Methods60 patients of Diabetes were enrolled in a randomized, controlled study and divided into treatment group and control group, both of which received conventional diabetic therapy.

方法将60例糖尿病患者，按照随机、对照的原则分为治疗组、对照组，两组均予糖尿病基础治疗。

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It is a randomized controlled study, meaning that similar patients were assigned at random to either get either Centrum or placebo.

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Because the Framingham Heart Study is not a randomized controlled trial, it's still not clear if vitamin D is the real reason for the link (the vitamin's levels could drop in unhealthy people for other reasons), or if taking a supplement would lower the risk.

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For one, the groups noted the analysis is a retrospective study, not a prospective, randomized controlled clinical trial, which many regard as a gold standard for ferreting out safety concerns.

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