The food chain refers to the network of all the plants and animals that together make up a particular food system. The word ‘food’ actually refers to a number of things that together make up this intricate network. Food is generally any material consumed to give nutrition to organisms, and is of plant, animal, or fungi origin. In fact, it is even possible to eat the organic material that makes up plants and some types of fungi.

Animals are classified as herbivores or carnivores, with plants being categorised as biovialivores, which feed on other living things. Herbivores and carnivores may eat almost the same amount of food, but they obtain different quantities of nutrients from their diet. Herbivores need more calories to obtain energy, whereas carnivores can derive energy from other food types. A human being requires about 4500 calories a day to maintain his body in a state of energy efficiency.

Plants are classified into two food groups – whole foods and parts of food. Fruits, vegetables, beans, grains and nuts are examples of whole foods. They provide the necessary nutrient intakes, in the right proportions, for the maintenance of the human body. Protein, iron, vitamin B12, zinc and other vitamins are contained in many whole foods, whereas other foods like meat, fish and other seafood provide only parts of the necessary food. Animal products, like milk and eggs, are included in parts of food.

The four food groups are separated by differences in the concentrations of different substances within the foods. Whole foods contain the necessary nutrients in abundance; to processed foods tend to contain less of the substances that are beneficial to the body. The fat content in whole foods is easily absorbed, while fats in processed foods are not readily absorbed. The sugar content in whole foods is not converted into sugar, whereas the sugar in processed foods is converted into glucose and stored as fat. Some of the important nutrients, present in both whole and processed foods, are protein, carbohydrates, minerals and vitamins.

Vitamins are soluble in water, while some vitamins are insoluble in water and others are both soluble and insoluble in water. Thus whole food vitamins and minerals can be assimilated by the body, either alone or together, as per the need. However, some vitamins and minerals need to be combined for greater benefits. Some of the commonly used vitamins are the B complex group of vitamins, which includes niacin, biotin, pantothenic acid, folic acid, calcium, iron and vitamin D. Vitamin E is also an important constituent of food, as it helps in the synthesis of many substances like lipid and carbohydrate molecules. In addition to these substances, food also contains small amounts of many other chemicals, called ‘carbons’, which are necessary for the existence of living organisms.

Chemical additives are added to food during processing, preparation, storage, cooling, heating and packaging. These ingredients may alter the physical form of the food, including taste, colour, scent, clarity and texture. The various chemicals used include salt, sugar, artificial flavours, as well as flavouring substances and colours. The food additives may be required for increasing the nutritional value of food, for preserving its freshness or to improve the taste. However, the chemicals used should be approved by the government for reasonable quantities, based on health and environmental effects.