Nutrition

Biogeochemical cycles that are performed by living organisms and natural processes are water, carbon, nitrogen, phosphorus, and sulfur cycles.^[13] Nutrient cycles allow these essential elements to return back into the environment after being absorbed or consumed. Without proper nutrient cycling, there would be risk of change in oxygen levels, climate, and ecosystem function.

Foraging

Foraging is the process of seeking out nutrients in the environment. It may also be defined to include the subsequent use of the resources. Some organisms, such as animals and bacteria, can navigate to find nutrients, while others, such as plants and fungi, extend outward to find nutrients. Foraging may be random, in which the organism seeks nutrients without method, or it may be systematic, in which the organism can go directly to a food source.^[14] Organisms are able to detect nutrients through taste or other forms of nutrient sensing, allowing them to regulate nutrient intake.^[15] Optimal foraging theory is a model that explains foraging behavior as a cost–benefit analysis in which an animal must maximize the gain of nutrients while minimizing the amount of time and energy spent foraging. It was created to analyze the foraging habits of animals, but it can also be extended to other organisms.^[16] Some organisms are specialists that are adapted to forage for a single food source, while others are generalists that can consume a variety of food sources.^[17]

Nutrient deficiency

Nutrient deficiencies, known as malnutrition, occur when an organism does not have the nutrients that it needs. This may be caused by suddenly losing nutrients or the inability to absorb proper nutrients. Not only is malnutrition the result of a lack of necessary nutrients, but it can also be a result of other illnesses and health conditions. When this occurs, an organism will adapt by reducing energy consumption and expenditure to prolong the use of stored nutrients. It will use stored energy reserves until they are depleted, and it will then break down its own body mass for additional energy.^[18]

A balanced diet includes appropriate amounts of all essential and nonessential nutrients. These can vary by age, weight, sex, physical activity levels, and more. A lack of just one essential nutrient can cause bodily harm, just as an overabundance can cause toxicity. The Daily Reference Values keep the majority of people from nutrient deficiencies. DRVs are not recommendations but a combination of nutrient references to educate professionals and policymakers on what the maximum and minimum nutrient intakes are for the average person. Food labels also use DRVs as a reference to create safe nutritional guidelines for the average healthy person.^{[citation needed]}

In organisms

Animal

Animals are heterotrophs that consume other organisms to obtain nutrients. Herbivores are animals that eat plants, carnivores are animals that eat other animals, and omnivores are animals that eat both plants and other animals.^[19] Many herbivores rely on bacterial fermentation to create digestible nutrients from indigestible plant cellulose, while obligate carnivores must eat animal meats to obtain certain vitamins or nutrients their bodies cannot otherwise synthesize. Animals generally have a higher requirement of energy in comparison to plants.^[20] The macronutrients essential to animal life are carbohydrates, amino acids, and fatty acids.^[6][21]

All macronutrients except water are required by the body for energy, however, this is not their sole physiological function. The energy provided by macronutrients in food is measured in kilocalories, usually called Calories, where 1 Calorie is the amount of energy required to raise 1 kilogram of water by 1 degree Celsius.^[22]

Carbohydrates are molecules that store significant amounts of energy. Animals digest and metabolize carbohydrates to obtain this energy. Carbohydrates are typically synthesized by plants during metabolism, and animals have to obtain most carbohydrates from nature, as they have only a limited ability to generate them. They include sugars, oligosaccharides, and polysaccharides. Glucose is the simplest form of carbohydrate.^[23] Carbohydrates are broken down to produce glucose and short-chain fatty acids, and they are the most abundant nutrients for herbivorous land animals.^[24]

Lipids provide animals with fats and oils. They are not soluble in water, and they can store energy for an extended period of time. They can be obtained from many different plant and animal sources. Most dietary lipids are triglycerides, composed of glycerol and fatty acids. Phospholipids and sterols are found in smaller amounts.^[25] An animal's body will reduce the amount of fatty acids it produces as dietary fat intake increases, while it increases the amount of fatty acids it produces as carbohydrate intake increases.^[26]

Protein consumed by animals is broken down to amino acids, which would be later used to synthesize new proteins. Protein is used to form cellular structures, fluids,

Early human nutrition consisted of foraging for nutrients, like other animals, but it diverged at the beginning of the

Humans are omnivores that eat a variety of foods. Cultivation of cereals and production of bread has made up a key component of human nutrition since the beginning of agriculture. Early humans hunted animals for meat, and modern humans domesticate animals to consume their meat and eggs. The development of animal husbandry has also allowed humans in some cultures to consume the milk of other animals and process it into foods such as cheese. Other foods eaten by humans include nuts, seeds, fruits, and vegetables. Access to domesticated animals as well as vegetable oils has caused a significant increase in human intake of fats and oils. Humans have developed advanced methods of food processing that prevent contamination of pathogenic microorganisms and simplify the production of food. These include drying, freezing, heating, milling, pressing, packaging, refrigeration, and irradiation. Most cultures add herbs and spices to foods before eating to add flavor, though most do not significantly affect nutrition. Other additives are also used to improve the safety, quality, flavor, and nutritional content of food.^[33]

Humans obtain most carbohydrates as starch from cereals, though sugar has grown in importance.^[23] Lipids can be found in animal fat, butterfat, vegetable oil, and leaf vegetables, and they are also used to increase flavor in foods.^[25] Protein can be found in virtually all foods, as it makes up cellular material, though certain methods of food processing may reduce the amount of protein in a food.^[34] Humans can also obtain energy from ethanol, which is both a food and a drug, but it provides relatively few essential nutrients and is associated with nutritional deficiencies and other health risks.^[35]

In humans, poor nutrition can cause deficiency-related diseases, such as

Most plants obtain nutrients through inorganic substances

Fungi are chemoheterotrophs that consume external matter for energy. Most fungi absorb matter through the root-like mycelium, which grows through the organism's source of nutrients and can extend indefinitely. The fungus excretes extracellular enzymes to break down surrounding matter and then absorbs the nutrients through the cell wall. Fungi can be parasitic, saprophytic, or symbiotic. Parasitic fungi attach and feed on living hosts, such as animals, plants, or other fungi. Saprophytic fungi feed on dead and decomposing organisms. Symbiotic fungi grow around other organisms and exchange nutrients with them.^[48]

Protist

Protists include all eukaryotes that are not animals, plants, or fungi, resulting in great diversity between them. Algae are photosynthetic protists that can produce energy from light. Several types of protists use mycelium similar to those of fungi. Protozoa are heterotrophic protists, and different protozoa seek nutrients in different ways. Flagellate protozoa use a flagellum to assist in hunting for food, and some protozoa travel via infectious spores to act as parasites.^[49] Many protists are mixotrophic, having both phototrophic and heterotrophic characteristics. Mixotrophic protists will typically depend on one source of nutrients while using the other as a supplemental source or a temporary alternative when its primary source is unavailable.^[50]

Prokaryote

Prokaryotes, including bacteria and archaea, vary greatly in how they obtain nutrients across nutritional groups. Prokaryotes can only transport soluble compounds across their cell envelopes, but they can break down chemical components around them. Some lithotrophic prokaryotes are extremophiles that can survive in nutrient-deprived environments by breaking down inorganic matter.^[51] Phototrophic prokaryotes, such as cyanobacteria and Chloroflexia, can engage in photosynthesis to obtain energy from sunlight. This is common among bacteria that form in mats atop geothermal springs. Phototrophic prokaryotes typically obtain carbon from assimilating carbon dioxide through the Calvin cycle.^[52]

Some prokaryotes, such as Bdellovibrio and Ensifer, are predatory and feed on other single-celled organisms. Predatory prokaryotes seek out other organisms through chemotaxis or random collision, merge with the organism, degrade it, and absorb the released nutrients. Predatory strategies of prokaryotes include attaching to the outer surface of the organism and degrading it externally, entering the cytoplasm of the organism, or by entering the periplasmic space of the organism. Groups of predatory prokaryotes may forgo attachment by collectively producing hydrolytic enzymes.^[53]

See also

• Liebig's law of the minimum – Growth is limited by the scarcest resource
• Nutrient density – the proportion of any array of a single nutrient or nutritional factor, or of numerous nutrients in foods, often ordered by different scalar indicesPages displaying wikidata descriptions as a fallback
• Nutrition analysis
• Resource (biology) – substance or object in the environment required by an organism for normal growth, maintenance, and reproductionPages displaying wikidata descriptions as a fallback
• Substrate (biology) – Surface on which a plant or animal lives
• Milan Charter 2015 Charter on Nutrition

References

Bibliography

• Andrews, John H. (2017). Comparative Ecology of Microorganisms and Macroorganisms (2nd ed.). New York:
  ISBN 978-1-4939-6897-8
  .
• Mann, Jim; Truswell, A. Stewart, eds. (2012). Essentials of Human Nutrition (4th ed.). Oxford:
  ISBN 978-0-19-956634-1
  .
• Mengel, Konrad; Kirkby, Ernest A.; Kosegarten, Harald; Appel, Thomas, eds. (2001). Principles of Plant Nutrition (5th ed.). New York:
  S2CID 9332099
  .
• Simpson, Stephen J.; Raubenheimer, David (2012). The Nature of Nutrition: A Unifying Framework from Animal Adaptation to Human Obesity. Princeton:
  ISBN 978-1-4008-4280-3
  .
• Wu, Guoyao (2017). Principles of Animal Nutrition. Boca Raton:
  ISBN 978-1-351-64637-6
  .

External links

Look up nutrition in Wiktionary, the free dictionary.

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