In this qualitative study with three ethnocultural groups in two regions of Canada, we explore how official dietary guidelines provide particular standards concerning 'healthy eating' that marginalize other understandings of the relationship between food and health. In families where parents and youth held shared ways of understanding healthy eating, the role of 'good mother' was constructed so as to include healthy eating expertise. Mothers expressed a perceived need to be personally responsible for providing skills and knowledge about healthy eating as well as guarding children against negative nutritional influences. Governing of family eating practices to conform to official nutritional advice occurred through information provision, monitoring in shopping and meal preparation, restricting and guiding food purchases, and directly translating expert knowledges into family food practices. In families where parents and youth held differing understandings of healthy eating, primarily families from ethnocultural minority groups, mothers often did not employ the particular western-originating strategies of conveying healthy eating information, or mentoring healthy meal preparation, nor did they regulate or restrict children's food consumption. Western dietary guidelines entered into the family primarily through the youth, emphasizing the nutritional properties of food, often devaluing 'traditional' knowledge about healthy eating. These processes exemplify techniques of governmentality which simultaneously exercise control over people's behaviour through normalizing some family food practices and marginalizing others.