Monday, August 12, 2013

What if Diet Soda Wasn't Diet?

Ideas are cheap, actually pulling off the experiments is the difficult part. Sometimes these experiments aren't even possible to do at the present time. I'm probably not the only one who has a running list of experiment ideas in a text document, many of which will never see the light of day. I'm going to start something new around here by posting about research/experiment ideas that I think would be interesting and informative, but which I have absolutely no time to carry out right now (however, if you're up for collaborating definitely shoot me an email!). I'm naturally curious, so it would give me great pleasure to see SOMEONE figure out the answers to these observations or actually carry out experiments. Hell, someone might have even already done the experiments (if so, please send me a link in the comments!). Use these posts for inspiration or even just to get a feel for how I think about science, especially if you're keen on being my grad student or postdoc in the future. Point is that ideas are cheap but my mind keeps grinding. So without further delay here's where it goes sometimes...

Since my undergraduate days I've had a thing for "diet" drinks. Soda, fruit juice, etc...I always go for the "light" version. First it was the deliciously aspartame-filled Diet Coke (I definitely don't have phenylketonuria) and I've since transitioned into deliciously sucralose-filled products. Supposedly, drinking diet products can help you shed weight (see here but also here). Diet soda et al. have no calories because they contain artificial sweeteners that can't be metabolized by your body. I've always believed this, I could be completely wrong but this seems right. Relevant to this story, it does seem as though drinking diet soda can actually make you gain weight and can increase the incidence of type II diabetes (Hmmmm...)

Here's the thing. Your body is also teeming with microbes, especially in your digestive tract, billions of them. Some of these can even aid digestion by breaking down products. If there is one thing I know that microbes are good at, it's adapting to use novel resources. Unexploited potential energy sources are just another niche that microbes can thrive in. I don't see why microbes can't break down, or easily evolve to break down, aspartame, sucralose, and Truvia.

So here's a couple of potential experiments. I'd like to take some gnotobiotic mice, as gut flora may influence their weight. In the lab I'd adapt a suite of common gut microbes to growing on one of the artificial sweeteners. Then I'd transplant these bacteria back into the gnotobiotic mice in one group, and "ancestral" bacteria that can't break down the sweetener into another group. Next I'd feed different groups of mice a diet supplemented with one of the three sweeteners (as well as a regular control diet). The null hypothesis in this case would be that there will be no different in weight gain attributable to evolved vs. un-evolved microbes. A second experiment is really just a converse of the first. Basically I'd feed mice with "normal" gut flora a diet supplemented with one of the three sweeteners or the control diet with none. Then I'd measure if the ability of gut microbes to digest the artificial sweeteners changes over time.  Null hypothesis here is that there would be no change in the microbe's abilities to break down artificial sweeteners over time.

So that's the outline. Thoughts? Has this been done? If someone does this will the artificial sweetener industry put a hit out on them?

UPDATE: Thanks for the input folks! Definitely understand now that there is much less artificial sweetener in diet soda than regular. Maybe not the best example, but, doesn't change the thought experiment. I know people who replace regular sugar with sucralose or Truvia in coffee and baking. They use the exact same amounts so, plus or minus differences in the molecular formulas, there's roughly the same potential mass going in.


  1. What is your point here? If bacteria in your gut are using artificial sweeteners as an energy source (which may well be the case) that isn't going to make you any fatter. The bacteria will have used up the energy, they are not shitting it out again as sugar. In any case, artificial sweeteners like aspartame do not work because we can't digest them (we can readily digest aspartame), but because they are much, much sweeter than sugar, so that you only need a tiny amount of them in your soda or other food to get the same level of sweetness that you would otherwise get from a whole lot of sugar.

    1. Bacteria excrete all kinds of waste products that the human body can use, including molecules like DNA/proteins/and sugars that are more reduced. So yeah, less aspartame in diet drinks definitely a less than perfect example. But hey, I learned something from this so win for me. Although I could argue that humans can't digest sucralose as well as regular sugar (and I've seen people use just as much artificial sweetener in coffee as they would use regular sugar). You could easily control for sugar content on sucralose dietary supplements.

  2. It's not necessarily about calories. 1 g of sugar has the same number of calories as 1 g of protein. However almost 1/3 of the energy in the protein would be lost in converting it into fat if there is little carbohydrate present. That's from a pure biochemical angle. In terms of physiology it's all about homeostasis and in what way do the various products from the microbiota influence homeostasis, the artificial sweeteners could also directly influence this, but that is far from demonstrated.


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