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Stevia is a genus of about 150 species of herbs and shrubs in the sunflower family (Asteraceae), native to subtropical and tropical South America and Central America. The species Stevia rebaudiana Bertoni, commonly known as sweetleaf, sweet leaf, sugarleaf, or simply stevia, is widely grown for its sweet leaves. As a sugar substitute, stevia's taste has a slower onset and longer duration than that of sugar, although some of its extracts may have a bitter or liquorice-like aftertaste at high concentrations.
With its extracts having up to 300 times the sweetness of sugar, stevia has garnered attention with the rise in demand for low-carbohydrate, low-sugar food alternatives. Stevia also has shown promise in medical research for treating such conditions as obesity and high blood pressure. Stevia has a negligible effect on blood glucose, even enhancing glucose tolerance; therefore, it is attractive as a natural sweetener to diabetics and others on carbohydrate-controlled diets. However, health and political controversies have limited stevia's availability in many countries; for example, the United States banned it in the early 1990s unless labeled as a supplement. Stevia is widely used as a sweetener in Japan, and it is now available in the US and Canada as a dietary supplement, although not as a food additive. Rebiana is the trade name for a stevia-derived sweetener being developed jointly by The Coca-Cola Company and Cargill with the intent of marketing in several countries and gaining regulatory approval in the US and EU.
History and use
For centuries, the Guaraní tribes of Paraguay and Brazil used Stevia species, primarily S. rebaudiana which they called ka'a he'ê ("sweet herb"), as a sweetener in yerba mate and medicinal teas for treating heartburn and other ailments.
In 1931, two French chemists isolated the glycosides that give stevia its sweet taste. These compounds were named stevioside and rebaudioside, and are 250–300 times sweeter than sucrose (ordinary table sugar), heat stable, pH stable, and non-fermentable.
In the early 1970s, Japan began cultivating stevia as an alternative to artificial sweeteners such as cyclamate and saccharin, suspected carcinogens. The plant's leaves, the aqueous extract of the leaves, and purified steviosides are used as sweeteners. Since the Japanese firm Morita Kagaku Kogyo Co., Ltd. produced the first commercial stevia sweetener in Japan in 1971, the Japanese have been using stevia in food products, soft drinks (including Coca Cola), and for table use. Japan currently consumes more stevia than any other country; it accounts for 40% of the sweetener market.
Today, stevia is cultivated and used in food elsewhere in east Asia, including in China (since 1984), Korea, Taiwan, Thailand, and Malaysia. It can also be found in Saint Kitts and Nevis, in parts of South America (Brazil, Colombia, Peru, Paraguay, and Uruguay) and in Israel. China is the world's largest exporter of stevioside.
Stevia species are found in the wild in semi-arid habitats ranging from grassland to mountain terrain. Stevia does produce seeds, but only a small percentage of them germinate. Planting cloned stevia is a more effective method of reproduction.
Stevia has been grown on an experimental basis in Ontario, Canada since 1987 for the purpose of determining the feasibility of growing the crop commercially. In the United States, it is legal to import, grow, sell, and consume stevia products if contained within or labeled for use as a dietary supplement, but not as a food additive. Stevia has also been approved as a dietary supplement in Australia, New Zealand and Canada. In Japan and South American countries, stevia may also be used as a food additive. Stevia is currently banned for use in food in the European Union It is also banned in Singapore and Hong Kong.
Rebiana is the tradename for a patent-pending, calorie-free, food and beverage sweetener derived from stevia and developed jointly by The Coca-Cola Company and Cargill. In May 2007, Coca-Cola announced plans to obtain approval for its use as a food additive within the United States by 2009. Coca-Cola has also announced plans to market rebiana-sweetened products in 12 countries that allow stevia's use as a food additive. The two companies are conducting their own studies in an effort to gain regulatory approval in the United States and the European Union.
A 1985 study reported that steviol, a breakdown product from stevioside and rebaudioside (two of the sweet steviol glycosides in the stevia leaf) is a mutagen in the presence of a liver extract of pre-treated rats — but this finding has been criticized on procedural grounds that the data were mishandled in such a way that even distilled water would appear mutagenic. More recent animal tests have shown mixed results in terms of toxicology and adverse effects of stevia extract, with some tests finding steviol to be a weak mutagen while newer studies find no safety issues.
Other studies have shown stevia improves insulin sensitivity in rats and may even promote additional insulin production, helping to reverse diabetes and metabolic syndrome. Preliminary human studies show stevia can help reduce hypertension  although another study has shown it has no effect on hypertension. Despite these more recent studies establishing the safety of stevia, government agencies have expressed concerns over toxicity, citing a lack of sufficient conclusive research.
Whole foods proponents draw a distinction between consuming (and safety testing) only parts, such as stevia extracts and isolated compounds like stevioside, versus the whole herb. In his book Healing With Whole Foods, Paul Pitchford cautions, "Obtain only the green or brown [whole] stevia extracts or powders; avoid the clear extracts and white powders, which, highly refined and lacking essential phyto-nutrients, cause imbalance". However, Pritchford does not support this statement with scientific evidence other than general findings about refined foods being less beneficial.
In 2006, the World Health Organization (WHO) performed a thorough evaluation of recent experimental studies of stevioside and steviols conducted on animals and humans, and concluded that "stevioside and rebaudioside A are not genotoxic in vitro or in vivo and that the genotoxicity of steviol and some of its oxidative derivatives in vitro is not expressed in vivo." The report also found no evidence of carcinogenic activity. Furthermore, the report noted that "stevioside has shown some evidence of pharmacological effects in patients with hypertension or with type-2 diabetes" but concluded that further study was required to determine proper dosage.
Indeed, millions of Japanese people have been using stevia for over thirty years with no reported or known harmful effects. Similarly, stevia leaves have been used for centuries in South America spanning multiple generations in ethnomedical tradition as a treatment of type II diabetes.
In 1991, at the request of an anonymous complaint, the United States Food and Drug Administration (FDA) labeled stevia as an "unsafe food additive" and restricted its import. The FDA's stated reason was "toxicological information on stevia is inadequate to demonstrate its safety." This ruling was controversial, as stevia proponents pointed out that this designation violated the FDA's own guidelines under which any natural substance used prior to 1958 with no reported adverse effects should be generally recognized as safe (GRAS).
Stevia occurs naturally, requiring no patent to produce it. As a consequence, since the import ban in 1991, marketers and consumers of stevia have shared a belief that the FDA acted in response to industry pressure. Arizona congressman Jon Kyl, for example, called the FDA action against stevia "a restraint of trade to benefit the artificial sweetener industry." Citing privacy issues, the FDA has not revealed the source of the original complaint in its responses to requests filed under the Freedom of Information Act.
The FDA requires proof of safety before recognizing a food additive as safe. A similar burden of proof is required for the FDA to ban a substance or label it unsafe. Nevertheless, stevia remained banned until after the 1994 Dietary Supplement Health and Education Act forced the FDA in 1995 to revise its stance to permit stevia to be used as a dietary supplement, although not as a food additive — a position that stevia proponents regard as contradictory because it simultaneously labels stevia as safe and unsafe, depending on how it is sold.
Although unresolved questions remain concerning whether metabolic processes can produce a mutagen from stevia in animals, let alone in humans, the early studies nevertheless prompted the European Commission to ban stevia's use in food in the European Union pending further research. Singapore and Hong Kong have banned it also. However, more recent data compiled in the safety evaluation released by the World Health Organization in 2006 suggest that these policies may be obsolete.
Names in other countries
Both the sweetener and the stevia plant Stevia rebaudiana Bertoni (also known as Eupatorium rebaudianum Bertoni) are known simply as "stévia" (pronounced /stɛvia/) in English-speaking countries as well as in France, Germany, Italy, Portugal, Israel, and Sweden — although some of these countries also use other terms as shown below. Similar pronunciations occur in Japan (sutebia or ステビア in katakana), and in Thailand (satiwia). In some countries (India, for example) the name translates literally as "sweet leaf." Below are some names for the stevia plant in various regions of the world:
Notes and references
Look up Stevia in Wiktionary, the free dictionary.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Stevia". A list of authors is available in Wikipedia.|