Kluyveromyces lactis is a species of yeast that is scientifically validated for use in supporting or treating lactose intolerance, primarily due to its ability to produce the enzyme β-galactosidase (lactase). Lactose intolerance results from insufficient lactase in the small intestine, leading to gastrointestinal symptoms upon dairy consumption. K. lactis is commonly used in the dairy industry to manufacture lactose-free or lactose-reduced products. The yeast’s lactase breaks down lactose into glucose and galactose, which are easily absorbed by lactose-intolerant individuals. There is robust scientific evidence, including controlled studies and commercial applications, demonstrating that K. lactis-derived lactase is effective at reducing or eliminating symptoms of lactose intolerance when used to pre-treat dairy products or as a dietary supplement. Products containing lactase from K. lactis are widely available and have been shown in clinical and consumer studies to significantly reduce symptoms such as bloating, diarrhea, and abdominal pain associated with lactose consumption. Regulatory authorities (such as the FDA and EFSA) recognize K. lactis-derived lactase as safe and effective. There is no significant traditional or folk use of the yeast itself for lactose intolerance; its application is entirely based on scientific discovery and biotechnological advances.