Stevia, a non-nutritive sweetener derived from the leaves of the Stevia rebaudiana plant, has become a popular sugar alternative. Native to South America, particularly Paraguay and Brazil, it has been used for centuries to sweeten foods and beverages. Its sweetening power comes from steviol glycosides, compounds hundreds of times sweeter than table sugar but containing zero calories. As people seek to reduce sugar intake, questions have arisen about the safety of this sweetener, especially concerning its potential effects on human fertility.
Understanding Stevia and Regulatory Status
The stevia products available commercially are highly purified extracts, not the crude or whole leaf of the plant. These sweeteners primarily contain specific steviol glycosides, such as Rebaudioside A, which are isolated and refined for a consistent taste. The final product is chemically distinct from the raw leaf historically used.
Global regulatory bodies have concluded that these high-purity steviol glycoside extracts are safe for general consumption. The United States Food and Drug Administration (FDA) has granted them a “Generally Recognized as Safe” (GRAS) status. Similarly, the European Food Safety Authority (EFSA) and the Joint Expert Committee on Food Additives (JECFA) have approved their use. This safety designation applies only to the highly purified extracts; crude leaf and minimally processed extracts are not approved for use as sweeteners in the US or Europe.
Historical Basis for Fertility Concerns
Concerns that stevia might affect fertility originated from its traditional use and early animal studies. Historically, the Guaraní people in Paraguay used the raw Stevia rebaudiana leaf as a traditional folk remedy, including as a contraceptive. This practice suggested that components in the crude leaf might interfere with reproduction.
Initial scientific investigations in the mid-20th century appeared to support this belief, though they were often flawed. For instance, a 1968 study reported reduced fertility in female rats fed large amounts of crude stevia extract. Other early animal studies using unpurified extracts and extremely high doses indicated potential effects like reduced reproductive organ weights or decreased sperm concentration. The primary issue is that these older studies used unrefined, whole-plant extracts, which are significantly different from the purified glycosides used today.
Current Scientific Consensus on Reproductive Health
Modern research focusing on highly purified steviol glycosides provides a clear picture of reproductive safety. Regulatory bodies have reviewed extensive data and found no evidence of reproductive toxicity in mammals at normal consumption levels. Studies meeting modern scientific standards have refuted the concerns raised by early research using crude extracts.
Current animal studies using purified stevioside found no negative effects on fertility, mating performance, or offspring health across multiple generations of hamsters and rats. Researchers found no adverse changes in male or female reproductive tissues, even when animals consumed doses far exceeding typical human intake. These comprehensive studies support the conclusion that purified steviol glycosides do not impair the ability to conceive.
A recent cross-sectional study in men who regularly consumed stevia found no significant effect on serum testosterone levels or sperm motility. This study did note a decrease in sperm count compared to the control group, though values remained within the normal range. This finding warrants further investigation to determine clinical relevance. Overall, the majority of contemporary, high-quality research supports the safety of purified stevia extracts for reproductive health.
Stevia Consumption and Acceptable Daily Intake
To ensure safe consumption, global health organizations establish an Acceptable Daily Intake (ADI) for steviol glycosides. The ADI is the amount that can be consumed daily without an appreciable health risk. For steviol glycosides, the ADI is set at 4 milligrams per kilogram of body weight per day, expressed as steviol equivalents.
This limit is conservative, incorporating a 100-fold safety factor applied to the highest dose showing no adverse effects in animal studies. For perspective, a 70 kg (150-pound) person would need to consume approximately 280 milligrams of steviol equivalents daily to reach the ADI. This translates to roughly 40 packets of typical tabletop stevia sweetener every day. Consuming stevia within the established ADI is considered safe for the general population, including pregnant women.