A nutrient is a substance that living things need to grow, stay healthy, and have energy. Your body gets nutrients from the food you eat: proteins help build strong muscles, carbohydrates give you energy to run and think, fats help your brain work properly, vitamins keep your immune system strong, and minerals like calcium build sturdy bones.

Plants need nutrients too, which they absorb from soil and water. That's why gardeners add fertilizer: it contains nutrients like nitrogen, phosphorus, and potassium that help plants grow thick stems and bright flowers.

Think of nutrients as fuel and building materials combined. Just as a car needs gasoline to run and a house needs bricks to stay standing, your body needs a variety of nutrients to function. When you eat a nutrient-rich meal like grilled chicken with vegetables and brown rice, you're giving your body many different nutrients it can use. Foods with lots of nutrients relative to their calories are called nutrient-dense, while foods high in calories but low in nutrients (like candy or soda) are sometimes called empty calories because they provide calories without the nutrients your body actually needs.