Lactitol is a sugar alcohol used as a replacement bulk sweetener for low caloriefoods with approximately 40% of the sweetness of sugar. It is also used medically as a laxative. Lactitol is produced by two manufacturers, Danisco and Purac Biochem.
Like most other sugar alcohols (with the exception of erythritol), lactitol can cause cramping, flatulence, and diarrhea in some individuals. This is because humans lack a suitable beta-galactosidase in the upper gastrointestinal (GI) tract, and a majority of ingested lactitol reaches the large intestine,3 where it then becomes fermentable to gut microbes (prebiotic) and can pull water into the gut by osmosis. In a human study with sweetened chocolate, consumption of 5 g per day or less resulted in no GI changes, and 10 g per day caused few changes.4 Those with other health conditions should consult their GP or dietician prior to consumption.
^Finney, Michelle; Smullen, Joanne; Foster, Howard A.; Brokx, Saskia; Storey, David M. (2007). "Effects of low doses of lactitol on faecal microflora, pH, short chain fatty acids and gastrointestinal symptomology". European Journal of Nutrition46 (6): 307–14. doi:10.1007/s00394-007-0666-7. PMID17623227.