06 May 2019 --- A new Cornell University study has found that a person’s genetic makeup could alter their gut bacteria, which in turn impacts how they digest food – in the case of this study, starch. People with a high number of copies of a gene called AMY1, which expresses a salivary enzyme for breaking down starch, correlated strongly with a certain profile of gut and mouth bacteria. The gene could have given certain groups nutritional benefits in times where calories were scarce, such as during cold seasons and famines, the researchers note. Now, medical professionals could take a patient’s AMY1 gene copy number into account when giving personalized dietary advice.