Meet the Father-Son Team Who Discovered Truvia’s Fatal Effects on Fruit Flies

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Daniel Marenda and his son Simon. Photo: Courtesy of Daniel Marenda

Given the number of people who use brand-name sugar substitutes like Splenda or Equal, it's hardly surprising that people freaked out when a recent study revealed the effects that Truvia had on fruit flies: It killed them, quickly. Fruit flies who subsisted on Truvia died in a matter of days, while flies given other sweeteners lived for much longer. But the most surprising part of the study wasn't necessarily the results — it was the teenager who was responsible for getting the study started.

In 2011, Drexel University biologist Daniel Marenda and his wife decided to reduce their sugar intake for health reasons. Inspired by his parents' dietary change, Simon Kaschock-Marenda, who is now 14, decided to study the effects of sweetners on fruit flies for his sixth grade science fair. That's when he discovered Truvia's lethal effects on fruit flies. Three years and countless research hours later, Simon and his dad are two of the co-authors of a published study that explains the full results. Grub talked to the father and son about their findings (and why, thankfully, they say Truvia is harmless for humans).

What inspired the move cut back on white sugar in 2011?
Daniel Marenda: We have three kids and full-time jobs so life tends to get very busy. There’s not a lot of time for things like exercising or even eating well. I took an estimate of how many cups of tea I was drinking a day, it was three or four, all with hefty amounts of sugar. I tried to cut back on the number of cups of tea, but you know, as a scientist, caffeine is necessary for work.

Was Truvia your go-to sugar substitute?
DM: No. My wife started using Equal in her coffee — though she now uses maple syrup — and I put honey in my tea.
Simon Kaschock-Marenda: I saw what they were doing and it seemed like a good science fair project.

In other words, your back was against the wall?
SKM: Kind of, yeah. I approached my dad to get him to help me since he’s an expert on the flies.
DM: I work with fruit flies in my laboratory but I study the brain, not sugar or metabolism or anything like that. Simon brought up the idea of looking at the effects of different sugars on the flies and I thought that would be really easy to do. We drove to our local supermarket and bought every sugar and sugar substitute we could find and then drove back to my laboratory. We made up the fly food with different sugars, gathered newly hatched flies, put them into separate vials and then placed them in the closet of Simon’s room. That’s where my participation stopped. I said, "Now it’s up to you, buddy, just count the number of dead flies around the same time every day." I thought that in about 30 days he’d get a bunch of negative data and that all of the flies would look fine. When he came to me around day five and said all the flies in the Truvia vial were dead, I figured we had screwed up somehow.
SKM: I thought I forgot to feed them or something.
DM: Scientists are skeptical by training so I said, "Let’s do this again." This time we went back to my laboratory and kept the vials in my incubators that regulate temperature, humidity and light, so it’s a much more controlled environment. I took more of an active hand in looking at the flies this second time but we got the exact same results. All of the flies in the Truvia vial died around day five. It was shocking.

Did you worry that somehow you’d discovered that Truvia was potential lethal to humans, too?
DM: Initially I had a concern. The reason I study fruit flies’ brains is because they’re remarkably similar to our own. We learn a lot about ourselves by studying them. Simon was, I think, very concerned.
SKM: I didn’t like having any Truvia in the house. I even stopped drinking Coca-Cola [which uses Truvia in some of its beverages] and I was telling all of my friends, "Don’t drink Coke!"

Did they listen?
SKM: Nah, they just ignored me. Now I’ve gone back to drinking it because we found out it’s harmless to humans.
DM: There really is nothing to worry about. So we sat on this research for a long time but it kept coming up. We’d be at Thanksgiving dinner and someone would ask, "Hey, whatever happened to Simon’s little Truvia study?" Simon even did a related science project in seventh grade where he looked at the effect of Truvia on the fruit fly nervous system.

Simon, did you win any prizes for these at the school science fairs?
SKM: Nope. There were no biologists grading the projects I don’t think — or any scientists, really. Their loss. [Laughs.]

So are you giving the teachers who overlooked you a hard time now?
SKM: I’ve been at a different school but I’m going back to my original school after the summer, so I can start taunting them then.

How did this go from school science experiment to published study?
DM: That was fortuitous as well. There was a lunch gathering at Drexel and I was sitting at a table with Sean O'Donnell, an entomologist here. I started talking about Simon’s data, asking what he thought of it. I remember his eyes got really wide and he said, "We’ve got to study this!" We brought in his graduate student and had her repeat all of the experiments and she got the exact same results. Ultimately, Sean and I determined that [Truvia ingredient] erythritol was the agent that was toxic to these particular flies. This has potential for real value considering that it does seem to be extraordinarily safe for human consumption but pretty lethal to fruit flies and possibly other insects. I think in a bait-type situation it could be an effective insecticide.

Simon, you’re a co-author of the study along with your dad, O’Donnell and a few graduate students. How involved were you?
SKM: Every so often my dad would show me what he was doing with the grad students and everything but other than that I didn’t really do much.
DM: Except come up with the idea and the preliminary data! I can honestly say that I would never have done this study without Simon’s science project. Some of the best scientific breakthroughs come when you’re thinking outside the box and you’re intellectually curious about something. The only reason this is out there is because of Simon.

Simon, is your newfound science cred useful socially?
SKM: My friends think I’m a science wiz — the best scientist at the school.

Have you tried using your sudden science fame to get dates?
SKM: Yeah, I have.
DM: Really? You didn’t tell me that!
SKM: Nah, I’m kidding. But now that you mentioned it I’m going to have to try it to see if it works.

Erythritol, a Non-Nutritive Sugar Alcohol Sweetener and the Main Component of Truvia®, Is a Palatable Ingested Insecticide [PLOS ONE]