Food is any material consumed in order to provide nutrition to an organism. Food is generally of animal, plant or even fungal source, and has necessary nutrients, including proteins, carbohydrates, vitamins, or minerals, which are required by the body for normal activity. Food eaten is divided into two categories: animal food and plant food. Animal food refers to meat, milk, eggs and fish; plant food is the main source of food on which the other foods depend, like carbohydrates, sugar, vitamins and so forth.

Food provides many important nutrients to the human body, including proteins. Proteins are the building blocks of muscles, tissues and organs, so without them, most people would be unable to survive. However, the type of protein that most people eat (that is, meat and eggs) is not healthy for their bodies, because it is full of hormones, antibiotics and other chemicals that can threaten the balance of the immune system. That is why many people have turned to vegetarianism, or diets that do not contain animal products, in order to keep their immune systems strong.

Vitamin B12 is a very important vitamin for healthy bones, teeth and blood vessels, so it is recommended that everyone eat enough vitamin B in their daily diet. Vitamin C is another vitamin that is very important to the body, because it helps in many ways. Two other substances that help keep the body healthy are iron and selenium, which are found in several common foods.