Stevia is a shrub that is native to the warmer areas of the Americas. The leaves when dried and ground can be used as a powerful sweetener, about 300 times as sweet as regular table sugar! Because it is so sweet, pure stevia is often sold with a very tiny scoop inside; less than half the scoop is plenty to sweeten a cup of coffee or tea. Commercial stevia-based sweeteners can be used in quantities closer to sugar due to the bulking agents they contain. Depending on the brand, the bulking agents may include erythritol (a sugar alcohol), inulin (a.k.a. fructans, long chains of mostly fructose), or even cane sugar.
The FDA has not yet approved whole leaf stevia or pure stevia extracts for use in food, so these pure products are currently sold only as supplements. Commercial stevia sweeteners are not pure but contain a highly purified component of the whole stevia plant called rebaudioside A, which is what gives the stevia its sweetness. The FDA has deemed rebaudioside A as “generally regarded as safe” (GRAS), and so the commercial stevia sweeteners are allowed on store shelves. Pure stevia has been used in food commercially and in homes outside the United States for decades.
When deciding if stevia is right for you, it is important to consider whether you will use pure stevia or a bulked-up commercial version. The sweet compound in stevia does not raise blood sugar, which makes it a desirable choice over cane sugar or other common sweeteners. In addition to not spiking blood sugar, multiple studies have shown that it also promotes the release of insulin (the hormone that lowers blood sugar) indicating that this sweetener may actually be helpful in treating Type II diabetes! Also the sweetness of stevia does not promote tooth decay as other sweeteners do, and since it has no calories, rebaudioside A does not contribute to weight gain and obesity.
Despite the benefits of rebaudioside A, the bulking agents used in the FDA-approved commercial stevia products can have undesirable side effects. Sugar alcohols like erythritol are poorly absorbed and can remain in the gut where they are fermented by bacteria. This results in excess gas and abdominal bloating. Since sugar alcohols hold excess water in the bowels, they can also trigger diarhhea for some. Inulin is made up of long chains of fructose; in individuals who absorb the fructose poorly it is metabolized by bacteria in the large intestine leading to many forms of digestive upset, plus excess fructose is readily stored as fat. Stevia sweeteners that are bulked with cane sugar may be misleading to consumers who think they are getting calorie-free stevia with all the benefits; instead they may still end up with the weight gain, blood sugar fluctuations and tooth decay that come with sugar.
So, the decision is yours. If you have concerns about blood sugar stabilization or dental problems, stevia may be an excellent choice for a sweetener. However, if you also experience IBS or other digestive symptoms, or you are concerned about weight gain, then it might be better to use the non-FDA approved pure stevia. In either case, before using stevia it is advisable to learn what else is in your chosen product and how it might affect you.