Stevia is a natural, zero-calorie sweetener derived from the leaves of the South American plant, Stevia rebaudiana. The sweetness comes from compounds known as steviol glycosides, such as stevioside and rebaudioside A, which are significantly sweeter than table sugar. To understand the nature of this sweetener, it is helpful to look at the pH scale, which measures the acidity or alkalinity of a substance. The scale runs from 0 to 14, where 7 is neutral, anything below 7 is acidic, and anything above 7 is alkaline. Determining whether Stevia is acidic or alkaline requires looking beyond the raw leaf to the refined products available to the consumer.
The pH of Stevia
Pure Stevia extract, specifically its primary sweetening compounds, is considered near neutral, often leaning slightly acidic. For example, a 70% ethanol extract of Stevia leaves or pure stevioside powder dissolved in water typically measures around pH 6. This places the isolated sweetening agent as a very weak acid, just below the neutral point of 7.
The pH measurement can vary depending on the product form. A hot water extract from dried Stevia leaves was measured at 5.7, while the whole leaf powder is reported to have a pH of about 6. The extraction and purification process, which isolates the steviol glycosides, confirms the nearly neutral characteristic, often operating within a pH range of 5.5 to 8.0.
Commercial Factors Influencing Stevia’s pH
Commercial Stevia products often have a pH that differs from the pure extract due to the addition of bulking agents and other ingredients. Since pure steviol glycosides are 200 to 400 times sweeter than sugar, only a tiny amount is needed for sweetening. This high potency requires bulking agents, such as erythritol, dextrose, or maltodextrin, to provide volume and make the product easier to measure.
These bulking agents can make up over 99% of a packaged blend by weight and significantly influence the final pH. For instance, a liquid Stevia concentrate, which includes carriers and stabilizers, has been measured to have a pH of about 8, making it weakly alkaline.
Other ingredients, such as flavor enhancers used to mask the slight aftertaste, can also shift the pH. The overall acidity or alkalinity of a commercial Stevia sweetener is a result of the entire blend, which manufacturers formulate for desired consistency, taste, and shelf stability.
Stevia and the Body’s Acid-Alkaline Balance
The measured pH of a food product does not directly translate to its effect on the body’s systemic acid-alkaline balance, which is tightly managed by the lungs and kidneys. A food’s impact on internal balance is better assessed by its Potential Renal Acid Load (PRAL) score, which estimates the acid or alkaline residue a food leaves after digestion.
Foods with a positive PRAL score are considered acid-forming, while those with an alkaline score promote a more alkaline environment. Stevia has virtually no protein, phosphorus, or sulfur—the components that typically contribute to a food’s acid load—so its PRAL score is negligibly low or neutral. Stevia is recognized as non-acidifying and does not disrupt the body’s natural pH regulatory mechanisms. Stevia consumption also does not cause the drop in oral plaque pH that fermentable sugars like sucrose do.