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Nutrition

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

   The updated USDA food pyramid, published in 2005, is a general
   nutrition guide for recommended food consumption.
   Enlarge
   The updated USDA food pyramid, published in 2005, is a general
   nutrition guide for recommended food consumption.

   Nutrition science studies the relationship between diet and states of
   health and disease. Dieticians are Health professionals who are
   specialized in this area of expertise, highly trained to provide safe,
   evidence-based dietary advice and interventions.

   Between the extremes of optimal health and death from starvation or
   malnutrition, there is an array of disease states that can be caused or
   alleviated by changes in diet. Deficiencies, excesses and imbalances in
   diet can produce negative impacts on health, which may lead to diseases
   such as scurvy, obesity or osteoporosis, as well as psychological and
   behavioural problems. Moreover, excessive ingestion of elements that
   have no apparent role in health, (e.g. lead, mercury, PCBs, dioxins),
   may incur toxic and potentially lethal effects, depending on the dose.
   The science of nutrition attempts to understand how and why specific
   dietary aspects influence health.

Overview

   Nutrition science seeks to explain metabolic and physiological
   responses of the body to diet. With advances in molecular biology,
   biochemistry, and genetics, nutrition science is additionally
   developing into the study of integrative metabolism, which seeks to
   connect diet and health through the lens of biochemical processes.

   The human body is made up of chemical compounds such as water, amino
   acids ( proteins), fatty acids ( lipids), nucleic acids (DNA/ RNA), and
   carbohydrates (e.g. sugars and fibre). These compounds in turn consist
   of elements such as carbon, hydrogen, oxygen, nitrogen, and phosphorus,
   and may or may not contain minerals such as calcium, iron, or zinc.
   Minerals ubiquitously occur in the form of salts and electrolytes. All
   of these chemical compounds and elements occur in various forms and
   combinations (e.g. hormones/vitamins, phospholipids, hydroxyapatite),
   both in the human body and in organisms (e.g. plants, animals) that
   humans eat.

   The human body necessarily comprises the elements that it eats and
   absorbs into the bloodstream. The digestive system, except in the
   unborn fetus, participates in the first step which makes the different
   chemical compounds and elements in food available for the trillions of
   cells of the body. In the digestive process of an average adult, about
   seven litres of liquid, known as digestive juices, exit the internal
   body and enter the lumen of the digestive tract. The digestive juices
   help break chemical bonds between ingested compounds as well as
   modulate the conformation and/or energetic state of the
   compounds/elements. However, many compounds/elements are absorbed into
   the bloodstream unchanged, though the digestive process helps to
   release them from the matrix of the foods where they occur. Any
   unabsorbed matter is excreted in the feces. But only a minimal amount
   of digestive juice is eliminated by this process; the intestines
   reabsorb most of it; otherwise the body would rapidly dehydrate; (hence
   the devastating effects of persistent diarrhea).

   Study in this field must take carefully into account the state of the
   body before ingestion and after digestion as well as the chemical
   composition of the food and the waste. Comparing the waste to the food
   can determine the specific types of compounds and elements absorbed by
   the body. The effect that the absorbed matter has on the body can be
   determined by finding the difference between the pre-ingestion state
   and the post-digestion state. The effect may only be discernible after
   an extended period of time in which all food and ingestion must be
   exactly regulated and all waste must be analyzed. The number of
   variables (e.g. 'confounding factors') involved in this type of
   experimentation is very high. This makes scientifically valid
   nutritional study very time-consuming and expensive, and explains why a
   proper science of human nutrition is rather new.

   In general, eating a variety of fresh, whole (unprocessed) plant foods
   has proven hormonally and metabolically favourable compared to eating a
   monotonous diet based on processed foods. In particular, consumption of
   whole plant foods slows digestion and provides higher amounts and a
   more favourable balance of essential and vital nutrients per unit of
   energy; resulting in better management of cell growth, maintenance, and
   mitosis (cell division) as well as regulation of blood glucose and
   appetite. A generally more regular eating pattern (e.g. eating
   medium-sized meals every 3 to 4 hours) has also proven more hormonally
   and metabolically favourable than infrequent, haphazard food intake.

History

   Humans have evolved as omnivorous hunter-gatherers over the past
   250,000 years. Early diets were primarily vegetarian with infrequent
   game meats and fish where available.

   Agriculture developed about 10,000 years ago in multiple locations
   throughout the world, providing grains such as wheat, rice, and maize,
   with staples such as bread and pasta. 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.

Antiquity through Enlightenment

     * c. 475 BC: Anaxagoras states that food is absorbed by the human
       body and therefore contained "homeomerics" (generative components),
       thereby deducing the existence of nutrients.
     * c. 400 BC: Hippocrates says, "Let food be your medicine and
       medicine be your food."
     * 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.
     * 1500s: Scientist and artist Leonardo da Vinci compared metabolism
       to a burning candle.
     * 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 recognized
       by scientists until the 1930s.
     * 1770: Antoine Lavoisier, the "Father of Nutrition and Chemistry"
       discovered the details of metabolism, demonstrating that the
       oxidation of food is the source of body heat.
     * 1790: George Fordyce recognized calcium necessary for fowl
       survival.

Modern era through 1941

     * Early 1800s: The elements carbon, nitrogen, hydrogen and oxygen
       were recognized as the primary components of food, and methods to
       measure their proportions were developed.
     * 1816: François Magendie discovers that dogs fed only carbohydrates
       and fat lost their body protein and died in a few weeks, but dogs
       also fed protein survived, identifying protein as an essential
       dietary component.
     * 1840: Justus Liebig discovers the chemical makeup of carbohydrates
       (sugars), fats (fatty acids) and proteins ( amino acids.)
     * 1860s: Claus Bernard discovers that body fat can be synthesised
       from carbohydrate and protein, showing that the energy in blood
       glucose can be stored as fat or as glycogen.
     * Early 1880s: Kanehiro Takaki observed that Japanese sailors
       developed beriberi (or endemic neuritis, a disease causing heart
       problems and paralysis) but British sailors did not. Adding milk
       and meat to Japanese diets prevented the disease.
     * 1896: Baumann observed iodine in thyroid glands.
     * 1897: Christiaan Eijkman worked with natives of Java, who also
       suffered from beriberi. Eijkman observed that chickens fed the
       native diet of white rice developed the symptoms of beriberi, but
       remained healthy when fed unprocessed brown rice with the outer
       bran intact. Eijkman cured the natives by feeding them brown rice,
       discovering that food can cure disease. Over two decades later,
       nutritionists learned that the outer rice bran contains vitamin B1,
       also known as thiamine.
     * Early 1900s: Carl Von Voit and Max Rubner independently measure
       caloric energy expenditure in different species of animals,
       applying principles of physics in nutrition.
     * 1906: Wilcock and Hopkins showed that the amino acid tryptophan was
       necessary for the survival of mice. Gowland Hopkins recognized
       "accessory food factors" other than calories, protein and minerals,
       as organic materials essential to health but which the body cannot
       synthesise.
     * 1907: Stephen M. Babcock and Edwin B. Hart conduct the Single-grain
       experiment. This experiment runs through 1911.
     * 1912: Casmir 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.
     * 1913: Elmer V. 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 names vitamin C as
       the then-unknown substance preventing scurvy.
     * 1919: Sir Edward Mellanby incorrectly identified rickets as a
       vitamin A deficiency, because he could cure it in dogs with cod
       liver oil.
     * 1922: McCollum destroys the vitamin A in cod liver oil but finds it
       still cures rickets, naming vitamin D
     * 1922: H.M. Evans and L.S. Bishop discover vitamin E as essential
       for rat pregnancy, originally calling it "food factor X" until
       1925.
     * 1925: Hart discovers trace amounts of copper are necessary for iron
       absorption.
     * 1927: Adolf Otto Reinhold Windaus synthesizes vitamin D, for which
       he won the Nobel Prize in Chemistry in 1928.
     * 1928: Albert Szent-Gyorgyi isolates ascorbic acid, and in 1932
       proves that it is vitamin C by preventing scurvy. In 1935 he
       synthesizes it, and in 1937 he wins a Nobel Prize for his efforts.
       Szent-Gyorgyi concurrently elucidates much of the citric acid
       cycle.
     * 1930s: William Cumming Rose identifies essential amino acids,
       necessary proteins which the body cannot synthesize.
     * 1935: Underwood and Marston independently discover the necessity of
       cobalt.
     * 1936: Eugene Floyd Dubois shows that work and school performance
       are related to caloric intake.
     * 1938: The chemical structure of vitamin E is discovered by Erhard
       Fernholz, and it is synthesised by Paul Karrer.
     * 1941: The first Recommended Dietary Allowances (RDAs) were
       established by the National Research Council.

Recent

     * 1992 The U.S. Department of Agriculture Introduces Food Guide
       Pyramid
     * 2002 Study shows relation between nutrition and violent behaviour
     * 2005 Obesity may be caused by adenovirus in addition to bad
       nutrition

Nutrition and Health

   There are six main nutrients in which the body needs to receive. These
   nutrients include carbohydrates, proteins, fats, vitamins, minerals,
   and water. It is important to consume these six nutrients on a daily
   basis to build and maintain healthy body systems.

   Ill health can be caused by an imbalance of nutrients, producing either
   an excess or deficiency, which in turn affects body functioning
   cumulatively. Moreover, because most nutrients are, in some way or
   another, involved in cell-to-cell signalling (e.g. as building block or
   part of a hormone or signalling 'cascades'), deficiency or excess of
   various nutrients affects hormonal function indirectly. Thus, because
   they largely regulate the expression of genes, hormones represent a
   link between nutrition and how our genes are expressed, i.e. our
   phenotype. The strength and nature of this link are continually under
   investigation, but observations especially in recent years have
   demonstrated a pivotal role for nutrition in hormonal activity and
   function and therefore in health.

   One source of articles on nutrition and health is the quarterly
   newsletter of the Nutrition for Optimal Health Association (NOHA).
   Articles since 1984 are indexed by subject, name, and chronology.

Essential and non-essential amino acids

   The body requires amino acids to produce new body protein (protein
   retention) and to replace damaged proteins (maintenance) that are lost
   in the urine. In animals amino acid requirements are classified in
   terms of essential (an animal cannot produce them) and non-essential
   (the animal can produce them from other nitrogen containing compounds)
   amino acids. Consuming a diet that contains adequate amounts of
   essential (but also non-essential) amino acids is particularly
   important for growing animals, who have a particularly high
   requirement.

Vitamins

   Mineral and/or vitamin deficiency or excess may yield symptoms of
   diminishing health such as goitre, scurvy, osteoporosis, weak immune
   system, disorders of cell metabolism, certain forms of cancer, symptoms
   of premature aging, and poor psychological health (including eating
   disorders), among many others.

   As of 2005, twelve vitamins and about the same number of minerals are
   recognized as "essential nutrients", meaning that they must be consumed
   and absorbed - or, in the case of vitamin D, alternatively synthesized
   via UVB radiation - to prevent deficiency symptoms and death. Certain
   vitamin-like substances found in foods, such as carnitine, have also
   been found essential to survival and health, but these are not strictly
   "essential" to eat because the body can produce them from other
   compounds. Moreover, thousands of different phytochemicals have
   recently been discovered in food (particularly in fresh vegetables),
   which have many known and yet to be explored properties including
   antioxidant activity (see below). Other essential nutrients include
   essential amino acids, choline and the essential fatty acids.

Fatty acids

   In addition to sufficient intake, an appropriate balance of essential
   fatty acids - omega-3 and omega-6 fatty acids - has been discovered to
   be crucial for maintaining health. Both of these unique "omega"
   long-chain polyunsaturated fatty acids are substrates for a class of
   eicosanoids known as prostaglandins which function as hormones. The
   omega-3 eicosapentaenoic acid (EPA) (which can be made in the body from
   the omega-3 essential fatty acid alpha-linolenic acid (LNA), or taken
   in through marine food sources), serves as building block for series 3
   prostaglandins (e.g. weakly- inflammation PGE3). The omega-6
   dihomo-gamma-linolenic acid (DGLA) serves as building block for series
   1 prostaglandins (e.g. anti-inflammatory PGE1), whereas arachidonic
   acid (AA) serves as building block for series 2 prostaglandins (e.g.
   pro-inflammatory PGE 2). Both DGLA and AA are made from the omega-6
   linoleic acid (LA) in the 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, which
   partly explains the importance of omega-3/omega-6 balance for
   cardiovascular health. In industrialised societies, people generally
   consume large amounts of processed vegetable oils that have reduced
   amounts of essential fatty acids along with an excessive amount of
   omega-6 relative to omega-3.

   The rate of conversions of omega-6 DGLA to AA largely determines the
   production of the respective prostaglandins PGE1 and PGE2. Omega-3 EPA
   prevents AA from being released from membranes, thereby skewing
   prostaglandin balance away from pro-inflammatory PGE2 made from AA
   toward anti-inflammatory PGE1 made from DGLA. Moreover, the conversion
   (desaturation) of DGLA to AA is controlled by the enzyme
   delta-5-desaturase, which in turn is controlled by hormones such as
   insulin (up-regulation) and glucagon (down-regulation). Because
   different types and amounts of food eaten/absorbed affect insulin,
   glucagon and other hormones to varying degrees, not only the amount of
   omega-3 versus omega-6 eaten but also the general composition of the
   diet therefore determine health implications in relation to essential
   fatty acids, inflammation (e.g. immune function) and mitosis (i.e. cell
   division).

Sugars

   Several lines of evidence indicate lifestyle-induced hyperinsulinemia
   and reduced insulin function (i.e. insulin resistance) as a decisive
   factor 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 overfatness 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 overfat 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 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. In addition,
   reduced leptin signalling to the brain may reduce leptin's normal
   effect to maintain an appropriately high metabolic rate.

   There is debate about how and to what extent different dietary factors
   -- e.g. 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 ' homeostasis', the recent explosive introduction
   of high 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).

   Antioxidants are another recent discovery. As cellular
   metabolism/energy production requires oxygen, potentially damaging
   (e.g. mutation causing) compounds known as radical oxygen species or
   free radicals form as a result. For normal cellular maintenance,
   growth, and division, these free radicals must be sufficiently
   neutralized by antioxidant compounds, some produced by the body with
   adequate precursors ( glutathione, Vitamin C in most animals) and those
   that the body cannot produce may only be obtained through the diet
   through direct sources (Vitamin C in humans, Vitamin A, Vitamin K) or
   produced by the body from other compounds ( Beta-carotene converted to
   Vitamin A by the body, Vitamin D synthesized from cholesterol by
   sunlight). Different antioxidants are now known to function in a
   cooperative network, e.g. vitamin C can reactivate free
   radical-containing glutathione or vitamin E by accepting the free
   radical itself, and so on. Some antioxidants are more effective than
   others at neutralizing different free radicals. Some cannot neutralize
   certain free radicals. Some cannot be present in certain areas of free
   radical development (Vitamin A is fat-soluble and protects fat areas,
   Vitamin C is water soluble and protects those areas). When interacting
   with a free radical, some antioxidants produce a different free radical
   compound that is less dangerous or more dangerous than the previous
   compound. Having a variety of antioxidants allows any byproducts to be
   safely dealt with by more efficient antioxidants in neutralizing a free
   radical's butterfly effect.

Intestinal bacterial flora

   It is now also known that the human digestion system contains a
   population of a range of bacteria which are essential to digestion, and
   which are also affected by the food we eat. The role and significance
   of the intestinal bacterial flora is under investigation. Both good and
   bad bacteria inhabit the digestive system. It is estimated that in the
   Western world, most people are no longer in a homeostatic balance. It
   is ideal to have 80% good to 20% bad, typically differentiated by gram
   negative and gram positive staining, respectively; however, in western
   diets it is more likely to be the other way around. Consuming processed
   food that are low in nutrients and high in sugar will allow bad
   bacteria to flourish.

Phytochemicals

   Blackberries are a source of polyphenol antioxidants
   Enlarge
   Blackberries are a source of polyphenol antioxidants

   A growing area of interest is the effect upon human health of trace
   chemicals, collectively called phytochemicals, nutrients typically
   found in edible plants, especially colorful fruits and vegetables (see
   Whole Foods Diet, below). Unlike the anecdotal and sometimes specious
   nutritional claims of medicinal herbs and compounds, the effects of
   phytochemicals increasingly survive rigorous testing by prominent
   health organizations. One of the principal classes of phytochemicals
   are polyphenol antioxidants, chemicals which are known to provide
   certain health benefits to the cardiovascular system and immune system.
   These chemicals are known to down-regulate the formation of reactive
   oxygen species, key chemicals in cardiovascular disease.

   Perhaps the most rigorously tested phytochemical is zeaxanthin, a
   yellow-pigmented carotenoid present in many yellow and orange fruits
   and vegetables. Repeated studies have shown a strong correlation
   between ingestion of zeaxanthin and the prevention and treatment of
   age-related macular degeneration (AMD). Less rigorous studies have
   proposed a correlation between zeaxanthin intake and cataracts. A
   second carotenoid, lutein, has also been shown to lower the risk of
   contracting AMD. Both compounds have been observed to collect in the
   retina when ingested orally, and they serve to protect the rods and
   cones against the destructive effects of light.

   Another caretenoid, beta-cryptoxanthin, appears to protect against
   chronic joint inflammatory diseases, such as arthritis. While the
   association between serum blood levels of beta-cryptoxanthin and
   substantially decreased joint disease has been established, neither a
   convincing mechanism for such protection nor a cause-and-effect have
   been rigorously studied. Similarly, a red phytochemical, lycopene, has
   substantial credible evidence of negative association with development
   of prostate cancer.

   The correlations between the ingestion of some phytochemicals and the
   prevention of disease are, in some cases, enormous in magnitude. For
   example, several studies have correlated high levels of zeaxanthin
   intake with roughly a 50% reduction in AMD. The difficulties in
   demonstrating causative properties and in applying the findings to
   human diet, however, are similarly enormous. The standard for rigorous
   proof of causation in medicine is the double-blind study, a
   time-consuming, difficult and expensive process, especially in the case
   of preventative medicine. While new drugs must undergo such rigorous
   testing, pharmaceutical companies have a financial interest in funding
   rigorous testing and may recover the cost if the drug goes to market.
   No such commercial interest exists in studying chemicals that exist in
   orange juice and spinach, making funding for medical research difficult
   to obtain.

   Even when the evidence is obtained, translating it to practical dietary
   advice can be difficult and counter-intuitive. Lutein, for example,
   occurs in many yellow and orange fruits and vegetables and protects the
   eyes against various diseases. However, it does not protect the eye
   nearly as well as zeaxanthin, and the presence of lutein in the retina
   will prevent zeaxanthin uptake. Additionally, evidence has shown that
   the lutein present in egg yolk is more readily absorbed than the lutein
   from vegetable sources, possibly because of fat solubility. At the most
   basic level, the question "should you eat eggs?" is complex to the
   point of dismay, including misperceptions about the health effects of
   cholesterol in egg yolk, and its saturated fat content.

   As another example, lycopene is prevalent in tomatoes (and actually is
   the chemical that gives tomatoes their red colour). It is more highly
   concentrated, however, in processed tomato products such as commercial
   pasta sauce, or tomato soup, than in fresh "healthy" tomatoes. Such
   sauces, however, tend to have high amounts of salt, sugar, other
   substances a person may wish or even need to avoid.

Nutrition and sports

   Nutrition is very important for improving sports performance. Contrary
   to popular belief, athletes need only slightly more protein than an
   average person. These needs are easily met by a balanced diet, and the
   recommended daily servings are generous enough to meet these needs.
   Additional protein intake is broken-down to be used as energy or stored
   as fat. Excess protein or grain consumption in the absence of
   alkalizing mineral intake (from fruits and vegetables) leads to chonic
   low grade acididosis in which calcium and glutamine are leached from
   bone and muscle respectively to keep the blood pH steady.

   Endurance, strength and sprint athletes have different needs. Many
   athletes may require an increased caloric intake.

   Maintaining hydration during periods of physical exertion is key to
   good performance. While drinking too much water during activities can
   lead to physical discomfort, dehydration hinders an athlete’s ability.
   It is recommended that an athlete drink about 400-600mL 2-3 hours
   before activity, during exercise he or she should drink 150-350mL every
   15 to 20 minutes and after exercise that he or she replace sweat loss
   by drinking 450-675 mL for every .5 Kg body weight loss during
   activity. Studies have shown that an athlete that drinks before they
   feel thirsty stays cooler and performs better than one who drinks on
   thirst cues. Additional carbohydrates and protein before, during, and
   after exercise increase time to exhuastion as well as speed recovery.
   Dosage is based on work performed, lean body mass, and environmental
   factors (heat)

   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. When glycogen is not present in muscles, the
   muscle cells perform anaerobic respiration producing lactic acid, which
   is responsible for fatigue and burning sensation, and post exercise
   stiffness in muscles. 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.

Nutrition and longevity

Calorie restriction

   Lifespan may be somehow related to the amount of food energy consumed.
   A pursuit of this principle of caloric restriction followed, involving
   research into longevity of those who reduced their food energy intake
   while attempting to optimize their micronutrient intake. Perhaps not
   surprisingly, some people found that cutting down on food reduced their
   quality of life so considerably as to negate any possible advantages of
   lengthening their lives. However, a small set of individuals persist in
   the lifestyle, going so far as to monitor blood lipid levels and
   glucose response every few months. See Calorie Restriction Society.

   Underlying this research was the hypothesis that oxidative damage was
   the agent which accelerated aging, and that aging was retarded when the
   amount of carbohydrates (and thereby insulin release) was reduced
   through dietary restriction.

   However, recent research has produced increased longevity in animals
   (and shows promise for increased human longevity) through the use of
   insulin uptake retardation. This was done through altering an animal’s
   metabolism to allow it to consume similar food-energy levels to other
   animals, but without building up fatty tissue.

   This has set researchers off on a line of study which presumes that it
   is not low food energy consumption which increases longevity. Instead,
   longevity may depend on an efficient fat processing metabolism, and the
   consequent long term efficient functioning of our organs free from the
   encumbrance of accumulating fatty deposits. Thus, longevity may be
   related to maintained insulin sensitivity. However, several other
   factors including low body temperature seem to promote longevity also
   and it is unclear to what extent each of them contribute.

   Antioxidants have recently come to the forefront of longevity studies
   which have included the Food and Drug Administration and Brunswick
   labs.

Whole Plant Food Diet

   Heart disease, cancer, obesity, and diabetes are commonly called
   "Western" diseases because these maladies are rarely seen in developing
   countries. Research in China finds the difference may be nutritional;
   the Western diet includes consumption of large quantities of animal
   foods which could promote these observed diseases of affluence. One
   study found that rural Chinese eat mostly whole plant-based foods and
   "Western" diseases are rare; they instead suffer "diseases of poverty"
   which can be prevented by basic sanitation, health habits, and medical
   care.

   In China “some areas have essentially no cancer or heart disease, while
   in other areas, they reflect up to a 100-fold increase.”
   Coincidentally, diets in China range from entirely plant-based to
   heavily animal-based, depending on the location. In contrast, diseases
   of affluence like cancer and heart disease are common throughout the
   United States. We observe large regional clusters of people in China
   (and other developing nations) who rarely suffer from these “Western”
   diseases possibly because their diets are rich in vegetables, fruits
   and whole grains.

   The United Healthcare/Pacificare nutrition guideline recommends a whole
   plant food diet, as does a cover article of the issue of National
   Geographic (November 2005), titled The Secrets of LIVING LONGER. The
   latter is a lifestyle survey of three populations, Sardinians,
   Okinawans, and Adventists, who generally display longevity and "suffer
   a fraction of the diseases that commonly kill people in other parts of
   the developed world, and enjoy more healthy years of life. In sum, they
   offer three sets of 'best practices' to emulate. The rest if up to
   you." In common with all three groups is to "Eat fruits, vegetables,
   and whole grains."

   The National Geographic article noted that a NIH funded study of 34,000
   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. And it found that not eating red
   meat had been helpful to avoid both cancer and heart disease."

The French paradox

   It has been discovered that people living in Southern France live
   longer. Even though they consume a comparable amount of saturated fats,
   the rate of heart disease is lower in Southern France than in North
   America. A number of explantions have been suggested:
     * Reduced consumption of processed carbohydrate and other junk foods;
     * Ethnic genetic differences allowing the body be harmed less by
       fats;
     * Regular consumption of red wine; or
     * Living in the South requires the body to produce less heat,
       allowing a slower, and therefore healthier, metabolic rate.

Nutrition, industry and food processing

   Since the Industrial Revolution some two hundred years ago, the food
   processing industry has invented many technologies that both help keep
   foods fresh longer and alter the fresh state of food as they appear in
   nature. Cooling is the primary technology that can help maintain
   freshness, whereas many more technologies have been invented to allow
   foods to last longer without becoming spoiled. These latter
   technologies include pasteurisation, autoclavation, drying, 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 downfalls as well.

   Modern separation techniques such as milling, centrifugation, and
   pressing have enabled upconcentration 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
   upconcentration 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.
   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 than do whole, fresh foods, regarding content of both sugar and
   high GI starches, potassium/sodium, vitamins, fibre, 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 1800's
   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 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
   both 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.

Advice and guidance on nutrition

Governmental policies

   Most Governments provide guidance on good nutrition, and some also
   impose mandatory labeling requirements upon processed food
   manufacturers to assist consumers in complying with such guidance.
   Current dietary guidelines in the United States are presented in the
   concept of a food pyramid. There is no apparent consistency in
   science-based nutritional recommendations between countries, indicating
   the role of politics as well as cultural bias in research emphasis and
   interpretation.

Teaching

   Nutrition is taught in schools in many countries. In England and Wales
   the Personal and Social Education and Food Technology curriculums
   nutrition included, stressing the importance of a balanced diet and
   teaching how to read nutrition labels on packaging. But in developing
   countries, it is a distant dream; misconceptions, gender bias, un
   awareness about hygienic conditions etc.are still existing in their
   full strength.

Issues

   Challenging issues in modern nutrition include:

   "Artificial" interventions in food production and supply:
     * Should genetic engineering be used in the production of food crops
       and animals?
     * Are the use of pesticides, and fertilizers damaging to the foods
       produced by use of these methods (see also organic farming)?
     * Are the use of antibiotics and hormones in animal farming ethical
       and/or safe?

   Sociological issues:
     * Is it possible to eat correctly on a low income? Is proper
       nutrition economically skewed? How do we increase access to whole
       foods in impoverished neighborhoods?
     * How do we minimise the current disparity in food availability
       between first and third world populations (see famine and poverty)?
     * How can public advice agencies, policy making and food supply
       companies be coordinated to promote healthy eating and make
       wholesome foods more convenient and available?
     * Do we need nutritional supplements in the form of pills, powders,
       liquids, etc.?
     * How can the developed world promote good worldwide nutrition
       through minimising import tariffs and export subsidies on food
       transfers?

   Research Issues:
     * How do different nutrients affect appetite and metabolism, and what
       are the molecular mechanisms?
     * Can a whole plant food diet, replete with diversity and colors, be
       instituted and implemented to improve health and reduce medical
       costs?
     * What yet to be discovered important roles do vitamins, minerals,
       and other nutrients play in metabolism and health?
     * Are the current recommendations for intake of vitamins and minerals
       appropriate?
     * How and why do different cell types respond differently to
       chronically elevated circulating levels of insulin, leptin, and
       other hormones?
     * What does it take for insulin resistance to develop?
     * What other molecular mechanisms may explain the link between
       nutrition and lifestyle-related diseases?
     * What role does the intestinal bacterial flora play in digestion and
       health?
     * How essential to proper digestion are the enzymes contained in food
       itself, which are usually destroyed in cooking (see Living foods
       diet)?
     * What more can we discover through what has been called the
       phytochemical revolution?

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