Imagine you are mid-afternoon, energy fading, and you reach for a sugar-free protein bar or a can of diet soda labeled "keto-friendly." That sweetener inside is probably erythritol, one of the most widely used sugar alcohols in processed foods. You are not alone. Millions of people use erythritol daily, believing it to be one of the safer sugar alternatives available.

New research from the University of Colorado Boulder is complicating that assumption [1]. The study, published in the Journal of Applied Physiology, found that erythritol may damage the cells that form the protective barrier around the brain, potentially increasing stroke risk. Combined with earlier findings linking erythritol to cardiovascular events, the evidence is beginning to suggest that this sweetener deserves more scrutiny than it has received.

What Erythritol Is and Where You Find It

Erythritol is a sugar alcohol that occurs naturally in some fruits and vegetables, though the version added to processed foods is typically manufactured [4]. It provides about 80% of sugar's sweetness while delivering almost no calories, which made it a favourite among food manufacturers after the FDA granted it "generally recognized as safe" status in 2001 [1]. You will find it in protein bars, energy drinks, sugar-free yogurts, low-carb ice cream, and baked goods marketed to people following ketogenic or diabetic eating patterns.

Unlike aspartame or sucralose, which are intense sweeteners requiring only tiny amounts, erythritol has a sweetness profile closer to table sugar. This makes it easier to use in baking and gives it a taste that many consumers describe as more natural. It also resists fermentation, meaning it does not cause the digestive upset that other sugar alcohols produce in large quantities.

That usability has made erythritol extraordinarily popular. It appears in thousands of products, and many consumers seek it out specifically because it avoids the WHO guidelines that discouraged certain artificial sweeteners [4].

The Blood-Brain Barrier: Why It Matters

Before understanding what the new research found, it helps to know what the blood-brain barrier actually does. This specialized layer of cells lining the brain's blood vessels acts as a gatekeeper, preventing harmful substances in the bloodstream from reaching delicate brain tissue while allowing essential nutrients to pass through.

The barrier also regulates clot formation. Brain endothelial cells produce a compound called tissue-type plasminogen activator, or t-PA, which acts as the body's natural clot-busting mechanism [1]. When a clot threatens to block blood flow to the brain, t-PA steps in to dissolve it. Keeping this system functioning properly is critical for preventing stroke.

What the Colorado Study Found

Researchers at the University of Colorado Boulder exposed brain endothelial cells to erythritol at concentrations equivalent to what you would find in your bloodstream after consuming a single sugar-free beverage [1]. After three hours of exposure, the results were concerning.

The treated cells showed significantly reduced nitric oxide production, a compound that acts as a vasodilator, helping blood vessels relax and maintain healthy blood flow [1]. Simultaneously, they produced more endothelin-1, a vasoconstrictor that narrows blood vessels [1]. Perhaps most notably, when challenged with thrombin, a compound that triggers clotting, the erythritol-treated cells produced markedly less t-PA than untreated cells [1].

The researchers also observed increased reactive oxygen species, molecules that cause oxidative stress and cell damage [1][4]. The cells' antioxidant defenses were simultaneously reduced, a double hit that accelerated cellular harm.

The senior author, Professor Christopher DeSouza of the Department of Integrative Physiology, noted that erythritol appeared to impair the very mechanisms the brain relies on to prevent clots [1].

A Pattern Emerging Across Cardiovascular Research

The Colorado findings gain more weight when viewed alongside existing cardiovascular research on erythritol. A 2023 Cleveland Clinic study involving over 4,000 people across the US and Europe found that those with the highest blood erythritol levels were approximately twice as likely to experience a major cardiac event, such as a heart attack or stroke, within three years [2]. This correlational data raised questions that the researchers wanted to explore further.

A 2024 follow-up human intervention study by the same group offered more direct evidence [3]. In twenty healthy volunteers, erythritol levels increased over 1,000-fold after consuming a single erythritol-sweetened food or drink. The researchers observed that erythritol made platelets more active, increasing the tendency of blood to clot. When the same test was run with glucose, no such effect occurred [3]. The dose used was typical of one sugarless soda or a single muffin serving [3]. This built on earlier findings showing that as little as 30g of erythritol, roughly the amount in a pint of sugar-free ice cream, could cause platelets to clump together [1].

It is important to note that these studies used different methodologies, and combining their findings into a single conclusion about causation would be misleading. Each study type has distinct strengths and limitations. The observational study can identify associations but cannot prove causation. The cell study provides mechanistic insight but cannot directly predict effects in living humans. The human intervention study shows short-term physiological effects but does not establish long-term health outcomes. Viewing them together helps form a broader picture of where the science is heading, but that picture is still incomplete.

The Regulatory Gap

Here is where things get complicated. Regulatory agencies including the FDA and EFSA continue to classify erythritol as "generally recognized as safe," or GRAS, a classification that predates much of the recent research [4]. The WHO has issued cautions about certain artificial sweeteners, but erythritol has avoided similar scrutiny because it falls into the sugar alcohol category rather than the synthetic sweetener classifications that attracted regulatory attention [4].

This creates a situation where the scientific evidence is accumulating faster than the regulatory frameworks can respond. Researchers acknowledge that the 2025 University of Colorado study was conducted on cells in a laboratory rather than in living humans, and larger human studies are still needed to confirm the effects [4]. Some nutrition experts maintain that erythritol remains among the safer sugar alternatives, pointing to the need for more long-term data before drawing firm conclusions.

What This Means for Daily Choices

The emerging research suggests a framework for thinking about erythritol that goes beyond "safe" or "unsafe." The science is still developing, and a single study on cells does not constitute proof of harm in living humans. However, the direction of evidence across multiple research groups and methodologies is worth noting, even if no single conclusion can be drawn yet.

One practical approach is to stay informed as new research emerges. If you have existing cardiovascular risk factors or other health concerns, discussing erythritol consumption with a healthcare professional makes sense, as it would for any emerging area of nutritional science.

For those who want to track developments independently, reading ingredient labels and identifying products that contain erythritol allows you to make informed choices based on your own health context and risk tolerance. The scientific process requires time, replication, and peer review before conclusions become definitive. Following reputable sources for updates as larger human studies are completed will give a clearer picture of what, if any, dietary changes are warranted.

The most important step is staying informed as research continues, recognizing that what we know now may shift as the science develops.