This study was conducted to evaluate changes in hydrogen breath test results and nutritional improvements when Korean adults diagnosed with lactose intolerance consumed processed milk containing approximately 10 g of lactose continuously. Participants consumed 240 mL of intervention food daily for a month and visited the research institute before and after the intervention to undergo nutrient intake survey and hydrogen breath tests. Data from 32 participants, with a mean age of 52.9 years, were analyzed. Hydrogen breath tests showed a significant decrease in hydrogen levels at all but baseline and the first of five 20-minute intervals of expiratory hydrogen concentration measurements. The third and fourth measurements showed the most significant changes (p <
0.001). The gastrointestinal symptoms showed a decreasing trend. Nutrient intake analysis demonstrated significant increases in animal protein (p <
0.001), calcium (p <
0.001), percentage of energy from protein (p = 0.032), vitamin A (p = 0.032), and retinol levels (p = 0.023). Regarding dietary habits, significant improvements were observed in nutritional quotient variables, including nutritional score (p = 0.042) and balance (p = 0.034). This study suggests that the removal of lactose and dairy products is not necessary for individuals with lactose intolerance. Incorporating low-lactose processed milk into their usual diet might be a practical dietary management strategy.