After her B.Ag.Sc., Cahn completed a Hospital Certificate of Dietetics at the newly opened Dietetics Unit at
St. Vincent's Hospital. Before leaving, she rose to the post of Chief Dietician at the hospital. She then took a position at Kraft Walker dairy factory in Drouin as a
microbiologist. She was employed as the first Chief Dietician for the Victorian Mental Hygiene Department, before spending a year at the
Royal Perth Hospital. During World War II, she enlisted in the
Australian Army Medical Women's Service on 11 February 1943. As part of the
Australian Army Medical Corps she became Chief Dietician at the Heidelberg Military Hospital. By her discharge on 13 September 1946, Cahn had obtained the rank of Major. From 1947 to 1959, she was a dietetics lecturer at the
University of Melbourne; from 1959 until 1968, when she retired, she was chief lecturer in nutrition and applied dietetics at the university. The research output of nutritional biochemist Cahn was well respected, having completed many studies in the field, including those undertaken during her time at the University of Melbourne from 1947 to 1968. These studies were important in examining the physical properties and energy values of common dietary foods so that calorie tables could be compiled. With colleagues in the anatomy department, she participated in the 17-year
longitudinal study entitled "Child Growth in Melbourne (1954-71)". The study found that Australian children weighed more and got less physical activity compared with their peers United States and Britain. ==Personal life==