Lactose digestion in humans depends upon the activity of the enzyme lactase. In adults, lactose maldigestion is often present due to a physiological decline in lactase expression in late childhood. Lactose maldigestion can lead to symptoms of lactose intolerance due to the presence of undigested lactose in the colon and the products of its fermentation by gut bacteria. Adaptive changes in the colonic microbiota are associated with decreased lactose intolerance. In addition to their role in the colonic digestion of lactose, bacteria can also be used in dairy products to ‘pre-digest’ lactose which can reduce intolerance symptoms. Other dietary interventions (such as prebiotics and probiotics) have been explored for their capacity to modulate the gut microbiota and thus improve lactose digestion. While the benefits of modulating the gut microbiota to address lactose maldigestion are evident, the consequences of these strategies on health need to be investigated.
