You hear it all the time—“this product has been tested on animals.” If it’s a product that’s made for humans, why is it tested on animals? Wouldn’t it be better to just use humans for testing in the first place? Then we’d get more relevant results, right?

Not necessarily. There are many reasons why scientists use animals rather than humans for testing. Below are some of the main reasons and an explanation of why this testing produces valid results for humans.

Let’s use mice as our example since many studies are performed on mice. Why is that?

  • Mice are mammals, so they have many of the same body systems and functionality as humans and are susceptible to many of the same diseases.
  • Mice can be bred in a controlled manner. Most mice used for research are inbred so that they are almost genetically identical; this helps make the results of studies more uniform. Today, scientists can even breed genetically-altered mice. In these mice, certain genes can be turned on or off to mimic human disease conditions making it easier to evaluate the effects of any given product on the chosen condition.
    • Side Note – Ever wonder why dietary supplement companies hesitate to fund studies looking at the effects of their products on human disease, whether it be in mice or in human subjects? The reason for this is two-fold:
      1. Dietary supplements are intended to be used to optimize normal human function. In other words, they are not meant to be used to treat disease nor can they claim to do so.
      2. Therefore, despite the fact that there is often a greater chance of seeing significant outcomes when studying subjects with disease, no claims can be made about the potentially positive impact the supplement had on any disease-related outcome. This is why supplement companies typically choose to study healthy subjects; so that the findings can actually be used to make claims about the product’s impact on health.
  • Mice can be kept in a controlled environment. They can be fed only certain substances, kept in a cage, and monitored for sleeping and other lifestyle habits. Humans are much more difficult to control, and they are nearly impossible to constantly observe. The variables that come into play from one human to the next affect study results dramatically.
  • Mice have a short life cycle. This allows scientists to study them in utero, through birth, maturity, old age, and death. To get the same breadth of study in a human life cycle would take a very long time.
  • There are lots of mice. Scientists can study many, many more mice than humans and can get more reliable, statistically significant results.
  • Mice are less expensive to study. Their upkeep is pretty inexpensive, and scientists don’t have to pay them for their time!

But how do scientists ensure that products that are studied in animals apply to how those products will work in humans? Well, they can’t know exactly, but they can make educated guesses. Here’s what they look for.

  • Is it safe? Does the product hurt the mice in any way? Does it cause any disease or negatively affect any systemic functions? As discussed above, since mice have a short lifespan, it’s easier for scientists to follow the animal through its entire life and watch for issues that arise.
  • Does it work? Does the product affect the mice’s systems in the way that it was intended to? Since mice are mammals and have the same body systems as humans and they function in much the same way, scientists can see if the product changes body processes in the way they think it will.
  • Does it work most of the time in most of the mice? Getting lots of results can help scientists determine whether the statistics are significant enough that the product is likely to work in humans, too.

Even though it’s hard to know for absolute certain that the scientific findings from an animal study will be exactly applicable to humans, scientists can make a good guess. Really good studies usually have some insights as to how the product actually works in the body systems it is intended to affect, which helps scientists extrapolate findings and judge how it will affect those same body systems in humans. Due to the high cost, small likelihood of coming up with statistically significant findings, inability to control all external variables that might impact study outcomes, and the relatively long lives humans have, the cost-benefit analysis of conducting a study on healthy humans often prevents supplement companies from moving forward with those type of studies. Of course, that doesn’t mean they won’t ever do human studies, but before they do, they need to make sure the human study has value.

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