Stevia is the newest sweetener on the market at the moment. Many times sweeter than sugar, that means that it is considered a zero-calorie sweetener. Stevia is an extract from the leaves of the stevia tree and therefore is considered a natural product. But does that mean it’s safe?
A word about the word ‘natural’
Just because something is natural, does not mean it is good for you. Hemlock extact is 100% natural, but was used in the ancient world to execute Socrates. All of the following are also 100% natural: arsenic, heroine, rattlesnake venom and Rush Limbaugh, and yet all are toxic in relatively low doses. Given the choice between chemically synthesized vitamin C pills and all-natural arsenic pills, I’ll take the vitamin C, thank you very much. In short, to me it means nothing that stevia is derived from plants.
What does the toxicity research say?
The US Food & Drug Administration has declared stevia to be GRAS — Generally Recognized As Safe. This is the same classification as other artificial sweeteners such as saccharine and aspartame (which I personally avoid, but that’s another story). Furthermore, Stevia has been in use in very limited quantities in some cultures of South America for centuries. The amount that people use in these cultures, however, is far short of what an American drinking two stevia-sweetened Diet Cokes would consume. Many consumer groups think that stevia should be subjected to further study. The Center for Science in the Public Interest commissioned Curtis Eckhert, professor of molecular toxicology at UCLA, and his graduate student, Sarah Kobylewski, to review the existing evidence on stevia available through mid-2008 (view full report as PDF). The UCLA experts raisd two potential issues:
DNA Damage and Cancer
In some studies, compounds in the stevia-derived sweeteners caused “mutations, chromosome damage or DNS breakage”. However, studies in rats did not find any increase in tumors. Professor Eckhert notes that definitive studies require that two species be exposed to a substance, so until lifetime carcinogenity study is done on mice or another mammal, there is no strong evidence one way or the other regarding stevia and cancer.
Early worries about impacts on fertility have been put to rest by a study sponsored by Cargill (manufacturer of stevia-based sweeteners). They found no impact on reproduction among rats fed very large doses of rebaudioside A, one of the main compounds in stevia sweeteners.
Blood sugar spikes
: similarly, early concerns about adverse effects on blood-sugar levels have been allayed by another Cargill-sponsored study of 122 diabetics fed large quantities if rebaudioside A. They found no impact on blood glucose levels in diabetics. So it appears that stevia is probably safe, though it would be nice to see another long-term study in a second species to fully put to rest the cancer concerns.
But is it good for you?
It’s one thing to be non-toxic and another thing to be good for you. In high quantities, alcohol is toxic, but in moderation, red wine is good for you. Fat is essential for life, but in large quantities it leads to obesity and heart disease.
Some research came out a few years ago suggesting that artificial sweeteners, by being sweet but providing no real satiety, would actually cause people to eat more. As of March 2009, this does not appear to be borne out by evidence. Researchers did find that adding non-nutritive sweeteners (NNS) to foods did increase appetite, but that the effect was the same as adding salt to food. So, all other things being equal, it does not seem that NNS consumption has any effect on hunger.
But what are you replacing?
This raises question of what the NNS foods, especially drinks, are replacing. In other words, is it a replacement for another no-calorie item, like water, or does it actually replace sugar you would have otherwise eaten? In other words, do you make up the savings by eating elsewhere? These studies are challenging to design, but some studies have shown “enhanced energy intake after ingestion of a sweetened, non-energy yielding beverage.” In plain English, some researchers have found that people who drink diet sodas tend to eat more. These studies are in the minority, however, and most evidence suggests that there is no effect. In fact, evidence indicates that people do in fact take in slightly fewer calories when they add drinks sweetened with NNS to their diet. At the same time, the best studies have shown that long-term, NNS substitution has essentially no effect on weight loss or gain.
So no, despite what you may have heard, diet sodas do not make you fat. Remember, though, they do not make you thin either!
- Richard D Mattes and Barry M Popkin, “Nonnutritive sweetener consumption in humans: effects on appetite and food intake and their putative mechanism”, American Journal of Clinical Nutrition, 2009, vol 89, p. 1–14. This is an excellent review of all the research taking up the question of calorie intake and the use of aspartame, saccharine and other NNS.
- David Schardt, “Stevia: Sweet… but How Safe?”, Nutrition Action Healthletter, October 2008, p. 9. More on the web at www.nutritionaction.org/stevia
- “Is Stevia Sweet News for You?”, Tufts University Health and Nutrition Newsletter, March 2009, p. 6.