The Human Body: Learn About Essential Nutrients
Americian Heart Association - Nutrition Basics
The USDA site includes tip sheets with information on all of the food groups, physical activity ideas, planning tools and printable resources. Use this clickable resource to learn more about each food group and its benefits. Each section of the collection provides a brief overview of a food group, with a link to more information and examples of healthy eating.
This resource from the Centers for Disease Control and Prevention provides basic concepts to help you sort through nutrition research and dietary advice.