Quoted from The Hundred Year Lie:

Two books by anesthesiologist C. Ray Greek and veterinarian Jean Swingle Greek, Specious Science (2003) and Sacred Cows and Golden Geese (2000), present devastating evidence that animal studies not only fail to accurately predict how drugs or toxins will affect humans, but that experimental results from animals often mislead scientists and harm human patients.

Here are a few of the many dozens of examples the authors cite:

  • The popular diet drug fen-phen passed all its animal tests for safety, but once humans began using it the discovery was made (as a result of death and illness) that it damaged the human heart but not animal hearts. The arthritis drug Opren passed all of its tests on monkeys, but then it killed sixty-one humans before it was withdrawn from the market. A drug called Cylert worked well in rats for symptoms of attention deficit/hyperactivity disorder but when given to children caused liver failure in thirteen of them before it was withdrawn. 
  • Tobacco companies claimed that cigarette smoking was safe because in their lab studies rats didn’t contract lung cancer, but several decades of epidemiological study of humans has determined that people’s lungs are susceptible to cigarette smoke even when rat’s lungs are unaffected. 
  • National Cancer Institute studies show that 63 percent of the time, drugs that were effective against human cancers failed to work against the same cancers in mice. 
  • Researchers gave animals six drugs known to have eighty-eight side effects in humans; twenty-two of these side effects also appeared in the lab animals, but other side effects common to humans failed to appear in the animals. About 76 percent of the time, the animal results had no application to human experience.

Most revealing of all has been what common household aspirin does to animals. “Our most popular drug, grandfathered in before the requirement for animal validation was legislated, would never have made it through the animal assays now required. Aspirin produces birth defects in mice, rats, guinea pigs, rabbits, cats, primates, and dogs.” Nor would penicillin have made it through clinical trials for use on humans—penicillin kills guinea pigs and cats, and causes deformities in rats and many other types of test animals.

Animals are generally not good predictors of what effects chemicals will have on humans because of differences in their anatomy and physiology at the celluar level, and a range of differences in metabolism and the absorption of substances. Difficulty in dosage control and an inability of laboratory conditions to imitate normal human habits also contribute to this failure of accurate extrapolation from animal to human.


So why are animal tests still performed—and given respect—when they can be so fatally flawed? The two physicians Greek and Greek say it is because industries, the pharmaceutical companies in particular, only want “to get the substance onto the pharmacy shelves and to protect themselves legally if a problem arises.” That is why experimental studies are often shortened before tests can turn up evidence of toxicity and why some researchers involved in clinical trials have been accused of underreporting drug safety problems.

Now that we know animal studies may incorrectly imply the absence of risk in humans and that animal tests showing harm may not indicate a real danger to people, where does that leave us regarding health concerns from chemical exposure? The simple answer is that we should use the results of animal tests in biomedical research as suggestive of harm or of safety and not as predictive.

This standard will obviously cut many different ways into the debate over chemical toxins and health, and it may dilute the impact of many of the experimental findings discussed on the pages of this book. But the most signficiant repercussion is the doubt this casts on the contentions of the chemical, food, drug, and other industries’ testing procedures. The truth is—we simply don’t know what is safe. It only makes sense to be cautious.

Fitzgerald, Randall. The Hundred-Year Lie: How to Protect Yourself from the Chemicals That Are Destroying Your Health (p. 162-64). Plume. Kindle Edition.