The Stevia rebaudiana Bertoni shrub, commonly known as Stevia, was first mentioned by the Spanish physician and botanist Pedro Jaime Esteve (1500-1556) who found it in the northeast of the territory now called Paraguay.

The Guarani Indians of this area as in southern Brazil are using “ka’a he’ê” (“sweet leaf”), as it is called in Guarani, for hundreds of years as a sweetener in yerba mate, and various Tribes reported the use of this plant in the control of women’s fertility, applying concentrated infusions of Stevia for prolonged periods.

It is precisely this contraceptive property that has been discussed from the 70s to the present in the scientific literature. The reason is simple: Who wants to consume a sweetener that suddenly leaves you sterile?

Stevia leaf contains a complex mixture of glycosides (compounds in which one or more sugar molecules are attached to a non-carbohydrate moiety). These compounds give the leaves an intensely sweet taste, 30 to 45 times sweeter than sucrose, the sweet substance in refined sugar. To date, ten different chemical compounds (chemically, all steviol glycosides) responsible for the sweet taste of the plant have been isolated: stevioside, rebaudioside A, B, C, D, E and F, dulcoside A, rubusoside and steviolbioside. The highest concentration of the sweetening effect comes from stevioside and rebaudioside A, responsible for Stevia extract being 250-300 times sweeter than sucrose with almost zero calories (around 0.2 calories per gram).

Both sweet glycosides of steviol are chemically diterpenic glycosides, substances made up of two molecules of different types of sugar and a molecule called steviol. Steviol serves as the “backbone” of the chemical structure and is structurally similar to the plant hormones gibberellin and kauren. Several studies show that these glycosides are, at least partially, metabolized in the body releasing sugar and steviol molecules.

Is it safe to use Stevia instead of sugar?

It is precisely this steviol compound that for many years attracted the attention of toxicologists. In studies with bacteria and in cell cultures, this compound was shown to be genotoxic (that is, it is capable of changing genetic information). However, more recent studies with mice, rats and hamsters indicated that relatively high concentrations of steviol are required to cause considerable damage to DNA, the molecule of life that contains all of our genetic information.

When looking at toxicology databases, there are hundreds of publications that discuss the possible adverse health effects of stevia extract, but the results are not very consistent. In particular, the effects on fertility and potential carcinogenicity of steviosides were controversial in the scientific world. It was a study published in 1968 by Professor Joseph Kuc Purdue University in Indiana, USA, that started a controversial discussion about stevia and fertility. Teacher. Kuc detected a clear contraceptive effect in female rats given high doses of stevia. The fertility rates of the rats fell by as much as 79 percent.

Although the result of this study was not confirmed by other scientific groups, a study published in 1999 by Prof. Melis from the University of Sao Paulo also reported a reduction in the amount of sperm in male rats after applying high doses of glycosides of Stevia. Carcinogenicity or mutagenicity concerns were not confirmed in the vast majority of toxicological studies.

Although the adverse health effects of Stevia have never been directly tested in humans, authorities in the United States, Canada, and the European Union considered Stevia extracts to be unsafe in application as a tabletop sweetener due to lack of long-term toxicological effects. studies. Instead, the authorities of other countries such as Japan, China, Australia, New Zealand, Brazil and Mexico have a different point of view and accepted the use of Stevia extracts as a natural sweetener. In several other countries, particularly in Latin America and Asia, Stevia and its extracts are available with unverified regulatory status. In Japan, Stevia extracts have been commercially available since 1971 as a tabletop sweetener and there are no reports of health problems associated with this product.

In the United States, the Food and Drug Administration (FDA) approved the use of Stevia extracts as a “nutritional supplement” but not as a tabletop sweetener. Only glycoside rebaudioside A in its pure form is considered a “Generally Recognized Safe Substance” (GRAS), since December 2008. In contrast, stevioside, the other main compound in Stevia extracts, was not recognized as GRAS by the FDA.

In both Canada and the European Union (EU), the use of Stevia as a tabletop sweetener was banned because there was insufficient evidence to show its safety. But now this situation is likely to change. In April 2010, the European Food Safety Authority (EFSA) carried out a new assessment of the available toxicological information. As a result of this review, stevioside and stevia extracts in general are now considered safe when used as tabletop sweeteners, at least under certain conditions.

The EFSA established an Acceptable Daily Intake (ADI) of 4 mg per kilogram of body weight for steviosides, the same ADI recommended by the World Health Organization according to a WHO document published in 2008. In common words, an adult weighing 70 kg you can consume 280 mg of Stevia extract every day without running any health risk. Since Stevia extract is approximately 250 times sweeter than table sugar, an adult can replace 70 grams of refined sugar with Stevia extract daily. This equates to about 4-5 tablespoons or about 20 teaspoons of sugar. As children have a lower body weight, the dose should be reduced in proportion to their weight.

It is interesting to compare these data with aspartame, the most widely used synthetic tabletop sweetener in the world. Food safety authorities around the world have established Acceptable Daily Intake (ADI) values ​​for aspartame at 40 mg / kg body weight based on a recommendation of the 1980 Joint FAO / WHO Expert Committee on Food Additives (Organization of the United Nations for Food and Agriculture). This means that, strictly based on available toxicological information, Stevia is considered approximately 10 times more “toxic” than Aspartame.

Although the sweetener Stevia is a product isolated from a plant and not a product of a classical chemical process, being critical is never out of place, because “natural” does not necessarily mean risk-free. As a conclusion, Stevia extracts can be considered safe if not consumed in large quantities. The common idea that this “natural” product is safer than other commercially available tabletop sweeteners is not supported by the available toxicological information.