The plant Stevia rebaudiana is widely known for the intense, zero-calorie sweetness of its leaves, which are processed into a common sugar substitute. Stevia is a popular alternative for those looking to reduce their sugar intake. However, subjecting its dried leaves or extracts to high heat for inhalation is distinct from its use in food. Analyzing stevia’s composition and the mechanics of combustion reveals significant health risks not associated with consuming the product.
Stevia’s Chemical Composition
The sweet taste of the stevia plant comes from steviol glycosides, which are large, complex molecules called diterpenes. The most abundant glycosides are stevioside and rebaudioside A, which are 30 to 320 times sweeter than regular table sugar. When ingested, these compounds are not broken down in the stomach, resulting in zero calories, and are safely excreted after being metabolized by gut bacteria. This metabolic pathway ensures safety for consumption, but it is bypassed when the material is burned. The extreme temperatures of combustion cause the molecules to degrade significantly, creating new, potentially harmful chemical byproducts.
Health Risks of Inhaling Combusted Plant Material
Smoking any dried plant material, including stevia leaves, exposes the lungs to universal dangers inherent to combustion. The incomplete burning of organic matter generates a complex mix of gaseous and solid pollutants. These include carbon monoxide, which binds to hemoglobin, displacing oxygen and hindering its transport throughout the body.
The most significant physical threat comes from particulate matter (PM), particularly fine particles (PM2.5). These microscopic particles penetrate deep into the lower respiratory tract and can enter the bloodstream. Inhaling PM can lead to respiratory irritation, aggravated asthma, and reduced lung function. Chronic exposure to these combustion products is linked to long-term cardiopulmonary issues, including heart disease and stroke.
Specific Safety Concerns Related to Steviol Glycosides
Highly purified steviol glycosides are designated as Generally Recognized As Safe (GRAS) for their intended use as a food additive. This designation confirms safety for oral consumption but does not imply safety for inhalation. The GRAS status is based on the compound’s known metabolic pathway when swallowed, which is irrelevant in a smoking context.
The primary concern with smoking stevia is pyrolysis, where the complex steviol glycoside molecules break down under intense heat. This thermal degradation generates novel compounds whose toxicity to the lungs is unknown. There is a complete absence of scientific research on the safety of inhaling the specific pyrolysis products of steviol glycosides. Without toxicological data, these untested breakdown products must be presumed to pose a serious risk to respiratory health.