The problem with health stories based on animal research

doctor and rat“Too Much Salt May Delay the Onset of Puberty, Study Suggests.”

Health conscious parents who strive to stay on top of current medical news may have paused at that headline, they might even have clicked it.

The title, lede and second paragraph of this story published on all state that too salty of a diet is bad for human adolescents.

“Think twice before allowing kids unlimited access to salty condiments” the article boldly warns, literally in bold type.

“Consuming too much sodium may stunt the commencement of puberty in humans, leading to reduced fertility and higher stress levels in affected individuals.”

But wait. In the next paragraph we learn that the University of Wyoming research involved not adolescent people but pre-pubescent rats. After these rats had been fed a diet that contained more than normal levels of salt (whatever normal levels are for lab rats) they experienced delayed puberty compared to the rats on a restricted sodium diet.

Now that the obligatory disclosure that this news is based on an animal study is out of the way, let’s leap forward again to people.

“Current salt-loading in Western populations has the potential to drastically affect reproductive health, and warrants further attention,” is a quote from the study author.

So initially we’re reading about reproductive health in adolescent people, then rats, then back to adolescent people again, this time engulfing all of those living in Western cultures. As an added warning, we are told not to cut back too much on salt, though, because “too little sodium may also delay the onset of puberty as well.” That advice comes from research, too, but we aren’t sure whether it pertains to rats or humans, or both.

There was one bit of partially useful advice in the article, a reminder that the World Health Organization recommends that adults should “consume less than 2,000 mg of sodium, or 5 grams of salt” daily. But wasn’t this article about adolescents?

The above example is just one of many general interest health stories that may be published in major media on any given day that were based on pre-clinical animal studies. In case you missed it, there was also “Tylenol During Pregnancy Could Harm Male Babies, Study Shows” (mice), “Fish Can Make Their Own Sunscreen; Could Humans Too?,” and “Skipping meals may increase belly fat, study finds” (mice again).

Time magazine headline

If you read these articles and the many others like them published nearly every day with a focused eye you’ll often see both journalists and researchers push the envelope – just a bit – to make you believe you can have faith that what happens in animal studies can also be applied to human health. In the CBS belly fat story we’re told, “While this study did not test the effects of fasting and gorging on human health, the researchers say there’s reason to believe we’d see similar results.”

Yes, if you have faith.


Now I’ll share a personal experience that impressed on me once and for all to be wary of applying breakthrough research in animals to humans.

As the media relations manager for a medical association in 2002, I was deeply involved in researching and writing a press kit and arranging media briefings for a prestigious member of the association who was to receive the association’s highest honor, the Potamkin Prize, considered by many in that community to be the “mini-Nobel” or even the pre-Nobel since some previous winners had gone on to win the Nobel Prize for their research.

Since 1999, Dale Schenk (of Elan Pharmaceuticals) had been conducting research into the development of a vaccine for Alzheimer’s disease that was heralded globally as the coming medical breakthrough of the century. Schenk had formulated a vaccine from synthetic a-beta amyloid compounds that triggered the immune system to rid the brain of the plaque deposits that, along with tau protein, are a hallmark of Alzheimer’s disease. The vaccine, it was believed, would effectively reverse the Alzheimer’s disease process.

CBS vaccine for Alzheimer's headlineFollowing this promising research in mice, a phase 1 safety trial in 100 human volunteers in the US and UK involving a single injection of the vaccine brought more hope as these patients tolerated the single vaccine jab without side effects. The research was presented at the 2000 World Alzheimer Congress and greeted with more fanfare and global publicity. But hopes were dashed when the more than 300 volunteers who were moved onto phase 2 of the trial received their multi-dose injections. This was to be the therapeutic part of the trial. Instead, over a dozen patient volunteers began developing serious brain inflammation, and the number of cases of serious side effects continued to grow.

The trial was halted and the vaccine was shelved. That’s not to say that the research was stopped. As we know, research discoveries are built on past research. Schenk launched a line of immunotherapy for Alzheimer’s research which continues today.

The bottom line is there are several different animal mouse models for Alzheimer’s and other diseases, but none of them perfectly mimic the human condition.

Those of us gearing up for our association’s annual meeting, where there was to be a major focus on the vaccine, shared a deep sense of disappointment upon hearing news that the trial had been stopped. Even those who were only involved on the periphery felt a deep sense of loss. But disappointment in professional circles, particularly the physician-researchers who treated Alzheimer’s patients and devoted their careers to basic and clinical research, could only have been surpassed by the personal disappointment felt by people recently diagnosed with Alzheimer’s and their families.

It was a bit like having a rug was pulled out from under all those who had growing hope and excitement about the vaccine as it had progressed through animal and initial human trials.

Since then, I’ve been extremely cautious when reading and writing about preliminary research involving animals.

lisa schwartz

Lisa Schwartz, MD

“All too often, the news media report on animal studies as if they apply to people,” says Lisa Schwartz, MD, professor of Medicine, Community & Family Medicine at The Dartmouth Institute
and co-director of the Medicine and the Media program.

“But people are not mice. Moving from animals to humans is hard. In fact, a systematic review of ‘high profile’ animal intervention studies found that only one-third translated to successful interventions in people. And those that did took an average of 14 years to make it to humans.” Schwartz says. publisher Gary Schwitzer has illustrated time and again on this site the different challenges writers face while reporting on animal studies, particularly those sold to us in news releases or media briefings as “breaking” and “hopeful” discoveries of interest to the general public. In fact, if you simply enter the word “mice” in the search engine of this site, you will come up with pages of results of things we’ve written about animal studies through the years.

Perhaps a comment left by a reader of another HNR blog post about reporting on animal studies offers the easiest solution.

I think all research studies should reveal the species of its subjects in the first paragraph.” — Louisa Dell’Amico

And since two TIME stories were highlighted above as examples of what not to do when writing about animal research, it was a nice surprise to see this TIME headline: “Research on Mice Suggests We Could Be Better Off Eating More Healthy Carbs and Less Protein.”

Kathlyn Stone is an associate editor with


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Comments (2)

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Pat bowne

July 28, 2015 at 10:45 am

So much YES!
If it’s about mice, the article’s title should say MICE – or every journalist who reports on it should ask why it didn’t in the first sentence of their article. I can’t fault scientists for publishing results on mice, but I do fault mainstream media for making a big hoopla about it. Anybody who knows enough about medical research to be reporting on it should know the problems with generalizing from mice to humans.

Susan Green

August 21, 2015 at 2:33 pm

I have written about this issue and we make Recommendation No. 10+ REPRESENT – ‘Debate and represent animal research honestly, openly and reliably in journals, press releases and the media supported by evidence-based material and references.’