The study was part of a larger randomized controlled trial conducted in Mexico by researchers from Emory University and local investigators.

该研究是在墨西哥进行的一个更大的随机控制实验的组成部分，研究者是埃默里大学和当地的研究者。

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One of the best ways scientists have to prove cause and effect in medicine is to conduct a randomized controlled trial, in which study subjects are randomly assigned to two groups.

证明药理和药效的最好方法之一就是进行随机临床对照试验，在这个试验中其研究对象会被随机地分成两组。

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METHODS: We conducted a multicenter, randomized, double - blind, parallel - treatment, placebo - controlled study in Japan.

方法：在日本进行一项多中心随机双盲对比治疗的安慰剂对照研究。

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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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