Crockett SD, et al. - In a large multicentre chemoprevention study, researchers determined the impacts of calcium and vitamin D supplementation on the incidence of serrated polyps (SPs) in general and hyperplastic polyps and sessile serrated adenomas or polyps (SSA/Ps) specifically. For this investigation, they randomized participants with one or more adenoma at baseline to receive 1200 mg/day of elemental calcium, 1000 IU/day of vitamin D3, both or neither agent. Investigators found that supplementation with calcium and vitamin D increased the risk of SSA/Ps. This seemed to be a late effect: 6-10 years after the start of supplementation. The benefits of calcium and vitamin D supplementation must be weighed against these possible risks.