Fans of the natural, calorie-free sweetener stevia might be surprised to find out that Truvia, one of its most popular representatives, doesn't just sweeten your coffee — it's also great at killing fruit flies.
A study published today in PLOS ONE demonstrates that if you put fruit flies in a jar containing food laced with Truvia, they'll die in about 6 days. If you do the same with food containing other sweeteners, however, they'll live for about 45 days. But before you start throwing all your stevia away, consider this: the ingredient that kills flies isn't the stevia extract itself, but erythritol — Truvia's main component, and a sugar alcohol that's harmless to humans. So this newly-discovered property is a good thing, because it means that the world might have a novel, human-safe insecticide on its hands.
discovered by a sixth-grader
This information comes to us thanks to Simon Kashock-Marenda, a ninth-grader from Philadelphia who was actually in the sixth-grade at the time of the discovery. He realized that Truvia could kill fruit flies while looking into the effect of various sweeteners on insect health and longevity for a science fair experiment. His parents had recently cut back on white sugar, so he was curious about the health effects of substitutes.
But when Kaschock-Marenda realized that Truvia was actually killing his flies, he knew something was up. So, he told his father, Daniel Marenda, who also happens to be a biologist at Drexel University. The two are now co-authors of the study.
It also impairs fly motor function
According to the experiment's results — it was recreated more rigorously in a Drexel lab once the sixth-grader reported the finding — erythritol is toxic to fruit flies in a dose-dependent manner, meaning that a higher dose is more effective. Truvia also appears to impair fly motor function shortly before they die, the researchers report. No other sweetener tested in the study had these effects, including another popular stevia brand called PureVia.
And the flies actually love the stuff. When they were given the option to eat either sugar or Truvia, they seemed to prefer the latter. Given these results, it should come as no surprise that the scientists are now trying to patent erythritol as an insecticide. But in the meantime, they hope to find out if it's capable of killing other types of insects, and what mechanism makes it so toxic. Another question they would like to answer is whether insects that consume fruit flies, such as the praying mantis, might also be affected by the sugar alcohol after eating Truvia-fed flies. Erythritol is actually naturally present in a number of fruits, in very small amounts, so the finding hints that it might serve a deeper purpose than sweetening our food.
In any case, erythritol probably isn't going to be sprayed on crops, or on campers' bodies any time soon, especially since flies seem to be attracted to it. But Truvia might make an effective kitchen fruit fly trap when the dog days of summer come around.