Can we trust the rat? Can we be sure that results obtained from lab experiments with this animal may also hold true for us humans? No, we can't. At least not always, and surely not in the case of type 2 diabetes.
Of course, medical research in its first stages must rely on so-called animal models. They serve as a first step before possible treatments can be applied to humans. And they serve as a filter that allows researchers to put aside drugs, supplements or other treatments that prove to be not safe and not efficient in the animal trial. So far so good.
Such tests also have been undertaken with diabetic rats, and their sugar illness improved when they were fed selenium. Hence the idea of giving selenium supplements to people in order to prevent diabetes. This effect has been studied in more than a thousand persons who have taken either selenium or placebo supplements for seven or more years on average. During that time, more selenium users than placebo users became diabetic. (The trial originally has been designed for cancer prevention.)
Stay cool but skeptic
This result has caused dramatic reports in the mass media about a fifty percent increase of diabetes risk. But let us keep feet on the ground: The selenium supplements have caused no more than one additional case of type 2 diabetes in every two hundred and fifty person years on average.
The real point is that we have one more case of a useless supplement. Its harm may be minimal, but there is no proven benefit (the anticancer effect is controversial, see Wikipedia). Our body needs selenium but only in trace doses that we normally get from healthy food. In my opinion, there is no need for selenium supplements at all. Save your money to buy better food instead.
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