Due to popular demand, I’ll conclude my series on sweeteners by writing about stevia. I actually wrote about stevia back in 2008, but times have changed (and I realize that perhaps not everyone had an opportunity to read my entry back then!).
Stevia is an herb that belongs to the sunflower family (Asteraceae). It’s grown primarily in Central and South America, and is sometimes called candy leaf. For many centuries, people living in Paraguay and Brazil have used stevia to sweeten a drink called yerba mate. In the early 1930’s, scientists isolated stevioside and rebaudioside, the ingredients that give stevia its sweetness. These ingredients, collectively known as glycosides, are about 300 times sweeter than sugar, but they are calorie-free and carbohydrate-free (meaning they have no effect on blood glucose). Stevia users sometimes describe stevia as tasting a bit like licorice.
Japan, which is the largest consumer of stevia in the world, has been manufacturing stevia since the 1970’s for use in products such as Diet Coke. Stevia is also used in other Asian countries, as well as in Central and South America. Stevia has been available in health food stores in the United States for a long time and was considered to be a dietary supplement until the FDA granted it “GRAS” (generally recognized as safe) status in 2008. However, only one of the stevia extracts, rebaudioside A, or rebiana, has been given the green light by the FDA; whole-leaf stevia has not be given GRAS status.
Cargill and Merisant are the companies that isolated rebaudioside A, the stevia extract that received FDA GRAS status. These companies submitted research to the FDA in 2008 and petitioned the FDA to approve the extract to be used as a sweetener. The rest is history. Cargill came out with Truvia and Merisant debuted Pure Via, which are two of the main stevia-based sweeteners on the market (other brands inlcude Stevia Extract in the Raw and SweetLeaf). Many consumers rejoiced at the arrival of these new sweeteners because they are free of the chemicals that make up the other popular sweeteners such as saccharin, aspartame, and sucralose.
Stevia-based sweeteners are about 300 times sweeter than sugar, calorie-free, very low carb, heat stable (so you can bake with them), and noncariogenic, meaning they don’t promote cavities. On the other hand, they’re somewhat expensive and can have a bitter taste, and there is some controversy surrounding stevia (more on that below).
The Acceptable Daily Intake (ADI) for stevioside equivalents is 4 milligrams per kilogram (mg/kg) of body weight, which translates into 12 mg/kg per day of steviol glycosides (which includes rebaudioside A). This means that a 68-kg (150 pound) person could safely consume 816 mg of rebaudioside A every day over his lifetime without any adverse effects. That would be like consuming roughly 23 teaspoons of Truvia every day. (Truvia and Pure Via are not 100% stevia-extract: Truvia contains natural flavors and erythritol, a sugar alcohol, while Pure Via contains dextrose, cellulose powder, and natural ingredients.)
It’s always a good idea to remember that “natural” doesn’t necessarily mean “safe.” Most of us understand this, but sometimes we can be lulled into believing that products made with natural ingredients surely are fine, since they’re made with products found in nature. Maybe, but cyanide is natural, and obviously that’s not safe.
Studies done several years ago implied that stevia could be harmful. In one study, male and female rodents given large amounts of stevia had fewer and smaller offspring. Large amounts of stevia given to animals have also been found to interfere with carbohydrate absorption. In test tubes, a compound in stevia can become mutagenic (meaning it increases the frequency of certain types of mutations); it’s not known if this could translate into cancer in humans. Another study found that stevioside, when given to rats, caused lesions in the liver, brain, and spleen, thus supporting an earlier study that concluded stevia to be potentially mutagenic.
The European Food Safety Authority published its opinion on stevia’s safety in 2010 and concluded that animal and some human studies did not indicate that steviosides lead to cancer, birth defects, problems with reproduction, or any other kind of damage, for that matter. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has further concluded that stevia-based sweeteners have no effect on either blood pressure or blood glucose response and that they are safe to use by people with diabetes. The Center for Science in the Public Interest (CSPI), a consumer watchdog group, also grades stevia as “safe,” but it notes that further safety testing of this sweetener would be useful.