Stevia, the herb, is used as a general health drink tisane in local native populations and their reproductive behaviour seems to be quite ordinary.
Some Western regulatory bodies seemed to be relatively unconvinced whether an exotic herb would be even less toxic than the chemical industry's well-trusted aspartame.
The actual use of stevia as birth control does not look too far fetched or too strange in the spectrum of different methods tried so far. Its effectiveness for that purpose seems very doubtful. Although there are some old reports that do note the use of stevia as a contraceptive agent by indeginous people:
Plants used as means of abortion, contraception, sterilization and ecundation by Paraguayan indigenous people(1977): Plan~ and Kue (1968) mention the contraceptive properties of Stevia rebaudiana Bert. ("ka'a he'e') used by the indigenous tribes of the Paraguayan Mato Grosso. (Cf Contraceptive Properties of Stevia rebaudiana)
In recent years these isolated findings are apparently either forgotten by researchers, not replicated or just quoted without reference.
But after trying really hard to paint a bad picture of this plant these reproductive effects seem really quite the opposite in reasonable doses:
At doses of 0.75 g/kg body weight/day, steviol is toxic to pregnant hamsters and their fetuses when given on days six through ten of gestation (Wasuntarawat et al. 1998). Steviol produces decreased maternal weight gain and high maternal mortality. The number of live births per litter is decreased and the mean fetal weight is lower. The no effect dose is 0.25 g/kg body weight/day. If 100% conversion of stevioside to steviol is assumed, this intake is equivalent to 625 mg/kg/day of stevioside. This is about 80 times the acceptable daily intake calculated by Xili et al. (1992). (From A. Douglas Kinghorn: "Stevia
The Genus Stevia", Taylor & Francis: London, New York, 2002, 172.)
It is indeed likely that for several decades the identity, ethnobotany, taxonomy and natural habitat for the species were all a bit unclear:
Pio Corrêa (1926) in his Diccionario das Plantas Uteis do Brasil, without documentation, mentioned that a sweet plant referred to by him as S. collina Gardn., under the name of ‘Caá-Ehé’, and a variety of this species, var. rebaudiana, are found in the Brazilian Mato Grosso and Minas Gerais. This report is erroneous. First, S. collina, a definitely Brazilian species, and S. rebaudiana are two different species; second, organoleptic tests by the author of leaves of S. collina did not present any sweet taste (Soejarto et al. 1982), while TLC and HPLC, followed by GC/MS analysis (Kinghorn et al. 1984) did not show the presence of steviol glycosides. In a 1967 paper, von Schmeling described a search of S. rebaudiana in Mato Grosso, the Brazilian territory bordering the northeastern Paraguay’s Cordillera of Amambay, where the species occurs. She reported that the search resulted in the collection of the plant in Ponta-Pora, the Brazilian town adjacent to PJC, the capital city of the Department of Amambay of Paraguay. She stated: Encontramo-la, defato, em Ponta-Pora, divisado Brasilcomo Paraguai (von Schmeling 1967:68) (‘Indeed, we found the plant in Ponta-Pora, in the border between Brazil and Paraguay’). The search crew returned to São Paulo with a ‘beautiful plant in a pot, a proof that the caá-heê plant is also found in Brazil.’ According to her account, this potted plant eventually gave off beautiful flowers in São Paulo and, based on the examination performed on 23 November 1944, at the Institute of Botany of the State of São Paulo, the identity of the potted plant as ‘the same Stevia plant’ (‘…se tratava mesmo da Stevia’) (sic!) was confirmed. Unfortunately, no mention at all is made anywhere in the paper that this discovery of the Stevia plant in Ponta-Pora was documented, namely, whether herbarium specimen(s) were prepared and whether it (they) have been deposited in a herbarium institution, giving the name of the institution, for future reference, as the botanical evidence of the finding. During the author’s 1981 trip, he crossed the border to Ponta-Pora, and made inquiries on the possible existence of natural populations of Caá-hê-hê or Caá-enhem in Ponta-Pora. He also went to an excursion to the fields some distance away from this town. To his disappointment, no sign of the presence of S. rebaudiana was found. To complicate matters, Sumida in his 1973 paper states that S. rebaudiana, with local names of ‘Caá-hê-hê or Caá-enhem’, has been used ‘…in some localities of Brazil from old times as a sweetening material’. Like von Schmeling, no botanical documentation to support the statement appears to exist. Interestingly, Felippe (1977), a biologist at the Instituto de Botánica in São Paulo, stated that ‘A planta [S. rebaudiana] foi introduzida no Brasil na dêcada de 60. A. instituciao responsavêl pel a introducâo foi o Instituto do Botânica de São Paulo’. (‘The plant was introduced to Brazil in the decade of the 1960s. The institution responsible for its introduction was the Institute of Botany of São Paulo.’) This statement contradicts the finding described by von Schmeling and the statement made by Sumida. (p 31–32.)
The identity of the plant material allegedly used as a contraceptive is therefore in doubt and the non-replication easily explainable. Recent studies on properly identified plants, extracts and constituents do not find any adverse effects, except for possible allergies or really extreme doses. To the contrary, many findings seem to indicate that consuming stevia might be more beneficial beyond giving a sweet taste.
Safety Evaluation of Aqueous Extracts from Aegle Marmelos and Stevia Rebaudiana on Reproduction of Female Rats: (2006)
Much of the controversy surrounding the existing literature on stevia results from inadequate research aimed at reproduction of both laboratory animals and human beings. The results of the present study clearly indicate the non-toxic effect of S. rebaudiana on the reproduction of female rats.
Dominant lethal testing also revealed that the aqueous extracts of these 2 plants had no toxic effects on male rats’ reproduction or progeny outcome (Aritajat et al, 2000). It is concluded that the aqueous extract of A. marmelos and S. rebaudiana at all doses used in this study had no adverse effects on female rat reproduction, and had no teratogenic effects.
Stevia rebaudiana Bertani does not produce female reproductive toxic effect: Study in Swiss albino mouse: (2008)
This study reports that the oral intake of water-based sweet stevia extract and stevioside, at doses 500mg/kg body weight and 800mg/kg body weight, respectively, does not cause any significant female reproductive toxic effect in Swiss albino mouse.
Overview: The history, technical function and safety of rebaudioside A, a naturally occurring steviol glycoside, for use in food and beverages:(2008)
Rebaudioside A is a sweet tasting steviol glycoside extracted and purified from Stevia rebaudiana (Bertoni). Steviol glycosides can currently be used as a food ingredient in only a handful of countries. Questions on specifications, safety and special population effects have prevented steviol glycosides from obtaining a legal status permitting their use as a sweetener in most countries. A set of papers reporting results of research studies and reviews has been compiled in this Supplement to definitively answer unresolved questions. Specifically, recently completed studies on the general and reproductive toxicity of rebaudioside A corroborate studies carried out with purified steviol glycosides demonstrating safety at high dietary intake levels. Comparative metabolism studies provide further affirmation of the common metabolic pathway for all steviol glycosides and the common metabolism between rats and humans. Finally, clinical studies provide further evidence that purified rebaudioside A has no effect on either blood pressure or glucose homeostasis. This paper summarizes the information used to conclude that high purity rebaudioside A (rebiana) produced to food-grade specifications and according to Good Manufacturing Practices is safe for human consumption under its intended conditions of use as a general purpose sweetener.
Stevia rebaudiana Bertoni, source of a high-potency natural sweetener:
A comprehensive review on the biochemical, nutritional and functional aspects: (2012)
A number of studies have demonstrated that oral in- take of stevioside has no effect on fertility, neither in mice (Akashi & Yokoyama, 1975), nor in rats (Mori, Sakanoue, Takcuchi, Shimpo, & Tanabe, 1981; Xili et al., 1992), nor in hamsters (Yodyingyuad & Bunyawong, 1991). Adverse effects of stevia have not really been observed. Its commercialisation, in France for example, as a food or a food ingredient has been prohibited based mainly on economical arguments and not on proven adverse health effects (Serio, 2010). However, it is thought that stevia could provoke allergic reactions in people sensitive to plants of the Asteraceae family and it is also recommended that pregnant women should avoid consuming stevia (Serio, 2010).
They are non-fermentative low-calorie, non-toxic sweeteners, flavour enhancing and have been tested objectively, based on direct observations on human and animals, showing them to be non-mutagenic, non-teratogenic and non-carcinogenic. Stevia has been consumed by human beings for centuries without any negative effects. This showed the advantages of stevia over other artificial sweeteners as an ingredient for the food industry, thereby making Stevia a more suitable substitute for saccharose in different drinks, beverages and bakery products. Apart from the sweet contents, S. rebaudiana with its secondary plant constituents also offers therapeutic benefits, having anti-hyperglycaemic, anti-hypertensive, anti-inflammatory, antitumour, anti-diarrhoeal, diuretic, and immunomodulatory effects.
A similar assessment concludes:
If stevia were an effective and safe contraceptive, wouldn’t we all be using it?
As stevia has been confirmed to be non-toxic by numerous toxicological studies, it is likely that if the contraceptive effect of stevia were real, researchers would have long ago discovered that fact and isolated the compounds responsible. That no studies have been able to reliably and repeatably confirm this, is a strong indication that the contraceptive properties of stevia are just unfounded folklore. The first study to imply a contraceptive effect from stevia was published in 1968, in the early days of pharmaceutical contraceptives and the flower power revolution. Contraception was a hot topic then. If there was substance to these claims they would very likely have been thoroughly researched by more than one team of scientists with the objective of adding to the growing arsenal of chemical contraception options.
Stevia seems not to be detrimental for reproductive health, its use as a contraceptive in far away places seems to have at least decreased, if it was ever reported correctly. Recent findings do not corroborate this contraceptive effect.