A new study from the Massachusetts Institute of Technology suggests that eating foods rich in the amino acid cysteine could help the small intestine repair itself. Researchers found that cysteine activates a biological process that encourages intestinal stem cells to regenerate new tissue, a finding that could one day help people recovering from radiation or chemotherapy.
The study, led by Dr. Omer Yilmaz, director of the MIT Stem Cell Initiative and associate professor of biology at MIT, shows how a single nutrient can influence immune activity and tissue repair. Here, we’ll look at what the researchers discovered about cysteine’s role in intestinal regeneration and how this amino acid could eventually be used to support gut healing.
How cysteine supports intestinal regeneration
For years, scientists have known that diet affects the body’s ability to repair itself. High-fat or low-calorie diets, for example, can alter how stem cells behave. What’s been less clear is how specific nutrients impact tissue health. To find out, Dr. Yilmaz’s team fed mice diets rich in different amino acids—the building blocks of proteins—and tracked how each one affected intestinal stem cell growth.
Cysteine stood out. The mice that consumed a cysteine-heavy diet showed significant boosts in stem cell and progenitor cell activity within the small intestine. Researchers discovered that when intestinal cells absorb cysteine, they convert it into a molecule called CoA. This molecule is then taken up by immune cells known as CD8 T cells, which begin producing a cytokine called IL-22.
IL-22 plays a key role in maintaining the gut lining and stimulating new cell growth after injury. What surprised the researchers was that these CD8 T cells—not typically associated with IL-22 production—became an unexpected source of it.
“Feeding mice a cysteine-rich diet leads to the expansion of an immune cell population that we typically don’t associate with IL-22 production”, Dr. Yilmaz said. The result: more IL-22 in the small intestine and stronger tissue regeneration.
The effects were most pronounced in the small intestine, where most proteins are absorbed. This suggests that dietary cysteine directly influences local immune and stem cell responses, rather than circulating throughout the entire body like cysteine produced in the liver.
The relevance of these findings around cysteine
The research has potential implications for people undergoing radiation or chemotherapy, treatments known to damage the intestinal lining. In experiments, mice on a cysteine-rich diet showed faster healing after radiation exposure. Similar results were seen in tests involving 5-fluorouracil, a chemotherapy drug that often harms the gut.
Cysteine occurs naturally in many protein-rich foods such as meat, dairy products, legumes, and nuts. The body can also synthesize it from another amino acid, methionine, but consuming it through food creates higher concentrations in the gut, where it seems to have the most impact.
While the study was conducted in mice, it opens the door for future clinical research. If these effects are confirmed in humans, cysteine-rich diets or supplements could become a simple way to support intestinal repair. The researchers also plan to test whether cysteine may help other tissues, such as hair follicles, regenerate more effectively.