Middle school student discovers sweet new insecticide

A middle school science project found that the sugar substitute Truvia is effective in shortening the life spans of fruit flies.

A natural, non-toxic insecticide might be in your kitchen, a new study says.

In what started out as a middle school science project, scientists discovered that erythritol, the main ingredient in the artificial sweetener Truvia, is toxic to fruit flies.

This does not mean anyone using Truvia to sweeten their coffee or tea is in danger. Erythritol is a natural compound that is present in several types of fruit. It's sweet like table sugar but has almost no calories. It was approved by the Food and Drug Administration as a food additive in 2001 and many studies have shown humans have a high tolerance for the compound.

So, unlike synthetic insecticides, an erythritol-based insecticide would be nontoxic to humans and would not act as a pollutant, the researchers said. [10 of the Most Polluted Places on Earth]

Not only does the sweetener kill the flies, but they actually prefer it to other food choices. The researchers who conducted the study are now seeking to patent an erythritol-based insecticide.

"We are not going to see the planet sprayed with erythritol, and the chances for widespread crop application are slim," Sean O'Donnell, a professor of biology at Drexel University in Philadelphia who worked on the experiment, said in a statement. "But on a small scale, in places where insects will come to a bait, consume it and die, this could be huge." 

The first part of the study came from a science project by Simon Kaschock-Marenda, who is now in ninth grade and is the son of Daniel Marenda, a biology professor at Drexel. The father-son team first tested the method on fruit flies raised in small vials in their home. They divided the flies into groups and fed them food mixed with the artificial sweeteners Truvia, Splenda, Equal, Sweet'N Low or Pure Via.

The flies that were raised on food containing Truvia had much shorter life spans than flies raised on the other sweeteners. Flies that ate food without Truvia lived between 38 and 51 days. But the average life span of flies raised on food with Truvia was only 5.8 days. Marenda realized it was time to move the experiment out of the house and into the lab, and he brought in O'Donnell for help.

The next step was to determine what part of the sweetener was causing the toxic effect. Erythritol is the main ingredient in Truvia, and the scientists suspected it might be the toxin. The researchers gave flies food with Truvia, Pure Via, pure erythritol or sucrose (table sugar). Flies that consumed food with either Truvia or erythritol were dead within a week. The other flies lived for two weeks before the researchers discontinued their observation.

The flies consumed more than twice as much erythritol as sucrose when given the choice between the two, suggesting that the files preferred the former. Because of this, scientists think erythritol could successfully be used to bait flies and act as an effective insecticide.

The researchers also wanted to know how much erythritol it would take to kill off the flies. Flies that were given food with low levels of erythritol (about 0.1 grams in 10 milliliters of water) showed no difference in life span than flies raised on food without any erythritol. But flies that were given food with high levels of erythritol (2.4 grams in 10 milliliters of water) were dead within two days.

The researchers don't know exactly how erythritol killed the flies, but other studies have shown that it can inhibit an insect's ability to absorb nutrients and water and their ability to move around. More studies are needed to determine if erythritol is toxic to any other insects.

The study is published today (June 4) in the journal PLOS ONE.

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