Carbohydrates. Both salivary and pancreatic amylase are responsible for the breakdown of more complex carbohydrates into simpler ones the body can use. The salivary amylase enzyme starts the process of breakdown as food is ingested, and the process is completed to a much greater degree in the GI tract. A mutation in the genes responsible for this enzyme will greatly impact the efficiency of this process, either enhancing or impairing carbohydrate digestion depending on the effect this mutation has on the process. In some cases, for instance, a doubling of the number of genes responsible for starch digestion has been observed; people with this mutation exhibit an enhanced starch digestion compared to those without.