The word food brings to mind a number of substances that are consumed by living beings to provide them with nourishment, and also to sustain their existence. Food is consumed to provide nutrition to an organism, and includes any material taken from plants, animals or fungi, which contains necessary nutrients, including vitamins, fats, carbohydrates, proteins or minerals. To ensure the right intake of food in humans, the basic dietary constituents are carbohydrate, protein, fat and minerals. There are three groups of carbohydrates: simple, complex and cereal grains. Fruits and vegetables are the richest in nutrient content.

Fat is another important source of food, but its quantity in our daily diet is limited mainly because it is derived from animal products. Meat, fish and poultry are the richest in fat content, while vegetable oils, dairy products and refined sugars are the other two major sources of fat. Carbohydrate provides energy to the body and may be obtained from grains, vegetables, fruits and legumes (such as beans and lentils). Complex carbohydrates are found in whole grain foods, whole grain breads and cereals, and in some nuts and seeds. Whole grain foods, moreover, contain the highest amounts of minerals, fiber, vitamins and phytochemicals.

Food habits are influenced by cultural factors and individual responses to food. The food habits of people in developed countries differ from those of hunters and gatherers. In developed countries, fresh fruits and vegetables, rice and other legume foods, meat and dairy products are more frequently used than in the less developed parts of the world. A well balanced diet is important for ensuring optimal health. Fishes, meats, nuts, pulses, sugar, dairy products, fruits, vegetables and legumes constitute a complete and balanced diet, which can be easily provided by using different types of food available in the market.