Stevia – the herb that is 300 times sweeter than sugar
But what is Stevia?
This morning, I found some Stevia plants in my local rastro, so I bought them for my herb garden. I knew it was the basis for the new sugar replacement which is advertised on the TV as Truvia. On tasting one of its leaves, it was indeed sweeter than sugar. But what is it. I have done my research and can now share it with you.
Stevia is a genus of about 240 species of herbs and shrubs in the sunflower family (Asteraceae), native to subtropical and tropical regions from western North America to South America. The species Stevia rebaudiana, commonly known as sweetleaf, sweet leaf, sugarleaf, or simply stevia, is widely grown for its sweet leaves. As a sweetener and 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 licorice-like aftertaste at high concentrations.
With its steviol glycoside 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. Because stevia has a negligible effect on blood glucose, it is attractive as a natural sweetener 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, stevia is widely used as a sweetener in Japan, where it has been available for decades. In some countries, health concerns and political controversies have limited its availability; for example, the United States banned stevia in the early 1990s unless labelled as a dietary supplement, but in 2008 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 starting in early December, 2011.
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. They were first researched by Spanish botanist and physician Petrus Jacobus Stevus (Pedro Jaime Esteve), from whose surname originates the Latinized word stevia. Human use of the sweet species S. rebaudianaoriginated 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 was used extensively by the Guaraní people for more than 1,500 years, and the plant has a long history of medicinal use in Paraguay and Brazil. The leaves have been traditionally used for hundreds of years in Paraguay and Brazil to sweeten local teas, medicines and as a “sweet treat”.
In 1899, the Swiss botanist Moisés Santiago Bertoni, during his 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 were named stevioside and rebaudioside, and are 250–300 times as sweet as sucrose, heat stable, pH stable, and not fermentable.
The exact structure of the aglycone and the glycoside were published in 1955.
In the early 1970s, Japan began cultivating stevia as an alternative to artificial sweeteners such as cyclamate and saccharin, which were 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, with stevia accounting 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 semiarid habitats ranging from grassland to mountain terrain. They do produce seeds, but only a small percentage of them 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 for the purpose of determining the feasibility of growing the crop commercially.
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.
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 0–25 °C, followed by purification by nanofiltration. A microfiltration pretreatment step is used to clarify the extract. Purification is by ultrafiltration followed by nanofiltration.
Health and safety
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 on procedural grounds that the data were mishandled in such a way that even distilled water would appear mutagenic. 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 revitalizing effect on ?-cells of pancreas, 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 concluded that stevia sweeteners would likely benefit diabetic patients.
Preliminary human studies suggest stevia can help reduce hypertension, although another study has shown it to have no effect on hypertension. Indeed, millions of Japanese 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 for diabetes mellitus type 2.
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 “stevioside and rebaudioside A are not genotoxic in vitro or in vivoand 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 “stevioside has shown some evidence of pharmacologicaleffects 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, anacceptable daily intake of steviol glycoside of up to 4 milligrams per kilogram of body weight.
Beginning in 2009 in the United States, the U.S. FDA considers “Rebiana (rebaudioside A) to be Generally Recognized As Safe (GRAS)”. With respect to the measure of toxicity, which can be described as the median lethal dose or LD , a report submitted to the FDA documents “the observed LD values were 5.2 g/kg bw for male hamsters and 6.1 g/kg bw for female hamsters.” The report includes a detailed list of international studies, references, and chemical analysis.
Two 2010 review studies found no health concerns with stevia or its sweetening extracts. In addition, a 2009 review study found that stevioside and related compounds have anti-hyperglycemic, anti-hypertensive, anti-inflammatory, anti-tumor, anti-diarrheal, diuretic, and immunomodulatory actions.
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 food additive, establishing maximum content levels for different types of foods and beverages.
Bill & Sheila’s A-Z of herbs
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