Stevia

From Wikipedia, the free encyclopedia

Stevia (/ˈstiːvɪə/, /ˈstiːvjə/ or /ˈstɛvɪə/) is a sweetener and sugar substitute made from the leaves of the plant species Stevia rebaudiana. Stevia's taste has a slower onset and longer duration than that of sugar, and some of its extracts may have a bitter or licorice-like aftertaste at high concentrations.

With its steviol glycoside extracts having up to 300 times the sweetness of sugar, stevia has attracted attention with the rise in demand for low-carbohydrate, low-sugar sweeteners. Because stevia has a negligible effect on blood glucose it is attractive to people on carbohydrate-controlled diets.

The availability of stevia varies from country to country. In a few countries, it has been available as a sweetener for decades or centuries; for example, it has been widely used for decades as a sweetener in Japan. In some countries health concerns and political controversies have limited its availability; for example, the United States banned stevia in the early 1990s unless labeled as a dietary supplement, but since 2008 it has accepted several specific glycoside extracts as being generally recognized as safe for use as food additives. Over the years, the number of countries in which stevia is available as a sweetener has been increasing. In 2011, stevia was approved for use in the EU.

History and use

The plant Stevia rebaudiana has a long history of ethnomedical use by the Guaraní, having been used extensively by them for more than 1,500 years. The leaves have been traditionally used for hundreds of years in both Brazil and Paraguay to sweeten local teas and medicines, and as a "sweet treat".

Steviol is the basic building block of stevia'ssweet glycosides.

In 1899 Swiss botanist Moisés Santiago Bertoni, while conducting research in eastern Paraguay, first described the plant and the sweet taste in detail. Only limited research was conducted on the topic until in 1931 two French chemists isolated the glycosides that give stevia its sweet taste. These compounds, stevioside and rebaudioside, are 250–300 times as sweet as sucrose and are heat-stable, pH-stable, and not fermentable.

The exact structure of the aglycone and the glycoside was published in 1955.

In the early 1970s, sweeteners such as cyclamate and saccharin were suspected of beingcarcinogens. Consequently, Japan began cultivating stevia as an alternative. The plant's leaves, as well as the aqueous extract of the leaves and purified steviosides, were developed as sweeteners. The first commercial stevia sweetener in Japan was produced by the Japanese firm Morita Kagaku Kogyo Co., Ltd. in 1971. The Japanese have been using stevia in food products and soft drinks, (including Coca Cola), and for table use. Japan currently consumes more stevia than any other country, with stevia accounting for 40% of the sweetener market.

Today, Stevia rebaudiana is cultivated and used to sweeten food elsewhere in East Asia including China (since 1984),Korea, Taiwan, Thailand, and Malaysia. It can also be found in Saint Kitts and Nevis, Brazil, Colombia, Peru, Paraguay,Uruguay, and Israel. China is the world's largest exporter of stevioside.

Stevia rebaudiana plants which are found in the wild in semiarid habitats ranging from grassland to mountain terrain, do produce seeds, but only a small percentage of the seeds germinate. Planting cloned stevia is a more effective method of reproduction.

Folk medicine

For centuries, the Guaraní peoples of Paraguay used Stevia rebaudiana, which they called ka'a he'ê ("sweet herb"), as a sweetener in yerba mate and other foods, and as a medicinal agent.

Availability

The Stevia rebaudianaplant may be grown legally in most countries, although some countries restrict its use as a sweetener.

Stevia tablets as widely sold in health food stores in Germany

Widely used as a sweetener

• Japan (1970)

Available as a food additive (Regulatory agency approved)

• Australia, and New Zealand (October 2008) – All steviol glycoside extracts
• Brazil (1986) – Stevioside extract
• Hong Kong (steviol glycosides, January 2010)^[17]
• Israel (January 2012)
• Mexico (2009) – mixed steviol glycoside extract, not separate extracts
• Norway (June 2012) As food additive – E 960 Steviol glycoside. The plant itself has not been approved as of September 2012
• Russian Federation (2008) – stevioside is allowed in the "minimal dosage required" to achieve the goal of the additive.
• Singapore (2005) steviol glycosides are a permitted sweetening agent in certain foods. Previously it was banned.

Available as both a food additive and dietary supplement

• Canada (November 2012)
  • Steviol glycosides became available as a food additive on 30 November 2012.
  • Stevia rebaudiana leaf and extracts are available as dietary supplements
• European Union – Steviol glycosides have been permitted as a food additive since 2 December 2011.
• United States (December 2008)
  • Rebaudioside A is available (December 2008) as a food additive (sweetener) sold under various trade names.
  • Stevia rebaudiana leaf and extracts are available as dietary supplements(1995)
• Indonesia (2012)
  • Steviol glycosides are available under the Regulation of Minister of Health No. 033 year 2012 on Food Additives)
  • Stevia leaf is available as a dietary supplement

Available (regulatory status unverified)

• Argentina, Chile, China (1984), Colombia, Korea, Malaysia, Paraguay, Peru, Philippines, Saudi Arabia, Taiwan, Thailand, Turkey, United Arab Emirates, Uruguay, and Vietnam

Stevia extract on sale in a supermarket in Paraguay

Availability notes[edit]

• In the United States, rebaudioside A is generally recognized as safe (GRAS) as of December 2008. The leaves and other extracts are available as dietary supplements.
• In Australia and New Zealand, all steviol glycoside extracts were approved in 2008. Prior to 2008, stevia leaves could be sold as food.

Commercialization

Steviol glycosides were first commercialized as a sweetener in 1971 by the Japanese firm Morita Kagaku Kogyo Co., Ltd., a leading stevia extract producer in Japan.

Stevia rebaudiana has been grown on an experimental basis in Ontario, Canada since 1987 to determine the feasibility of commercial cultivation. Duke University researchers developed a strategic plan to assist farmers and exporters in Paraguay to compete in the global market for stevia.

In 2007 The Coca-Cola Company announced plans to obtain approval for their stevia-derived sweetener, rebiana, for use as a food additive within the United States by 2009, as well as plans to market rebiana-sweetened products in 12 countries that allow stevia's use as a food additive. In May 2008 Coca Cola and Cargill announced the availability of Truvia, a consumer brand stevia sweetener containing erythritol and rebiana, which the FDA permitted as a food additive in December 2008. Coca-Cola announced intentions to release stevia-sweetened beverages in late December 2008.

Shortly afterward, PepsiCo and Pure Circle announced PureVia, their brand of stevia-based sweetener, but withheld release of beverages sweetened with rebaudioside A until receipt of FDA confirmation. Since the FDA permitted Truvia and PureVia, both Coca Cola and PepsiCo have introduced products that contain their new sweeteners.

Extraction of sweet compounds

Rebaudioside A has the least bitterness of all the steviol glycosides in the Stevia rebaudiana plant. To produce rebaudioside A commercially, stevia plants are dried and subjected to a water extraction process. This crude extract contains about 50% rebaudioside A; its various glycoside molecules are separated via crystallization techniques, typically using ethanol or methanol as solvent. This allows the manufacturer to isolate pure rebaudioside A.

The National Research Council of Canada has patented a process for extracting sweet compounds from stevia by column extraction at temperatures from 0 to 25 °C, followed by purification by nanofiltration. A microfiltration pretreatment step is used to clarify the extract. Purification is by ultrafiltration followed by nanofiltration.

Mechanism of action

Glycosides are molecules that contain glucose and other non-sugar substances called aglycones (molecules with other sugars are polysaccharides). The tongue's taste receptors react to the glucose in the glycosides – those with more glucose (rebaudioside) taste sweeter than those with less (stevioside). Some of the tongue's bitter receptors react to the aglycones.

In the digestive tract, rebaudiosides are metabolised into stevioside. Then stevioside is broken down into glucose andsteviol. The glucose released in this process is used by bacteria in the colon and not absorbed into the bloodstream. Steviol cannot be further digested and is excreted.

Safety

Steviol and rebaudioside A are not mutagenic at doses and routes of administration at which humans are exposed to them. Two 2010 review studies found no health concerns with stevia or its sweetening extracts.

The WHO's Joint Experts Committee on Food Additives has approved, based on long-term studies, an acceptable daily intake of steviol glycoside of up to 4 milligrams per kilogram of body weight.

While the FDA does not consider whole-leaf Stevia or crude Stevia extracts to be "generally recognized as safe" ("GRAS")food additives, several companies have submitted notices to the FDA that they consider specific rebaudiosides to be GRAS for use as food additives, and have had these notices accepted by the FDA.

The European Food Safety Authority evaluated the safety of steviol glycosides, extracted from the leaves of the Stevia rebaudiana Bertoni plant, as sweetener and expressed its opinion on 10 March 2010. The Authority established an Acceptable Daily Intake (ADI) for steviol glycosides, expressed as steviol equivalents, of 4 mg/kg bodyweight/day. On 11 November 2011, the European Commission allowed the usage of steviol glycosides as a food additive, establishing maximum content levels for different types of foods and beverages.

Potential health effects

A 2009 review study found that stevioside and related compounds may have anti-hyperglycemic, anti-hypertensive, anti-inflammatory, anti-tumor, anti-diarrheal, diuretic, and immunomodulatory actions. A 2011 review found that the use of stevia sweeteners as replacements for sugar would likely benefit diabetic patients. Furthermore, the report noted "stevioside has shown some evidence of pharmacological effects in patients with hypertension or with diabetes mellitus type 2," but concluded further study was required to determine proper dosage.

Controversy

In 1991, after receiving an anonymous industry 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."

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". To protect the complainant, the FDA deleted names in the original complaint in its responses to requests filed under the Freedom of Information Act.

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 regarded as contradictory because it simultaneously labels stevia as safe and unsafe, depending on how it is sold.

Early studies prompted the European Commission in 1999 to ban stevia's use in food in the European Union pending further research. In 2006, research data compiled in the safety evaluation released by the World Health Organization found no adverse effects. Since 2008, the Russian Federation has allowed stevioside as a food additive "in the minimal dosage required".

In December 2008, the FDA gave a "no objection" approval for GRAS status to Truvia (developed by Cargill and The Coca-Cola Company) and PureVia (developed by PepsiCo and the Whole Earth Sweetener Company, a subsidiary of Merisant), both of which use rebaudioside A derived from the Stevia plant. However, FDA said that these products are not Stevia, but a highly purified product. In 2012, FDA posted a note on their website regarding crude Stevia plant: "FDA has not permitted the use of whole-leaf Stevia or crude Stevia extracts because these substances have not been approved for use as a food additive. FDA does not consider their use in food to be GRAS in light of reports in the literature that raise concerns about the use of these substances. Among these concerns are control of blood sugar and effects on the reproductive, cardiovascular, and renal systems."