8. We Need to Eat and Drink to Live
All creatures need fuel in order to function, and humans are no exception. We get our fuel from food in the form of chemical compounds that are collectively known as nutrients.
These nutrients work together to provide energy, growth, and maintenance, and to regulate numerous body processes. Three of the six classes of nutrients—carbohydrates, fats (part of the larger class of lipids), and protein—provide energy in the form of kilocalories.
Two other classes of nutrients, vitamins and minerals, help regulate many body processes, including metabolism. Some also play other supporting roles. The last class of nutrient, water, is found in all foods and beverages, and is so vital to life that you couldn't live more than a few days without it.
Foods also provide nonnutrient compounds like phytochemicals and other substances that help maintain and repair your body in order to keep it healthy. We will explore each of these nutrients in more depth later. Beyond the basic need to replenish our bodies with daily fuel are other factors that drive our food choices.