You’ve seen the headlines. Of the 80,000 or so synthetic chemicals in the market place only a few thousand have been adequately tested. And as far as the others are concerned, activist groups grumble that we are the guinea pigs that will determine their safety. According to them. we are all part of a massive, uncontrolled experiment, the consequences of which may turn out to be dire. No chemical should be introduced until it has been proven to be safe, they say. Sounds admirable, but just how does one prove safety? Testing for chemical safety is a very complex, time-consuming and unfortunately often unreliable process. And testing individual chemicals may not present a realistic scenario. For example, when mice are exposed in the womb to bisphenol A, the plastic component that is causing quite a commotion these days, they have a greater risk of developing diabetes, obesity and cancer. But when the pregnant mothers are given the B vitamin folic acid or genistein, a compound found in soy, the effects of bisphenol A are negated.What does this type of information mean for us? Hard to say. Because a human is not a giant rat, a dog or a chimp.
There are plenty of examples of substances that have appeared to be safe in animals and turned out to be toxic in humans, and vice versa. It wasn’t long ago that six men in England who volunteered for an experiment to test a drug designed to treat diseases such as rheumatoid arthritis, leukemia and multiple sclerosis by dampening the body’s immune reaction, ended up in hospital, some suffering permanent organ damage. Mice, rats, rabbits and monkeys had shown no ill effects at all. But the men certainly did. As one of the volunteers who luckily had been given a placebo described, “The men went down like dominoes. They began tearing their shirts off complaining of fever, then some screamed that their heads were going to explode. After that they started fainting, vomiting and writhing around their beds.” And this from a drug that had been shown to be “safe” in animals.
There are also cases of substances that cause problems in animals, but not in humans. If we used dogs as the standard animal to test food components, we could say good-bye to chocolates. This delicacy is highly poisonous to dogs! Twenty-five grams of chocolate, a quarter of a chocolate bar, can kill a dog within a few hours. The culprits in the chocolate are compounds in the “methylxanthine” family, namely theobromine, theophylline and caffeine. In humans, they just deliver a small kick before they’re metabolized by our liver enzymes. But dogs don’t produce the same set of liver enzymes as we do, and the breakdown of the methylxanthines takes a much longer time. As these compounds circulate in the bloodstream, they affect the heart, the central nervous system and the kidneys. Unsweetened baking chocolate contains the highest concentration of these compounds, ten times as much as milk chocolate. So keep your dogs away from your chocolate cake.