The goal of this Interventional study is to validate the Smart Underwear device's ability to detect lactose intolerance by comparing its results to self-reported symptoms in adult participants aged 18 and above, divided equally between self-reported lactose-tolerant and lactose-intolerant individuals. The main questions it aims to answer are: Can the Smart Underwear device reliably measure flatus events after lactose consumption? Does the Microbiome Activity Index differentiate between responses to lactose and sucrose consumption? Researchers will compare participants consuming lactose (experimental arm) with their results after consuming sucrose (placebo arm) to see if the device detects increased flatus events and higher Microbiome Activity Index values in the lactose arm. Participants will: * Follow a low-fiber/low-FODMAP diet for four days. * Record meals using a food log and a custom smartphone app. * Wear the Smart Underwear device for 8 hours daily for three days. * Fast for 12 hours overnight, consume 20 grams of either lactose or sucrose dissolved in water, and continue fasting for an additional 4 hours. * Fast for 12 hours overnight, consume 20 grams of the carbohydrate they did not consume the first time (lactose or sucrose) dissolved in water, and continue fasting for an additional 4 hours. * Complete digestive symptom surveys after each carbohydrate intake. The randomized crossover design ensures that participants consume both lactose and sucrose on separate days, with blinding maintained for both participants and researchers.