Steviol glycoside sweeteners are extracted and purified from the Stevia rebaudiana Bertoni plant, a member of the Asteraceae (Compositae) family that is native to South America, where it has been used for its sweet properties for hundreds of years. With continued increasing rates of obesity, diabetes, and other related comorbidities, in conjunction with global public policies calling for reductions in sugar intake as a means to help curb these issues, low- and no-calorie sweeteners (LNCSs, also known as high-potency sweeteners) such as stevia are gaining interest among consumers and food manufacturers. This appeal is related to stevia being plant-based, zero calorie and with a sweet taste that is 50–350 times sweeter than sugar, making it an excellent choice for use in sugar- and calorie-reduced food and beverage products. Despite the fact that the safety of stevia has been affirmed by several food regulatory and safety authorities around the world, insufficient education about stevia’s safety and benefits, including continuing concern with regard to the safety of LNCSs in general, deters health professionals and consumers from recommending or using stevia. Therefore, the aim of this review and the stevia symposium that preceded this review at the ASN’s annual conference in 2017 was to examine, in a comprehensive manner, the state of the science for stevia, its safety and potential health benefits, and future research and application. Topics covered included metabolism, safety and acceptable intake, dietary exposure, impact on blood glucose and insulin concentrations, energy intake and weight management, blood pressure, dental caries, naturality and processing, taste and sensory properties, regulatory status, consumer insights, and market trends. Data for stevia are limited in the case of energy intake and weight management as well as for the gut microbiome; therefore, the broader literature on LNCSs was reviewed at the symposium and therefore is also included in this review.
Introduction
Stevia rebaudiana Bertoni is a small perennial shrub of the Asteraceae (Compositae) family that is native to Paraguay, Brazil, and Argentina. The leaves of this plant have been used by indigenous people for centuries in medicines and to sweeten drinks such as maté, a green herbal tea (1–3). The plant was first brought to the attention of the rest of the world by the botanist Moises Santiago Bertoni in 1887, who learned of its properties from the Paraguayan Indians (1, 3). The chemical characterization of the natural constituents of the plant known as steviol glycosides, which are responsible for its distinct sweet taste, was not identified until 1931 when 2 French chemists, Bridel and Lavielle, isolated stevioside, a primary steviol glycoside from stevia leaves (1). Japan was the first country to commercialize and use crude, unpurified extracts of S. rebaudiana in the 1970s on a large scale (2). Its use eventually spread to several countries in Asia and Latin America (4). In the 1990s, stevia extract was available in the United States as a dietary supplement in health food stores; however, early formulations were known to have a licorice flavor with a sweet or bitter aftertaste, which limited their widespread commercial development (2, 5). The presence of essential oils, tannins, and flavonoids in the crude extracts was partly responsible for some of the off tastes; hence, efforts were made to purify extracts and chemically characterize steviol glycosides (5).
After the isolation of stevioside, several other steviol glycosides, such as rebaudiosides (Reb) A, B, C, D, and E and dulcoside A, were identified and isolated from stevia leaves (6). Generally, the most abundant steviol glycosides in stevia leaves are stevioside (4–13% wt:wt), Reb A (2–4%), and Reb C (1–2% wt:wt) (7, 8). To date, >40 steviol glycosides have been identified (e.g., Reb F, G, H, I, J, K, L, M, N, O, and Q; stevioside A, D, and E, etc.) (9–12). Most of the steviol glycosides derived from the plant are 4-ring diterpenes that have a backbone of 13-hydroxy-ent-kaur-16-en-19-oic acid, known as steviol (1, 12). The various glycosides differ only in the number and type of monosaccharides attached at the R1 (OH) and R2 (H) position of the aglycone steviol. Glucose, fructose, rhamnose, xylose, and deoxyglucose are examples of sugars that are attached to the steviol backbone (12). The 2 primary steviol glycosides, stevioside and Reb A, differ only by 1 glucose moiety at R1; stevioside has 2 glucose molecules, whereas Reb A has 3.
The stevia plant is now commercially cultivated in Argentina, Brazil, Columbia, Paraguay, China, Japan, Malaysia, South Korea, Vietnam, Israel, Australia, Kenya, and the United States. High-purity steviol glycosides are approved as sweeteners by all major regulatory authorities across the globe, and >150 countries have approved or adopted its use in foods and beverages. Reb A was the first commercial steviol glycoside launched in the marketplace (13).
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