Copy number polymorphism of the salivary amylase gene: implications in human nutrition research.

The salivary α-amylase is a calcium-binding enzyme that initiates starch digestion in the oral cavity. The α-amylase genes are located in a cluster on the chromosome that includes salivary amylase genes (AMY1), two pancreatic α-amylase genes (AMY2A and AMY2B) and a related pseudogene. The AMY1 genes show extensive copy number variation which is directly proportional to the salivary α-amylase content in saliva. The α-amylase amount in saliva is also influenced by other factors, such as hydration status, psychosocial stress level, and short-term dietary habits. It has been shown that the average copy number of AMY1 gene is higher in populations that evolved under high-starch diets versus low-starch diets, reflecting an intense positive selection imposed by diet on amylase copy number during evolution. In this context, a number of different aspects can be considered in evaluating the possible impact of copy number variation of the AMY1 gene on nutrition research, such as issues related to human diet gene evolution, action on starch digestion, effect on glycemic response after starch consumption, modulation of the action of α-amylases inhibitors, effect on taste perception and satiety, influence on psychosocial stress and relation to oral health.