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Human Nutrition

Human nutrition is the provision to obtain the materials necessary to support citation needed].


[edit] Overview

Nutritional science investigates the metabolic pathways: the sequences of biochemical steps through which substances in living things change from one form to another.

The human body and in the plant and animal organisms that humans eat.

The human body consists of elements and compounds ingested, digested, absorbed, and circulated through the feces.

Studies of nutritional status must take into account the state of the body before and after experiments, as well as the experiments is high, making nutritional studies time-consuming and expensive, which explains why the science of human nutrition is still slowly evolving.

[edit] Nutrients

There are seven major classes of nutrients: water.

These nutrient classes can be categorized as either micronutrients (needed in smaller 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), [3] 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., non-digestible material such as cellulose), seems also to be required, for both mechanical and biochemical reasons, though the exact reasons remain unclear.

Molecules of carbohydrates and fats consist of carbon, hydrogen, and oxygen atoms. Carbohydrates range from simple atrophy takes place, or during periods of starvation.

Other micronutrients include phytochemicals which are said to influence (or protect) some body systems. Their necessity is not as well established as in the case of, for instance, vitamins.

Most foods contain a mix of some or all of the nutrient classes, together with other substances such as toxins or various sorts. Some nutrients can be stored internally (e.g., the fat soluble vitamins), while others are required more or less continuously. Poor health can be caused by a lack of required nutrients or, in extreme cases, too much of a required nutrient. For example, both salt and water (both absolutely required) will cause illness or even death in too large amounts.

[edit] Carbohydrates

Grain products: rich sources of complex and simple carbohydrates

Carbohydrates may be classified as grain-based products.

Monosaccharides contain one sugar unit, disaccharides two, and polysaccharides three or more. Polysaccharides 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 frequent in recent times. Simple sugars form a greater part of modern diets than formerly, perhaps leading to more cardiovascular disease. The degree of causation is still not clear, however.

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.

[edit] Fat

A molecule of dietary fat typically consists of several hydrogenation.

Many studies have shown that unsaturated fats, particularly monounsaturated fats, are best in the human diet. Saturated fats, typically from animal sources, are next, while trans fats are to be avoided. Saturated and some trans fats are typically solid at room temperature (such as citation needed]

[edit] Essential fatty acids

Most fatty acids are non-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 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.

Omega-3 EPA prevents fat from being released from the wild, thereby skewing prostaglandin balance away from pro-inflammatory PGE2 (made from AA) toward fat PGE1 (made from DGLA). Moreover, the conversion (desaturation) of DGLA to AA is controlled by the fat mitosis (cell division).

Good sources of essential fatty acids include most vegetables, nuts, seeds, and marine oils.[4] Some of the best sources are fish, flax seed oils, soy beans, pumpkin seeds, sunflower seeds, and walnuts.

[edit] Fiber

Dietary fiber is a citation needed]

[edit] Protein

Proteins are the basis of many animal body structures (e.g. muscles, skin, and hair). They also form the enyzmes which catalyse chemical reactions throughout the body. Each molecule is composed of amino acids which are characterized by containing 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 metabolised as required or excreted in the urine.

For all animals, some amino acids are non-essential (the animal can produce them from other amino acids). Twenty two amino acids can be found in the human body, and about ten of these are essential, and therefore must be included in the diet. A diet that contains adequate amounts of amino acids (especially those that are essential) is particularly important in some situations: during early development and maturation, pregnancy, lactation, or injury (a burn, for instance). A complete protein source contains all the essential amino acids; an incomplete protein source lacks one or more of the essential amino acids.

It is a common misconception that a vegans of any age and gender, with a healthy diet, can flourish throughout all stages of life, although the latter group typically need to pay more attention to their nutrition than the former.

Rice and beans supply amino acids as protein sources

Sources of dietary protein include gluconeogenesis; this is done in quantity only during starvation.

[edit] Minerals

Dietary minerals are the goiter.

A [6]

[edit] Essential dietary minerals

Many elements are essential in relative quantity; they are usually called “bulk minerals” requiring daily milligram quantities. Some are structural, but many play a role as electrolytes.[7] Elements with recommended dietary allowance (RDA) greater than 200 mg/day are, in alphabetical order (with informal or folk-medicine perspectives in parentheses):

  • Calcium, a common electrolyte, but also needed structurally (for muscle and digestive system health, bones, some forms neutralize acidity, may help clear toxins, and provide signaling ions for nerve and membrane functions). 99% of calcium is found in bones and teeth. Food sources include , milk products, sardines, clams, oysters, kale, turnip greens, mustard greens, and tofu. </ref>{{cite book [ authors= L. Kathleen Mahan, Janice L. Raymond, Sylvia Escott-Stump ] title= Krausw’s Food and the Nutrition Care Process ] [13th edition] [publisher=Elsevier] [Location=St. Louis] [year=2012] [isbn=978-1-4377-2233-8}}</ref>
  • chloride ions; very common electrolyte; see sodium, below
  • 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 Whole-grain cereals, tofu nuts, meat, milk, green vegetables, legumes, and chocolate. </ref>{{cite book [ authors= L. Kathleen Mahan, Janice L. Raymond, Sylvia Escott-Stump ] title= Krausw’s Food and the Nutrition Care Process ] [13th edition] [publisher=Elsevier] [Location=St. Louis] [year=2012] [isbn=978-1-4377-2233-8}}</ref>
  • Phosphorus, required component of bones; essential for energy processing[8] 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. </ref>{{cite book [ authors= L. Kathleen Mahan, Janice L. Raymond, Sylvia Escott-Stump ] title= Krausw’s Food and the Nutrition Care Process ] [13th edition] [publisher=Elsevier] [Location=St. Louis] [year=2012] [isbn=978-1-4377-2233-8}}</ref>
  • 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 fruits, vegetables, fresh meat, and dairy products. </ref>{{cite book [ authors= L. Kathleen Mahan, Janice L. Raymond, Sylvia Escott-Stump ] title= Krausw’s Food and the Nutrition Care Process ] [13th edition] [publisher=Elsevier] [Location=St. Louis] [year=2012] [isbn=978-1-4377-2233-8}}</ref>
  • sodium chloride, or common salt

[edit] Trace minerals

Many elements are required in smaller amounts (microgram quantities), usually because they play a catalytic role in enzymes.[9] Some trace mineral elements (RDA < 200 mg/day) are, in alphabetical order:

[edit] Vitamins

As with the minerals discussed above, some vitamins are recognized as essential nutrients, necessary in the diet for good health. (above), and the minerals discussed in the preceding section.

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.[10] Excess of some vitamins is also dangerous to health (notably vitamin A), and for at least one vitamin, B6, toxicity begins at levels not far above the required amount. Deficiency or excess of minerals can also have serious health consequences.

[edit] Water

A manual China

About 70% of the non-fat mass of the human body is made of water.[11] To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors.[citation needed] With physical exertion and heat exposure, water loss increases and daily fluid needs will eventually increase as well.

It is not fully clear how much water intake is needed by healthy people, although some experts assert that 8–10 glasses of water (approximately 2 liters) daily is the minimum to maintain proper hydration.[17]

For those who have healthy kidneys, it is somewhat difficult to drink too much water,[water intoxication, which can be fatal. In particular, large amounts of de-ionized water are dangerous.

Normally, about 20 percent of water intake comes in food,[water vapor in the exhaled breath.

[edit] Phytochemicals

Other food compounds include antioxidant phytochemicals. These substances are generally more recent discoveries which have not yet been recognized as vitamins or as required nutrients. Phytochemicals may act as antioxidants citation needed]

[edit] Antioxidants

Antioxidants are a recent discovery.[free radicals can form. Most of these are oxidizers (i.e. acceptors of electrons) and some react very strongly. For normal cellular maintenance, growth, and division, these free radicals must be sufficiently neutralized by antioxidant compounds.

[edit] Other compounds

A growing area of interest is the effect upon human health of undefined natural compounds, collectively called reactive oxygen species which may be involved in certain diseases, but there remains no scientific evidence for the activity or benefit of polyphenols as antioxidants in the human body.

A well-studied example phytochemical is [19] A second carotenoid, lutein, has also been shown in preliminary studies to possibly affect AMD. Both compounds have been observed to collect in the retina following digestion and possibly to protect the rods and cones against intense light.

Pro-vitamin A carotenoids, such as beta-carotene and beta-cryptoxanthin, contribute to vitamin A levels in the body, and are under research for potential anti-disease mechanisms, such as in arthritis.[20] Similarly, a red carotenoid, lycopene in preliminary research for its effects on prostate cancer, is prevalent in tomatoes. It is released more effectively from cells in processed tomato products such as commercial pasta sauce or tomato soup, than in fresh intact tomatoes. Yet, such sauces tend to have high amounts of salt, sugar, and other substances a person may wish or even need to avoid.

Lutein, as another carotenoid example, occurs in many yellow and orange fruits and vegetables. One study indicates that the lutein present in egg yolk may be more readily absorbed than the lutein from vegetable sources, possibly because of fat solubility.[21]

The following table presents phytochemical groups and common sources, arranged by family:

Family Sources Preliminary research
flavonoids tea general antioxidant
phytoestrogens) kudzu root general antioxidant
isothiocyanates cruciferous vegetables enzymes
monoterpenes citrus peels, essential oils, herbs, spices, green plants, atmosphere[22] anti-cancer research in vitro
organosulfur compounds onions research on LDLs
saponins herbs possible antioxidant
capsaicinoids all capiscum (chile) peppers research on cancer cell apoptosis in vitro

[edit] Intestinal bacterial flora

It is also known that human vitamin B12; and defending against some infectious diseases.

[edit] Advice and guidance

[edit] United States Governmental policies

The updated humans.

In the US, mandatory disclosure/labeling requirements for processed food manufacturers and restaurants to assist consumers in complying with such guidance.

In the US, nutritional standards and recommendations are established jointly by the C-SPAN as seen here.

The U.S. Department of Health and Human Services provides a sample week-long menu which fulfills the nutritional recommendations of the government.[23] Canada’s Food Guide is another governmental recommendation.

[edit] Teaching

Nutrition is Personal and Social Education and Food Technology curricula include nutrition, stressing the importance of a balanced diet and teaching how to read nutrition labels on packaging. In many schools a Nutrition class will fall within the Family and Consumer Science or Health departments. In some American schools, students are required to take a certain number of FCS or Health related classes. Nutrition is offered at many schools, and if it is not a class of its own, nutrition is included in other FCS or Health classes such as: Life Skills, Independent Living, Single Survival, Freshmen Connection, Health etc. In many Nutrition classes, students learn about the food groups, the food pyramid, Daily Recommended Allowances, calories, vitamins, minerals, malnutrition, physical activity, healthy food choices and how to live a healthy life.

A 1985 US [25]

[edit] Healthy diets

The United Healthcare / Pacificare nutrition guideline recommends the following foods per day to enhance your health (based on a 2,000 calorie diet)[26]

  • Grains: 6 oz per day ‘Make half your grains whole’
  • Vegetables: 2.5 cups per day ‘Vary your veggies’
  • Fruits: 2 cups per day ‘Focus on fruits ‘
  • Milk: 3 cups per day ‘Get your calcium-rich foods’
  • Meat and beans: 5.5 oz per day ‘Go lean with protein’.

Heart disease, cancer, obesity, and diabetes are commonly called “Western” diseases because these maladies were once rarely seen in developing countries. [27]

A citation needed]

The National Geographic article noted that an Seventh-day Adventists between 1976 and 1988 “…found that the Adventists’ habit of consuming beans, soy milk, tomatoes, and other fruits lowered their risk of developing certain cancers. It also suggested that eating whole grain bread, drinking five glasses of water a day, and, most surprisingly, consuming four servings of nuts a week reduced their risk of heart disease.”

[edit] The French “paradox”

It has been discovered that people living in France live longer.[citation needed] A number of explanations have been suggested:

  • Reduced consumption of processed carbohydrate and other junk foods.
  • Regular consumption of red wine.
  • More active lifestyles involving plenty of daily exercise, especially walking; the French are much less dependent on cars than Americans.
  • Higher consumption of artificially produced trans-fats by Americans, which has been shown to have greater lipoprotein effects per gram than saturated fat.[28]

However, statistics collected by the World Health Organization from 1990-2000 show that the incidence of heart disease in France may have been underestimated and in fact be similar to that of neighboring countries.[29]

[edit] Sports nutrition

Individuals with highly active lifestyles require more nutrients.

[edit] Protein

Protein milkshakes, made from protein powder (center) and milk (left), are a common bodybuilding supplement.

Protein is an important component of every cell in the body. Hair and nails are mostly made of protein. The body uses protein to build and repair tissues. Also protein is used to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin, and blood.

The protein requirement for each individual differs, as do opinions about whether and to what extent physically active people require more protein. The 2005 [31]

[edit] Water and salts

Water is one of the most important nutrients in the sports diet. It helps eliminate food waste products in the body, regulates body temperature during activity and helps with digestion. Maintaining hydration during periods of physical exertion is key to peak performance. While drinking too much water during activities can lead to physical discomfort, dehydration in excess of 2% of body mass (by weight) markedly hinders athletic performance.[32] Water and salt dosage is based on work performed, lean body mass, and environmental factors, especially ambient temperature and humidity. Maintaining the right amount is key.

Additional carbohydrates and protein taken before, during, and after exercise will improve endurance (increase time to exhaustion) as well as speed recovery as long as the exercise is compatible with digestion of the substance taken, e.g. a steak eaten while running a marathon may not be fully digested and may hinder performance.

[edit] Carbohydrates

The main fuel used by the body during exercise is carbohydrates, which is stored in muscle as glycogen—a form of sugar. During exercise, muscle glycogen reserves can be used up, especially when activities last longer than 90 min.[citation needed] Because the amount of glycogen stored in the body is limited, it is important for athletes to replace glycogen by consuming a diet high in carbohydrates. Meeting energy needs can help improve performance during the sport, as well as improve overall strength and endurance.

There are different kinds of carbohydrates: simple (for example from fruits) and complex (for example from grains such as wheat). Simple sugars can be from an unrefined natural source, or may be refined and added to processed food. A typical American consumes about 50% of their carbohydrates as refined sugars. Over the course of a year, the average American consumes 204 [34]

[edit] 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 real challenge in developing nations today, more than starvation, is combating insufficient nutrition — the lack of nutrients necessary for the growth and maintenance of vital functions.

[edit] Illnesses caused by improper nutrient consumption

Nutrients Deficiency Excess
Energy marasmus cardiovascular disease
Simple carbohydrates none obesity
Complex carbohydrates none obesity
Saturated fat low sex hormone levels [35] cardiovascular disease[citation needed][dubious ]
Trans fat none cardiovascular disease
Unsaturated fat none obesity
Fat malabsorption of fat-soluble vitamins, rabbit starvation (if protein intake is high), during development: stunted brain development and reduced brain weight.[36] cardiovascular disease[citation needed]
Omega-3 fats cardiovascular disease bleeding, hemorrhages
Omega-6 fats none cardiovascular disease, cancer
Cholesterol during development: deficiencies in myelinization of the brain.[37] cardiovascular disease[citation needed][dubious ]
Protein kwashiorkor rabbit starvation
Sodium hyponatremia hypertension
Iron anemia cirrhosis, cardiovascular disease
Iodine hypothyroidism Iodine toxicity (goiter, hypothyroidism)
Vitamin A xerophthalmia and night blindness, low testosterone levels hypervitaminosis A (cirrhosis, hair loss)
Vitamin B1 beriberi
Vitamin B2 cracking of skin and corneal unclearation
Niacin pellagra cardiac arrhythmias, birth defects
Vitamin B12 pernicious anemia
Vitamin C scurvy dehydration
Vitamin D rickets hypervitaminosis D (dehydration, vomiting, constipation)
Vitamin E nervous disorders hypervitaminosis E (anticoagulant: excessive bleeding)
Vitamin K hemorrhage
Calcium cardiac arrhythmias increased urination
Magnesium hypertension weakness, nausea, vomiting, impaired breathing, and hypotension
Potassium cardiac arrhythmias palpitations

[edit] Mental agility

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.[42]

“Better learning performance is associated with diet induced effects on learning and memory ability”.[43]

The “nutrition-learning nexus” demonstrates the correlation between diet and learning and has application in a higher education setting.

“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.”[44]
91% of college students feel that they are in good health while only 7% eat their recommended daily allowance of fruits and vegetables.[39]
Nutritional education is an effective and workable model in a higher education setting.[46]
More “engaged” learning models that encompass nutrition is an idea that is picking up steam at all levels of the learning cycle.[47]

There is limited research available that directly links a student’s Grade Point Average (G.P.A.) to their overall nutritional health. Additional substantive data is needed to prove that overall intellectual health is closely linked to a person’s diet, rather than a correlation fallacy.

[edit] Mental disorders

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.[48] 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.

[edit] Cancer

Cancer has recently become common in developing countries. According 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.”[49]

A comprehensive worldwide report, pulses (legumes).

[edit] Metabolic syndrome

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. The negative impact of hyperinsulinemia on prostaglandin PGE1/PGE2 balance may be significant.

The state of obesity clearly contributes to insulin resistance, which in turn can cause type 2 diabetes. Virtually all obese and most type 2 diabetic individuals have marked insulin resistance. Although the association between overweight and insulin resistance is clear, the exact (likely multifarious) causes of insulin resistance remain less clear. Importantly, it has been demonstrated that appropriate exercise, more regular food intake and reducing glycemic load (see below) all can reverse insulin resistance in overweight individuals (and thereby lower blood sugar levels in those who have type 2 diabetes).

Obesity can unfavourably alter hormonal and metabolic status via resistance to the hormone hypothalamus in the brain; however, insulin/leptin resistance may reduce this signal and therefore allow continued overfeeding despite large body fat stores. In addition, reduced leptin signalling to the brain may reduce leptin’s normal effect to maintain an appropriately high metabolic rate.

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. In any case, analogous to the way modern man-made pollution may potentially overwhelm the environment’s ability to maintain glycemic index and processed foods into the human diet may potentially overwhelm the body’s ability to maintain homeostasis and health (as evidenced by the metabolic syndrome epidemic).

[edit] Hyponatremia

Excess water intake, without replenishment of sodium and potassium salts, leads to hyponatremia, which can further lead to water intoxication at more dangerous levels. A well-publicized case occurred in 2007, when Jennifer Strange died while participating in a water-drinking contest.[50] More usually, the condition occurs in long-distance endurance events (such as marathon or triathlon competition and training) and causes gradual mental dulling, headache, drowsiness, weakness, and confusion; extreme cases may result in coma, convulsions, and death. The primary damage comes from swelling of the brain, caused by increased osmosis as blood salinity decreases. Effective fluid replacement techniques include Water aid stations during running/cycling races, trainers providing water during team games such as Soccer and devices such as Camel Baks which can provide water for a person without making it too hard to drink the water.

[edit] Processed foods

Since the salting, and separation of various components, and all appear to alter the original nutritional contents of food. Pasteurisation and autoclavation (heating techniques) have no doubt improved the safety of many common foods, preventing epidemics of bacterial infection. But some of the (new) food processing technologies undoubtedly have downsides as well.

Modern separation techniques such as milling, centrifugation, and pressing have enabled concentration of particular components of food, yielding flour, oils, juices, and so on, and even separate fatty acids, amino acids, vitamins, and minerals. Inevitably, such large-scale concentration changes the nutritional content of food, saving certain nutrients while removing others. Heating techniques may also reduce food’s content of many heat-labile nutrients such as certain vitamins and phytochemicals, and possibly other yet to be discovered substances.[51] Because of reduced nutritional value, processed foods are often ‘enriched’ or ‘fortified’ with some of the most critical nutrients (usually certain vitamins) that were lost during processing. Nonetheless, processed foods tend to have an inferior nutritional profile compared to whole, fresh foods, regarding content of both sugar and high glycemic index starches, potassium/sodium, vitamins, fiber, and of intact, unoxidized (essential) fatty acids. In addition, processed foods often contain potentially harmful substances such as oxidized fats and trans fatty acids.

A dramatic example of the effect of food processing on a population’s health is the history of epidemics of beri-beri in people subsisting on polished rice. Removing the outer layer of rice by polishing it removes with it the essential vitamin thiamine, causing beri-beri. Another example is the development of scurvy among infants in the late 19th century in the United States. It turned out that the vast majority of sufferers were being fed milk that had been heat-treated (as suggested by Pasteur) to control bacterial disease. Pasteurisation was effective against bacteria, but it destroyed the vitamin C.

As mentioned, lifestyle- and obesity-related diseases are becoming increasingly prevalent all around the world. There is little doubt that the increasingly widespread application of some modern food processing technologies has contributed to this development. The food processing industry is a major part of the modern economy, and as such it is influential in political decisions (e.g. nutritional recommendations, agricultural subsidising). In any known profit-driven economy, health considerations are hardly a priority; effective production of cheap foods with a long shelf-life is more the trend. In general, whole, fresh foods have a relatively short shelf-life and are less profitable to produce and sell than are more processed foods. Thus the consumer is left with the choice between more expensive but nutritionally superior whole, fresh foods, and cheap, usually nutritionally inferior processed foods. Because processed foods are often cheaper, more convenient (in purchasing, storage, and preparation), and more available, the consumption of nutritionally inferior foods has been increasing throughout the world along with many nutrition-related health complications.

[edit] History

Humans have evolved as omnivorous hunter-gatherers over the past 250,000 years. The diet of early modern humans varied significantly depending on location and climate. The diet in the tropics tended to be based more heavily on plant foods, while the diet at higher latitudes tended more towards animal products. Analysis of postcranial and cranial remains of humans and animals from the Neolithic, along with detailed bone modification studies have shown that cannibalism was also prevalent among prehistoric humans.[52]

Agriculture developed about 10,000 years ago in multiple locations throughout the world, providing grains such as wheat, rice, maize, and potatoes, with staples such as bread, pasta, and tortillas. Farming also provided milk and dairy products, and sharply increased the availability of meats and the diversity of vegetables. The importance of food purity was recognized when bulk storage led to infestation and contamination risks. Cooking developed as an often ritualistic activity, due to efficiency and reliability concerns requiring adherence to strict recipes and procedures, and in response to demands for food purity and consistency.[53]

[edit] From antiquity to 1900

Around 3000 BC the Vedic texts had mentions of scientific research on nutrition.

The first recorded nutritional experiment is found in the Bible’s Book of Daniel. Daniel and his friends were captured by the king of Babylon during an invasion of Israel. Selected as court servants, they were to share in the king’s fine foods and wine. But they objected, preferring vegetables (pulses) and water in accordance with their Jewish dietary restrictions. The king’s chief steward reluctantly agreed to a trial. Daniel and his friends received their diet for 10 days and were then compared to the king’s men. Appearing healthier, they were allowed to continue with their diet.[54]


Around 475 BC, [55]

In the 16th century, scientist and artist Leonardo da Vinci compared metabolism to a burning candle. In 1747, Dr. James Lind, a physician in the British navy, performed the first scientific nutrition experiment, discovering that lime juice saved sailors who had been at sea for years from scurvy, a deadly and painful bleeding disorder. The discovery was ignored for forty years, after which British sailors became known as “limeys.” The essential vitamin C within lime juice would not be identified by scientists until the 1930s.

Around 1770, oxygen were recognized as the primary components of food, and methods to measure their proportions were developed.

In 1816, glycogen.

In the early 1880s, Kanehiro Takaki observed that Japanese sailors (whose diets consisted almost entirely of white rice) developed beriberi (or endemic neuritis, a disease causing heart problems and paralysis) but British sailors and Japanese naval officers did not. Adding various types of vegetables and meats to the diets of Japanese sailors prevented the disease.

In 1896, Baumann observed thiamine.

[edit] From 1900 to the present

In the early 20th century, Carl von Voit and Max Rubner independently measured caloric energy expenditure in different species of animals, applying principles of physics in nutrition. In 1906, Wilcock and Hopkins showed that the amino acid tryptophan was necessary for the survival of rats. He fed them a special mixture of food containing all the nutrients he believed were essential for survival, but the rats died. A second group of rats to which he also fed an amount of milk containing vitamins.[56] Gowland Hopkins recognized “accessory food factors” other than calories, protein and minerals, as organic materials essential to health but which the body cannot synthesize. In 1907, Stephen M. Babcock and Edwin B. Hart conducted the single-grain experiment. This experiment ran through 1911.

In 1912, Casimir Funk coined the term vitamin, a vital factor in the diet, from the words “vital” and “amine,” because these unknown substances preventing scurvy, beriberi, and pellagra, were thought then to be derived from ammonia. The vitamins were studied in the first half of the 20th century.

In 1913, Elmer McCollum discovered the first vitamins, fat soluble vitamin A, and water soluble vitamin B (in 1915; now known to be a complex of several water-soluble vitamins) and named vitamin C as the then-unknown substance preventing scurvy. Lafayette Mendel and Thomas Osborne also performed pioneering work on vitamins A and B. In 1919, Sir Edward Mellanby incorrectly identified rickets as a vitamin A deficiency, because he could cure it in dogs with cod liver oil.[57] In 1922, McCollum destroyed the vitamin A in cod liver oil but found it still cured rickets, and named it vitamin D. Also in 1922, H.M. Evans and L.S. Bishop discovered vitamin E as essential for rat pregnancy, and originally called it “food factor X” until 1925.

In 1925, Hart discovered that trace amounts of citric acid cycle.

In the 1930s, Paul Karrer.

In 1940, National Research Council.

In 1992, The U.S. Department of Agriculture introduced the Food Guide Pyramid. In 2002, a Natural Justice study showed a relation between nutrition and violent behavior. In 2005, a study found that obesity may be caused by adenovirus in addition to bad nutrition.[58]

[edit] See also

Balanced Eating:


Dangers of poor nutrition


Food (portal)
Healthy diet:






Related topics

[edit] Further reading

  • Curley, S., and Mark (1990). The Natural Guide to Good Health, Lafayette, Louisiana, Supreme Publishing
  • Galdston, I. (1960). Human Nutrition Historic and Scientific. New York: International Universities Press.
  • Mahan, L.K. and Escott-Stump, S. eds. (2000). Krause’s Food, Nutrition, and Diet Therapy (10th ed.). Philadelphia: W.B. Saunders Harcourt Brace. ISBN 0-7216-7904-8.
  • Human Nutrition. Readings from Scientific American. San Francisco: W.H. Freeman & Co.. 1978. ISBN 0-7167-0183-9
  • Thiollet, J.-P. (2001). Vitamines & minéraux. Paris: Anagramme.
  • Walter C. Willett and Meir J. Stampfer (January 2003). “Rebuilding the Food Pyramid”. Scientific American 288 (1): 64–71. doi:10.1038/scientificamerican0103-64. PMID 12506426.

[edit] References

  1. ^ United Nations Information Service. “Independent Expert On Effects Of Structural Adjustment, Special Rapporteur On Right To Food Present Reports: Commission Continues General Debate On Economic, Social And Cultural Rights”. United Nations, March 29, 2004, p. 6. “Around 36 million people died from hunger directly or indirectly every year.”.
  2. 9164317.
  3. 0-7167-4684-0.
  4. 48917971
  5. ^ He FJ, MacGregor GA. Effect of longer-term modest salt reduction on blood pressure. Cochrane Database of Systematic Reviews 2004, Issue 1. Art. No.: CD004937. doi:10.1002/14651858.CD004937.
  6. ^ “Your Guide To Lowering Your Blood Pressure With DASH” (PDF). http://www.nhlbi.nih.gov/health/public/heart/hbp/dash/new_dash.pdf. Retrieved 2009-06-08.
  7. 1-57259-153-6.
  8. 0-444-89307-5.
  9. 0-935702-73-3.
  10. 0-7817-4133-5.
  11. ^ Goldwater, William. “Analysis of Adipose Tissue in relation to Body Weight Loss in Man”. Journal of Applied Physiology. http://jap.physiology.org/search?author1=William+H.+Goldwater&sortspec=date&submit=Submit. Retrieved June, 28, 2011.
  12. ^ “Healthy Water Living”. BBC. http://www.bbc.co.uk/health/healthy_living/nutrition/drinks_water.shtml. Retrieved 2007-02-01.
  13. ^ “Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8 × 8”? by Heinz Valdin, Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire
  14. ^ Drinking Water – How Much?, Factsmart.org web site and references within
  15. ^ Food and Nutrition Board, National Academy of Sciences. Recommended Dietary Allowances, revised 1945. National Research Council, Reprint and Circular Series, No. 122, 1945 (Aug), p. 3-18.
  16. ^ Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate, Food and Nutrition Board
  17. ^ “Water: How much should you drink every day? – MayoClinic.com”. MayoClinic.com<!. http://www.mayoclinic.com/health/water/NU00283. Retrieved 2009-05-21.
  18. http://www.mdsupport.org/library/zeaxanthin.html.
  19. 10221316.
    Yeum KJ, Taylor A, Tang G, Russell RM (December 1995). “Measurement of carotenoids, retinoids, and tocopherols in human lenses”. Invest. Ophthalmol. Vis. Sci. 36 (13): 2756–61. PMID 7499098.
    Chasan-Taber L, Willett WC, Seddon JM, et al. (October 1999). “A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women”. Am. J. Clin. Nutr. 70 (4): 509–16. PMID 10500020.
    Brown L, Rimm EB, Seddon JM, et al. (October 1999). “A prospective study of carotenoid intake and risk of cataract extraction in US men”. Am. J. Clin. Nutr. 70 (4): 517–24. PMID 10500021.
  20. 16087992.
    Am J Epidemiology 2006 163(1).
  21. 10426702.
  22. ^ Monoterpenes are enormously widespread among green plant life (including algae).
  23. ^ http://www.mypyramid.gov/downloads/sample_menu.pdf
  24. ^ Commission on Life Sciences. (1985). Nutrition Education in US Medical Schools, p. 4. National Academies Press.
  25. 16600952. //www.ncbi.nlm.nih.gov/pmc/articles/PMC2430660/.
  26. ^ Nutrition and diet – Making Better Dietary Decisions Daily Food Choices, Pacificare. Retrieved on 15 November 2010.
  27. ^ 1-932100-38-5.
  28. http://circ.ahajournals.org/cgi/reprint/115/16/2231.
  29. http://www.bmj.com/cgi/content/full/320/7229/249/a.
  30. 978-0-8493-7950-5.
  31. 978-0-8493-7950-5.
  32. ^ http://www.winforum.org/GamePlan-bw.pdf. page 19
  33. 0-8121-0682-2.
  34. ^ “Nutrition — Healthy eating: Bread, cereals and other starchy foods”. BBC. July 2008. http://www.bbc.co.uk/health/healthy_living/nutrition/basics_carbos.shtml. Retrieved 2008-11-09.
  35. ^ http://deepfitness.com/705/The-Big-T-How-Your-Lifestyle-Influences-Your-Testosterone-Levels.aspx
  36. http://www.ncbi.nlm.nih.gov/pubmed/7245988.
  37. http://www.ncbi.nlm.nih.gov/pubmed/1369207.
  38. ^ Jere R. Behrman (1996). “The impact of health and nutrition on education”. World Bank Research Observer 11 (1): 23–37.
  39. ^ 17319325.
  40. 1525295.
  41. 2310175.
  42. 14880969.
  43. 10024623.
  44. ^ Glewwe P, Jacoby H, King E (2001). “Early childhood nutrition and academic achievement: A longitudinal analysis”. Journal of Public Economics 81 (3): 345–68. doi:10.1016/S0047-2727(00)00118-3.
  45. ^ Managed food service contractors react quickly to the demands of their clients achievement: A longitudinal analysis. Journal of Public Economics, 81(3), 345-368.
  46. ^ Guernsey L (1993). “Many colleges clear their tables of steak, substitute fruit and pasta”. Chronicle of Higher Education 39 (26): A30.
  47. ^ Duster T, Waters A (2006). “Engaged learning across the curriculum: The vertical integration of food for thought”. Liberal Education 92 (2): 42.
  48. http://www.nutritionj.com/content/7/1/2.
  49. ^ Coren, Michael (2005-03-10). “Study: Cancer no longer rare in poorer countries”. CNN. http://www.cnn.com/2005/HEALTH/03/09/cancer.study/index.html. Retrieved 2007-01-01.
  50. ^ “Why is too much water dangerous?”. BBC News. 2007-01-15. http://news.bbc.co.uk/1/hi/magazine/6263029.stm. Retrieved 2008-11-09.
  51. ^ Morris, Audrey; Audia Barnett, Olive-Jean Burrows (2004). “Effect of Processing on Nutrient Content of Foods” (PDF). Cajanus 37 (3): 160–164. http://www.paho.org/English/CFNI/cfni-caj37No304-art-3.pdf. Retrieved 2006-10-26.
  52. 17794567.
  53. ^ History of the Study of Nutrition in Western Culture (Rai University lecture notes for General Nutrition course, 2004)
  54. alternative translation)
  55. dead link]
  56. ^ Heinemann 2e Biology Activity Manual by Judith Brotherton and Kate Mundie
  57. ^ Unraveling the Enigma of Vitamin D – a paper funded by the United States National Academy of Sciences
  58. ^ “Can a virus make you fat?” at BBC News; “Contagious obesity? Identifying the human adenoviruses that may make us fat” at Science Blog

[edit] External links

[edit] Databases and search engines

  • Nutrition Data
  • Recipe Nutrition – extends USDA database with friendly names for common ingredients, recipe nutrition calculator and additional specialized ingredients

This article uses material from the Wikipedia article Human Nutrition, which is released under the Creative Commons Attribution-Share-Alike License 3.0.