Some children are born with a decreased or absent ability to metabolize “table sugar” (sucrose) because their genes produce a defect version of the enzyme (sucrase-isomaltase) which is involved in the cleavage of “table sugar” (sucrose). The child inherits a defect gene both from the mother and the father to develop the disease, but depending on the type of genetic alteration, the severity of symptoms may vary.
“Table sugar” (sucrose) is a so called disaccharide and consists of two simple sugar molecules (monosacharides) linked together. In “table sugar” (sucrose) the two monosacharides are glucose and fructose. Humans cannot absorb sucrose directly from the intestine and the enzyme sucrase isomaltase needs to separate the two monosacharides glucose and fructose from one another so they can be absorbed from the intestinal tract and enter the blood stream.