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 in 2008 it approved rebaudioside A extract as a food additive. 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.
The genus Stevia consists of 240 species of plants native to South America, Central America, and Mexico, with several species found as far north as Arizona, New Mexico, and Texas. The genus was named for Spanish botanist and physician Petrus Jacobus Stevus (Pedro Jaime Esteve 1500–1556) author of commentaries on Nicander and Hippocrates and of an unpublished flora of the Kingdom of Valencia. Human use of the sweet species S. rebaudiana originated in South America. The leaves of the stevia plant have 30–45 times the sweetness of sucrose (ordinary table sugar). The leaves can be eaten fresh, or put in teas and foods.
The plant has a long history of medicinal 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".
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 being carcinogens. 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.
Stevia species, which are found in the wild in semiaridhabitats 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.
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 has been grown on an experimental basis in Ontario, Canada since 1987 to determine the feasibility of commercial cultivation.
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
S. rebaudiana foliage
Rebaudioside A has the least bitterness of all the steviol glycosides in the stevia 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
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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 and steviol. 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.
Health and safety
Stevia leaves have been used for centuries in South America, spanning multiple generations in ethnomedical tradition as a treatment for diabetes mellitus type 2. Millions of Japanese have been using stevia for over thirty years with no reported or known harmful effects.
In 2012, the FDA stated that it has not permitted the use of whole-leaf Stevia or crude Stevia extract citing possible concerns on blood sugar and effects on the reproductive, cardiovascular, and renal systems. In 2009 the FDA considered "Rebiana (rebaudioside A) to be generally recognized as safe (GRAS)". The report includes a detailed list of international studies, references, and chemical analysis.
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.
Preliminary human studies suggest stevia may lower blood pressure, although another study has shown it to have no effect on hypertension.
In 2006 the World Health Organization (WHO) evaluated experimental studies of stevioside and steviols conducted on animals and humans, and concluded "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 WHO also found no evidence of carcinogenic activity. 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. 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.
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 rats pretreated with a PCB blend – but this finding was criticized. Over the following years, bioassay, cell culture, and animal studies have shown mixed results in terms of toxicology and adverse effects of stevia constituents. While reports emerged that found steviol and stevioside to be weak mutagens, the bulk of studies show an absence of harmful effects. In a 2008 review, 14 of 16 studies cited showed no genotoxic activity for stevioside, 11 of 15 studies showed no genotoxic activity for steviol, and no studies showed genotoxicity for rebaudioside A. No evidence for stevia constituents causing cancer or birth defects has been found.
In relation to diabetes, studies have shown stevia to have a possible trophic effect on β-cells of pancreas, to improve insulin sensitivity in rats, and possibly even to promote additional insulin production, helping to reverse diabetes and metabolic syndrome. Stevia consumed before meals significantly reduced postprandial insulin levels compared to both aspartame and sucrose. A 2011 review study stated that stevia sweeteners would likely benefit diabetic patients. In 2013 a study with stevia leaves on diabetic rats identified a renal and hepatic protective effect and a reduction in the risk of oxidative stress, in addition to the better known hypoglycemic benefits.
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 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."
^"Stevia". British & World English. Oxforddictionaries.com. 2013-02-07. Retrieved 2013-02-13.
^"Stevia". US English. Oxforddictionaries.com. 2013-02-07. Retrieved 2013-02-13.
^Both /ˈstiːvɪə/ and /ˈstɛvɪə/ are recorded by at least some US and UK dictionaries, but the former is more common in US English (listed first or exclusively) and the latter is more common in UK English.
^Bridel, M.; Lavielle, R. (1931). "Sur le principe sucre des feuilles de kaa-he-e (stevia rebaundiana B)". Academie des Sciences Paris Comptes Rendus (Parts 192): 1123–5.Cite uses deprecated parameters (help)
^Koyama, E., et al. "In vitro metabolism of the glycosidic sweeteners, stevia mixture and enzymatically modified stevia in human intestinal microflora." Food and Chemical Toxicology 41.3 (2003) 359–374.
^Ulbricht, C.; Isaac, R.; Milkin, T.; Poole, E. A.; Rusie, E. et al. (Apr 2010). "An evidence-based systematic review of stevia by the Natural Standard Research Collaboration". Cardiovasc Hematol Agents Med Chem8 (2): 113–27. PMID20370653.
^"Commission Regulation (EU) No 1131/2011" (PDF). Official Journal of the European Union: 7. 11 November 2011. Retrieved 15 November 2011. "The CE regulation establishes steviol glycosides as food additive, and establishes maximum content levels in foodstuff and beverages."
^Hsieh MH, Chan P, Sue YM, et al. (November 2003). "Efficacy and tolerability of oral stevioside in patients with mild essential hypertension: a two-year, randomized, placebo-controlled study". Clin Ther25 (11): 2797–808. doi:10.1016/S0149-2918(03)80334-X. PMID14693305.
^Ferri LA, Alves-Do-Prado W, Yamada SS, Gazola S, et al. (September 2006). "Investigation of the antihypertensive effect of oral crude stevioside in patients with mild essential hypertension". Phytother Res20 (9): 732–6. doi:10.1002/ptr.1944. PMID16775813.
^Matsui M, Matsui K, Kawasaki Y, et al. (November 1996). "Evaluation of the genotoxicity of stevioside and steviol using six in vitro and one in vivo mutagenicity assays". Mutagenesis11 (6): 573–9. doi:10.1093/mutage/11.6.573. PMID8962427.
^Jeppesen PB, Gregersen S, Rolfsen SE, et al. (March 2003). "Antihyperglycemic and blood pressure-reducing effects of stevioside in the diabetic Goto-Kakizaki rat". Metab. Clin. Exp.52 (3): 372–8. doi:10.1053/meta.2003.50058. PMID12647278.
^Dyrskog SE, Jeppesen PB, Colombo M, Abudula R, Hermansen K (September 2005). "Preventive effects of a soy-based diet supplemented with stevioside on the development of the metabolic syndrome and type 2 diabetes in Zucker diabetic fatty rats". Metab. Clin. Exp.54 (9): 1181–8. doi:10.1016/j.metabol.2005.03.026. PMID16125530.