The blood-brain barrier surrounds the blood vessels that run through the brain, letting in oxygen and nutrients while keeping out toxins and pathogens. It's an absolutely essential line of defense that protects the brain from damage.Researchers now believe they have discovered a significant threat to this barrier and its stability – and from something we're willingly putting into our bodies.Erythritol has been used as an artificial sweetener for decades.It's a favorite with consumers and food producers because it has almost zero calories, is 60–80 percent as sweet as table sugar, and doesn't impact insulin levels.The blood-brain barrier controls what can get into the brain. (Wu et al., Signal Transduct. Target. Ther., 2026)However, in a study published in the Journal of Applied Physiology, a team from the University of Colorado, Boulder found that it had damaging effects on blood-brain barrier cells (brain endothelial cells) grown in the lab.Past studies have suggested a link between higher erythritol levels and a greater risk of heart attack or stroke, and this additional research could explain why, if the same effects occur in the body."The results presented herein support and experimentally extend epidemiological studies reporting a link between erythritol and increased stroke risk," write the researchers in their published paper."Additional clinical studies are warranted on the potential long-term health effects of erythritol consumption."The experiments led by the researchers found that adding erythritol to endothelial cells caused them to produce less nitric oxide, which makes blood vessels wider and more relaxed. It also created more endothelin-1, a protein that constricts blood vessels – so a double strike for keeping blood vessels clear.