
Food is any substance consumed by an
organism
An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
for
nutritional support. Food is usually of plant, animal, or
fungal origin and contains essential nutrients such as
carbohydrates,
fats,
proteins
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, re ...
,
vitamins, or
minerals. The substance is
ingested by an organism and assimilated by the organism's
cells to provide energy, maintain life, or stimulate growth. Different species of animals have different
feeding behaviours that satisfy the needs of their
metabolisms and have evolved to fill a specific
ecological niche within specific geographical contexts.
Omnivorous humans are highly adaptable and have adapted to obtaining food in many different ecosystems. Humans generally use
cooking
Cooking, also known as cookery or professionally as the culinary arts, is the art, science and craft of using heat to make food more palatable, digestible, nutritious, or Food safety, safe. Cooking techniques and ingredients vary widely, from ...
to prepare food for consumption. The majority of the
food energy required is supplied by the industrial
food industry, which produces food through
intensive agriculture and distributes it through complex
food processing
Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing takes many forms, from grinding grain into raw flour, home cooking, and complex industrial methods used in the mak ...
and
food distribution systems. This system of conventional agriculture relies heavily on
fossil fuels, which means that the food and agricultural systems are one of the
major contributors to climate change, accounting for as much as 37% of total
greenhouse gas emissions
Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...
.
The food system has a significant impact on a wide range of other social and political issues, including
sustainability
Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...
,
biological diversity,
economics
Economics () is a behavioral science that studies the Production (economics), production, distribution (economics), distribution, and Consumption (economics), consumption of goods and services.
Economics focuses on the behaviour and interac ...
,
population growth
Population growth is the increase in the number of people in a population or dispersed group. The World population, global population has grown from 1 billion in 1800 to 8.2 billion in 2025. Actual global human population growth amounts to aroun ...
,
water supply, and
food security
Food security is the state of having reliable access to a sufficient quantity of affordable, healthy Human food, food. The availability of food for people of any class, gender, ethnicity, or religion is another element of food protection. Simila ...
.
Food safety and security are monitored by international agencies, like the
International Association for Food Protection, the
World Resources Institute, the
World Food Programme, the
Food and Agriculture Organization
The Food and Agriculture Organization of the United Nations; . (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security. Its Latin motto, , translates ...
, and the
International Food Information Council.
Definition and classification
Food is any substance consumed to provide
nutritional support and energy to an
organism
An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
.
It can be raw, processed, or formulated and is consumed orally by animals for growth, health, or pleasure. Food is mainly composed of water,
lipids,
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s, and
carbohydrates. Minerals (e.g., salts) and organic substances (e.g.,
vitamins) can also be found in food. Plants,
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, and some microorganisms use
photosynthesis to make some of their own nutrients. Water is found in many foods and has been defined as food by itself. Water and
fiber have low energy densities, or
calories, while fat is the most energy-dense component.
Some inorganic (non-food) elements are also essential for plant and animal functioning.
Human food can be classified in various ways, either by related content or by how it is processed. The number and composition of
food groups can vary. Most systems include four basic groups that describe their origin and relative nutritional function: Vegetables and Fruit, Cereals and Bread, Dairy, and Meat. Studies that look into diet quality group food into whole grains/cereals, refined grains/cereals, vegetables, fruits, nuts, legumes, eggs, dairy products, fish, red meat, processed meat, and sugar-sweetened beverages. The
Food and Agriculture Organization
The Food and Agriculture Organization of the United Nations; . (FAO) is a specialized agency of the United Nations that leads international efforts to defeat hunger and improve nutrition and food security. Its Latin motto, , translates ...
and
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
use a system with nineteen food classifications: cereals, roots, pulses and nuts, milk, eggs, fish and shellfish, meat, insects, vegetables, fruits, fats and oils, sweets and sugars, spices and condiments, beverages, foods for nutritional uses, food additives, composite dishes and savory snacks.
Food sources

In a given ecosystem, food forms a
web of interlocking
chains with
primary producers at the bottom and
apex predators at the top.
Other aspects of the web include
detrovores (that eat
detritis) and
decomposers (that break down dead organisms).
Primary producers include algae, plants, bacteria and protists that acquire their energy from sunlight. Primary consumers are the
herbivores that consume the plants, and secondary consumers are the
carnivores that consume those herbivores. Some organisms, including most mammals and birds, have diets consisting of both animals and plants, and are considered omnivores.
The chain ends with the apex predators, the animals that have no known predators in its ecosystem. Humans are considered apex predators.
Humans are omnivores, finding sustenance in vegetables, fruits, cooked meat, milk, eggs, mushrooms and seaweed.
Cereal grain is a
staple food that provides more food energy worldwide than any other type of crop.
Corn (maize), wheat, and rice account for 87% of all grain production worldwide.
Just over half of the world's crops are used to feed humans (55 percent), with 36 percent grown as animal feed and 9 percent for
biofuels. Fungi and bacteria are also used in the preparation of
fermented foods like
bread
Bread is a baked food product made from water, flour, and often yeast. It is a staple food across the world, particularly in Europe and the Middle East. Throughout recorded history and around the world, it has been an important part of many cu ...
,
wine,
cheese
Cheese is a type of dairy product produced in a range of flavors, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk (usually the milk of cows, buffalo, goats or sheep). During prod ...
and
yogurt.
Photosynthesis
During
photosynthesis, energy from the sun is absorbed and used to transform water and carbon dioxide in the air or soil into oxygen and glucose. The oxygen is then released, and the glucose stored as an energy reserve. Photosynthetic plants, algae and certain bacteria often represent the lowest point of the food chains, making photosynthesis the primary source of energy and food for nearly all life on earth.
Plants also absorb important nutrients and minerals from the air, natural waters, and soil. Carbon, oxygen and hydrogen are absorbed from the air or water and are the basic nutrients needed for plant survival.
The three main nutrients absorbed from the soil for plant growth are nitrogen, phosphorus and potassium, with other important nutrients including calcium, sulfur, magnesium, iron boron, chlorine, manganese, zinc, copper molybdenum and nickel.
Microorganisms
Bacteria and other microorganisms also form the lower rungs of the food chain. They obtain their energy from photosynthesis or by breaking down dead organisms, waste or chemical compounds. Some form symbiotic relationships with other organisms to obtain their nutrients. Bacteria provide a source of food for protozoa, who in turn provide a source of food for other organisms such as small invertebrates. Other organisms that feed on bacteria include nematodes, fan worms, shellfish and a species of snail.
In the marine environment, plankton (which includes
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
,
archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
,
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
,
protozoa and microscopic
fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
)
provide a crucial source of food to many small and large aquatic organisms.
Without bacteria, life would scarcely exist because bacteria convert atmospheric nitrogen into nutritious
ammonia. Ammonia is the precursor to proteins, nucleic acids, and most vitamins. Since the advent of the industrial process for nitrogen fixation, the
Haber-Bosch Process, the majority of ammonia in the world is human-made.
Plants
Plants as a food source are divided into seeds, fruits, vegetables, legumes, grains and nuts.
Where plants fall within these categories can vary, with botanically described fruits such as the tomato, squash, pepper and eggplant or seeds like peas commonly considered vegetables. Food is a fruit if the part eaten is derived from the
reproductive tissue, so seeds, nuts and grains are technically fruit.
From a culinary perspective, fruits are generally considered the remains of botanically described fruits after grains, nuts, seeds and fruits used as vegetables are removed.
Grains can be defined as seeds that humans eat or harvest, with cereal grains (oats, wheat, rice, corn, barley, rye, sorghum and millet) belonging to the
Poaceae
Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...
(grass) family and pulses coming from the
Fabaceae (legume) family.
Whole grains are foods that contain all the elements of the original seed (bran, germ, and
endosperm
The endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the Embryo#Pla ...
). Nuts are dry fruits, distinguishable by their woody shell.
Fleshy fruits (distinguishable from dry fruits like grain, seeds and nuts) can be further classified as
stone fruits (cherries and peaches),
pome fruits (apples, pears),
berries (blackberry, strawberry),
citrus (oranges, lemon),
melons (watermelon, cantaloupe), Mediterranean fruits (grapes, fig),
tropical fruits (banana, pineapple).
Vegetables refer to any other part of the plant that can be eaten, including roots, stems, leaves, flowers, bark or the entire plant itself.
These include
root vegetables (potatoes and carrots), bulbs (onion family), flowers (cauliflower and broccoli),
leaf vegetables (
spinach and lettuce) and
stem vegetables (celery and
asparagus
Asparagus (''Asparagus officinalis'') is a perennial flowering plant species in the genus ''Asparagus (genus), Asparagus'' native to Eurasia. Widely cultivated as a vegetable crop, its young shoots are used as a spring vegetable.
Description ...
).
The carbohydrate, protein and lipid content of plants is highly variable. Carbohydrates are mainly in the form of starch, fructose, glucose and other sugars.
Most vitamins are found from plant sources, with the exception of
vitamin D and
vitamin B12.
Minerals can also be plentiful or not. Fruit can consist of up to 90% water, contain high levels of
simple sugars that contribute to their sweet taste, and have a high
vitamin C content.
Compared to fleshy fruit (excepting Bananas) vegetables are high in starch,
potassium, dietary fiber,
folate and vitamins and low in fat and calories. Grains are more starch based
and nuts have a high protein, fiber, vitamin E and B content.
Seeds are a good source of food for animals because they are abundant and contain fiber and healthful fats, such as
omega-3 fats.
Complicated chemical interactions can enhance or depress bioavailability of certain nutrients.
Phytates can prevent the release of some sugars and vitamins.
Animals that only eat plants are called
herbivores, with those that mostly just eat fruits known as
frugivores, while leaf and shoot eaters are
folivores (pandas) and wood eaters termed
xylophages (termites).
Frugivores include a diverse range of species from annelids to elephants, chimpanzees and many birds. About 182 fish consume seeds or fruit. Animals (domesticated and wild) use as many types of grasses that have adapted to different locations as their main source of nutrients.
Humans eat thousands of plant species; there may be as many as 75,000 edible species of
angiosperm
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed within a fruit ...
s, of which perhaps 7,000 are often eaten. Plants can be processed into breads, pasta, cereals, juices and jams or raw ingredients such as sugar, herbs, spices and oils can be extracted.
Oilseeds are pressed to produce rich oils
sunflower,
flaxseed,
rapeseed (including
canola oil) and
sesame.
[McGee, Chapter 9.]
Many plants and animals have
coevolved in such a way that the fruit is a good source of nutrition for the animal, who then excretes the seeds some distance away, allowing greater dispersal. Even
seed predation can be mutually beneficial, as some seeds can survive the digestion process. Insects are major eaters of seeds,
with ants being the only real seed dispersers. Birds, although being major dispersers, only rarely eat seeds as a source of food and can be identified by their thick beak that is used to crack open the seed coat. Mammals eat a more diverse range of seeds, as they are able to crush harder and larger seeds with their teeth.
Animals
Animals are used as food either directly or indirectly. This includes meat, eggs, shellfish and dairy products like milk and cheese. They are an important source of protein and are considered complete proteins for human consumption as they contain all the essential amino acids that the human body needs.
One steak, chicken breast or pork chop contains about 30 grams of protein. One large egg has 7 grams of protein. A serving of cheese has about 15 grams of protein. And of milk has about 8 grams of protein.
Other nutrients found in animal products include calories, fat, essential vitamins (including B12) and minerals (including zinc, iron, calcium, magnesium).
Food products produced by animals include milk produced by
mammary glands, which in many cultures is drunk or processed into
dairy products (cheese, butter, etc.).
Eggs laid by birds and other animals are eaten and
bees produce
honey
Honey is a sweet and viscous substance made by several species of bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of pl ...
, a reduced
nectar from flowers that is used as a popular sweetener in many cultures. Some cultures
consume blood, such as in
blood sausage, as a thickener for sauces, or in a
cured,
salted form for times of food scarcity, and others use blood in stews such as
jugged hare.
Taste
Animals, specifically humans, typically have five different types of tastes:
sweet,
sour
The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste. Taste is the perception stimulated when a substance in the mouth biochemistry, reacts chemically with taste receptor cells l ...
,
salty,
bitter, and
umami. The differing tastes are important for distinguishing between foods that are nutritionally beneficial and those which may contain harmful toxins.
As animals have
evolved, the tastes that provide the most energy are the most pleasant to eat while others are not enjoyable, although humans in particular can acquire a preference for some substances which are initially unenjoyable.
Water, while important for survival, has no taste.
Sweetness is almost always caused by a type of simple sugar such as
glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
or
fructose, or
disaccharides such as
sucrose, a molecule combining glucose and fructose.
[New Oxford American Dictionary] Sourness is caused by
acid
An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...
s, such as vinegar in alcoholic beverages. Sour foods include citrus, specifically lemons and
limes. Sour is evolutionarily significant as it can signal a food that may have gone
rancid due to bacteria. Saltiness is the taste of
alkali metal ions such as
sodium
Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
and potassium. It is found in almost every food in low to moderate proportions to enhance flavor. Bitter taste is a sensation considered unpleasant characterised by having a sharp, pungent taste. Unsweetened dark chocolate,
caffeine, lemon rind, and some types of fruit are known to be bitter. Umami, commonly described as savory, is a marker of proteins and characteristic of broths and cooked meats. Foods that have a strong umami flavor include cheese, meat and mushrooms.

While most animals taste buds are located in their mouth, some insects taste receptors are located on their legs and some fish have taste buds along their entire body.
Dogs, cats and birds have relatively few taste buds (chickens have about 30),
adult humans have between 2000 and 4000, while
catfish can have more than a million.
Herbivores generally have more than carnivores as they need to tell which plants may be poisonous.
Not all
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s share the same tastes: some
rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
s can taste
starch, cats cannot taste sweetness, and several
carnivores (including
hyenas, dolphins, and sea lions) have lost the ability to sense up to four of the five taste modalities found in humans.
Digestion
Food is broken into nutrient components through digestive process. Proper digestion consists of mechanical processes (
chewing,
peristalsis
Peristalsis ( , ) is a type of intestinal motility, characterized by symmetry in biology#Radial symmetry, radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an wikt:anterograde, anterograde dir ...
) and chemical processes (
digestive enzymes and
microorganisms). The digestive systems of herbivores and carnivores are very different as plant matter is harder to digest.
Carnivores mouths are designed for tearing and biting compared to the grinding action found in herbivores.
Herbivores however have comparatively longer digestive tracts and larger stomachs to aid in digesting the cellulose in plants.
Food safety
According to the
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
(WHO), about 600 million people worldwide get sick and 420,000 die each year from eating contaminated food.
Diarrhea is the most common illness caused by consuming contaminated food, with about 550 million cases and 230,000 deaths from diarrhea each year. Children under five years of age account for 40% of the burden of foodborne illness, with 125,000 deaths each year.
A 2003
World Health Organization
The World Health Organization (WHO) is a list of specialized agencies of the United Nations, specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Gen ...
(WHO) report concluded that about 30% of reported
food poisoning outbreaks in the WHO European Region occur in private homes. According to the WHO and
CDC, in the US alone, annually, there are 76 million cases of foodborne illness leading to 325,000 hospitalizations and 5,000 deaths.
From 2011 to 2016, on average, there were 668,673 cases of foodborne illness and 21 deaths each year.
In addition, during this period, 1,007 food poisoning outbreaks with 30,395 cases of food poisoning were reported.
See also
*
Food pairing
*
List of food and drink monuments
References
Further reading
* Collingham, E. M. (2011). ''The Taste of War: World War Two and the Battle for Food''
* Katz, Solomon (2003). ''The Encyclopedia of Food and Culture'', Scribner
* Mobbs, Michael (2012). ''Sustainable Food'' Sydney: NewSouth Publishing,
* Nestle, Marion (2007). ''Food Politics: How the Food Industry Influences Nutrition and Health'', University Presses of California, revised and expanded edition,
The Future of Food(2015). A panel discussion at the 2015 ''
Digital Life Design (DLD)'' Annual Conference. "How can we grow and enjoy food, closer to home, further into the future? ''
MIT Media Lab
The MIT Media Lab is a research laboratory at the Massachusetts Institute of Technology, growing out of MIT's Architecture Machine Group in the MIT School of Architecture and Planning, School of Architecture. Its research does not restrict to fi ...
's'' Kevin Slavin hosts a conversation with food artist, educator, and entrepreneur Emilie Baltz, professor Caleb Harper from ''MIT Media Lab's'' CityFarm project, the Barbarian Group's Benjamin Palmer, and Andras Forgacs, the co-founder and CEO of ''Modern Meadow'', who is growing 'victimless' meat in a lab. The discussion addresses issues of sustainable
urban farming, ecosystems, technology, food supply chains and their broad environmental and humanitarian implications, and how these changes in food production may change what people may find delicious ... and the other way around." Posted on the official YouTube Channel of ''
DLD''
External links
*
*
*
*
* of Food Timeline
Food BBC Radio 4 discussion with Rebecca Spang, Ivan Day and Felipe Fernandez-Armesto (''
In Our Time'', 27 December 2001)
{{Authority control
*
Food watchlist articles