Stevia: A Sweetener Shrouded in Mystery and Debate

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Over the past several weeks, we’ve taken a closer look at various nutritive, or caloric, sweeteners, including high-fructose corn syrup. Thank you all for your comments, questions, and suggestions. The use of sweeteners is obviously an important, and often emotionally charged, topic.

This week, I thought I’d write about stevia, a sweetener that has grown more popular with many people who are uncomfortable with using artificial sweeteners, such as aspartame and sucralose.

Stevia is an herb that belongs to the sunflower family (Asteraceae). It’s grown primarily in Central and South America and is sometimes called sweet leaf or sugar leaf. For many centuries, people living in Paraguay and Brazil have used stevia to sweeten a drink called yerba mate.

In the early 1930s, scientists isolated the ingredients, stevioside and rebaudioside, that give stevia its sweetness. These ingredients, collectively known as glycosides, are about 300 times sweeter than sucrose, although they are calorie-free and carbohydrate-free (meaning they don’t affect blood glucose levels). Stevia users describe stevia as tasting a bit like licorice.

Japan has been manufacturing stevia since the 1970s and happens to be the largest consumer of stevia compared to other countries. Stevia is also used in other Asian countries as well as in Central and South America. Interestingly, stevia has yet to be approved for use as a sweetener by the U.S. Food and Drug Administration (FDA), by Canada, or by the European Union. It is, however, available as a dietary supplement. Why?

Studies done several years ago hinted that stevia may be harmful in several ways. First, large amounts of stevia given to both male and female rodents affected their fertility and led to fewer and smaller-sized offspring. Second, in test tubes, a compound in stevia can become mutagenic; it’s not known if this could translate into cancer in humans. And third, large amounts of stevia given to animals can interfere with carbohydrate absorption. More recently, another study found that stevioside, when given to rats, caused lesions in the liver, brain, and spleen, thus supporting an earlier study that proposed that stevia might be potentially mutagenic.

On the flip side, a study published this past March showed that, in people with Type 1 and Type 2 diabetes with either normal or high blood pressure, stevia didn’t adversely affect blood glucose levels, HbA1c, or blood pressure. I’ll note that this study was conducted at the National University Asunción in Paraguay, a country that happens to grow stevia. However, to be fair, a review study published in 2003 by the Laboratory of Plant Physiology at Catholic University of Leuven in Belgium concluded that stevioside is safe to use as a sweetener. And still another study points to stevia as being a source of natural antioxidants.

So, what is one to do? Is stevia safe or not? There are plenty of Web sites on the Internet that rave about stevia (and a few that warn us of the dangers). You’ll also find recipes and even some food products that contain stevia (although I’m not sure how they’ve managed to slip by the FDA). You’ll find stevia sold as a supplement in the aisles of your neighborhood whole foods/natural foods store, and you can purchase stevia over the Internet as well.

Until we learn more about stevia, it’s probably safe to use in small amounts—say, to sweeten your tea or coffee. The FDA’s concern is that if stevia is used to sweeten soft drinks and food products, intake within a large population will greatly increase, and the health consequences just aren’t known. As the saying goes, “buyer beware.”

What are your thoughts on using stevia?

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