Reviewed by the Global Stevia Institute Scientific Advisory Board
The story of sweet
Humans are born with a sweet tooth. We have an innate preference for foods that taste sweet.1 Scientists surmise that our "sweet tooth" is actually an evolutionary advantage as non-toxic foods tended to be sweet and fruit was easily obtained from plants and trees.1 For centuries, worldwide, this 'sweet' desire drove people to seek out sweet foods and ingredients in nature.
Since the early days of agriculture, sweeter varieties of fruit and vegetables (such as sweet corn) were preferentially cultivated. The discovery of honey in ancient times led to one of the first cultivations of a sweet ingredient. Beekeeping was developed to gain better access to this natural sweet source. Another natural sweet is maple syrup which is derived from the sap of sugar maple trees and was discovered by Native Americans living in North America.2
Other plants were also discovered to have components with a sweet taste. The most commercially important ones are sugar cane and sugar beets, which are easy to grow in appropriate climates, but need further processing to obtain the sugar. The processing includes crushing the plant followed by extracting and purifying the sugar.3 Sweeteners have also been derived from other plants, such as agave, rice and corn.
Too much of a good thing
As the opportunities to feed our sweet tooth grew, so did consumers' use, and perhaps overuse, of sweet foods and beverages. Before the days of convenience foods, when home cooking was the norm rather than the exception, the sugar bowl was a permanent fixture on kitchen counters and tables. With the advent of convenience foods that have sweetness added during manufacturing, the sugar bowl became a thing of the past. Sweet foods are more accessible than ever before.
But while the desire for sweet has not changed, modern lifestyles have changed. This has led to fewer opportunities to be physically active and more occasions to eat and drink. In combination with genetic, metabolic and hereditary conditions, excess consumption of added sugars has been linked to an energy imbalance, leading to overweight and obesity around the world.4 According to the World Health Organization the global epidemic of overweight and obesity – "globesity" – is rapidly becoming a major public health problem in many parts of the world, as is the epidemic of obesity-driven type 2 diabetes – termed "diabesity."5
As energy expenditure diminished, daily energy requirement has similarly decreased, resulting in today's need to concentrate nutrients in fewer calories. Added sugars provide energy but few, if any, nutrients and therefore may dilute the relationship of nutrients to calories (energy density). In fact, one of the main reasons for dietary recommendations to decrease sugar is because of its contribution to excess calories and focus on nutrient-dense calories.6 Additional reasons to limit sugar intake include the fact that excess consumption may displace important nutrients as well as its promotion of tooth decay.4, 7
Yet the desire for sweet has not declined. And despite the emergence of sugar substitutes, consumers still express preference for a natural sweet source with few or no calories.8
The stevia solution
Stevia is a plant-based, no-calorie, natural sweetener that has been used for hundreds of years as a regular part of the diet in many parts of the world. Stevia's history began in Paraguay, Uruguay, Argentina and some parts of Brazil where the indigenous people used leaves of the plant known as Kaá Heé ("sweet herb") to sweeten beverages such as mate or tereré or chewed them for their sweet taste.8,9 Traditionally, the leaves were dried and used to sweeten tea and medicines or chewed as a sweet treat. In the 1970s, Japan was the first country to commercially adopt the use of stevia.10 Japan continues to be the largest and most diverse user of stevia in the world; although its use in South Korea is increasing, particularly to sweeten an alcoholic beverage called soju.10
The genus Stevia is a subtropical plant that can be grown much like other agricultural crops.11 It requires warm temperatures with minimal frost, adequate rainfall and lots of sunshine.10 It is a woody shrub that can reach 80 centimeters (about 32 inches) in height when fully grown.11 The Stevia genus includes more than 100 species and different species of Stevia contain sweet compounds. But only two species contain steviol glycosides – the variety with the sweetest compounds is Stevia rebaudiana Bertoni.11,12 The sweet compounds are found mostly in the leaves of the plants. Stevia plants are cultivated today throughout the world, but most significantly in China, Paraguay, Colombia, India, Kenya, and Brazil, with the expansion of development beginning in the United States and a number of other countries. Conventional breeding techniques are being pursued to produce varieties of Stevia rebaudiana that have increased sweet compounds.10
The leaves of Stevia rebaudiana Bertoni contain several glycoside compounds which are sweet. All steviol glycosides share a common molecular core, steviol.10 The only difference among various steviol glycosides is the number and arrangement of sugar molecules attached to the steviol core (Table 1: Steviol Glycosides). Extracts of the leaves contain a mixture of these, which share a common base, steviol. Based on the dry weight, the four major glycosides are dulcoside A, rebaudioside C, rebaudioside A and stevioside (typically at 0.3, 0.6, 3.8 and 9.1%, respectively).12 Other, less prominent glycosides include rebaudioside B, D, E, and F, steviolbioside and rubusoside.
Extracting and purifying the different steviol glycosides produces an ingredient with a taste similar to sugar. Sugar is extracted from plants. So too, is stevia. The steviol glycosides are extracted from the leaves using water. The water extracts are typically further purified through techniques such as ion-exchange chromatography and/or membrane filtration. Purified stevia is 100% natural, with no calories, up to 400 times sweeter than sucrose, heat stable, non-fermentable and non-cariogenic (i.e. does not promote tooth decay).11
Steviol glycosides can be hydrolyzed to steviol in the presence of high acid and certain microorganisms.13 As an example, rebaudioside A is first metabolized by microbes in the colon to stevioside and then through other steps to steviol, which is then converted to steviol glucuronide and excreted from the body.14,15 Any released glucose is utilized by the bacteria in the colon and is not absorbed. The European Food Safety Authority (EFSA) considers that the results of toxicology studies on either stevioside or rebaudioside A are applicable for the safety assessment of steviol glycosides as both rebaudioside A and stevioside are metabolized and excreted by similar pathways, with steviol being the common metabolite for both.16
General Safety Evaluation
The safety of steviol glycosides has been the subject of numerous scientific publications spanning many years.17 After reviewing all the toxicity data, including in vitro and in vivo animal studies, and human tolerance studies, the EFSA Panel on Food Additives and Nutrient Sources concluded that steviol glycosides (comprising not less than 95% of the following steviol glycosides: stevioside, rebaudiosides A, B, C, D, E and F, steviolbioside, rubusoside and dulcoside A), are not carcinogenic, genotoxic or associated with any reproductive/ developmental toxicity.16
Stevia has been used in Japan for more than 40 years and numerous clinical trials have been performed there.11 No allergic reactions have been found.11 To obtain Generally Recognized as Safe (GRAS) regulatory affirmation from the Food and Drug Administration (FDA) in the United States, extensive toxicology studies on steviol glycosides, specifically rebaudioside A, were submitted, including its effect on hemodynamics, glucose homeostasis, genotoxicity, mutagenicity, carcinogenicity and reproductive toxicity (Link to FDA GRAS Notice Inventory).17,18
In human clinical trials, no safety concerns were noted within accepted consumption levels.15, 19-21 These clinical studies have shown that consumption of purified rebaudioside A has no effect on either blood pressure or glucose homeostasis. Stevia consumption is well tolerated by people with hypertension, Type 1 and Type 2 diabetes. 19,20,22,23 Stevia is appropriate for use by people with phenylketonuria (PKU).24 When given stevia or sucrose, both lean and overweight adults reported similar levels of hunger and satiety, and stevia participants did not increase their calorie intake at the next meal.25 After consuming the meal, those given stevia did see significantly reduced postprandial glucose and insulin levels compared to sucrose consumers.
The Joint World Health Organization/Food and Agriculture Organization Expert Committee on Food Additives (JECFA) reviewed the safety of steviol glycosides in 2000, 2005, 2006, 2007, 2009 and 2010 and established an Acceptable Daily Intake (ADI) for steviol glycosides (expressed as steviol equivalents) of 4 milligrams per kilogram of body weight per day.17 After considering all the data on stability, degradation products, metabolism and toxicology, the EFSA Panel in 2010 concurred with 4 mg/kg of body weight per day based on the application of a 100-fold uncertainty factor. 16
Stevia use in foods and beverages
Sweet compounds from the stevia plant can be extracted from the leaf and used in products to achieve a taste very similar to sucrose. Historically, stevia in its raw form has had a subtle licorice flavor and at higher usage levels, these flavor notes are more noticeable. However, extraction and purification of the best tasting glycosides minimizes such flavor notes. Depending on the formulation, some complementary flavors also can be used to round out the flavor and sweetness profile. In particular, combinations with sugar have been found to reduce total calories and achieve a similar taste profile to sucrose.
Stevia glycosides have additional qualities that are beneficial to manufacturers. They tend to maintain their sweetness during normal conditions of food processing and storage and are stable across a broad spectrum of manufacturing conditions.26 Today, stevia can be found in hundreds of food and beverage products from around the world including teas, soft drinks, juices, yogurt, soymilk, baked goods, cereal, salad dressings, confections and as a tabletop sweetener.8
Regulatory status of stevia
Stevia is approved for food and beverage use in a number of countries across the globe including Japan, Korea, Australia, Russia, Malaysia, Indonesia, Switzerland, France, Mexico, Brazil and the United States (Regulatory). The GRAS notification in 2008, GRN 252, received a "no objection letter" from the United States' FDA, which deemed rebaudioside A with purity of more than 95% as a GRAS ingredient in the United States.18 The GRAS notification GRN 287 sought GRAS status of stevia extract containing more than 95% of total steviol glycosides and received a "no objection letter" from FDA.18 In April 2010, the European Food Safety Authority issued a positive opinion on the safety of steviol glycosides from stevia which could lead to stevia approval in a number of European countries.16 The leaves of the Stevia plant have not been approved for use by the U.S. FDA; only purified extracts of the leaves can be used in foods and beverages in the United States.
Changing the conversation around sugar reduction:
Stevia is redefining what sweet should be
The unique nature of stevia represents a new type of sweet. As such, previous terminology around sweeteners does not accurately describe the role stevia could play in promoting healthful, tasty diets within energy (calorie) needs. Therefore, stevia is neither an artificial sweetener nor does it have the caloric properties of sugar. Defining it as a non-nutritive sweetener, appropriately characterizes its no-calorie properties, but groups stevia with ingredients that are not natural. Stevia is, therefore, a new kind of sweetener. We propose that the term stevia refer to no calorie, natural sweeteners from the Stevia plant.
A proposed standard terminology for stevia in consumer communications
All extracts and derivatives of the plant genus Stevia that have been approved for human use be referred to as stevia
Sweeteners called stevia must be naturally derived from the plant genus Stevia
All extracts and derivatives of the genus Stevia called stevia must taste sweet
Sweeteners called stevia add no calories to food
The Global Stevia Institute proposes that the industry and influencers use a common language with consumers when communicating about sweeteners derived from the plant genus Stevia. The sweetness found in the Stevia plant is being referred to by many different names including reb A, rebiana, stevia extract and steviol glycosides, among other scientific, generic and branded names. Scientists and manufacturers understand that these names refer to specific molecular compounds and that additional extracts from the Stevia leaf continue to gain approval. However, consumers can find the use of various scientific names confusing, misleading and unappealing. A generic term for sweet compounds of a similar origin has precedence in sugar. Those with training in chemistry know that there are molecular differences among glucose, fructose, sucrose, maltose, galactose, and lactose, but these mono- and disaccharides are commonly referred to as sugar. A similar approach in discussing sweetness from stevia will help eliminate confusion and further an understanding of its use in a healthful diet. Therefore:
The Global Stevia Institute hereby proposes that all sweet tasting extracts and derivatives from the genus Stevia, approved for human use, be generically referred to as 'stevia' when communicating with consumers.
Financial support and editorial assistance for the preparation of this document were provided through The Global Stevia Institute and PureCircle Limited.
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