The terms "stevia" and "steviol glycosides" are often used interchangeably, but they do not refer to the exact same thing. Stevia is the plant (Stevia rebaudiana), while steviol glycosides are the specific compounds extracted from the plant's leaves that provide the characteristic sweetness. Understanding this crucial distinction is key to navigating the world of natural, zero-calorie sweeteners and interpreting product labels correctly.
What is Stevia?
Stevia refers to the plant itself, a species native to South America that belongs to the sunflower family. The leaves of the stevia plant have been used for centuries by indigenous peoples to sweeten teas and medicines. Today, the term "stevia" on a label can sometimes be ambiguous. It might refer to unpurified or crude extracts, which are not approved by major regulatory bodies like the FDA for use in foods. The FDA, for example, only recognizes the high-purity steviol glycoside extracts as safe for consumption. For this reason, buying raw stevia leaves or unpurified extracts from a health food store is not advisable for food use, as their safety has not been fully evaluated by regulatory authorities.
What are Steviol Glycosides?
Steviol glycosides are the specific sweet-tasting molecules found in the leaves of the stevia plant. The most common types include Stevioside and Rebaudioside A (often abbreviated as Reb A). There are more than 70 different steviol glycosides, each with a unique taste profile and intensity of sweetness. The reason processed stevia sweeteners taste different from raw leaves is due to the purification process, which removes other plant compounds that can contribute a bitter, licorice-like aftertaste. Newer steviol glycosides, such as Rebaudioside M (Reb M), are often produced through advanced techniques like fermentation to achieve an even cleaner, more sugar-like taste.
The Extraction and Purification Process
To produce commercial stevia sweeteners, the steviol glycosides must be extracted and highly purified from the stevia leaves. The process is similar to how sugar is extracted from sugarcane or beets.
- Harvesting and Drying: The stevia leaves are harvested and dried.
- Extraction: The dried leaves are steeped in hot water, much like making tea.
- Filtration: The liquid extract is filtered to remove plant matter.
- Purification: The extract undergoes a purification process, often using food-grade alcohol and ion-exchange resins, to isolate the specific steviol glycosides and remove other components.
- Crystallization: The purified extract is dried into a white, crystalline powder of high-purity steviol glycosides.
The Core Difference: Plant vs. Compound
The fundamental difference can be explained through a simple analogy: Stevia is the sugar cane plant, while steviol glycosides are the refined sucrose extracted from it. The raw plant material contains a complex mixture of compounds, while the purified extract is a concentrated version of the desired sweet molecules. This distinction is critical for regulatory approval, safety, and consumer understanding. Regulators have extensive data on the safety of high-purity steviol glycoside extracts, leading to their approval as food additives in many countries. However, the same cannot be said for the unrefined leaves or crude extracts.
Navigating the Label: What to Look For
When you see a product labeled with "stevia," it's essential to check the ingredient list for clarity. The ingredient panel should list specific steviol glycosides or reference a purified extract. Common phrases include:
- "Stevia leaf extract": Indicates that the sweetener is derived from the plant and has undergone purification.
- "Steviol glycosides": A clear, technical term for the sweet compounds.
- "Rebaudioside A" or "Reb M": Identifies the specific, highly purified glycoside used.
Labels that simply list "stevia leaf" should be treated with caution, as they likely contain unpurified extracts.
Stevia vs. Steviol Glycosides Comparison
| Feature | Stevia (Plant/Crude Extract) | Steviol Glycosides (Purified Extract) |
|---|---|---|
| Origin | The Stevia rebaudiana plant | Extracted from the Stevia rebaudiana plant |
| Form | Whole leaves, crude extracts, or powdered leaves | High-purity crystalline powder or liquid |
| Composition | Contains steviol glycosides plus other plant compounds | At least 95% total steviol glycosides |
| Regulatory Status | Generally not approved for food additives (e.g., FDA) | Approved for use as a food additive in most countries |
| Sweetness | Less intense than the purified extract, often with a bitter aftertaste | 200-400 times sweeter than sugar, with a cleaner taste profile |
| Use | Traditionally used for herbal teas or dietary supplements | Used widely as a zero-calorie sweetener in food and beverage products |
How Steviol Glycosides are Metabolized
Once ingested, steviol glycosides are not absorbed in the upper gastrointestinal tract. Instead, they travel to the colon, where gut bacteria break them down into steviol. Steviol is then absorbed, processed by the liver, and excreted in the urine. Because the glycosides are not absorbed as sugar, they provide virtually zero calories and do not impact blood glucose or insulin levels, making them a suitable option for individuals with diabetes.
Conclusion
While the terms are often conflated, stevia and steviol glycosides are not the same thing. Stevia is the plant source, while steviol glycosides are the specific, purified sweetening compounds extracted from it. It is the high-purity steviol glycoside extract that is approved and used as a safe, zero-calorie sweetener in thousands of food and beverage products worldwide. When shopping, look for product labels that specify "steviol glycosides" or "stevia leaf extract" to ensure you are getting the purified and regulated version of this natural sweetener.
Learn more about how food additives are regulated by visiting the FDA's official website for authoritative information.
