Disposable e-cigarettes, with their vibrant colors and an ever-expanding menu of enticing flavors, have become a common sight, particularly among younger demographics. While often marketed with an air of playful appeal, a recent study from researchers at Yale University and Duke University School of Medicine has cast a new light on what might be lurking within these popular devices. The study, published and drawing attention in mid-2025, found that a significant majority of popular disposable e-cigarettes sold in the US contain neotame, an artificial sweetener far more potent than sugar or even aspartame. This discovery raises fresh questions about the ingredients in vaping products, their appeal to youth, and the largely unknown health implications of inhaling such compounds.
Neotame: An Intensely Sweet and Thermally Stable Additive
The research team analyzed 73 e-cigarette products available on the American market, including popular disposable brands, nicotine-free options, devices with synthetic nicotine analogues like 6-methyl nicotine, and even some products that had been submitted for FDA approval or were already FDA-authorized (like Vuse and NJOY). Their findings were striking: neotame was detected in 57 of the 73 samples, a prevalence of 78%. Crucially, in most cases, neotame was not listed as an ingredient on the product packaging, leaving consumers unaware of its presence.
Neotame is an artificial sweetener with remarkable potency – it's estimated to be 7,000 to 13,000 times sweeter than table sugar and approximately 35 to 65 times sweeter than aspartame. Its intense sweetness allows manufacturers to use very small quantities to achieve a desired flavor profile. Another key reason for its use in e-cigarettes, as suggested by the researchers, is its relative thermal stability compared to other sweeteners. This means it can better withstand the heating process involved in vaping without significantly degrading or altering its sweetening properties, making it an attractive additive for e-liquid formulators, particularly for fruity or menthol-like "cooling" flavors designed to create a pleasant and intense taste experience. The study noted the Cherry Lemonade flavor from Tauro Vape as one example where such intense sweeteners might be employed.
The average concentration of neotame found in the tested e-cigarette liquids was 1.75 micrograms per milligram of liquid (µg/mg). To put this in perspective, the researchers noted this was approximately 4.6 times higher than the neotame concentration found in a strongly flavored mint candy used as a comparison product in their analysis. This suggests a deliberate and significant use of the sweetener to enhance flavor profiles.
Where Was Neotame Found (and Not Found)?
The distribution of neotame across different product categories was revealing:
- It was found in all tested disposable e-cigarette products.
- It was present in all tested nicotine-free e-cigarettes.
- It was detected in all devices containing the synthetic nicotine analogue 6-methyl nicotine, with these products showing particularly high levels (average 2.69 µg/mg, with some reaching up to 18.3 µg/mg).
Conversely, and significantly, neotame was NOT detected in any of the FDA-authorized cartridge systems tested, such as those from Vuse, NJOY, or any JUUL device. This finding suggests that products undergoing the rigorous FDA Premarket Tobacco Product Application (PMTA) process, which involves detailed scrutiny of ingredients and their potential health impacts, may be less likely to contain such unlisted or poorly understood additives for inhalation.
The study also analyzed a few e-cigarettes purchased in 2021, finding neotame in two of the four samples. This indicates that the use of this potent sweetener in e-cigarettes is not a brand-new phenomenon but has likely been an established practice for several years, growing with the popularity of intensely flavored disposable products.
Why the Concern? Inhalation vs. Ingestion and Unknown Risks
While neotame is approved as a food additive in many countries and considered safe for ingestion within certain limits, its safety when heated and *inhaled* is a critical unknown. Hanno Erythropel, PhD, lead author of the study and a research scientist at Yale University's Department of Chemical and Environmental Engineering, emphasized this crucial distinction: "Eating a chemical is fundamentally different from inhaling it. Many compounds are safe to eat but dangerous when inhaled."
The lungs are not designed to process chemicals in the same way the digestive system is. When substances are inhaled, they can bypass the body's natural metabolic and detoxification pathways in the liver, potentially reaching the bloodstream and sensitive lung tissues more directly and in different forms. The researchers highlighted several unanswered questions:
- How much of the neotame present in the e-liquid actually transfers to the aerosol during vaping?
- How much of that aerosolized neotame reaches the sweet taste receptors to produce a sweet sensation, versus being deposited elsewhere in the respiratory system?
- What happens to neotame when it's heated to vaping temperatures? Could it produce chemical degradation products whose effects on the lungs, immune system, or central nervous system are currently unstudied and unknown?
These questions are complex and influenced by many variables, including the type of e-cigarette device, its power output, coil design, and the user's individual puffing behavior (duration, intensity). The study also pointed to previous research published in the journal Frontiers in Nutrition in 2023, which suggested that neotame, even when consumed in foods, might negatively impact gut health. The implications of inhaling it, especially its degradation products, are a significant knowledge gap.
Sweeteners, Youth Appeal, and Addictive Potential
The deliberate use of intense sweeteners like neotame is seen by researchers and public health advocates as a strategy to optimize flavor and make e-cigarettes more appealing, particularly to adolescents and young adults. Previous research has consistently shown that sweetening and cooling additives (like sucralose or menthol) can significantly enhance the attractiveness and potentially the addictive potential of e-cigarettes, especially for young or novice users. The study suggests that even nicotine-free versions containing these potent sweeteners could have a significant addictive potential due to their highly palatable and appealing taste profiles, potentially acting as a gateway to nicotine products or normalizing the act of vaping.
This is particularly concerning given the ongoing "youth vaping epidemic" reported in many countries. Manufacturers have long relied on flavors to enhance the taste of tobacco and nicotine products and to attract younger consumers. The use of intense, unlisted sweeteners like neotame appears to be another tactic in this playbook.
Calls for Stricter Regulation and Further Research
In light of their findings, the Yale and Duke researchers advocate for stricter control of sweetening additives in e-cigarettes. Disposable products, which are popular among youth and were found to consistently contain neotame in this study, are singled out as a particular concern. A spokesperson for Germany's Federal Institute for Risk Assessment (BfR) told Medscape Medical News that the BfR had not yet specifically addressed neotame in its e-cigarette assessments and lacked information on its prevalence in products on the German market, indicating a potential regulatory blind spot in some regions as well.
The researchers strongly urge comprehensive toxicological studies on the effects of inhaling neotame and its potential thermal degradation products. They also call for research into the abuse potential of these highly sweetened substances. Only with such data, they argue, can informed decisions be made about whether sweeteners like neotame should be more strictly regulated or potentially banned from use in e-cigarette liquids in the future. The fact that neotame was not found in FDA-authorized products suggests that regulatory scrutiny can indeed influence product formulation towards potentially safer profiles.
As the vaping market continues to evolve, and with public health authorities worldwide grappling with how to balance adult smokers' access to potentially less harmful alternatives with the urgent need to protect youth, understanding the full chemical composition of e-liquids and the effects of all inhaled ingredients is more critical than ever.
