In hospitals, nutrition may refer to the food requirements of patients, including nutritional solutions delivered via an IV (intravenous) or IG (intragastric) tube.
Nutritional science studies how the body breaks food down (catabolism) and how it repairs and creates cells and tissue (anabolism). Catabolism and anabolism combined can also be referred to as metabolism. Nutritional science also examines how the body responds to food.
- The human body requires seven major types of nutrients.
- Not all nutrients provide energy but are still important, such as water and fiber.
- Micronutrients are important but required in smaller amounts.
- Vitamins are essential organic compounds that the human body cannot synthesize.
What is nutrition?
As molecular biology, biochemistry, and genetics advance, nutrition has become more focused on metabolism and metabolic pathways - biochemical steps through which substances inside us are transformed from one form to another.
Nutrition also focuses on how diseases, conditions, and problems can be prevented or reduced with a healthy diet.
Similarly, nutrition involves identifying how certain diseases and conditions may be caused by dietary factors, such as poor diet (malnutrition), food allergies, and food intolerances.
Dietitian vs. nutritionist
A registered dietitian nutritionist (RD or RDN) studies food, nutrition, and dietetics through an accredited university and approved curriculum, then completes a rigorous internship and passes a licensure exam to become a registered dietitian.
A nutritionist (without the title of an RD or RDN) studies nutrition via self-study or through formal education but does not meet the requirements to use the titles RD or RDN. The two terms are often interchangeable, but they are not identical.
Dietetics is the interpretation and communication of the science of nutrition; it helps people make informed and practical choices about food and lifestyle in both health and disease.
Part of a dietician's course includes both hospital and community settings. Dietitians work in a variety of areas, from private practice to healthcare, education, corporate wellness, and research, while a much smaller proportion work in the food industry.
A dietitian must have a recognized degree or postgraduate degree in nutrition and dietetics and meet continuing education requirements to work as a dietitian.
Nutritionists sometimes carry out research for food manufacturers.
Nutrition is the study of nutrients in food, how the body uses nutrients, and the relationship between diet, health, and disease.
Major food manufacturers employ nutritionists and food scientists.
Nutritionists may also work in journalism, education, and research. Many nutritionists work in the field of food science and technology.
There is a lot of overlap between what nutritionists and dietitians do and study. Some nutritionists work in a healthcare setting, some dietitians work in the food industry, but a higher percentage of nutritionists work in the food industry and in food science and technology, and a higher percentage of dietitians work in healthcare, corporate wellness, research, and education.
A nutrient is a source of nourishment, a component of food, for instance, protein, carbohydrate, fat, vitamin, mineral, fiber, and water.
- Macronutrients are nutrients we need in relatively large quantities.
- Micronutrients are nutrients we need in relatively small quantities.
Macronutrients can be further split into energy macronutrients (that provide energy), and macronutrients that do not provide energy.
Energy macronutrients provide energy, which is measured either in kilocalories (kcal or calories) or Joules. 1 kilocalorie (calorie) = 4185.8 joules. Energy macronutrients include:
Carbohydrates - 4 kcal per gram
Carbohydrate molecules include monosaccharides (glucose, fructose, galactose), disaccharides, and polysaccharides (starch).
Nutritionally, polysaccharides are favored over monosaccharides because they are more complex and therefore take longer to break down and be absorbed into the bloodstream; this means that they do not cause major spikes in blood sugar levels, which are linked to heart and vascular diseases.
Proteins - 4 kcal per gram
There are 20 amino acids - organic compounds found in nature that combine to form proteins. Some amino acids are essential, meaning they need to be consumed. Other amino acids are non-essential because the body can make them.
Fats - 9 kcal per gram
Fats are triglycerides - three molecules of fatty acid combined with a molecule of the alcohol glycerol. Fatty acids are simple compounds (monomers) while triglycerides are complex molecules (polymers).
Fats are required in the diet for health as they serve many functions, including lubricating joints, helping organs produce hormones, assisting in absorption of certain vitamins, reducing inflammation, and preserving brain health.
Macronutrients that do not provide energy
These do not provide energy, but are still important:
Fiber consists mostly of carbohydrates. However, because it is not easily absorbed by the body, not much of the sugars and starches get into the blood stream. Fiber is a crucial part of nutrition, health, and fuel for gut bacteria.
For more details go to "What is fiber? What is dietary fiber?"
About 70 percent of the non-fat mass of the human body is water. It is vital for many processes in the human body.
Nobody is completely sure how much water the human body needs - claims vary from 1-7 liters per day to avoid dehydration. We do know that water requirements are very closely linked to body size, age, environmental temperatures, physical activity, different states of health, and dietary habits; for instance, somebody who consumes a lot of salt will require more water than another similar person.
Claims that 'the more water you drink, the healthier you are' are not backed with scientific evidence. The variables that influence water requirements are so vast that accurate advice on water intake would only be valid after evaluating each person individually.
Micronutrients are required in smaller quantities:
Minerals are found in a range of food types.
Dietary minerals are the other chemical elements our bodies need, other than carbon, hydrogen, oxygen, and nitrogen.
People with a well-balanced diet will, in most cases, obtain all the minerals they need from what they eat.
Minerals are sometimes added to certain foods to make up for any shortages.
The best example of this is iodized salt - iodine is added to prevent iodine deficiency, which affects about 2 billion people, globally; it causes mental retardation and thyroid gland problems. Iodine deficiency remains a serious public health problem in over half the planet.
Experts at the University of Florida say that 16 key minerals are essential for human biochemical processes:
What it does - a systemic (affects entire body) electrolyte, essential in co-regulating ATP (an important carrier of energy in cells in the body, also key in making RNA) with sodium.
Deficiency - hypokalemia - can profoundly affect the nervous system and heart.
Excess - hyperkalemia - can also profoundly affect the nervous system and heart.
What it does - key for producing stomach acid, important in the transport of molecules between cells, and vital for the proper functioning of nerves.
Deficiency - hypochloremia - low salt levels, which, if severe, can be very dangerous.
Excess - hyperchloremia - usually no symptoms, linked with excessive fluid loss.
What it does - a systemic electrolyte, and essential in regulating ATP with potassium. Important for nerve function and regulating body fluid levels.
Deficiency - hyponatremia - causes cells to malfunction; extremely low sodium can be fatal.
Excess - hypernatremia - can also cause cells to malfunction, extremely high levels can be fatal.
What it does - important for muscle, heart, and digestive health. Builds bone, assists in the synthesis and function of blood cells.
Deficiency - hypocalcaemia - muscle cramps, abdominal cramps, spasms, and hyperactive deep tendon reflexes.
Excess - hypercalcemia - muscle weakness, constipation, undermined conduction of electrical impulses in the heart, calcium stones in the urinary tract, impaired kidney function, and impaired absorption of iron, leading to iron deficiency.
What it does - important for the structure of DNA, transporter of energy (ATP), component of cellular membrane, helps strengthen bones.
Deficiency - hypophosphatemia, an example is rickets.
Excess - hyperphosphatemia, often a result of kidney failure.
What it does - processes ATP; required for good bones and management of proper muscle movement. Hundreds of enzymes rely on magnesium to work properly.
Deficiency - hypomagnesemia - irritability of the nervous system with spasms of the hands and feet, muscular twitching and cramps, constipation, and larynx spasms.
Excess - hypermagnesemia - nausea, vomiting, impaired breathing, low blood pressure. Very rare, but may occur if patient has renal problems.
What it does - required by many enzymes. Important for reproductive organ growth. Also important in gene expression and regulating the nervous and immune systems.
Deficiency - short stature, anemia, increased pigmentation of skin, enlarged liver and spleen, impaired reproductive function, impaired wound healing, and immune deficiency.
Excess - suppresses copper and iron absorption.
What it does - required for proteins and enzymes, especially hemoglobin, the oxygen-carrying compound in blood.
Deficiency - anemia.
Excess - iron overload disorder; iron deposits can form in organs, particularly the heart.
What it does - a cofactor in enzyme functions.
Deficiency - wobbliness, fainting, hearing loss, weak tendons and ligaments. Less commonly, can be a cause of diabetes.
Excess - interferes with the absorption of dietary iron.
What it does - component of many enzymes.
Deficiency - anemia or pancytopenia (reduction in the number of red and white blood cells, as well as platelets) and neurodegeneration.
Excess - can interfere with body's formation of blood cellular components; in severe cases, convulsions, palsy, and eventually death (similar to arsenic poisoning).
What it does - required for the biosynthesis of thyroxine (one type of thyroid hormone).
Deficiency - developmental delays, enlarged thyroid gland (in the neck), and fatigue.
Excess - can affect the function of the thyroid gland.
What it does - essential cofactor for antioxidant enzymes.
Deficiency - Keshan disease - myocardial necrosis (tissue death in the heart) leading to weakening of the heart; Kashin-Beck disease - break down of cartilage.
Excess - garlic-smelling breath, gastrointestinal disorders, hair loss, sloughing of nails, fatigue, irritability, and neurological damage.
What it does - vital part of three important enzyme systems, xanthine oxidase, aldehyde oxidase, and sulfite oxidase. It has a vital role in uric acid formation, in carbohydrate metabolism, and sulfite detoxification.
Deficiency - may affect metabolism and blood counts, but as this deficiency often occurs at the same time as other mineral deficiencies, it is hard to say which deficiency caused which health problem.
Excess - there is very little data on toxicity.
Our bodies cannot synthesize vitamins, so we must consume them.
These are organic compounds we require in tiny amounts.
An organic compound is any molecule that contains carbon.
It is called a vitamin when our bodies cannot synthesize (produce) enough or any of it, so we need to get it from our food.
Vitamins are classified as water soluble (they can be dissolved in water) or fat soluble (they can be dissolved in fat). For humans, there are four fat-soluble vitamins (A, D, E, and K) and nine water-soluble vitamins (eight B vitamins and vitamin C).
Water-soluble vitamins need to be consumed more regularly because they are eliminated faster (in urine) and are not easily stored.
Fat-soluble vitamins are absorbed through the intestines with the help of fats (lipids). They are more likely to accumulate in the body because they are harder to get rid of quickly. If too many vitamins build up, it is called hypervitaminosis. A very low-fat diet can affect the absorption of fat-soluble vitamins.
We know that most vitamins have many different functions. Below is a list of vitamins, and some of their roles. Note that most often vitamin overdose symptoms are related to supplementation or impaired metabolism or excretion, not vitamin intake from foods.
Chemical names - retinol, retinoids, and carotenoids.
Solubility - fat.
Deficiency disease - Night-blindness.
Overdose disease - Keratomalacia (degeneration of the cornea).
Chemical name - thiamine.
Solubility - water.
Deficiency disease - beriberi, Wernicke-Korsakoff syndrome.
Overdose disease - rare hypersensitive reactions resembling anaphylactic shock when an overdose is due to injection.
Chemical name - riboflavin.
Solubility - water.
Deficiency disease - ariboflavinosis (mouth lesions, seborrhea, and vascularization of the cornea).
Overdose disease - no known complications. Excess is excreted in urine.
Chemical name - niacin.
Solubility - water.
Deficiency disease - pellagra.
Overdose disease - liver damage, skin problems, and gastrointestinal complaints, plus other problems.
Chemical name - pantothenic acid.
Solubility - water.
Deficiency disease - paresthesia (tingling, pricking, or numbness of the skin with no apparent long-term physical effect).
Overdose disease - none reported.
Chemical names - pyridoxamine, pyridoxal.
Solubility - water.
Deficiency disease - anemia, peripheral neuropathy.
Overdose disease - nerve damage, proprioception is impaired (the ability to sense where parts of the body are in space).
Chemical name - biotin.
Solubility - water.
Deficiency disease - dermatitis, enteritis.
Overdose disease - none reported.
Chemical name - folinic acid.
Solubility - water.
Deficiency disease - birth defects.
Overdose disease - increased risk of seizures.
Chemical names - cyanocobalamin, hydroxycobalamin, methylcobalamin.
Solubility - water.
Deficiency disease - megaloblastic anemia (a defect in the production of red blood cells).
Overdose disease - none reported.
Chemical name - ascorbic acid.
Solubility - water.
Deficiency disease - scurvy, which can lead to a large number of complications.
Overdose disease - vitamin C megadose - diarrhea, nausea, skin irritation, burning upon urination, depletion of copper in the body, and higher risk of kidney stones.
Chemical names - ergocalciferol, cholecalciferol.
Solubility - fat.
Deficiency disease - rickets, osteomalacia (softening of bone), recent studies indicate higher risk of some cancers, autoimmune disorders, and chronic diseases
Overdose disease - hypervitaminosis D (headache, weakness, disturbed digestion, increased blood pressure, and tissue calcification).
Chemical name - tocotrienols.
Solubility - fat.
Deficiency disease - very rare, may include hemolytic anemia in newborn babies.
Overdose disease - dehydration, vomiting, irritability, constipation, build up of excess calcium.
Chemical names - phylloquinone, menaquinones.
Solubility - fat.
Deficiency disease - greater tendency to bleed and bruise.
Overdose disease - may undermine effects of warfarin.
Most foods contain a combination of some or all of the seven nutrient classes. We require some nutrients regularly, and others less frequently.
For nutrition science not specific to humans, see Nutrition.
Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and health. Generally, people can survive up to 40 days without food, a period largely dependent on the amount of water consumed, stored body fat, muscle mass and genetic factors.[medical citation needed]
Poor nutrition is a chronic problem often linked to poverty, a poor understanding of nutrition and dietary practices, and deficient sanitation and food security. Malnutrition and its consequences are large contributors to deaths and disabilities worldwide. Good nutrition helps children grow physically, promotes human biological development and helps in the eradication of poverty.
The human body contains chemical compounds, such as water, carbohydrates (sugar, starch, and fiber), amino acids (in proteins), fatty acids (in lipids), and nucleic acids (DNA and RNA). These compounds consist of elements such as carbon, hydrogen, oxygen, nitrogen, phosphorus, calcium, iron, zinc, magnesium, manganese, and so on. All the chemical compounds and elements contained in the human body occur in various forms and combinations such as hormones, vitamins, phospholipids and hydroxyapatite. These compounds may be found in the human body as well as in the various types of organisms that humans consume.[medical citation needed]
Any study done to determine nutritional status must take into account the state of the body before and after experiments, as well as the chemical composition of the whole diet and of all the materials excreted and eliminated from the body (including urine and feces). Comparing food to waste material can help determine the specific compounds and elements absorbed and metabolized by the body.[medical citation needed] The effects of nutrients may only be discernible over an extended period of time, during which all food and waste must be analyzed. The number of variables involved in such experiments is high, making nutritional studies time-consuming and expensive, which explains why the science of human nutrition is still slowly evolving.[medical citation needed]
Main article: Nutrient
The seven major classes of nutrients are carbohydrates, fats, fiber, minerals, proteins, vitamins, and water. These nutrient classes are categorized as either macronutrients or micronutrients (needed in small quantities). The macronutrients are carbohydrates, fats, fiber, proteins, and water. The micronutrients are minerals and vitamins.
The macronutrients (excluding fiber and water) provide structural material (amino acids from which proteins are built, and lipids from which cell membranes and some signaling molecules are built), and energy. Some of the structural material can also be used to generate energy internally, and in either case it is measured in Joules or kilocalories (often called "Calories" and written with a capital 'C' to distinguish them from little 'c' calories). Carbohydrates and proteins provide 17 kJ approximately (4 kcal) of energy per gram, while fats provide 37 kJ (9 kcal) per gram, though the net energy from either depends on such factors as absorption and digestive effort, which vary substantially from instance to instance.
Vitamins, minerals, fiber, and water do not provide energy, but are required for other reasons. A third class of dietary material, fiber (i.e., nondigestible material such as cellulose), seems also to be required, for both mechanical and biochemical reasons, though the exact reasons remain unclear. For all age groups, males need to consume higher amounts of macronutrients than females. In general, intakes increase with age until the second or third decade of life.
Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simple monosaccharides (glucose, fructose, galactose) to complex polysaccharides (starch). Fats are triglycerides, made of assorted fatty acidmonomers bound to a glycerol backbone. Some fatty acids, but not all, are essential in the diet: they cannot be synthesized in the body. Protein molecules contain nitrogen atoms in addition to carbon, oxygen, and hydrogen. The fundamental components of protein are nitrogen-containing amino acids, some of which are essential in the sense that humans cannot make them internally. Some of the amino acids are convertible (with the expenditure of energy) to glucose and can be used for energy production just as ordinary glucose. By breaking down existing protein, some glucose can be produced internally; the remaining amino acids are discarded, primarily as urea in urine. This occurs naturally when atrophy takes place, or during periods of starvation.
Main article: Carbohydrate
Carbohydrates may be classified as monosaccharides, disaccharides or polysaccharides depending on the number of monomer (sugar) units they contain. They are a diverse group of substances, with a range of chemical, physical and physiological properties. They make up a large part of foods such as rice, noodles, bread, and other grain-based products, but they are not an essential nutrient, meaning a human does not need to eat carbohydrates.
Monosaccharides contain one sugar unit, disaccharides two, and polysaccharides three or more. Monosaccharides include glucose, fructose and galactose. Disaccharides include sucrose, lactose, and maltose; purified sucrose, for instance, is used as table sugar. Polysaccharides, which include starch and glycogen, are often referred to as 'complex' carbohydrates because they are typically long multiple-branched chains of sugar units. The difference is that complex carbohydrates take longer to digest and absorb since their sugar units must be separated from the chain before absorption. The spike in blood glucose levels after ingestion of simple sugars is thought to be related to some of the heart and vascular diseases, which have become more common in recent times. Simple sugars form a greater part of modern diets than in the past, perhaps leading to more cardiovascular disease. The degree of causation is still not clear.[medical citation needed]
Simple carbohydrates are absorbed quickly, and therefore raise blood-sugar levels more rapidly than other nutrients. However, the most important plant carbohydrate nutrient, starch, varies in its absorption. Gelatinized starch (starch heated for a few minutes in the presence of water) is far more digestible than plain starch, and starch which has been divided into fine particles is also more absorbable during digestion. The increased effort and decreased availability reduces the available energy from starchy foods substantially and can be seen experimentally in rats and anecdotally in humans. Additionally, up to a third of dietary starch may be unavailable due to mechanical or chemical difficulty.[medical citation needed]
Main articles: Fat and Nutrition § Fat
A molecule of dietary fat typically consists of several fatty acids (containing long chains of carbon and hydrogen atoms), bonded to a glycerol. They are typically found as triglycerides (three fatty acids attached to one glycerol backbone). Fats may be classified as saturated or unsaturated depending on the detailed structure of the fatty acids involved. Saturated fats have all of the carbon atoms in their fatty acid chains bonded to hydrogen atoms, whereas unsaturated fats have some of these carbon atoms double-bonded, so their molecules have relatively fewer hydrogen atoms than a saturated fatty acid of the same length. Unsaturated fats may be further classified as monounsaturated (one double-bond) or polyunsaturated (many double-bonds). Furthermore, depending on the location of the double-bond in the fatty acid chain, unsaturated fatty acids are classified as omega-3 or omega-6 fatty acids. Trans fats are a type of unsaturated fat with trans-isomer bonds; these are rare in nature and in foods from natural sources; they are typically created in an industrial process called (partial) hydrogenation.
Many studies have shown that consumption of unsaturated fats, particularly monounsaturated fats, is associated with better health in humans. Saturated fats, typically from animal sources, are next in order of preference, while trans fats are associated with a variety of disease and should be avoided. Saturated and some trans fats are typically solid at room temperature (such as butter or lard), while unsaturated fats are typically liquids (such as olive oil or flaxseed oil). Trans fats are very rare in nature, but have properties useful in the food processing industry, such as rancidity resistance.
Most fatty acids are not essential, meaning the body can produce them as needed, generally from other fatty acids and always by expending energy to do so. However, in humans, at least two fatty acids are essential and must be included in the diet. An appropriate balance of essential fatty acids – omega-3 and omega-6 fatty acids – seems also important for health, though definitive experimental demonstration has been elusive. Both of these "omega" long-chain polyunsaturated fatty acids are substrates for a class of eicosanoids known as prostaglandins, which have roles throughout the human body. They are hormones, in some respects. The omega-3 eicosapentaenoic acid (EPA), which can be made in the human body from the omega-3 essential fatty acid alpha-linolenic acid (LNA), or taken in through marine food sources, serves as a building block for series 3 prostaglandins (e.g. weakly inflammatory PGE3). The omega-6 dihomo-gamma-linolenic acid (DGLA) serves as a building block for series 1 prostaglandins (e.g. anti-inflammatory PGE1), whereas arachidonic acid (AA) serves as a building block for series 2 prostaglandins (e.g., pro-inflammatory PGE 2). Both DGLA and AA can be made from the omega-6 linoleic acid (LA) in the human body, or can be taken in directly through food. An appropriately balanced intake of omega-3 and omega-6 partly determines the relative production of different prostaglandins: one reason a balance between omega-3 and omega-6 is believed important for cardiovascular health. In industrialized societies, people typically consume large amounts of processed vegetable oils, which have reduced amounts of the essential fatty acids along with too much of omega-6 fatty acids relative to omega-3 fatty acids.[medical citation needed]
Main article: Dietary fiber
Dietary fiber is a carbohydrate, specifically a polysaccharide, which is incompletely absorbed in humans and in some animals. Like all carbohydrates, when it is metabolized, it can produce four Calories (kilocalories) of energy per gram, but in most circumstances, it accounts for less than that because of its limited absorption and digestibility. The two subcategories are insoluble and soluble fiber. Insoluble dietary fiber consists mainly of cellulose, a large carbohydrate polymer that is indigestible by humans, because humans do not have the required enzymes to break it down, and the human digestive system does not harbor enough of the types of microbes that can do so. Soluble dietary fiber comprises a variety of oligosaccharides, waxes, esters, resistant starches, and other carbohydrates that dissolve or gelatinize in water. Many of these soluble fibers can be fermented or partially fermented by microbes in the human digestive system to produce short-chain fatty acids which are absorbed and therefore introduce some caloric content.[medical citation needed]
Whole grains, beans and other legumes, fruits (especially plums, prunes, and figs), and vegetables are good sources of dietary fiber. Fiber is important to digestive health and is thought to reduce the risk of colon cancer. For mechanical reasons, fiber can help in alleviating both constipation and diarrhea. Fiber provides bulk to the intestinal contents, and insoluble fiber especially stimulates peristalsis – the rhythmic muscular contractions of the intestines which move digesta along the digestive tract. Some soluble fibers produce a solution of high viscosity; this is essentially a gel, which slows the movement of food through the intestines. Additionally, fiber, perhaps especially that from whole grains, may help lessen insulin spikes and reduce the risk of type 2 diabetes.
Main article: Protein (nutrient)
Proteins are the basis of many animal body structures (e.g. muscles, skin, and hair) and form the enzymes which catalyse chemical reactions throughout the body. Each protein molecule is composed of amino acids which contain nitrogen and sometimes sulphur (these components are responsible for the distinctive smell of burning protein, such as the keratin in hair). The body requires amino acids to produce new proteins (protein retention) and to replace damaged proteins (maintenance). Amino acids are soluble in the digestive juices within the small intestine, where they are absorbed into the blood. Once absorbed, they cannot be stored in the body, so they are either metabolized as required or excreted in the urine.[medical citation needed]
Proteins consist of amino acids in different proportions. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition. Amino acids which an animal cannot synthesize on its own from smaller molecules are deemed essential. The synthesis of some amino acids can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress, and those are called conditionally essential.
A vegetarian diet can adequately supply protein, support pregnancy, childhood and athletic endeavors, and lower the risk of cardiovascular disease and cancer.
Main article: Mineral (nutrient)
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen that are present in nearly all organic molecules. The term "mineral" is archaic, since the intent is to describe simply the less common elements in the diet. Some are heavier than the four just mentioned – including several metals, which often occur as ions in the body. Some dietitians recommend that these be supplied from foods in which they occur naturally, or at least as complex compounds, or sometimes even from natural inorganic sources (such as calcium carbonate from ground oyster shells). Some are absorbed much more readily in the ionic forms found in such sources. On the other hand, minerals are often artificially added to the diet as supplements; the most well-known is likely iodine in iodized salt which prevents goiter.[medical citation needed]
Essential dietary minerals
include the following:[medical citation needed]
- Chlorine as chloride ions; very common electrolyte; see sodium, below.
- Magnesium, required for processing ATP and related reactions (builds bone, causes strong peristalsis, increases flexibility, increases alkalinity). Approximately 50% is in bone, the remaining 50% is almost all inside body cells, with only about 1% located in extracellular fluid. Food sources include oats, buckwheat, tofu, nuts, caviar, green leafy vegetables, legumes, and chocolate.
- Phosphorus, required component of bones; essential for energy processing. Approximately 80% is found in inorganic portion of bones and teeth. Phosphorus is a component of every cell, as well as important metabolites, including DNA, RNA, ATP, and phospholipids. Also important in pH regulation. Food sources include cheese, egg yolk, milk, meat, fish, poultry, whole-grain cereals, and many others.
- Potassium, a very common electrolyte (heart and nerve health). With sodium, potassium is involved in maintaining normal water balance, osmotic equilibrium, and acid-base balance. In addition to calcium, it is important in the regulation of neuromuscular activity. Food sources include bananas, avocados, vegetables, potatoes, legumes, fish, and mushrooms.
- Sodium, a very common electrolyte; not generally found in dietary supplements, despite being needed in large quantities, because the ion is very common in food: typically as sodium chloride, or common salt.
Many elements are required in smaller amounts (microgram quantities), usually because they play a catalytic role in enzymes. Some trace mineral elements (RDA < 200 mg/day) are, in alphabetical order:[medical citation needed]
- Cobalt as a component of the vitamin B12 family of coenzymes
- Copper required component of many redox enzymes, including cytochrome c oxidase
- Chromium required for sugar metabolism
- Iodine required not only for the biosynthesis of thyroxin, but probably, for other important organs as breast, stomach, salivary glands, thymus etc. (see Iodine deficiency); for this reason iodine is needed in larger quantities than others in this list, and sometimes classified with the macrominerals; It can be found in ionized salt
- Iron required for many enzymes, and for hemoglobin and some other proteins
- Manganese (processing of oxygen)
- Molybdenum required for xanthine oxidase and related oxidases
- Selenium required for peroxidase (antioxidant proteins)
- Zinc required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, carbonic anhydrase
Main article: Vitamin
As with the minerals discussed above, some vitamins are recognized as essential nutrients, necessary in the diet for good health. (Vitamin D is the exception: it can alternatively be synthesized in the skin, in the presence of UVB radiation.) Certain vitamin-like compounds that are recommended in the diet, such as carnitine, are thought useful for survival and health, but these are not "essential" dietary nutrients because the human body has some capacity to produce them from other compounds. Moreover, thousands of different phytochemicals have recently been discovered in food (particularly in fresh vegetables), which may have desirable properties including antioxidant activity (see below); experimental demonstration has been suggestive but inconclusive. Other essential nutrients not classed as vitamins include essential amino acids (see above), essential fatty acids (see above), and the minerals discussed in the preceding section.[medical citation needed]
Vitamin deficiencies may result in disease conditions: goiter, scurvy, osteoporosis, impaired immune system, disorders of cell metabolism, certain forms of cancer, symptoms of premature aging, and poor psychological health (including eating disorders), among many others.
Main article: Malnutrition
Malnutrition refers to insufficient, excessive, or imbalanced consumption of nutrients. In developed countries, the diseases of malnutrition are most often associated with nutritional imbalances or excessive consumption. Although there are more people in the world who are malnourished due to excessive consumption, according to the United Nations World Health Organization, the greatest challenge in developing nations today is not starvation, but insufficient nutrition – the lack of nutrients necessary for the growth and maintenance of vital functions. The causes of malnutrition are directly linked to inadequate macronutrient consumption and disease, and are indirectly linked to factors like “household food security, maternal and child care, health services, and the environment.” 
|Food Energy||starvation, marasmus||obesity, diabetes mellitus, cardiovascular disease|
|Simple carbohydrates||None.||diabetes mellitus, obesity|
|Saturated fat||low sex hormone levels||cardiovascular disease|
|Trans fat||none||cardiovascular disease|
|Fat||malabsorption of fat-soluble vitamins, rabbit starvation (if protein intake is high), during development: stunted brain development and reduced brain weight.||cardiovascular disease|
|Omega-3 fats||cardiovascular disease||bleeding, hemorrhages|
|Omega-6 fats||none||cardiovascular disease, cancer|
|Cholesterol||during development: deficiencies in myelinization of the brain.||cardiovascular disease|
|Iron||anemia||cirrhosis, cardiovascular disease|
|Iodine||goiter, hypothyroidism||Iodine toxicity (goiter, hypothyroidism)|
|Vitamin A||xerophthalmia and night blindness, low testosterone levels||hypervitaminosis A (cirrhosis, hair loss)|
|Vitamin B2||cracking of skin and corneal unclearation|
|Niacin||pellagra||dyspepsia, cardiac arrhythmias, birth defects|
|Vitamin B12||pernicious anemia|
|Vitamin C||scurvy||diarrhea causing dehydration|
|Vitamin D||rickets, osteoporosis, balance, immune system, inflammation||hypervitaminosis D (dehydration, vomiting, constipation)|
|Vitamin E||nervous disorders||hypervitaminosis E (anticoagulant: excessive bleeding)|
|Calcium||osteoporosis, tetany, carpopedal spasm, laryngospasm, cardiac arrhythmias||fatigue, depression, confusion, anorexia, nausea, vomiting, constipation, pancreatitis, increased urination|
|Magnesium||hypertension||weakness, nausea, vomiting, impaired breathing, and hypotension|
|Potassium||hypokalemia, cardiac arrhythmias||hyperkalemia, palpitations|
See also: Nootropic
Research indicates that improving the awareness of nutritious meal choices and establishing long-term habits of healthy eating has a positive effect on a cognitive and spatial memory capacity, potentially increasing a student's potential to process and retain academic information.
Some organizations have begun working with teachers, policymakers, and managed foodservice contractors to mandate improved nutritional content and increased nutritional resources in school cafeterias from primary to university level institutions. Health and nutrition have been proven to have close links with overall educational success. Currently less than 10% of American college students report that they eat the recommended five servings of fruit and vegetables daily. Better nutrition has been shown to affect both cognitive and spatial memory performance; a study showed those with higher blood sugar levels performed better on certain memory tests. In another study, those who consumed yogurt performed better on thinking tasks when compared to those who consumed caffeine free diet soda or confections. Nutritional deficiencies have been shown to have a negative effect on learning behavior in mice as far back as 1951."Better learning performance is associated with diet induced effects on learning and memory ability".
- The "nutrition-learning nexus" demonstrates the correlation between diet and learning and has application in a higher education setting..[medical citation needed]
- We find that better nourished children perform significantly better in school, partly because they enter school earlier and thus have more time to learn but mostly because of greater learning productivity per year of schooling."
- 91% of college students feel that they are in good health while only 7% eat their recommended daily allowance of fruits and vegetables.
- Nutritional education is an effective and workable model in a higher education setting.
- More "engaged" learning models that encompass nutrition is an idea that is picking up steam at all levels of the learning cycle.
Nutritional supplement treatment may be appropriate for major depression, bipolar disorder, schizophrenia, and obsessive compulsive disorder, the four most common mental disorders in developed countries. It is because Lakhan and Vieira mentioned that the supplements possess amino acids that may change into neurotransmitters and improve mental disorders. Supplements that have been studied most for mood elevation and stabilization include eicosapentaenoic acid and docosahexaenoic acid (each of which are an omega-3 fatty acid contained in fish oil, but not in flaxseed oil), vitamin B12, folic acid, and inositol.[medical citation needed]
Cancer has become common in developing countries. According to a study by the International Agency for Research on Cancer, "In the developing world, cancers of the liver, stomach and esophagus were more common, often linked to consumption of carcinogenic preserved foods, such as smoked or salted food, and parasitic infections that attack organs." Lung cancer rates are rising rapidly in poorer nations because of increased use of tobacco. Developed countries "tended to have cancers linked to affluence or a 'Western lifestyle' – cancers of the colon, rectum, breast and prostate – that can be caused by obesity, lack of exercise, diet and age."
A comprehensive worldwide report, "Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective", compiled by the World Cancer Research Fund and the American Institute for Cancer Research, reports that there is a significant relation between lifestyle (including food consumption) and cancer prevention. The same report recommends eating mostly foods of plant origin and aiming to meet nutritional needs through diet alone, while limiting consumption of energy-dense foods, red meat, alcoholic drinks and salt and avoiding sugary drinks, processed meat and moldy cereals (grains) or pulses (legumes). Protein consumption leads to an increase in IGF-1, which plays a role in cancer development.[medical citation needed]
Metabolic syndrome and obesity
Several lines of evidence indicate lifestyle-induced hyperinsulinemia and reduced insulin function (i.e. insulin resistance) as decisive factors in many disease states. For example, hyperinsulinemia and insulin resistance are strongly linked to chronic inflammation, which in turn is strongly linked to a variety of adverse developments such as arterial microinjuries and clot formation (i.e. heart disease) and exaggerated cell division (i.e. cancer). Hyperinsulinemia and insulin resistance (the so-called metabolic syndrome) are characterized by a combination of abdominal obesity, elevated blood sugar, elevated blood pressure, elevated blood triglycerides, and reduced HDL cholesterol.[medical citation needed]
Obesity can unfavourably alter hormonal and metabolic status via resistance to the hormone leptin, and a vicious cycle may occur in which insulin/leptin resistance and obesity aggravate one another. The vicious cycle is putatively fuelled by continuously high insulin/leptin stimulation and fat storage, as a result of high intake of strongly insulin/leptin stimulating foods and energy. Both insulin and leptin normally function as satiety signals to the hypothalamus in the brain; however, insulin/leptin resistance may reduce this signal and therefore allow continued overfeeding despite large body fat stores.[medical citation needed]
There is a debate about how and to what extent different dietary factors – such as intake of processed carbohydrates, total protein, fat, and carbohydrate intake, intake of saturated and trans fatty acids, and low intake of vitamins/minerals – contribute to the development of insulin and leptin resistance. Evidence indicates that diets possibly protective against metabolic syndrome include low saturated and trans fat intake and foods rich in dietary fiber, such as high consumption of fruits and vegetables and moderate intake of low-fat dairy products.
Global nutrition challenges
The challenges facing global nutrition are disease, child malnutrition, obesity, and vitamin deficiency.[medical citation needed]
The most common non-infectious diseases worldwide, that contribute most to the global mortality rate, are cardiovascular diseases, various cancers, diabetes, and chronic respiratory problems, all of which are linked to poor nutrition. Nutrition and diet are closely associated with the leading causes of death, including cardiovascular disease and cancer. Obesity and high sodium intake can contribute to ischemic heart disease, while consumption of fruits and vegetables can decrease the risk of developing cancer.
Foodborne and infectious diseases can result in malnutrition, and malnutrition exacerbates infectious disease. Poor nutrition leaves children and adults more susceptible to contracting life-threatening diseases such as diarrheal infections and respiratory infections. According to the WHO, in 2011, 6.9 million children died of infectious diseases like pneumonia, diarrhea, malaria, and neonatal conditions, of which at least one third were associated with undernutrition.
Main article: Child malnutrition
According to UNICEF, in 2011, 101 million children across the globe were underweight and one in four children, 165 million, were stunted in growth. Simultaneously, there are 43 million children under five who are overweight or obese. Nearly 20 million children under 5 suffer from severe acute malnutrition, a life-threatening condition requiring urgent treatment. According to estimations at UNICEF, hunger will be responsible for 5.6 million deaths of children under the age of five this year. These all represent significant public health emergencies. This is because proper maternal and child nutrition has immense consequences for survival, acute and chronic disease incidence, normal growth, and economic productivity of individuals.
Childhood malnutrition is common and contributes to the global burden of disease. Childhood is a particularly important time to achieve good nutrition status, because poor nutrition has the capability to lock a child in a vicious cycle of disease susceptibility and recurring sickness, which threatens cognitive and social development. Undernutrition and bias in access to food and health services leaves children less likely to attend or perform well in school.
Main article: Undernutrition
UNICEF defines undernutrition “as the outcome of insufficient food intake (hunger) and repeated infectious diseases. Under nutrition includes being underweight for one’s age, too short for one’s age (stunted), dangerously thin (wasted), and deficient in vitamins and minerals (micronutrient malnutrient). Under nutrition causes 53% of deaths of children under five across the world. It has been estimated that undernutrition is the underlying cause for 35% of child deaths. The Maternal and Child Nutrition Study Group estimate that under nutrition, “including fetal growth restriction, stunting, wasting, deficiencies of vitamin A and zinc along with suboptimum breastfeeding- is a cause of 3.1 million child deaths and infant mortality, or 45% of all child deaths in 2011”.
When humans are undernourished, they no longer maintain normal bodily functions, such as growth, resistance to infection, or have satisfactory performance in school or work. Major causes of under nutrition in young children include lack of proper breast feeding for infants and illnesses such as diarrhea, pneumonia, malaria, and HIV/AIDS. According to UNICEF 146 million children across the globe, that one out of four under the age of five, are underweight. The amount of underweight children has decreased since 1990, from 33 percent to 28 percent between 1990 and 2004. Underweight and stunted children are more susceptible to infection, more likely to fall behind in school, more likely to become overweight and develop non-infectious diseases, and ultimately earn less than their non-stunted coworkers. Therefore, undernutrition can accumulate deficiencies in health which results in less productive individuals and societies 
Many children are born with the inherent disadvantage of low birth weight, often caused by intrauterine growth restriction and poor maternal nutrition, which results in worse growth, development, and health throughout the course of their lifetime. Children born at low birthweight (less than 5.5 pounds or 2.5 kg), are less likely to be healthy and are more susceptible to disease and early death. Those born at low birthweight also are likely to have a depressed immune system, which can increase their chances of heart disease and diabetes later on in life. Because 96% of low birthweight occurs in the developing world, low birthweight is associated with being born to a mother in poverty with poor nutritional status that has had to perform demanding labor.
Stunting and other forms of undernutrition reduces a child’s chance of survival and hinders their optimal growth and health. Stunting has demonstrated association with poor brain development, which reduces cognitive ability, academic performance, and eventually earning potential. Important determinants of stunting include the quality and frequency of infant and child feeding, infectious disease susceptibility, and the mother’s nutrition and health status. Undernourished mothers are more likely to birth stunted children, perpetuating a cycle of undernutrition and poverty. Stunted children are more likely to develop obesity and chronic diseases upon reaching adulthood. Therefore, malnutrition resulting in stunting can further worsen the obesity epidemic, especially in low and middle income countries. This creates even new economic and social challenges for vulnerable impoverished groups.
Data on global and regional food supply shows that consumption rose from 2011-2012 in all regions. Diets became more diverse, with a decrease in consumption of cereals and roots and an increase in fruits, vegetables, and meat products. However, this increase masks the discrepancies between nations, where Africa, in particular, saw a decrease in food consumption over the same years. This information is derived from food balance sheets that reflect national food supplies, however, this does not necessarily reflect the distribution of micro and macronutrients. Often inequality in food access leaves distribution which uneven, resulting in undernourishment for some and obesity for others.
Undernourishment, or hunger, according to the FAO, is dietary intake below the minimum daily energy requirement. The amount of undernourishment is calculated utilizing the average amount of food available for consumption, the size of the population, the relative disparities in access to the food, and the minimum calories required for each individual. According to FAO, 868 million people (12% of the global population) were undernourished in 2012. This has decreased across the world since 1990, in all regions except for Africa, where undernourishment has steadily increased. However, the rates of decrease are not sufficient to meet the first Millennium Development Goal of halving hunger between 1990 and 2015. The global financial, economic, and food price crisis in 2008 drove many people to hunger, especially women and children. The spike in food prices prevented many people from escaping poverty, because the poor spend a larger proportion of their income on food and farmers are net consumers of food. High food prices cause consumers to have less purchasing power and to substitute more-nutritious foods with low-cost alternatives.
Adult overweight and obesity
Main articles: Overnutrition, Obesity, and Overweight
Malnutrition in industrialized nations is primarily due to excess calories and non-nutritious carbohydrates, which has contributed to the obesity epidemic affecting both developed and some developing nations. In 2008, 35% of adults above the age of 20 years were overweight (BMI 25 kg/m), a prevalence that has doubled worldwide between 1980 and 2008. Also 10% of men and 14% of women were obese, with an BMI greater than 30. Rates of overweight and obesity vary across the globe, with the highest prevalence in the Americas, followed by European nations, where over 50% of the population is overweight or obese.
Obesity is more prevalent amongst high income and higher middle income groups than lower divisions of income. Women are more likely than men to be obese, where the rate of obesity in women doubled from 8% to 14% between 1980 and 2008. Being overweight as a child has become an increasingly important indicator for later development of obesity and non-infectious diseases such as heart disease. In several western European nations, the prevalence of overweight and obese children rose by 10% from 1980 to 1990, a rate that has begun to accelerate recently.
Vitamin and mineral malnutrition
vitamins and minerals are essential to the proper functioning and maintenance of the human body. Globally, particularly in developing nations, deficiencies in Iodine, Iron, and Zinc among others are said to impair human health when these minerals are not ingested in an adequate quantity. There are 20 trace elements and minerals that are essential in small quantities to body function and overall human health.
Iron deficiency is the most common inadequate nutrient worldwide, affecting approximately 2 billion people. Globally, anemia affects 1.6 billion people, and represents a public health emergency in children under five and mothers. The World Health Organization estimates that there exists 469 million women of reproductive age and approximately 600 million preschool and school-age children worldwide who are anemic. Anemia, especially iron-deficient anemia, is a critical problem for cognitive developments in children, and its presence leads to maternal deaths and poor brain and motor development in children. The development of anemia affects mothers and children more because infants and children have higher iron requirements for growth. Health consequences for iron deficiency in young children include increased perinatal mortality, delayed mental and physical development, negative behavioral consequences, reduced auditory and visual function, and impaired physical performance. The harm caused by iron deficiency during child development cannot be reversed and result in reduced academic performance, poor physical work capacity, and decreased productivity in adulthood. Mothers are also very susceptible to iron-deficient anemia because women lose iron during menstruation, and rarely supplement it in their diet. Maternal iron deficiency anemia increases the chances of maternal mortality, contributing to at least 18% of maternal deaths in low and middle income countries.
Vitamin A plays an essential role in developing the immune system in children, therefore, it is considered an essential micronutrient that can greatly affect health. However, because of the expense of testing for deficiencies, many developing nations have not been able to fully detect and address vitamin A deficiency, leaving vitamin A deficiency considered a silent hunger. According to estimates, subclinical vitamin A deficiency, characterized by low retinol levels, affects 190 million pre-school children and 19 million mothers worldwide. The WHO estimates that 5.2 million of these children under 5 are affected by night blindness, which is considered clinical vitamin A deficiency. Severe vitamin A deficiency (VAD) for developing children can result in visual impairments, anemia and weakened immunity, and increase their risk of morbidity and mortality from infectious disease. This also presents a problem for women, with WHO estimating that 9.8 million women are affected by night blindness. Clinical vitamin A deficiency is particularly common among pregnant women, with prevalence rates as high as 9.8% in South-East Asia.
Estimates say that 28.5% of the global population is iodine deficient, representing 1.88 billion individuals. Although salt iodization programs have reduced the prevalence of iodine deficiency, this is still a public health concern in 32 nations. Moderate deficiencies are common in Europe and Africa, and over consumption is common in the Americas. Iodine-deficient diets can interfere with adequate thyroid hormone production, which is responsible for normal growth in the brain and nervous system. This ultimately leads to poor school performance and impaired intellectual capabilities.
Infant and young child feeding
Improvement of breast feeding practices, like early initiation and exclusive breast feeding for the first two years of life, could save the lives of 1.5 million children annually. Nutrition interventions targeted at infants aged 0–5 months first encourages early initiation of breastfeeding. Though the relationship between early initiation of breast feeding and improved health outcomes has not been formally established, a recent study in Ghana suggests a causal relationship between early initiation and reduced infection-caused neo-natal deaths. Also, experts promote exclusive breastfeeding, rather than using formula, which has shown to promote optimal growth, development, and health of infants.