Low lactase activity in a small-bowel biopsy specimen: Should dietary lactose intake be restricted in children with small intestinal mucosal damage?

Objective. Small intestinal mucosal damage can result in decreased lactase activity (LA). When LA is low in a small-bowel biopsy (SBB) specimen, a reduction of dietary lactose intake is usually advised. This is often done by reducing dietary dairy products, which also reduces the intake of calcium, protein and vitamins. Since intestinal damage can have a patchy character and LA varies along the horizontal axis of the small intestine, the relevance of SBB measurement for intestinal LA could be questioned. We compared LA in the SBB with the in vivo capacity to digest lactose using the Lactose Digestion Index (LDI). Material and methods. LA was measured in 18 children aged 0.8-10.9 years (mean 3.9, SD 2.4) undergoing SBB for various indications. In all children the LDI was determined using the 13C-lactose/2H-glucose test. Results. In 9/18 biopsy specimens LA was low (