The plant native to the subtropical and tropical South and Central American continents continues to raise issues all over the world. Whereas Stevia is admitted in Japan and, to a certain extent, tolerated in the US, it is far from being licensed by the EU. Poor knowledge concerning the toxicological effects causes bewilderment, not only on the consumer’s part …

It is widelyacknowledged that sweeteners such as honey, cane sugar or beet sugar are harmful to our teeth and cause caries. In South America as well as in many Asian countries one values the dried leafs of Stevia as natural sweetener which is both, low-caloric and friendly to our teeth.

Stevia rebaudiana is part of the sunflower family and a perennial herb which is usually cultivated for a period of one year. In natural surroundings, Stevia reaches a hight of up to 60 cm, but cultivated species may grow as high as 90 cm. The leaves are rather small and turn darker and stronger as time goes by. Stevia rebaudiana Bertoni, named after the botanist Moisés Santiago Bertoni, is native to the Amambi mountain range between Brazil and Paraguay. The indigenous people call it “honeyleaf“ and use it for cooking and as a sweetener.

A small plant with intense ingredients

The glycosides stevioside and rebausioside are responsible for the immense sweetness of Stevia. The molecule containing the glycoside is very robust and passes the human digestive tract unharmed. As the substance is not metabolized, it is practically calorie-free and has a negligible effect on blood glucose. Leaves from Stevia have between 10- to 30-times the sweetness of sugar; pure stevioside is 300 times stronger than white sugar.

Powder from stevioside has been industrially marketed in Japan for more than 30 years. In the USA, steviosides are only sold as nutritional supplement without indicating its sweetening properties. The European Commision has continually turned down all applications for legalizing Stevia, while referring to a lack in studies concerning the tolerance of Stavia. In the course of our research, however, we came across numerous studies, causing us to question the Commision’s arguments.

Stevioside: 300 times sweeter than sugar

On top of that, one should not fail to consider that this plant has already been in use for centuries in its native areas. This sweetener is industrially manufactured and marketed accordingly in China and South America.

Through experiments using LD50 we tried to investigate the toxicological effect of stevioside. The result was a value of about 8g to 15g or stevioside per kilogramme body weight. LD50 is a value indicating that 50% of the animals used in an experiment died. Through this experiment we were able to calculate a daily dose of about 0,008 g stevioside/kg body weight (1/1000). Therefore, the daily dose for a person weighing 80 kg should not exceed 0,640g. Even if the total amount of our daily sugar uptake (the average is 131g sugar/day) was substituted by stevioside (0,436 g), one would not reach the toxic limit.

In the name of science

The main argument supporting the EU’s dismissal of Stavia was based on the lack of according toxicologic research and data. Only steviosides, the substances responsible for the sweet taste, had been scrutinized in studies to that point. These studies are quoted to have indicated an inexplicable effect on blood glucose levels. The Commission also criticized that possible allergic reactions had not been subject to study. Laboratory rats reportedly started to suffer from fertility problems at extremely high doses. Another argument was that the agricultural parameters for production, such as the plants’ need for fertilizer, had not been considered– should the leaves be grown on a big scale or not?

Studies on the pharmacological effects of Stevia show varying results: It was considered to be possible that the constituents of Stevia inhibit the growth of bacteria and formation of plaque on teeth, while lowering the blood glucose level.
On the one hand it is desirable not to rely on experience and habit as far as the food safety of novel food products is concerned.

On the other hand it is, from the present perspective, hardly possible to gather the necessary proofs for complex food such as Stevia. Ironically, “natural“ products from exotic plants are doomed to fail the Novel Food regulations, while chemicals or simple synthesized substances are easily allowed to be commercialized.

One degradation product of stevioside, steviole, might turn out to be toxic. In experiments with rats and isolated cell constituents, the inhibition of the formation of glucose and the impediment of the cells’ energy production by steviole could be observed. Nevertheless, numerous short-term as well as long-term tests on humans in Japan could not provide sufficient evidence for a toxic effect of Stevia leaves.

Working in the sterilized area protects us against Streptococcus mutans

Today products containing Stevia are easily available, even though various economic lobbies disapprove of this development. Until Stevia products are admitted by the EU’s Scientific Committee on Food, they may not be used as sweeteners, food or food ingredient and have to labelled accordingly.