Can aspartame in diet foods damage your gut lining?

What's actually in it

Aspartame is one of the most widely used artificial sweeteners. It's in diet sodas, sugar-free gum, light yogurt, protein bars, and thousands of "zero sugar" products. When you swallow it, it passes through your digestive system and comes into direct contact with the cells lining your gut.

What the research says

A 2026 study in Allergy tested what aspartame does to gut epithelial cells, the single layer of cells that forms the barrier between your intestine and your bloodstream. The results weren't good.

Aspartame caused cellular stress in the gut lining cells. It triggered inflammation and damaged the tight junctions between cells. Those tight junctions are what keeps bacteria, toxins, and undigested food particles from leaking through your gut wall into your blood.

When the gut barrier weakens, it leads to what's sometimes called "leaky gut." Inflammatory molecules and bacterial fragments escape into the bloodstream and trigger immune reactions throughout the body. This has been linked to allergies, autoimmune conditions, and chronic inflammation.

The study showed these effects at concentrations you'd realistically encounter from drinking a couple of diet sodas. For people who consume multiple aspartame-sweetened products daily, the cumulative exposure to the gut lining is constant.