Professor Riddell is known for her expertise in food nutrition. Her research mainly focuses on the impact of the micronutrients iron, zinc, sodium and iodine on the health of general population and dietary changes that occur in young adults as they transition into independent living and the influence of prior expose to food and nutrition education.

Her current research projects investigate the impact of salt and iodine on the health of children; dietary strategies to improve intake and status of iron and zinc in adult women and an ongoing cross sectional study investigating food habits of young adults as they enter university.