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Eijkman cured the natives by feeding them brown rice, discovering that food can cure disease. Mineral nutrient and Composition of the human body. For Nutrition in humans, see Human nutrition. Health effects of non-nutrient phytochemicals such as polyphenols were not assessed in this review. His assistant, Gerrit Grijns correctly identified and described the anti-beriberi substance in rice. To date, there is no conclusive evidence in humans that polyphenols or other non-nutrient compounds from plants have health benefit effects. Since nutrients are invisible, policy makers rely on nutrition experts to advise on food choices.
Saturated fats have all of the carbon atoms in their fatty acid chains bonded to hydrogen atoms, whereas unsaturated fats have some of these carbon atoms double-bonded , so their molecules have relatively fewer hydrogen atoms than a saturated fatty acid of the same length. Unsaturated fats may be further classified as monounsaturated one double-bond or polyunsaturated many double-bonds.
Furthermore, depending on the location of the double-bond in the fatty acid chain, unsaturated fatty acids are classified as omega-3 or omega-6 fatty acids. Trans fats are a type of unsaturated fat with trans -isomer bonds; these are rare in nature and in foods from natural sources; they are typically created in an industrial process called partial hydrogenation.
There are nine kilocalories in each gram of fat. Fatty acids such as conjugated linoleic acid , catalpic acid, eleostearic acid and punicic acid , in addition to providing energy, represent potent immune modulatory molecules. Saturated fats typically from animal sources have been a staple in many world cultures for millennia. Saturated and some trans fats are typically solid at room temperature such as butter or lard , while unsaturated fats are typically liquids such as olive oil or flaxseed oil.
Trans fats are very rare in nature, and have been shown to be highly detrimental to human health, but have properties useful in the food processing industry, such as rancidity resistance. 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 essential and must be included in the diet. An appropriate balance of essential fatty acids— omega-3 and omega-6 fatty acids —seems also important for health, although definitive experimental demonstration has been elusive. Both of these "omega" long-chain polyunsaturated fatty acids are substrates for a class of eicosanoids known as prostaglandins , which have roles throughout the human body.
They are hormones , in some respects. The omega-3 eicosapentaenoic acid EPA , which can be made in the human body from the omega-3 essential fatty acid alpha-linolenic acid ALA , or taken in through marine food sources, serves as a building block for series 3 prostaglandins e. The omega-6 dihomo-gamma-linolenic acid DGLA serves as a building block for series 1 prostaglandins e. An appropriately balanced intake of omega-3 and omega-6 partly determines the relative production of different prostaglandins, which is one reason why 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. Moreover, the conversion desaturation of DGLA to AA is controlled by the enzyme deltadesaturase , which in turn is controlled by hormones such as insulin up-regulation and glucagon down-regulation.
The amount and type of carbohydrates consumed, along with some types of amino acid, can influence processes involving insulin, glucagon, and other hormones; therefore, the ratio of omega-3 versus omega-6 has wide effects on general health, and specific effects on immune function and inflammation , and mitosis i.
Proteins are structural materials in much of the animal body e. They also form the enzymes that control chemical reactions throughout the body. Each protein molecule is composed of amino acids , which are characterized by inclusion of 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.
As there is no protein or amino acid storage provision, amino acids must be present in the diet. Excess amino acids are discarded, typically in the urine. For all animals, some amino acids are essential an animal cannot produce them internally and some are non-essential the animal can produce them from other nitrogen-containing compounds.
About twenty amino acids are 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: 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 possible with protein combinations of two incomplete protein sources e. However, complementary sources of protein do not need to be eaten at the same meal to be used together by the body. Water is excreted from the body in multiple forms; including urine and feces , sweating , and by water vapour in the exhaled breath. Therefore, it is necessary to adequately rehydrate to replace lost fluids. Early recommendations for the quantity of water required for maintenance of good health suggested that 6—8 glasses of water daily is the minimum to maintain proper hydration.
Most of this quantity is contained in prepared foods. For healthful hydration, the current EFSA guidelines recommend total water intakes of 2. These reference values include water from drinking water, other beverages, and from food.
The EFSA panel also determined intakes for different populations. Recommended intake volumes in the elderly are the same as for adults as despite lower energy consumption, the water requirement of this group is increased due to a reduction in renal concentrating capacity.
Dehydration and over-hydration - too little and too much water, respectively - can have harmful consequences. Drinking too much water is one of the possible causes of hyponatremia , i. Pure ethanol provides 7 calories per gram. For distilled spirits , a standard serving in the United States is 1. A 5 ounce serving of wine contains to calories. A 12 ounce serving of beer contains 95 to calories. Alcoholic beverages are considered empty calorie foods because other than calories, these contribute no essential nutrients.
The micronutrients are minerals , vitamins , and others. Dietary minerals are inorganic chemical elements required by living organisms,  other than the four elements carbon , hydrogen , nitrogen , and oxygen that are present in nearly all organic molecules. The term "mineral" is archaic, since the intent is to describe simply the less common elements in the diet.
Some are heavier than the four just mentioned, including several metals , which often occur as ions in the body. Some dietitians recommend that these be supplied from foods in which they occur naturally, or at least as complex compounds, or sometimes even from natural inorganic sources such as calcium carbonate from ground oyster shells.
Some minerals are absorbed much more readily in the ionic forms found in such sources. On the other hand, minerals are often artificially added to the diet as supplements; the most famous is likely iodine in iodized salt which prevents goiter. Many elements are essential in relative quantity; they are usually called "bulk minerals". Some are structural, but many play a role as electrolytes. Many elements are required in trace amounts, usually because they play a catalytic role in enzymes.
Vitamins are essential nutrients,  necessary in the diet for good health. Vitamin D is an exception, as it can be synthesized in the skin in the presence of UVB radiation , and many animal species can synthesize vitamin C. Vitamin deficiencies may result in disease conditions, including goitre , scurvy , osteoporosis , impaired immune system, disorders of cell metabolism, certain forms of cancer, symptoms of premature aging, and poor psychological health , among many others.
Phytochemicals such as polyphenols are compounds produced naturally in plants phyto means "plant" in Greek. In general, the term is used to refer to compounds which do not appear to be nutritionally essential and yet may have positive impacts on health. To date, there is no conclusive evidence in humans that polyphenols or other non-nutrient compounds from plants have health benefit effects.
While initial studies sought to reveal if nutrient antioxidant supplements might promote health, one meta-analysis concluded that supplementation with vitamins A and E and beta-carotene did not convey any benefits and may in fact increase risk of death. Vitamin C and selenium supplements did not impact mortality rate. Health effects of non-nutrient phytochemicals such as polyphenols were not assessed in this review.
Animal intestines contain a large population of gut flora. In humans, the four dominant phyla are Firmicutes , Bacteroidetes , Actinobacteria , and Proteobacteria. Bacteria in the large intestine perform many important functions for humans, including breaking down and aiding in the absorption of fermentable fiber, stimulating cell growth, repressing the growth of harmful bacteria, training the immune system to respond only to pathogens, producing vitamin B 12 , and defending against some infectious diseases.
There is not yet a scientific consensus as to health benefits accruing from probiotics or prebiotics. Carnivore and herbivore diets are contrasting, with basic nitrogen and carbon proportions vary for their particular foods. Many herbivores rely on bacterial fermentation to create digestible nutrients from indigestible plant cellulose, while obligate carnivores must eat animal meats to obtain certain vitamins or nutrients their bodies cannot otherwise synthesize.
Plant nutrition is the study of the chemical elements that are necessary for plant growth. Some elements are directly involved in plant metabolism. However, this principle does not account for the so-called beneficial elements, whose presence, while not required, has clear positive effects on plant growth. A nutrient that is able to limit plant growth according to Liebig's law of the minimum is considered an essential plant nutrient if the plant cannot complete its full life cycle without it.
There are 16 essential plant soil nutrients, besides the three major elemental nutrients carbon and oxygen that are obtained by photosynthetic plants from carbon dioxide in air, and hydrogen , which is obtained from water. Plants uptake essential elements from the soil through their roots and from the air consisting of mainly nitrogen and oxygen through their leaves.
Green plants obtain their carbohydrate supply from the carbon dioxide in the air by the process of photosynthesis. Carbon and oxygen are absorbed from the air, while other nutrients are absorbed from the soil. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen.
The carbon dioxide molecules are used as the carbon source in photosynthesis. Although nitrogen is plentiful in the Earth's atmosphere, very few plants can use this directly. Most plants, therefore, require nitrogen compounds to be present in the soil in which they grow. This is made possible by the fact that largely inert atmospheric nitrogen is changed in a nitrogen fixation process to biologically usable forms in the soil by bacteria.
Plant nutrition is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone. Elements present at low levels may cause deficiency symptoms, and toxicity is possible at levels that are too high. Furthermore, deficiency of one element may present as symptoms of toxicity from another element, and vice versa.
Canada's Food Guide is an example of a government-run nutrition program. Produced by Health Canada , the guide advises food quantities, provides education on balanced nutrition, and promotes physical activity in accordance with government-mandated nutrient needs. Like other nutrition programs around the world, Canada's Food Guide divides nutrition into four main food groups: Dietary and physical activity guidelines from the USDA are presented in the concept of MyPlate , which superseded the food pyramid , which replaced the Four Food Groups.
Department of Health and Human Services provides a sample week-long menu that fulfills the nutritional recommendations of the government. Governmental organisations have been working on nutrition literacy interventions in non-primary health care settings to address the nutrition information problem in the U. The FNP has developed a series of tools to help families participating in the Food Stamp Program stretch their food dollar and form healthful eating habits including nutrition education.
It is designed to assist limited-resource audiences in acquiring the knowledge, skills, attitudes, and changed behavior necessary for nutritionally sound diets, and to contribute to their personal development and the improvement of the total family diet and nutritional well-being.
Launched in , this program promotes lifelong healthful eating patterns and physically active lifestyles for children and their families. It is an interactive educational program designed to help prevent childhood obesity through classroom activities that teach children healthful eating habits and physical exercise.
Nutrition is taught in schools in many countries. In England and Wales , the 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: In many Nutrition classes, students learn about the food groups, the food pyramid, Daily Recommended Allowances, calories, vitamins, minerals, malnutrition, physical activity, healthful food choices, portion sizes, and how to live a healthy life.
In the US, Registered dietitian nutritionists RDs or RDNs  are health professionals qualified to provide safe, evidence-based dietary advice which includes a review of what is eaten, a thorough review of nutritional health, and a personalized nutritional treatment plan. They also provide preventive and therapeutic programs at work places, schools and similar institutions. Certified Clinical Nutritionists or CCNs, are trained health professionals who also offer dietary advice on the role of nutrition in chronic disease, including possible prevention or remediation by addressing nutritional deficiencies before resorting to drugs.
These Board Certified Nutritionists typically specialize in obesity and chronic disease. In order to become board certified, potential CNS candidate must pass an examination, much like Registered Dieticians. This exam covers specific domains within the health sphere including; Clinical Intervention and Human Health.
The study found that health literacy increases with education and people living below the level of poverty have lower health literacy than those above it. Another study examining the health and nutrition literacy status of residents of the lower Mississippi Delta found that 52 percent of participants had a high likelihood of limited literacy skills. For example, only 12 percent of study participants identified the My Pyramid graphic two years after it had been launched by the USDA.
The study also found significant relationships between nutrition literacy and income level and nutrition literacy and educational attainment  further delineating priorities for the region. Among these problems are the lack of information about food choices, a lack of understanding of nutritional information and its application to individual circumstances, limited or difficult access to healthful foods, and a range of cultural influences and socioeconomic constraints such as low levels of education and high levels of poverty that decrease opportunities for healthful eating and living.
The links between low health literacy and poor health outcomes has been widely documented  and there is evidence that some interventions to improve health literacy have produced successful results in the primary care setting. More must be done to further our understanding of nutrition literacy specific interventions in non-primary care settings  in order to achieve better health outcomes.
Malnutrition refers to insufficient, excessive, or imbalanced consumption of nutrients by an organism. In developed countries, the diseases of malnutrition are most often associated with nutritional imbalances or excessive consumption.
In developing countries, malnutrition is more likely to be caused by poor access to a range of nutritious foods or inadequate knowledge. The aim was to boost nutrition and livelihoods by producing a product that women could make and sell, and which would be accepted by the local community because of its local heritage. Although under- and over-nutrition are often viewed as human problems, pet animals can be under- or overfed by their owners, domesticated animals can be undernourished for macro- and micro-nutrients, affecting growth and health, and wild animals can be undernourished to the point of starvation and death.
Nutritionism is the view that excessive reliance on food science and the study of nutrition can lead to poor nutrition and to ill health.
It was originally credited to Gyorgy Scrinis ,  and was popularized by Michael Pollan. Since nutrients are invisible, policy makers rely on nutrition experts to advise on food choices. Because science has an incomplete understanding of how food affects the human body, Pollan argues, nutritionism can be blamed for many of the health problems relating to diet in the Western World today.
ULs are set a safe fraction below amounts shown to cause health problems. ULs are part of Dietary Reference Intakes. When too much of one or more nutrients is present in the diet to the exclusion of the proper amount of other nutrients, the diet is said to be unbalanced. High calorie food ingredients such as vegetable oils, sugar and alcohol are referred to as "empty calories" because they displace from the diet foods that also contain protein, vitamins, minerals and fiber.
Research indicates that improving the awareness of nutritious meal choices and establishing long-term habits of healthy eating have a positive effect on cognitive and spatial memory capacity, with potential to increase a student's ability 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. There is limited research available that directly links a student's Grade Point Average G. Additional substantive data is needed to prove that overall intellectual health is closely linked to a person's diet, rather than just another correlation fallacy. 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.
Cancer is now common in developing countries. According to a study by the International Agency for Research on Cancer , "In the developing world, cancers of the liver, stomach and esophagus were more common, often linked to consumption of carcinogenic preserved foods, such as smoked or salted food, and parasitic infections that attack organs. Several lines of evidence indicate lifestyle-induced hyperinsulinemia and reduced insulin function i.
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 microtrauma and clot formation i. 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 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.
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 their blood sugar level , in those with type 2 diabetes. In addition, reduced leptin signaling to the brain may reduce leptin's normal effect to maintain an appropriately high metabolic rate.
In any case, analogous to the way modern man-made pollution may possess the potential to overwhelm the environment's ability to maintain homeostasis , the recent explosive introduction of high glycemic index and processed foods into the human diet may possess the potential to overwhelm the body's ability to maintain homeostasis and health as evidenced by the metabolic syndrome epidemic.
Antinutrients are natural or synthetic compounds that interfere with the absorption of nutrients. Nutrition studies focus on antinutrients commonly found in food sources and beverages.
The relatively recent increased consumption of sugar has been linked to the rise of some afflictions such as diabetes, obesity, and more recently heart disease. Increased consumption of sugar has been tied to these three, among others. In the same time span that obesity doubled, diabetes numbers quadrupled in America. Increased weight, especially in the form of belly fat, and high sugar intake are also high risk factors for heart disease.
Elevated amounts of Low-density lipoprotein LDL cholesterol, is the primary factor in heart disease. In order to avoid all the dangers of sugar, moderate consumption is paramount. 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 used to 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, all of which appearing 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 have downfalls 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. 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 modern economy, and as such it is influential in political decisions e. 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.
From Wikipedia, the free encyclopedia. This article is about Nutrition in general. For Nutrition in humans, see Human nutrition. For Nutrition in animals, see Animal nutrition.
For nutrition in plants, see Plant nutrition. For the medical journal, see Nutrition journal. Mineral nutrient and Composition of the human body.
List of antioxidants in food. Animal nutrition and Human nutrition. Nutrition portal Food portal. Food Balance Wheel Biology: Bioenergetics Digestion Enzyme Dangers of poor nutrition Deficiency Avitaminosis is a deficiency of vitamins.
Boron deficiency medicine Chromium deficiency Iron deficiency medicine Iodine deficiency Magnesium deficiency medicine Diabetes Eating disorders Illnesses related to poor nutrition Malnutrition Obesity Childhood obesity Starvation Food: Dieting Eating Healthy eating pyramid Nutritional rating systems Lists: Diets list List of food additives List of illnesses related to poor nutrition List of life extension related topics List of publications in nutrition List of unrefined sweeteners List of antioxidants List of phytochemicals Nutrients: Dietitian Nutritionist Food Studies Tools: Human Nutrition and Food".
Retrieved 13 December Understanding Nutrition 13 ed. Deficiency, How Much, Benefits, and More. The New York Times. Archived from the original on L'émulsifiant est la bile , produite par le foie et stockée dans la vésicule biliaire.
L'émulsion passe ensuite dans l'intestin grêle où les lipides sont dégradés par un processus appelé lipolyse et associés à d'autres molécules au sein d'une lipoprotéine pour être transportés dans le sang [ A 9 ]. Une lipoprotéine est montrée dans le schéma ci-contre: Il existe cinq classes de lipoprotéines, remplissant différentes fonctions. La concentration de LDL augmente avec la prise d'acides saturés ou d'acide gras trans, ce qui augmente également le risque de maladie cardio-vasculaire [ A 8 ].
Enlever ces acides du régime peut nécessiter des changements profonds pouvant donner lieu à des carences, mais il est possible d'en réduire la quantité, par exemple dans le régime méditerranéen. Les protéines d'origine animale sont la principale source en Amérique du Nord et Europe de l'ouest. Les végétariens ne consommant pas de viandes, et les végétaliens rejetant l'ensemble des produits d'origine animale, leurs protéines doivent provenir des légumes et des céréales, qui sont également les deux principales sources en Afrique, Asie et Amérique Latine [ A 10 ].
Une protéine est formée d' acides aminés liés par des liaisons peptidiques. Ces acides aminés sont séparés en deux catégories: Ce qui est indispensable dépend de l'organisme considéré: Ces catégories sont affinées en considérant les acides aminés indispensables sous conditions.
En effet, certains acides aminés peuvent être synthétisés mais avec des capacités limitées en général et variants selon les conditions du sujet: Les protéines sont un composant essentiel du corps et remplissent un très grand nombre de rôles. Des problèmes liés aux protéines peuvent aussi être associés à des pathologies, tel le glutamate qui est impliqué dans les crises de convulsion épileptique [ A 11 ].
Un apport inapproprié en protéines peut donc avoir des conséquences fortes et variées sur le corps. Le PDCAAS protein digestibility corrected amino acid scoring pattern résume les quantités par acide aminé mais, en raison de controverses et d'évolutions techniques, les quantités conseillées par la FAO et l' OMS peuvent différer fortement selon les rapports. La digestion des protéines se passe principalement dans l'intestin grêle et libère les acides aminés qui continuent vers d'autres organes.
En cas de sous-alimentation , certains acides aminés peuvent être transformés en glucose par néoglucogenèse. Les sels minéraux sont essentiels au bon fonctionnement du corps.
On les retrouve dans l'eau sous forme de composés chimiques. On peut aussi les retrouver dans la viande et les légumes. Une carence peut entraîner des maladies par exemple, un manque de fer dans le sang cause l'anémie.
Les minéraux sont des éléments du tableau périodique. Les sels minéraux sont un des éléments nécessaires à la photosynthèse.
Le fait qu'une vitamine soit un composé la distingue par exemple des minéraux, et la nécessité signifie qu'elle ne peut pas être synthétisée. Les organismes étant capables de différentes synthèses, la dénomination de vitamine est relative à l'organisme considéré. Ainsi, la vitamine C peut-être synthétisée par la plupart des animaux à partir de glucose, et elle n'est donc considérée comme vitamine que pour les espèces incapables de cette synthèse telles que l'homme et autres espèces du taxon Haplorrhini , les chauves-souris ou les cochons d'inde [ B 2 ].
La raison de cette déficience chez l'homme vient de l'inactivité du gène responsable de l'enzyme L-gulonolactone oxidase, nécessaire pour la synthèse à partir du glucose, sur le chromosome 8. Les légumes et fruits frais et crus sont la meilleure source, puisque la teneur en vitamine C décroît très fortement avec le vieillissement ou la coupe, et fortement en cuisinant [ B 1 ].
Un antioxydant est une molécule qui diminue ou empêche l'oxydation d'autres substances chimiques. Les composés phytochimiques sont des composés chimiques organiques qu'on peut trouver dans des aliments d'origine végétale. La malnutrition se réfère à une consommation insuffisante ou excessive des nutriments par un organisme. Dans les pays développés, la malnutrition est souvent associée à l'insuffisance ou l'excès dans la consommation.
Bien qu'il existe des maladies liées à la sous-alimentation, d'autres organismes souffrent d'une nutrition excessive. Des travaux de recherche [réf. La mortalité augmente de manière abrupte dès que les individus dépassent le seuil du surpoids. La sensation de soif se comprend en étudiant les mécanismes des globules rouges. L'intérieur d'un globule rouge, nommé cytoplasme , est séparé de l'extérieur par une membrane qui laisse passer l'eau, et est appelée pour cette raison semi-perméable.
Une pression s'exerce entre l'intérieur de la cellule et l'extérieur, selon les concentrations respectives en solutés. Si la concentration à l'extérieur est moins élevée que dans la cellule, alors celle-ci se met à gonfler en raison du phénomène d' osmose et peut éventuellement exploser puisque sa membrane n'est pas extensible. L'extérieur, c'est-à-dire le plasma, est alors qualifié d'hypotonique. À l'inverse, il peut être hypertonique et la cellule essaye alors de rétablir la pression en laissant passer de l'eau vers l'extérieur.
Ce second cas de figure se pose lorsqu'il n'y a pas assez d'eau dans l'organisme: Cette pression est un mécanisme extrêmement sensible pour déclencher des sensations de soif: Cet effet est vérifiable en injectant une solution avec une concentration élevée en sel, et l'intensité de la soif est proportionnelle à la pression [ 1 ]. Cependant, le corps a également ses mécanismes de régulation: Cette pression augmente lorsqu'un individu mange, et cette action agit aussi sur les reins qui ont besoin de plus d'eau pour les déchets.
Ainsi, boire avant ou pendant le repas contribue à l'équilibre. Par ailleurs, une autre réponse du corps à l'augmentation de pression est une bouche sèche due à une réduction de salive. Cependant, il ne peut être conclu qu'avoir une bouche sèche est un mécanisme du corps pour s'assurer que l'individu boive: La compréhension de la pression osmotique offre un aperçu des mécanismes de base, mais de nombreux problèmes restent ouverts, tels que savoir comment un organisme détermine la quantité d'eau à boire.
La nutrition se définit ici comme étant la science qui analyse les rapports entre la nourriture et la santé: Ces études conduisent à la diététique. On prend également en compte, dans le cadre de la nutrition, les comportements alimentaires des individus, notamment lors des repas ou lors de grignotage.
Cependant, à partir de l'observation clinique de maladies dont l'origine était une carence alimentaire par exemple, le scorbut , la nutrition concerne également aujourd'hui des maladies tels que les problèmes cardio-vasculaires et le cancer avec la méthode Kousmine par exemple , l' ostéoporose et l' hypertension artérielle excès de sel notamment , le diabète de type 2 , l' obésité , les maladies auto-immunes , la maladie d'Alzheimer [ 3 ].