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September 2011

The Truth About Stevia—The So-called "Healthy" Alternative Sweetener

 

Stevia

By NATALIE DIGATE MUTH, M.D., M.P.H., R.D.


Americans now can get their calorie-free sugar fix from an all-natural alternative to artificial sweeteners. Once limited to the health-food market as an unapproved herb, the plant-derived sweetener known as stevia is now widely available and rapidly replacing artificial sweeteners in consumer products. Thirty times sweeter than sugar and with no effect on blood sugar and little aftertaste, stevia sales are predicted to reach about $700 million in the next few years, according to the agribusiness finance giant Rabobank.

Stevia’s history goes back to ancient times. Grown naturally in tropical climates, stevia is an herb in the chrysanthemum family that grows wild as a small shrub in Paraguay and Brazil, though it can easily be cultivated elsewhere. Paraguayans have used stevia as a food sweetener for centuries while other countries, including Brazil, Korea, Japan, China and much of South America, have a shorter, though still long-standing, record of stevia use.

Stevia’s Rocky History With the FDA
Though widely available throughout the world, in 1991 stevia was banned in the U.S. due to early studies that suggested the sweetener may cause cancer. A follow-up study refuted the initial study and in 1995, the Food and Drug Administration (FDA) allowed stevia to be imported and sold as a food supplement, but not as a sweetener. Several companies argued to the FDA that stevia should be categorized similarly to its artificial-sweetener cousins as “Generally Recognized as Safe” (GRAS). Substances that are considered GRAS have been determined to be safe through expert consensus, scientific review or widespread use without negative complications. They are exempt from the rigorous approval process required for food additives. If designated as GRAS, stevia could be used as a sweetener in a wide variety of food products and beverages. In December 2008, the FDA accepted this argument, declared stevia GRAS, and allowed its use in mainstream U.S. food production. It has taken food manufacturers a couple of years to work out the right formulations, but stevia is now present in a number of foods and beverages in the U.S., including Gatorade’s G2, VitaminWater Zero, SoBe Lifewater Zero, Crystal Light and Sprite Green. Around the world it has been used in soft drinks, chewing gums, wines, yogurts, candies and many other products. Stevia powder can also be used for cooking and baking (in markedly decreased amounts compared to table sugar due to its high sweetness potency).

In its initial form, Stevia was sold as a ground-up powder of the stevia plant leaves. Though sweet, the powder also had a bitter aftertaste (mostly attributed to a compound found in the stevia plant called stevioside), which limited its acceptability as a sugar substitute for the health-store-shopping crowd. But now manufacturers have figured out how to retain the sweet taste and all of stevia’s benefits without the aftertaste. There are more than 100 species of stevia plant, but one stands out for its excellent properties as a sweetener—stevia rebaudiana, which contains the compound rebaudioside A, the sweetest-flavored component of the stevia leaf. Rebaudioside A acts chemically similar to sugar in onset, intensity and duration of sweetness, and is free of aftertaste. A majority of stevia-sweetened products contain mostly extracted Rebaudioside A with some proportion of stevioside, which is a white crystalline compound present in stevia that tastes 100 to 300 times sweeter than table sugar.
Stevia is marketed under the trade names of Truvia (Coca-Cola and agricultural giant Cargill), PureVia (PepsiCo and Whole Earth Sweetener Company), and SweetLeaf (Wisdom Natural Brands). Despite the three different names, the sweetener is essentially the same product, each containing slightly different proportions of rebaudioside A and stevioside. Both Coca-Cola and PepsiCo intend to use stevia as a soft-drink sweetener in the U.S., but haven’t yet unveiled their stevia-sweetened versions of Coke or Pepsi.

But is it Safe?
Though stevia is most likely as safe as artificial sweeteners (or more so), few long-term studies have been done to document its health effects in humans. A review conducted by toxicologists at UCLA, which was commissioned by nutrition advocate Center for Science in the Public Interest (Kobylewski & Eckhert, 2008), raised concerns that stevia could contribute to cancer. The authors noted that in some test tube and animal studies, stevioside (but not rebaudioside A) caused genetic mutations, chromosome damage and DNA breakage. These changes presumably could contribute to malignancy, though no one has actually studied if these compounds cause cancer in animal models. Notably, initial concerns that stevia may reduce fertility or worsen diabetes seem to have been put to rest after a few good studies showed no negative outcomes. In fact, one study of human subjects showed that treatment with stevia may improve glucose tolerance. Another found that stevia may induce the pancreas to release insulin, thus potentially serving as a treatment for type 2 diabetes. (These studies are reviewed in Goyal, Samsher and Goyal, 2010.) After artificial sweeteners were banned in Japan more than 40 years ago, the Japanese began to sweeten their foods with stevia. And while they have conducted more than 40,000 clinical studies on stevia and concluded that it is safe for human use, there is a general lack of long-term studies on stevia’s use and effects.

All in all, stevia’s sweet taste and all-natural origins make it a popular sugar substitute. With little long-term outcomes data available on the plant extract, it is possible that stevia in large quantities could have harmful effects. However, it seems safe to say that when consumed in reasonable amounts, stevia may be an exceptional natural plant-based sugar substitute. Check the label next time you eat a favorite low-calorie sweet. You’re likely to find stevia near the top of the ingredient list.

References
Goyal, S.K., Samsher and Goyal, R.K. (2010). Stevia (Stevia rebaudiana) a bio-sweetener: A review. International Journal of Food Sciences and Nutrition, 61, 1, 1-10.
Kobylewski, S. and Eckhert, C.D. (2008). Toxicology of rabaudioside A: A review. Retrieved July 20, 2011.

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digate muthNatalie Digate Muth, M.D., M.P.H., R.D., is a pediatrics resident at UCLA Medical Center, a registered dietitian and a spokesperson for the American Council on Exercise (ACE). She holds fitness certifications from ACE, the American College of Sports Medicine, and the National Strength and Conditioning Association.



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