• Lactulose is a disaccharide (double-sugar) formed from one molecule each of the simple sugars (monosaccharides) fructose and galactose.


  • Lactulose is α-D-galctopyranosyl-(1→4)-β-D-fructofuranose.


  • Heated milk (small amounts). Mainly obtained synthetically.


  • Lactulose is not normally present in raw milk but is a product of heat-processes: the greater the heat, the greater amount of this substance (from 3.5 mg/L in low temperature pasteurized milk to 744 mg/L in in-container sterilized milk).
  • It is produced commercially, by isomerization of lactose.

Clinical significance:

  • Not hydrolysed by intestinal enzymes, but fermented by intestinal bacteria.
  • It is used clinically in medicine as an osmotic laxative.

Lactulose in the treatment of constipation and liver disease:

  • Lactulose is a synthetic sugar used in the treatment of constipation and liver disease.
  • Lactulose is not absorbed in the small intestine nor broken down by human enzymes, thus stays in the digestive bolus through most of its course, causing retention of water through osmosis leading to softer, easier to pass stool.
  • In the colon, lactulose is broken down primarily to lactic acid, and also to small amounts of formic and acetic acids, by the action of via evolved-beta galactosidase from colonic bacteria, which results in an increase in osmotic pressure and slight acidification of the colonic contents.
  • This in turn causes an increase in stool water content and softens the stool.
  • Lactic acid and acetic acid partially dissociate, acidifying the colonic contents (increasing the H+ concentration in the gut).
  • This favors the formation of the nonabsorbable NH+4from NH3, trapping NH3 in the colon and effectively reducing plasma NH3


Leave a Reply

Your email address will not be published. Required fields are marked *