Thursday, 25 September 2014

Calorie-free Sweetener Safe for Humans, Kills Fruit Flies

Janet Fang

Forget capturing, forget honey. You can kill more flies with sugar substitute.

Many common insecticides are made of synthetic molecules, and they’re used all over, often to the detriment of the environment, human and animal health, and non-targeted insects like bees. Insect pests are even developing resistance to them. Now, researchers show that the main component of a top-selling sweetener, Truvia, is toxic to fruit flies (Drosophila melanogaster). The findings may lead to an effective, small scale insecticide that leaves humans unharmed.

Erythritol is a naturally occurring, non-nutritive sugar alcohol that was approved for use as a flavor enhancer and food additive by the U.S. Food and Drug Administration back in 2001. The agency labeled it: “generally recognized as safe” (GRAS). You can find it in little green and white packets of Truvia, marketed as a natural sweetener born from the leaves of the stevia plant.

A Drexel University team led by Daniel Marenda and Sean O'Donnell raised fruit flies on food containing erythritol and other sweeteners, including artificial sugar substitutes as well as table sugar and corn syrup. The flies seemed to prefer erythritol even when sugar was around. But those flies raised on food containing Truvia showed noticeable motor impairments​ and lived for only 5.8 days on average -- compared to the 38.6 to 50.6 days for flies raised on control and experimental foods without Truvia. Pictured above, (dead) flies raised in tubes containing Truvia.

The study began as a sixth-grade science fair project three years ago. Study coauthor Simon Kaschock-Marenda asked his parents why they stopped eating white sugar when they were trying to eat healthier. “He asked if he could test the effects of different sugars and sugar substitutes on fly health and longevity for his science fair, and I said, 'Sure!'" Marenda recalls in a news release. The two bought every type of sugar and sugar substitute they could find at their local supermarket; Marenda’s lab supplied baby flies and growth medium.

“After six days of testing these flies in our house, he came back to me and said, ‘Dad, all the flies in the Truvia vials are dead…” Marenda says. “To which I responded, ‘OK… we must have screwed up somehow. Let’s repeat the experiment!'" Under more rigorous testing conditions in the lab, they replicated their results. That's when they teamed up with O'Donnell, an entomologist down the hall, and turned the science project into a full-blown study. “Indeed what we found is that the main component of Truvia, the sugar erythritol, appears to have pretty potent insecticidal activity in our flies,” Marenda says.

No other sweeteners tested had these toxic effects -- not even PureVia, which also contains the same stevia plant extract found in Truvia. The team is now pursuing a patent on erythritol as an insecticide to be used on small scales. They’re also continuing to study its effectiveness (or toxicity) in other insects like termites, roaches, and bed bugs, as well as bugs higher up in the food chain, like the mantis.