Artificial Sweetener Update
Chester J. Zelasko, Ph.D. | February 26, 2008

Every day seems to bring a new batch of forwarded e-mails about the hazards of artificial sweeteners. Debilitating disease or conspiracies between the chemical industry and the U.S. Food and Drug Administration are the basis for these e-mails. Two studies have been published recently that will have the artificial-sweetener critics leaping up and shouting “I told you so!” But maybe they shouldn’t start jumping up and down just yet. Here’s a summary of the latest research about artificial sweeteners and their possible relationship with obesity.

Saccharin and Metabolism
In this series of three studies, researchers examined the relationship between saccharin and overeating, metabolism changes, and weight gain in male rats (1). The researchers wanted to know if the use of an artificial sweetener such as saccharin, when mixed with yogurt, would modify the animals’ appetite mechanism to cause weight gain. If it did affect appetite, would the artificial sweetener somehow negatively affect metabolic rate as well, which would contribute to the weight gain?

While the questions are valid and the studies were complex in their design, there were just too few rats in each study (as few as eight) and too many unresolved questions to suggest that this was anything more than a curiosity. For example, when examining metabolism after eating an appetizer, the scientists found that the metabolic rate of saccharin-using rats was lower than sugar-using rats. What they dismissed, because it was not statistically significant, was a difference in activity level between the two groups after eating their appetizer: when examining the graphs of the metabolic rates, it’s clear that the saccharin rats did not exercise as much as the sugar-eating rats. That would more than explain the difference in metabolism.

The results of this study indicated a point that’s really a no-brainer: when you overfeed animals by making the food really sweet, they eat too much of it and they gain weight. Not exactly rocket science, is it?

Appetite is a curious thing, controlled by many factors. But when it comes to humans, we have a distinct advantage over the rats: we can use self-control and not overeat in the first place.

Diet Soda and Metabolic Syndrome
Metabolic Syndrome (MetS) is a group of risk factors associated with heart disease and diabetes. In a large multi-region study, researchers wanted to examine whether a Western diet high in fat, sugar, and fried foods was associated with a higher rate of development of MetS than a prudent diet made up of vegetables, fruits, and whole grains (2). What they found was that parts of the Western diet did, in fact, contribute to MetS. What they also found out was that eating a prudent diet did not lower that risk; it didn’t make the risk worse, but it didn’t protect against MetS as they expected. That should have been the headline.

Diet soda did grab the headlines. The researchers found there was a 34% increased risk of MetS if a person drank less than one serving of diet soda per day. Just like the previous study, there may be some compelling chemical attribute to diet soda that causes a person to eat more and gain weight--except that the study also showed that if a person averaged one diet soda per week, the risk of MetS was actually 21% lower than drinking none at all. How can drinking a little be less risky than drinking none at all? It makes no sense. This didn’t make the press and the researchers didn’t discuss it.

The real problem with this study, and with many others like it, was the use of the food-frequency questionnaire. No matter how well done and no matter how many studies validate its use, the food-frequency questionnaire always results in curious results. And why wouldn’t it? How many servings of fried foods have you had in the past 30 days? The first choice is None. That was easy. But wait--did you forget that your microwaved frozen dinner contained fried chicken? How about the last time you took the kids to a fast-food restaurant? Yes, you got a salad, but you ate some of their fries--how many did you eat? The results of food-frequency questionnaires may provide a general overview of diet, but that’s about it--they’re a blunt instrument, not a sharp scalpel. They aren’t precise enough to determine whether a diet soda per day has anything to do with the development of MetS, obesity, or anything else.

Bottom Line
Artificial sweeteners were developed as a means to provide the taste that we love without the calories. To that end, they have been successful. But even as the artificial sweeteners grow in popularity, we get fatter. Is it cause and effect? Probably not, but only time and more research will tell--so if you want a Diet Coke, go ahead and have one.

I think that at the end of the day, the solution for obesity will still be eat less, exercise more, for life. Period.

  1. Swithers, SE and Davidson, TL. A Role for Sweet Taste: Calorie Predictive Relations in Energy Regulation in Rats. Neuroscience. e-pub February 2008.

  2. Pamela L. Lutsey, Lyn M. Steffen, and June Stevens. Dietary Intake and the Development of the Metabolic Syndrome: The Atherosclerosis Risk in Communities Study. Circulation, Feb 2008; 117: 754--761.
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