Food is any material consumed to provide nutrition to an organism for its continued growth and development. The word ‘food’ refers to any of the matter that an animal or human consumes to maintain health. In the simplest terms, food is a substance used to promote life. Animal food like meat, fish and dairy products are examples of food. Food is generally of animal, plant or fungi origin, and is used to supply energy, including proteins, carbohydrates, vitamins, or minerals for the ongoing growth and development of an animal or human.

Plants, like food, have certain characteristics that allow them to be preserved and kept for a long period of time in most cases. The main characteristics of these plants include photosynthesis, energy conversion to energy, storage of carbohydrates and proteins. Some plants even manufacture some of their own food, but the main components of plant food, sugar and starch, are inorganic in nature. These substances are combined in various proportions and combinations to make food that an organism can eat.

Because plant food supplies the body with all the elements it needs to sustain life, when there is enough food available to an animal or human, they will remain healthy. Human beings, on the other hand, need much more food than animals do, and therefore suffer from obesity, diet deficiency, chronic diseases and malnutrition. It is estimated that most people in industrialized nations do not meet the recommended daily allowance (RDA) of the amount of food that they need to maintain health. The increasing population of these countries leads to more food scarcity, creating the need for increased amounts of food production.

Plant food, apart from having all the nutrients that the body needs, also contain carbohydrates, sugars and other non-protein substances. A lot of these substances are not soluble in water, making them very bulky, so food needs to be processed to a certain degree to remove these substances before it can be consumed. Processing of food also removes some nutrients, although this is only possible if the processing is done at a temperature which minimizes biological degradation of carbohydrates, fats and proteins. High temperatures and acid conditions are required during the extraction process, which is one of the reasons why fibre becomes a major component of processed foods, because these processes tend to destroy a large part of the fiber molecules.

Fats, oils and salt are also important nutrients in food. The fat in plants is used for energy production by the organisms that consume them for energy. The oils are used to give foods a fatty, moist texture, while salt helps in preservation of the tastes of the food. However, the fats and oils are not the only sources of these nutrients, as some plant foods also contain compounds called vitamins and minerals, together with a variety of other chemical compounds.

Some of these food items are more soluble in water than others, which makes them less likely to be broken down into compounds that are excreted in the feces, while some are more resistant to degradation than others. This means that they are absorbed slowly by the digestive tract, and so their nutrients remain available to the human body throughout the entire day. Legumes and some other plant foods are examples of legumes, as they are one of the easiest foods to digest.