Stevia has been studied for its contraceptive properties, and South American women are rumored to use the plant extract for this property, according to Certified Herbalist Hethir Rodriguez. Other, more general side effects of using stevia include nausea or bloating, muscle pain, numbness and dizziness, reports FitDay.
The major concern of using stevia as a sweetener is its possible negative effect on female fertility. A study by Purdue University in the 1960s found that female rats given high doses of stevia produce fewer offspring than those who were not given the herbal extract. Researchers warn that these results can be misleading, however, as the dosages given were much higher than a human ingests for sweetening purposes. This study was repeated a second time in 1988 by Brazilian researchers, who found stevia had similar effects in mice, adds Hethir Rodriguez.
More recent studies have not found any correlation between stevia and reduced fertility, reports Hethir Rodriguez. In 1999, Thai researchers found no lowered rates of fertility in both male and female hamsters administered high doses of stevia. Another study published in the Journal of Endocrinology and Reproduction in 2008 revoked the findings of previous studies using mice, as have several other studies conducted by the U.S. Department of Agriculture and Herb Research Foundation.