Do Animal Studies Transfer to Humans?

Animal Research Has Both Pluses and Minuses

There are good reasons why scientists use animal studies to study drugs and supplements, but should you be skeptical of the results?

Animal Studies: The Pros and Cons

I report on a lot of scientific studies, many of them involving supplements. Much of the time, the animal studies I write about were conducted on rats or mice, and that’s often when the rat/mouse turds hit the cage-ventilator fan.

I invariably have to field a few deprecating or patronizing remarks in the comments section about how “rats and mice have been on their own evolutionary path for tens of millions of years, and as such, the studies involving them don’t apply to humans.”

Thank you, intellectual heir of Watson and Crick.

Here’s the thing, though: There’s evidence that rats and mice, while not miniature, four-legged, long-tailed, furrier humans, are the most pragmatic tool we currently have to gauge the effectiveness of drugs, supplements, dietary strategies, or almost any medical or biological premise we might want to test.

But first, I need to get something off my chest.

Excuse Me While I Spew

Few reader comments piss me off but having to read some peckerwood mansplaining basic genetics to me is an exception. I KNOW rodents aren’t genetically the same as humans. It’s why my Uncle Todd only looks a little bit like Rizzo the Rat from Sesame Street.

You are, after all, talking to a nerd who tried to duplicate (unsuccessfully) some of Gregor Mendel’s experiments with pea plants when he was 10.

You’re talking to a nerd who told schoolmates that he wanted to be a geneticist when he was 13: “You know, someone who messes around with your genes.” (Only they heard it as “jeans” instead of “genes” and I was mercilessly teased and bullied and my family had to move to Aurora, Illinois where I was home-schooled and got much of my education from public access TV.)

Well, maybe that last part about moving to Wayne’s World isn’t so much true, but the rest of it is, and while I didn’t pursue genetics, I went to college and studied microbiology, of which, surprise, genetics play a big part.

So, while my knowledge of genetics is still rudimentary compared to the people who work in the field, I understand that g-damn rats and mice are not genetically identical to humans; that we can’t marry (in Northern states anyhow), can’t produce offspring, and can’t compete in ballroom dancing contests, among other things.

Now that I’ve got that off my chest, maybe the tachycardia will pass. The point remains, though: Why do scientists use mice and rats in studies, and how well do the results transfer to us human types?

1 Out of 10,000

Despite the many differences, especially appearance-wise, rats and mice have a surprising number of anatomical, physiological, and, yes, genetic similarities to humans. Case in point: Rats, mice, and humans each have about 30,000 genes of which approximately 95% are shared between all three species.

Moreover, the small size, short life cycle, and ease of maintenance with rats and mice make them almost ideal for laboratory testing.

Let me throw some economic stats at you that might help you see the wisdom of using these animals in lab experiments: It takes a new drug, on average, 15 years to see the inside of a CVS or Walgreen’s, at an average cost of $900 million. Of the 5,000 to 10,000 new drugs that enter the drug development pipeline, only about 250 make it to preclinical trials. Of those 250, only about 5 make it to human trials, and of those 5, only 1 makes it to your pharmacist’s shelves.

So maybe you could show a little g-dam respect for all those Trulicity ads and their like. Well, maybe not. They’re pretty annoying. Still, can you even imagine how much more difficult and expensive it would be (ethical considerations, non-withstanding) to bring these drugs to market if we used, say, humans in early drug development studies?

Most two-legged lab animals would chafe, or at least feel uncomfortable, at the prospect of having their heads sliced off at the end of a preliminary study.

Fat Mice, Muscular Mice, Even Mice with Chicken Pox

Given the short life spans of mice and rats, scientists can easily develop unique genetic strains of them that model human ailments like diabetes, obesity, or cardiovascular disease. This makes them especially useful in researching those and other human ailments.

Then there’s what’s known as “knockout gene” versions of mice and rats. That’s when one or more genes (double knockout, triple knockout, or even quadruple knockout) have been made inoperative (often by CRISPR genome editing).

“Knocking out” certain genes allows scientists to discover the functions of human genes so that they might learn how to better treat human diseases. Scientists can actually order tailor-made knockout mice, some examples of which follow:

  • Fat mice that are prone to obesity due to a deficiency in carboxypeptidase-E deficiency.
  • Strong mice that have had their myostatin gene disabled.
  • Cold-tolerant mice that lack the sodium channel that transfers the perception of pain when exposed to cold.

Let’s Talk About Supplements

Much of what I wrote about the use of mice and rats in medical trials also applies to supplement research. After all, sometimes the difference between a drug and a supplement is a matter of who got to it first, a pharmaceutical company or a supplement company.

Animal studies might even be more important to supplement companies because they don’t have the deep pockets that pharmaceutical companies have. Besides, who’s going to cough up big bucks for a study on something that you can’t patent – for a natural substance that’s been around for years – like any vitamin or mineral or any polyphenol or carotenoid?

A supplement company might shell out the money to study a compound and the results might help prove its efficacy in humans, but without a patent you’ve also given every other competing company research ammo they can use to promote their version of the product (the bastards).

Still, supplement companies, on occasion, can afford mouse and rat studies, whereas human studies might be cost-prohibitive. At the very least, supplement companies pay attention to any supplement research using mice or rats, regardless of whether it was in-house or done by third parties, because, flatly, there’s a decent chance the results might correlate with humans.

The Negative Side of Rat/Mouse Research

Okay, here’s where I appear to contradict everything I wrote above: It’s true that rats/mice and humans have been on their own evolutionary paths for millions of years, and, despite sharing 95% of our genes, the 5% we don’t share counts for a lot. It explains why Remy in Ratatouille probably couldn’t hold down a real-life job in a French restaurant.

And, despite efforts by scientists worldwide to make everything as uniform as possible between mouse/rat testing facilities, differences in care – differences that might change results – ultimately creep in.

For instance, the diet the animals receive might differ from facility to facility, as might their bedding or how close their cages are to natural or fluorescent light. They might even respond differently to different handlers.

Those possible variations, while seemingly minor, could very well lead to false results that account for differences between two “identical” studies conducted in two separate labs. They might also lead to results that give false hope in their ability to treat human conditions.

Skeptics Are Welcome

I declared earlier “that rats and mice, while not miniature, four-legged, long-tailed, furry humans, are the most pragmatic tool we currently have to gauge the effectiveness of drugs, supplements, dietary strategies, or almost any other medical or biological premise we might want to test.”

I still believe that statement while openly confessing that rodent studies sometimes don’t mean a thing in gauging the effectiveness of a certain drug or supplement’s efficacy in humans.

However, these studies almost always give us interesting clues about how a substance might work. If the results can be repeated often enough, they stand a decent chance of proving their effectiveness in humans.

Go ahead and read supplement studies using rats or mice with a grain of skepticism. That’s smart, but at the same time, don’t automatically dismiss the results because the results just might correlate perfectly with human physiology.




  1. Bryda EC. The Mighty Mouse: The Impact of Rodents on Advances in Biomedical Research. Mo Med. May-Jun 2013;110(3):207-11. PubMed.
  2. Harris R. Drugs That Work in Mice Often Fail When Tried in People. Shots – Health News from NPR. April 10, 2017.
  3. Schipani S. The History of the Lab Rat is Full of Scientific Triumphs and Ethical Quandaries. Smithsonian Magazine. February 27, 2019. NCBI.