Understanding Steviol Glycosides
What is Stevia?
Stevia is a natural sweetener derived from the leaves of the Stevia rebaudiana plant, an herbal shrub native to South America. Indigenous peoples have used the plant for its sweet taste for centuries. However, the 'stevia' you find in grocery stores isn't simply the leaf; it's a highly refined extract.
What are Steviol Glycosides?
The intense sweetness of the stevia leaf comes from compounds called steviol glycosides. The most abundant of these are Rebaudioside A (Reb A) and Stevioside. Modern manufacturing processes purify these glycosides to create the zero-calorie sweetener approved for use in foods and beverages worldwide. It is crucial to distinguish between these purified extracts and whole-leaf stevia or crude extracts, which the U.S. FDA has not approved for use as food additives.
Global Regulatory Approval and Safety Assessments
The safety of steviol glycosides has been rigorously assessed by numerous international food safety authorities based on a large body of scientific evidence.
The FDA's 'Generally Recognized As Safe' (GRAS) Status
In the United States, the Food and Drug Administration (FDA) has reviewed over 50 Generally Recognized As Safe (GRAS) notices for high-purity steviol glycosides and has issued no objection letters. GRAS status signifies that a substance is considered safe by experts for its intended use, based on scientific data and information. This approval covers high-purity extracts, typically those with at least 95% steviol glycosides.
JECFA's Assessment and ADI
The Joint FAO/WHO Expert Committee on Food Additives (JECFA), a global panel of food ingredient safety experts, conducted a comprehensive review of steviol glycoside safety. Based on extensive toxicological data, JECFA established an Acceptable Daily Intake (ADI) of 4 mg per kilogram of body weight per day, expressed as steviol equivalents.
The ADI is a conservative estimate derived using a significant safety factor. For most people, average daily consumption remains well below this level, even for high consumers.
Key findings from regulatory assessments include:
- No Genotoxicity or Carcinogenicity: Extensive studies have shown that high-purity steviol glycosides are not genotoxic or carcinogenic.
- No Reproductive Toxicity: Animal studies, including a two-generation reproductive toxicity study, have shown no adverse effects on fertility or reproductive health from high-purity steviol glycosides.
- Safe for Special Populations: Regulatory bodies have concluded that high-purity steviol glycosides are safe for children and pregnant/breastfeeding women when consumed within the ADI.
Common Concerns and Scientific Evidence
Impact on Blood Sugar and Diabetes
One of the main reasons for steviol glycosides' popularity is their zero-calorie nature, making them suitable for managing blood sugar. Numerous studies have confirmed that steviol glycosides do not raise blood glucose or insulin levels. For individuals with diabetes, swapping sugar-sweetened items for stevia-sweetened ones can help manage carbohydrate intake. However, consumers should read labels carefully, as some stevia blends may include sugar alcohols or other sweeteners that could affect blood sugar.
Potential Effects on the Gut Microbiome
Early research raised questions about whether non-nutritive sweeteners, including stevia, could disrupt the gut microbiome. However, as the field has advanced, newer evidence suggests there is no conclusive data showing a negative impact on the human gut microbiota at relevant human consumption levels. The metabolism of steviol glycosides involves gut microbes, but current research does not provide adequate evidence that they negatively impact gut health.
Comparison with Other Sweeteners
This table outlines key differences between high-purity steviol glycosides and other common sweeteners.
| Feature | High-Purity Steviol Glycosides | Sucrose (Table Sugar) | Aspartame (Equal/NutraSweet) |
|---|---|---|---|
| Source | Stevia rebaudiana plant leaves | Sugarcane or sugar beets | Synthetically produced from amino acids |
| Calories | Zero | ~16 calories per teaspoon | ~4 calories per packet |
| Sweetness | 200-400x sweeter than sugar | Standard sweetness reference | ~200x sweeter than sugar |
| Effect on Blood Sugar | Does not raise blood glucose | Raises blood glucose | Minimal to no effect |
| Safety Profile | Extensive safety studies; GRAS status from FDA | Generally recognized as safe in moderation | Extensive safety studies; FDA approved |
| Potential Concerns | Digestive issues from sugar alcohols in some blends | Linked to obesity, diabetes, and dental issues | Some subjective reports of side effects, not proven |
Side Effects and Considerations
While high-purity steviol glycosides themselves are not known to cause significant adverse effects, some products may lead to minor issues, most of which are associated with other ingredients.
- Digestive Discomfort: Some stevia products, particularly blends, contain sugar alcohols like erythritol. In sensitive individuals, these can cause bloating, gas, and digestive discomfort if consumed in large quantities.
- Aftertaste: Older stevia formulations sometimes had a bitter, licorice-like aftertaste, but this is less common with modern, highly-purified Reb A extracts.
- Drug Interactions: Steviol glycosides can lower blood pressure and blood glucose levels. Individuals taking medication for these conditions should consult a doctor before adding stevia to their diet regularly.
The Verdict: Are Steviol Glycosides Safe to Consume?
The weight of scientific evidence and the consensus among major global food safety authorities support the conclusion that high-purity steviol glycosides are safe for consumption when used within the recommended Acceptable Daily Intake. Regulators have dismissed concerns related to genotoxicity, carcinogenicity, and reproductive toxicity based on robust data for the refined extracts used in the food supply. For those seeking to reduce sugar intake, high-purity steviol glycosides offer a plant-derived, zero-calorie, and well-vetted alternative.
