Nutrition plays a role in nearly every major chronic disease, yet the science behind what we eat often feels confusing or contradictory. Nutritional epidemiology is the field that tries to make sense of these patterns by studying diet and health across populations. In this conversation, we are going to explore what this field can—and can’t—tell us about how food affects our health. Dr. Russell de Souza is a registered dietitian and Associate Professor in the Mary Heersink School of Global Health and Social Medicine and the Department of Health Research Methods, Evidence, and Impact at McMaster University. His passion lies in understanding how what we eat and the environments we live in shape our health throughout life. He conducts everything from clinical trials to in-depth interviews, and works with teams to use cutting-edge ‘omics’ science to dig deeper into our diets. What really drives him is finding ways to help communities that often get overlooked, like pregnant women, South Asian immigrants and Indigenous Peoples, reduce their risk of chronic diseases. Along the way, he has earned prestigious recognition, including the 2023 CNS Young Investigator Award, and his department’s Justice, Equity, Diversity, and Inclusion Award. In this episode, Dr. de Souza discusses how nutritional epidemiology shapes our understanding of diet and health.