Lactulose can selectively promote the growth and reproduction of beneficial bacteria such as Bifidobacterium and Lactobacillus in the intestine, while inhibiting the proliferation of harmful bacteria like Escherichia coli and Salmonella. Beneficial bacteria ferment lactulose to produce short - chain fatty acids (such as acetic acid, propionic acid, and butyric acid), which lower the intestinal pH value, improve the intestinal environment, enhance the intestinal barrier function, and reduce the occurrence of intestinal inflammation.

Lactulose is not decomposed by digestive enzymes in the intestine, so it can retain water, increase fecal volume, and stimulate intestinal peristalsis, thereby promoting defecation. Compared with traditional stimulant laxatives, lactulose has a milder effect, does not cause intestinal spasms and electrolyte disorders, and is safe for long - term use, especially suitable for patients with chronic constipation and the elderly. Since the 1960s, lactulose has been used to treat constipation in patients of all ages, including infants. As an osmotic laxative, it usually takes effect within 24 - 48 hours. When it reaches the intestine, it is decomposed by intestinal bacteria into active components, which increase intestinal peristalsis and retain intestinal fluid, making feces easier to pass.

Hepatic encephalopathy is a central nervous system dysfunction caused by severe liver damage, which leads to ammonia metabolism disorders and elevated blood ammonia levels. Lactulose is decomposed by bacteria in the colon to produce lactic acid and acetic acid, creating an acidic intestinal environment that reduces ammonia absorption. At the same time, it can also promote the excretion of ammonia in the intestine, lower blood ammonia levels, improve the symptoms of patients with hepatic encephalopathy, and enhance their quality of life. Studies have shown that patients with hepatic encephalopathy who take lactulose have significant improvements in the number of abnormal neuropsychological tests, cognitive function, and quality of life.

Intestine is the largest immune organ of the human body. Lactulose can regulate the intestinal microecological balance, promote the development and maturation of intestinal - associated lymphoid tissues, enhance the immune barrier function of the intestinal mucosa, improve the immune response ability of the body, and reduce the occurrence of infectious diseases. In addition, some metabolites produced by beneficial bacteria, such as vitamins and amino acids, also help maintain the normal physiological functions of the body.