Stevia is a non-caloric sweetener derived from the leaves of the \(Stevia\) \(rebaudiana\) plant, a species native to South America. The sweetness comes from compounds called steviol glycosides, such as stevioside and rebaudioside A, which can be 200 to 400 times sweeter than table sugar. Modern food products use highly purified extracts of these glycosides to replace sugar in beverages and foods. For decades, a persistent question has surrounded this popular sweetener: Is Stevia actually used as a contraceptive? Claims of an anti-fertility effect exist, but their scientific validity is highly questionable, especially when considering the purified product consumed today.
The Historical Roots of the Contraceptive Claim
The origin of Stevia’s association with fertility control lies in the traditional practices of indigenous South American communities, specifically the Guaraní people of Paraguay and Brazil. These groups have used the \(Stevia\) \(rebaudiana\) plant, which they call ka’a he’ê or “sweet herb,” for centuries. Traditionally, the whole leaves or unrefined aqueous extracts were used to sweeten local teas like yerba mate and for various medicinal purposes. Some reports suggest that women would consume a strong tea made from the whole Stevia leaf to potentially reduce fertility. This practice involves consuming the unpurified plant material at concentrations far exceeding normal dietary intake, providing the initial context for the idea that Stevia possesses contraceptive properties.
Analyzing the Scientific Evidence on Reproductive Effects
The primary scientific concern about Stevia’s reproductive effects stems from two early animal studies that have since been heavily scrutinized. A 1968 study on female rats, and a subsequent one in 1988 on mice, suggested that high-dose administration of Stevia extracts could lead to a reduction in fertility, including fewer offspring and extended gestation periods. The methodology of these initial experiments was widely criticized for using whole leaf extracts and administering doses exponentially higher than any realistic human consumption. The authors of the original studies later acknowledged the methodological flaws and the difficulty in translating those findings to humans.
Subsequent research using purified steviol glycosides has largely contradicted the earlier findings, even at very high doses. Studies on hamsters administered a high dose of purified stevioside—up to 2.5 grams per kilogram of body weight per day—showed no negative impact on fertility, normal reproductive tissue structure, or growth over three generations. This level of exposure is vastly greater than the acceptable daily intake established for humans.
Studies focusing on male reproduction have also provided mixed results. One study on pre-pubertal male rats given a crude aqueous extract showed a decrease in the final weight of reproductive organs and reduced sperm concentration. In contrast, other research has suggested potential benefits for male fertility, such as increased sperm count and motility in diabetic rats treated with Stevia.
A complex mechanism involving progesterone has been explored. A Stevia compound was observed to increase progesterone production in human sperm cells while simultaneously blocking progesterone receptors. This dual action is a mechanism sometimes employed by clinical contraceptives. However, the effect was observed in a laboratory setting and does not confirm a contraceptive effect in a living human body. The overall conclusion from modern toxicological data is that anti-fertility effects are only observable under conditions of extremely high exposure to crude extracts in animal models, which do not reflect typical human use.
Stevia’s Modern Use and Consumption Safety
Stevia’s status as a contemporary food ingredient is strictly regulated and relies on the safety of its purified compounds. Regulatory bodies, including the U.S. Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA), have granted approval only to high-purity steviol glycosides, which must contain a minimum of 95% of the sweet compounds. The FDA specifically recognizes these purified extracts as Generally Recognized As Safe (GRAS) for use as a general-purpose sweetener.
The raw Stevia leaf and crude extracts, which were the basis for the historical contraceptive claims and the criticized early studies, do not have regulatory approval for use in food. Regulatory approval is based on extensive toxicological data that established a safe daily consumption limit for the purified product. The Acceptable Daily Intake (ADI) for steviol glycosides is set at 4 milligrams per kilogram of body weight per day, expressed as steviol equivalents.
To reach a dose that showed effects in some animal studies, a person would need to consume an unrealistic amount of the purified sweetener, far exceeding the established ADI. Therefore, the purified Stevia sweeteners found in stores and food products pose no known risk to reproductive health for the general population. Purified Stevia is not a substitute for clinical birth control, and consumers should rely on established medical methods for contraception.