The Digestive System Reading Comprehension Digestion allows the body to receive the nutrients and the energy from the food that is eaten. During digestion, all of the food a person eats is eventually turned into the building blocks and fuel a person needs. The system actually begins to work when a person sees or smells the food. Science Reading Warm-Up: The Digestive System - TeacherVision Science Reading Warm-Up: The Digestive System Read about the digestive system. This printable warm-up includes a science reading passage about the human body and questions to check reading comprehension.