TIGblogs - Peter Man

Nutrition and Your Health
From Wikipedia

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. There is a spectrum ranging from malnutrition to optimal health, including many common symptoms and diseases which can often be prevented or alleviated with better nutrition.

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 behavioral 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 fiber). 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 liters 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 favorable 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 favorable 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 favorable 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 synthesized 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 synthesized 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 behavior..
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.

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 industrialized 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

Some information in this article or section has not been verified and may not be reliable. Please check for any inaccuracies, and modify and cite sources as needed. 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. 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 color). 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.

for more details go to
http://www.consumersresearchcncl.org/Healthcare/Ophthalmologists/ophth_nutrition.html

[أونتيتلد]
Automatically translated into Arabic thanks to WorldLingo

يدرس تغذية وصحتك
من [ويكيبديا]

تغذية علم العلاقة بين حمية و [ستت وف هلث] ومرض. [ديتيسن] [هلث بروفسّيونل] الذي يكون اختصّت في هذا [أرا وف إكسبرتيس], جدّا يدرّب أن يزوّد خزينة, [إفيدنس-بسد] إشعار حمييّة وتدخلات. هناك طيف يتراوح من حالة سوء تغذية إلى صحة أفضل, بما في ذلك كثير عاديّة أعراض وأمراض أيّ يستطيع غالبا كنت منعت أو خفّفت مع تغذية جيّدة.

أعجاز, تجاوزات وإختلالات في حمية يستطيع أنتجت تأثير صدمة سلبيّة على صحة, أيّ يمكن قدت إلى أمراض مثل مرض حفر, بدانة أو [أستيوبوروسس], [أس ولّ س] نفسانيّة ومشاكل [بهفيورل]. فضلا عن ذلك, ابتلاع مفرّطة عناصر أنّ يتلقّى ما من دور ظاهرة في صحة, ([إ.غ.]. رصاص, زئبق, [بكبس], [ديوإكسين]), يمكن تكبّدت مسمّة وتأثيرات قاتلة احتماليّا, [دبندينغ ون] الجرعة. يحاول العلم التغذية أن يفهم كيف ولما مظاهر خاصّة حمييّة يأثرون صحة.

نظرة عامّة

تغذية يبحث علم أن يفسّر أيضيّة وإستجابات [فسولوجكل] من الجسم إلى حمية. مع تقدمات في جزيئيّة علم الأحياء, كيمياء حيويّة, وعلم وراثة, تغذية يطوّر علم إضافة إلى ذلك داخل الدراسة من أيض [إينتغرتيف], أيّ [سك] أن يربط حمية وصحة من خلال العدسة من عمليات كيميائيّ حيويّ.

اصطلحت ال [هومن بودي] من مركبات كيميائيّ مثل ماء, [أمينو سد] (بروتين), [فتّي سد] (أدهان), [نوكليك سد] ([دن/رنا]), وكربوهيدر ([إ.غ.]. [سوغرس] وليف). يتألّف هذا مركبات بالتّالي عناصر مثل كربون, هيدروجين, أكسجين, نيتروجين, وفسفور, ويمكن أو يمكن لا يحتوي معدنات مثل كالسيوم, حديد, أو زنك. يقع معدنات بالوجود الكلّيّ [إين ث فورم وف] ملاح و [إلكترولت]. يقع كلّ من هذا كيميائيّة مركبات وعناصر في مختلفة أشكال وإدماجات ([إ.غ.]. هرمونات/حيمينات, دهن فوسفات, [هدروإكسبتيت]), على حدّ سواء في ال [هومن بودي] وفي كائن حيّ ([إ.غ.]. يأكل معامل, حيوانات) أنّ أناس. [كمبريز] ال [هومن بودي] بالضّرورة العناصر أنّ هو يأكل ويمتصّ داخل الدورة دمويّة. يساهم ال [ديجستيف سستم], ماعدا في ال [أونبورن] جنين, في الخطوة أولى أيّ يجعل المختلفة كيميائيّة مركبات وعناصر في طعام يتوفّر للترليونات الخلايا من الجسم. في العملية هضمية من بالغ معدّلة, يخرج حوالي سبعة [ليتر] السائل, يعرف ك [ديجستيف جويس], الجسم داخليّة ويدخل التجويف صغير من المسلك منشور هضمية.

يساعد ال [ديجستيف جويس] كسرت روابط كيميائيّ بين يبتلع مركبات [أس ولّ س] ضمنت التكيف [أند/ور] دولة نشيطة من المركبات/عناصر. مهما, كثير [كمبووندس/] امتصّت عناصر داخل الدورة دمويّة [أونشنجد] [, ثوو] العملية هضمية يساعد أن يطلقهم من المادّة ترابط من الأطعمة حيث هم يقعون. أيّ [أونبسربد] أمر أفرزت في البراز. غير أنّ فقط أزلت مبلغة أدنى [ديجستيف جويس] ب هذا عملية; يعيد الأمعية أكثر من هو; خلاف ذلك نزع الجسم بسرعة; (بالتّالي التأثيرات مدمّرة من إسهال مستمرّة).

دراسة في هذا مجال ينبغي أخذت بعناية [إينتو كّوونت] الدولة من الجسم قبل ابتلاع وبعد هضم [أس ولّ س] ال [شميكل كمبوسأيشن] من الطعام والنفاية. يقارن النفاية إلى الطعام يستطيع حددت الأنواع خاصّة مركبات وعناصر يمتصّ بالجسم. التأثير أنّ ال يمتصّ أمر يتلقّى على الجسم يستطيع كنت حددت ب يجد الفرق بين ال [بر-ينجسأيشن] دولة وال [بوست-ديجسأيشن] دولة. التأثير يمكن فقط كنت سهل تمييز بعد فترة زمنيّة موسّعة في أيّ كلّ طعام وابتلاع ينبغي كنت تماما نظّمت وكلّ نفاية ينبغي كنت حللت. الرقم المتغيرات ([إ.غ.]. "يتيّه عاملات") يتضمّن في هذا نوع التجريب جدّا عال. هذا يجعل علميّا دراسة شرعيّة غذائيّة جدّا مستغرق وقتا طويلا وغالية, ويفسّر لما علم مناسبة [هومن نوتريأيشن] يكون بالأحرى جديدة.

[إين جنرل,] قد برهن يأكل تشكيل من طازجة, كاملة ([أونبروسسّد]) [بلنت فوود] هرمونيّا وأيضيّا مواتي يقارن إلى يأكل حمية رتيبة يؤسّس على يعالج أطعمة. [إين برتيكلر], يتمهّل إستهلاك من أطعمة [وهول بلنت] هضم ويزوّد مبلغات [هيغر] وأكثر [ففوربل بلنس] من أساسيّة ومغذيات حيويّة لكلّ وحدة الطاقة; [رسولتينغ ين] إدارة جيّدة من خلية حالة نموّ, صيانة, و [ميتوسس] (خلية تقسيم) [أس ولّ س] نظام تعديل من دم سكروز وشهية. عموما أكثر نظاميّة يأكل أسلوب ([إ.غ.]. يأكل وجبات [مديوم-سزد] كلّ 3 [تو] 4 يبرهن ساعات) يتلقّى أيضا أكثر هرمونيّا وأيضيّا مواتي من نادرة, [فوود ينتك] اتّفاقيّة.

تاريخ

قد تطوّر أناس ك [هونتر-غثررس] ملتهمة على السابقة 250,000 سنون. كان حمية مبكّرة أوّلا نباتيّة مع نادرة لعبة لحام وسمكة حيث يتوفّر. زراعة طوّر حوالي 10,000 سنون [أغو] في يتعدّد موقعات طوال العالم, يزوّد حبات مثل قمح, أرز, وحبّ ذرة, مع مشابك مثل خبز وباستا. يزرع أيضا يزوّد لبن و [ديري برودوكت], وبحدّة يزيد التوفر الألحاظ والتنوع الخضر. ميّزت الأهمية من طعام نقاوة كان عندما [بولك ستورج] قاد إلى عيث وتلوث أخطار. يتعلّق يطبخ يطوّر كنشاط [ريتثليستيك] غالبا, واجبة إلى فعالية وإعتمادية يتطلّب إلتزام إلى صارمة وصفات وإجراءات, و [إين رسبونس تو] طلبات لطعام نقاوة وتماسك.

العصور القديمة من خلال تنوير

[ك.]. 475 قبل المسيح: [أنإكسغرس] يفيد أنّ امتصّت طعام ب ال [هومن بودي] ولذلك يحتوى "[هوميومريكس]" (عناصر مولدة), بذلك يستنتج الوجود المغذيات.
[ك.]. 400 قبل المسيح: تركت [هيبّوكرتس] يقول, "طعام الطبّك والطبّ طعامك."
الأولى أسّست يسجّل تجربة غذائيّة في الكتاب مقدّس كتاب دانييل. على قبض دانييل وصديقاته كان بالملك بابل أثناء غزوة إسرائيل. ينتقي كمحكمة خادمات, كان هم أن يشارك في الملك أطعمة دقيقة وخمر. غير أنّ اعترض هم, يفضّل خضر (ذبذبات) وماء وفق حصورهم [جويش] حمييّة. الملك وافق مضيفة رئيسيّة على مضض إلى محاكمة. استلم دانييل وصديقاته حميتهم ل 10 أيام وكان بعد ذلك قارنت إلى الملك رجال. يظهر صحّ, سمحت هم كان أن يستمرّ مع حميتهم.
[1500س]: عالمة وفن ليوناردو قارن [دا] [فينس] أيض إلى شمعة مشتعلة.
1747: [در.]. أنجز جيمس [ليند], طبيبة في القوّة بحريّة بريطانيّة, الأولى علميّة تغذية تجربة, يكتشف أنّ [ليم جويس] أنقذ بحارات الذي كان قد كان في بحث لسنون من مرض حفر, مميتة ومؤلمة نزيف اضطراب. تجاهلت الإكتشاف كان ل [فورتي] سنون, [أفتر وهيش] بحارات بريطانيّة أصبحوا يعرف بما أنّ "[ليمس]." ميّزت ال [فيتمين ك] أساسيّة ضمن [ليم جويس] لم يكن بعالمات حتّى الثلاثينات.
1770: اكتشف [أنتوين] [لفويسر], ال "أب من تغذية وكيمياء" التفاصيل الأيض, يعرض أنّ التأكسد الطعام المصدر من جسم حرارة.
1790: ميّز جورج [فوردس] كالسيوم ضروريّة لطائر بقاء.
عصر حديثة من خلال 1941

[1800س] مبكّرة: ميّزت العناصر كربون, نيتروجين, هيدروجين وأكسجين كان كالعناصر أوّليّة طعام, وطرق أن يقيس نسبهم كان طوّرت.
1816: يكتشف [فرنويس] [مجندي] أنّ كلاب غذّوا فقط كربوهيدر ودهن خسر هم جسم بروتين ومات في [ا فو] أسابيع, غير أنّ كلاب أيضا غذّوا بروتين بقي, يعيّن بروتين كعنصر أساسيّة حمييّة.
1840: يكتشف [جوستثس] ليبج البنية كيميائيّ من كربوهيدر ([سوغرس]), أدهان ([فتّي سد]) وبروتين ([أمينو سد].)
[1860س]: يكتشف كلاوس برنارد أنّ جسم دهن يستطيع كنت اصطنعت من كربوهيدر وبروتين, يبدي أنّ الطاقة في دم سكروز يستطيع كنت خزّنت بما أنّ سمينة أو كسكاكرين.
[1880س] مبكّرة: لاحظ [كنهيرو] [تككي] أنّ بحارات يابانيّة طوّروا [بريبري] (أو [نيوريتيس] مستوطنة, مرض يسبّب قلب مشاكل وحالة شلل) غير أنّ بحارات بريطانيّة أتمّوا لم. منع يضيف لبن ولحظ إلى يابانية حمية المرض.
1896: [بومنّ] يلاحظ عنصر يود في [ثرويد غلند].
1897: عمل [كريستين] [إيجكمن] مع ساكن محلّيّ جاوة, الذي أيضا عانى من [بريبري]. [إيجكمن] لاحظ أنّ غذّى دجاج الحمية أهليّ طبيعيّ [وهيت ريس] طوّر الأعراض ال [بريبري], غير أنّ بقي يصحّ عندما مجلس نظام الاحتياطيّ الفيدراليّ [بروون ريس] [أونبروسسّد] مع النخالة خارجيّة مصونة. [إيجكمن] عالج الساكن محلّيّ ب يغذّيهم [بروون ريس], يكتشف أنّ طعام يستطيع عالجت مرض. على اثنان عقود فيما بعد, علم [نوتريأيشنيست] أنّ ال [ريس برن] خارجيّة يحتوي حيمين [ب1], أيضا يعرف كثيمين.
[1900س] مبكّرة: يقيس كارل [فون] [فويت] وحدّ أقصى [روبنر] بشكل مستقلّ [إنرج إكسبنديتثر] حراريّة في نوع مختلفة حيوانات, يطبّق مبادئ الفيزياء في تغذية.
1906: أبدى [ويلكك] و [هوبكينس] أنّ ال [أمينو سد] [تربتوفن] كان ضروريّة للبقاء الفؤوس. ميّز [غولند] [هوبكينس] "ثانويّة طعام عاملات" غير حريرة, بروتين ومعدنات, ك [متريلس] عضويّة أساسيّة إلى صحة غير أنّ أيّ الجسم يستطيع لا يصطنع.
1907: إسطفان [م.]. [ببكك] وأدوين [ب.]. أيّل تصرّف إداريّ ال [سنغل-غرين] تجربة. يركض هذا تجربة من خلال 1911.
1912: [كسمير] سكّ جبانة العبارة حيمين, عاملة حيويّة في الحمية, من الكلمات "حيويّة" و" أمينة," لأنّ هذا مواد مجهولة يمنع مرض حفر, [بريبري], وحصاف, كان فكّرت بعد ذلك أن يكون استنتجت من أمونيوم.
1913: [إلمر] [ف.]. [مكّولّوم] اكتشف الأولى حيمينات, [فت سلوبل] [فيتمين ا], وحيمين [وتر-سلوبل] [ب] (في 1915; الآن يعرف أن يكون مركبة من عدّة حيمينات [وتر-سلوبل]) واسم [فيتمين ك] كالمادة [ثن-وننوون] يمنع مرض حفر.
1919: عيّن سيد إدوارد [ملّنبي] بشكل غير لائق كساح الأطفال ك [فيتمين ا] عجز, لأنّ هو استطاع عالجت هو في كلاب مع [كد ليفر] زيت.
1922: [مكّولّوم] يدمّر ال [فيتمين ا] في [كد ليفر] زيت غير أنّ اكتشافات هو بعد يعالج كساح الأطفال, يعيّن حيمين [د.].
1922: [ه.م.]. [إفنس] و [ل.س.]. أسقف يكتشف حيمين [إ] بما أنّ أساسيّة لفأرة حالة حمل, أصلا يدعو هو "طعام عاملة [إكس]" حتّى 1925.
1925: أيّل يكتشف [ترس موونت] النحاسة ضروريّة لحديد امتصاص.
1927: يصطنع أدولف أوتو [رينهولد] [ويندوس] [فيتمين د], ل أيّ هو ربح ال [نوبل بريز] في كيمياء في 1928.
1928: يعزل [ألبرت] [سزنت-جورجي] [أسكربيك سد], وفي 1932 يبرهن أنّ هو [فيتمين ك] ب يمنع مرض حفر. في 1935 يصطنع هو هو, وفي 1937 هو يربح [نوبل بريز] لجهوده. يوضح [سزنت-جورجي] بتزامن كثير من ال [ستريك سد] دورة.
ثلاثينات: يعيّن وليام [كمّينغ] [روس] [إسّنتيل مينو سد], بروتين ضروريّة أيّ الجسم يستطيع لا يصطنع.
1935: يكتشف [أوندرووود] و [مرستون] بشكل مستقلّ الحاجة الكوبلت.
1936: يبدي [إيوجن] [فلود] [دوبويس] أنّ عمل ومدرسة أداء ارتبطت إلى [كلوريك ينتك].
1938: اكتشفت ال [شميكل ستروكتثر] الحيمين [إ] ب [إرهرد] [فرنهولز], وهو اصطنعت ببول [كرّر].
1941: الأولى أسّست يوصى تسامحات حمييّة ([ردس]) كان ب ال [رسرش كونسل] وطنيّة.
أخيرة

1992 الولايات المتّحدة الأمريكيّة [دبرتمنت وف غريكلتثر] يقدّم طعام مرشدة هرم.
2002 دراسة أعراض علاقة بين تغذية وتصرف عنيفة.
2005 بدانة يمكن كنت سبّبت ب [أدنوفيروس] [إين دّيأيشن تو] تغذية سيّئة.
تغذية وصحة

هناك ستّة مغذيات رئيسيّة في أيّ الجسم يحتاج أن يستلم. يتضمّن هذا مغذيات كربوهيدر, بروتينات, أدهان, حيمينات, معدنات, وماء. هو مهمّة أن يستهلك هذا ستّة مغذيات على أساس يوميّة أن يبني وأبقيت يصحّ جسم نظامات.

[إيلّ هلث] يستطيع كنت سبّبت بإختلال المغذيات, ينتج إمّا تجاوز أو عجز, أيّ بالتّالي يأثر جسم يعمل تراكميّا. فضلا عن ذلك, لأنّ كثير مغذيات يكونون, [إين سم وي] أو آخر, يتضمّن في [سلّ-تو-سلّ] يشير ([إ.غ.]. يسقط كبناية قالب أو جزء من هرمون أو يشير ""), عجز أو تجاوز من مغذيات مختلفة يأثر عمل هرمونيّة بشكل غير مباشر. لذلك, لأنّ هم كثيرا ينظّمون التعبير المورثات, يمثّل هرمونات خطوة بين تغذية وكيف مورثاتنا يكون عبّر عن, [إي.]. نمط ظاهريّنا.

القوة وطبيعة من هذا خطوة باستمرار تحت تحقيق, غير أنّ قد عرض بطاقات خصوصا [إين رسنت رس] دور محورية لتغذية في هرمونيّة نشاط وعمل ولذلك في صحة. واحدة مصدر المواد على تغذية وصحة الالرسالة الإخباريّة فصليّة من التغذية لأفضل صحة جمعية ([نوها]). مواد بما أنّ 1984 يكون فهرست بموضوع, اسم, وجدول زمنيّ.

أساسيّة ويتطلّب [أمينو سد]

غير أساسيّ الجسم [أمينو سد] أن ينتج جديدة جسم بروتين (بروتين احتجاز) وأن يستبدل يضرّر بروتينات (صيانة) أنّ يكون خسرت في البول. في حيوانات [أمينو سد] صنّفت متطلبات بخصوص أساسيّة (حيوان يستطيع لا ينتجهم) وغير أساسيّ (الحيوان يستطيع أنتجتهم من أخرى [نيتروجن كنتينينغ] مركبات) [أمينو سد].

يستهلك حمية أنّ يحتوي مبلغات كافية من أساسيّة (غير أنّ أيضا غير أساسيّ) [أمينو سد] بشكل خاصّ مهمّة ل ينمو حيوانات, الذي يتلقّى متطلب عال بشكل خاصّ.

اكتشفت [فتّي سد]

[إين دّيأيشن تو] مدخل كاف, ميزان مناسبة من [فتّي سد] أساسيّة - [أمغ-3] و [أمغ-6] [فتّي سد] - يتلقّى يكون أن يكون حاسمة ل يبقي صحة. [بوث وف ثيس] فريدة "أوميغا" [فتّي سد] [لونغ-شين] [بولونستثرتد] طبقة سفليّة لصنف ال [إيكسنويدس] يعرف ك [بروستغلندين] أيّ يعمل كهرمونات. ال [أمغ-3] حامض [إيكسبنتنويك] ([إبا]) (أيّ يستطيع كنت جعلت في الجسم من ال [أمغ-3] أساسيّة [فتّي سد] حامض [ألف-لينولنيك] ([لنا]), أو يأخذ داخل من خلال بحريّة طعام مصادر), خدمات كبناية قالب ل [سري] 3 [بروستغلندين] ([إ.غ.]. [وكل-ينفلمّأيشن] [بج3]). ال [أمغ-6] يخدم حامض [ديهومو-غمّ-لينولنيك] ([دغلا]) كبناية قالب ل [سري] 1 [بروستغلندين] ([إ.غ.]. [بج1] [أنتي-ينفلمّتوري]), حيث أنّ [أرشدونيك سد] ([أا]) يخدم كبناية قالب ل [سري] 2 [بروستغلندين] ([إ.غ.]. [برو-ينفلمّتوري] [بج] 2). على حدّ سواء جعلت [دغلا] و [أا] من ال [أمغ-6] [لينوليك سد] (لا) في الجسم, أو يستطيع كنت أخذت داخل مباشرة من خلال طعام. يحدث مدخل متوازنة بشكل مناسب من [أمغ-3] و [أمغ-6] جزئيّا الإنتاج نسبيّة من [بروستغلندين] مختلفة, أيّ جزئيّا يفسّر الأهمية من [أمغ-3/] [أمغ-6] ميزان لصحة قلبيّ وعائيّ. عمّرت في يصنع مجتمعات, عموما يستهلك مبلغات كبيرة من يعالج [فجتبل ويل] أنّ قد قلّل مبلغات من [فتّي سد] أساسيّة مع مبلغة مفرّطة [أمغ-6] [أمغ-3] [رلتيف تو].

يحدّ ال [رت وف كنفرسون] من [أمغ-6] [دغلا] إلى [أا] كثيرا الإنتاج من ال [بروستغلندين] شخصيّة [بج1] و [بج2]. يمنع [أمغ-3] [إبا] [أا] من يكون يطلق من أغشية, بذلك يميل [بروستغلندين] ميزان بعيدا من [بج2] [برو-ينفلمّتوري] يجعل من [أا] نحو [بج1] [أنتي-ينفلمّتوري] يجعل من [دغلا]. فضلا عن ذلك, ضبطت التحويل (إزالة تشبّع) من [دغلا] إلى [أا] بالأنزيم [دلت-5-دستثرس], أيّ بالتّالي يكون ضبطت بهرمونات مثل أنسولين ([أوب-رغلأيشن]) ومضاعف سكّر ([دوون-رغلأيشن]). لأنّ أنواع مختلفة ومبلغات الطعام يؤكل/يمتصّ يأثرون أنسولين, مضاعف سكّر وأخرى هرمونات إلى يتغيّر درجات, ليس فحسب يحدّ المبلغة ال [أمغ-3] ضدّ [أمغ-6] يؤكل غير أنّ أيضا التركيب عامّة من الحمية لذلك صحة تضمنات [إين رلأيشن تو] [فتّي سد] أساسيّة, التهاب ([إ.غ.]. عمل محصّنة) و [ميتوسس] ([إي.]. خلية تقسيم).

يسكّر

عدّة خطوط البيّنة يشير [ليفستل-يندوسد] [هبرينسولينميا] ويقلّد أنسولين عمل ([إي.]. [إينسولين رسستنس]) كعاملة حاسمة في كثير مرض دول. مثلا, [هبرينسولينميا] واقترنت [إينسولين رسستنس] بقوّة إلى التهاب مزمنة, أيّ بالتّالي يكون بقوّة اقترنت إلى تشكيل من تطويرات عكسيّة مثل شريانيّة [ميكروينجوريس] وجلطة تشكيل ([إي.]. مرض القلب) ويبالغ خلية تقسيم ([إي.]. سرطان).

ميّزت [هبرينسولينميا] و [إينسولين رسستنس] (التناذر ما يسمّى أيضيّة) بإدماج من بدانة بطنيّة, يعزّز [بلوود سوغر], يعزّز [بلوود برسّور], يعزّز دم [تريغلسريد], ويقلّد [هدل] كوليستيرول. التأثير صدمة سلبيّة [هبرينسولينميا] على [بروستغلندين] [بج1/بج2] ميزان يمكن كنت هامّة.

يسهم الدولة البدانة بوضوح إلى [إينسولين رسستنس], أيّ بالتّالي يستطيع سبّبت نوع 2 داء سكّريّ. قد علم كلّ في الواقع بدينة وكثير نوع 2 فردات مصاب بالسّكّريّ [إينسولين رسستنس]. رغم أنّ الجمعية بين [أفرفتنسّ] و [إينسولين رسستنس] يكون واضحة, الدقيقة (مرجّحة متنوّعة) يبقى أسباب ال [إينسولين رسستنس] أقلّ واضحة. بأهمّيّة, عرضت هو يتلقّى يكون أنّ تمرين عمليّ مناسبة, أكثر [فوود ينتك] نظاميّة ويقلّد تحميل سكّريّ دمّ (يرى أدناه) كلّ يستطيع عكست [إينسولين رسستنس] في [أفرفت] فردات (وبذلك خفّضت [بلوود سوغر لفل] في أنّ الذي يتلقّى نوع 2 داء سكّريّ).

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

Some information in this article or section has not been verified and may not be reliable. Please check for any inaccuracies, and modify and cite sources as needed. 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. 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 color). 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.

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http://www.consumersresearchcncl.org/Healthcare/Ophthalmologists/ophth_nutrition.html