95% [CI], 0.85-1.06). The adjusted RR among patients taking vitamin D plus calcium versus those taking neither agent was 0.93 (95% [CI], 0.80 to 1.08). There were no significant effects of supplementation in subgroup analyses. However, there was a significant association between BMI and calcium effect on adenoma risk.
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