The Stevia Plant
Steviafarma S.A.

CONTRACEPTIVE EFFECT OF THE STEVIA AND OF ITS SWEETENING PRINCIPLES

Prof. Mauro Alvarez Ph.D.
State University of Maringa
Dept. of Pharmacy and Pharmacology
Maringa, Brazil
October 1994

!- General Evaluation
Among certain indigenous tribes of Paraguay and the State of Mato Grosso in Brazil, the women used the Stevia rebaudiana ( Kaa-he-e) as oral contraceptive , drinking daily a syrup from the leaves of the plant. To confirm this fact methodically, Planas and Kuk (1968) performed an experiment where virgin female rats and females of proven fertility , in groups of 14 rats, were interned with normal rations except that the water was replaced daily with 10 ml of aqueous extract from the Stevia leaves at 5% until the animals ingested all the liquid. Later the water was resupplied ad libitum. The control group received only food and water. All females were copulated with male rats also of proven fertility. Even after 50 to 60 days after the administration of the aqueous extract had been stopped, the females continued showing a reduction of 50 to 57% in their fertility. 
Evidently, the effects shown by Planas and Kuk are very pronounced , except that , since then they have never been duplicated, which raises questions of how it was carried out. 

These results stimulated, therefore, great interest among researchers for the verification if the contraceptive component was one of the sweetening molecules found in the Stevia. With this objective, Akashi and Yokoma ( 1975), used rats to verify the contraceptive effect of the crude extract, of the semi-purified extract and of the pure stevioside. The animals were divided in 4 groups , one group the control group, and 3 groups, to which they administered the 3 types of products from the Stevia described above , respectively. Each group was composed of 5 males and 5 females. The animals were fed ad libitum with foods mixed with the samples of the products in a manner to maintain the daily dose of stevioside at 100 mg/kg. The period of administration was of 21 days for both sexes. After this period the animals were place to copulate. The doses applied were from 14 to 15 times greater than the maximum dose that a person could take. Akashi and Yokoyama did not report any difference in the average of conception and copulation. Also, they did not find any variation in the weight and daily ingestion. The pregnant females were sacrificed and the fetus examined and no abnormality was found. 

Similar experiments also were performed by the Stevia Safety Committee of Japan ( Mori et al, 1981), where groups of 20 male rats and 20 female rats to which the crude extract of the Stevia and the purified stevioside were administered forcibly, per os, in dosages of up to 525 mg/kg/day equivalent of stevioside , during 60 days for the males and 14 days before the copulation and 7 days after , for the female. The doses administered represented a volume 75 times greater than what could be ingested by an adult individual. In certain groups, the dose of stevioside administered was approximately 500 times greater. The results were also similar to the reported before. There were no significant differences in the averages of conception, in the variation in the body weight, in the ingestion and in the weight of the organs. Hystological exams of the sexual organs of the animals , even of those which in the average did not induce conception, did not reveal changes which could be attributed to the test. The fetuses also did not show abnormalities. 

Another study on the contraceptive issue also was performed by Silva et al ( 1986), at the University of Santa Maria in Brazil. These researchers used 5 groups with 20 female rats in each. The G1 group was the control group and received water and food at will; the G2 group received the aqueous extract of the Stevia rebaudiana at 4%, group G3 received extract at 10%, group G4 received stevioside at 0.04% and group G5 received aqueous extract at 10% by cold infusion. All the animals received food and water at will. The animals received the treatment before, during the mating and following the mating until the final pregnancy. In group G! there was a pregnancy rate of 90%, with average of 8 births, in group G2 the pregnancy was of 80%, with average of 9 births, in group G3 85%, with average of 8 births, in G4 80% with 7 births and in group G5 85% with average of 8 births. The researchers concluded therefore that there was no reduction in significant pregnancy among the various groups and thus the use of Stevia rebaudiana or the stevioside, to prevent pregnancy is merely folkloric. 

Nunes and Pereira (1988) studied the effect of extracts of the Stevia rebaudiana over the reproductive activity of adult female mice. The Stevia was used by these researchers in the form of tea ( infusion), in the concentrations of 1 and 5%, administered intragastrically. The fertility of the adult females was reduced by 14.3% after the administration of infusions at 1% before and during the copulation. The infusion administered during the copulation reduced the number of uterine implants and/or increased the number of reabsorbtions. According to the authors, however, when administered before the copulation, the number of implants did not decline significantly, not even the number of baby mice born per breed. The fertility in this last case had a reduction of 20 to 40% after the administration of the infusion at 1 and 5% respectively during a period of 12 days before the copulation. The positive results of this experiment causes concern for the lack of data regarding the quantities administered and how the infusions were prepared ( simple infusions, decoction, hot concentration, etc. ), considering that mice, because its low bodily weight, can not receive administration by gavage of high volumes without suffering strong stress , in addition to the fact that, any tea in high dosage, depending on its preparation, can contain cytotoxic substances such as the phytosterols and others which can cause damage to the health of the animal. Another aspect to consider regarding this experiment refers to the very small number of animals that were used under observation. This is an experiment very susceptible to external unmeasurable influences such as behavior of the animals, lineage, stress, influence of the sweet taste, etc., which can interfere considerably on the results of the experiment. There were no controls over these parameters. Furthermore, some of the data obtained were quite contradictory, as for example, in one group treated with saline there were no reabsorbtion of the implants, whereas in the group treated with tea at 1% there were an reabsorbtion of 30 implants in a total of 44 and that meanwhile the difference in the fertility was of just 14% approximately. Another observation which one can make refers to the similarity of this experiment with the experiment performed by Planas and Kuk ( 1968). Practically the same methods were used, however, with the results far from the ones obtained by the Uruguayan researchers. It appears that the experiment referred above should be repeated in more adequate conditions to obtain a more precise evaluation on the contraceptive parameters suggested. 

2 - Test of dominant lethality
This type of test, using just crude extract of Stevia, was performed by the Food and Drug Safety Center of Japan in 1976. Samples of the crude extract of the Stevia were administered orally to male rats of 9 weeks old. Each male rat was placed in company of 2 females during periods of 6 - 9 days, 19 - 22 days and 34 - 37 days. After the period of copulation the females were sacrificed for the counting of numbers of yellow bodies, implants and live fetuses . In addition to the control group, the rats were divided in 3 groups which received doses of 10 g/kg and 20 g/kg of body weight. The results showed that the group that took 15 g/kg in the period of 6 - 9 days, showed a significant difference in the number of implantations, without any other abnormality. There were no correlation’s with the doses. The results were, therefore, evaluated as negative. 

3 - Hormonal activity
Uehara et al (1982) examined the affinity of the stevioside by androgenic receptors directly in homogenization of cells of the submandibular salivating glands of male mice and normal puberty females and of prostate of normal puberty mice. Quotas of the overskimming of centrifugation of the homogenates were incubated with (H3) 5 -a- di-hidrotestoreron in the absence and in the presence of concentration 100 times greater than 5a-DHT radio inert or stevioside, for the evaluation of the connecting activity. Evaluating further the effects of aqueous extract of Stevia in the endocrinous sphere, the same authors ( Silva Filho et al, 1986), demonstrated that the chronic administration (60 days) of these extracts to rats, since the pre-puberty age, did not produce significant alteration on the following parameters: glycemia, sericeous levels of tri-idotironin, tyrosine and T3 reversa; content of zinc in the prostate, testicles, submandibular salivating glands and pancreas; hydric content in the testicles and prostate; curve of gain of bodily weight; terminal weights of testicles, prostate, submandibular and adrenal glands, union of [3H]- methyltrienolon ( a synthetic androgen) to the cytostatic fraction of the prostate. It was observed only a reduction of about 60% in the weight of the seminal vesicle, both in absolute terms and in relation to the corporal weight. The authors observed also that the stevioside showed a small activity of displacing the DHT previously connected to its receptors in the prostate. No activity related to the stevioside was observed in relation to the receptors of the salivating glands of male and female rats. They concluded that there were no possibilities , relying just on the data obtained, to confirm that the stevioside has any anti-androgenic activity. 

Still with hormonal connotation, Dorfman and Nes ( 1960), studied the activity anti-androgenic of steviol and di-idrosteviol, di-terpenic acids not steroidals derived from the sweet glycosides of the Stevia. The reader is reminded that these two substances are not found free in the Stevia rebaudiana. 

The anti-androgenic action was measured using the method of monitoring the growth of the crest of two days old male chicks, stimulated by testosterone. The drugs were injected daily during 7 days. At the end of the treatment the crests of the chicks were removed and weighed. Both the steviol and the di-idrosteviol showed significant results when the doses applied to each chick reached 3.0 mg. Studying these results , even assuming that all stevioside were hydrolyzed to steviol in the gastrointestinal tract, after the ingestion ( Wingar et al, 1980), this level would be reached only if the amount ingested, all at once, equaled 1.26 g/kg of body weight in an adult individual, representing 180 times its maximum daily necessity in terms of sweetening needs. 

Dorfman and Nes ( 1960) tested also the di-idrosteviol on the activity anti-androgenic in castrated rats. The results showed that this molecule does not produce any effect on the seminal vesicle, prostate and supporting anal muscles and also it was not effective to inhibit the action of the testosterone in rats, even in doses of 5 to 20 mg per animal of average weight of 90 g. 

5 - Conclusion
In light of the results of the scientific studies related above, the conclusion is that the effects of hormonal connotation and the contraceptive effects are of remote possibility, with the possibility of some effect only with extremely high concentrations, much beyond of the maximum necessities for daily ingestion. And if there is any effect, very probably they are not due to the sweetening principles in the plant such as stevioside and ribaudioside. 

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