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| == '''[[Potassium in nutrition and human health]]''' ==
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| To maintain [[Life|life]] and [[health]], the diet of humans must contain the chemical element,<b>[[potassium]]</b>, in its ionic form (K<sup>+</sup>), usually consumed as potassium salts of organic acids in food (e.g., potassium citrate), found most abundantly in non-grain plant foods (vegetables and fruits).
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| In 2004-2006, and again in 2010, the ''Institute of Medicine of the National Academies of Science'' <ref name=ottendribook>Otten JJ, Hellwig JP, Meyers LD (editors) (2006) Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press. Pages 370-379. ISBN 0-309-65646-X</ref> and its ''Food and Nutrition Board'' <ref name=napdri04>Panel on Dietary Reference Intakes for Electrolytes and Water. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Food and Nutrition Board. Institute of Medicine of The National Academies (2004) [http://books.nap.edu/openbook.php?record_id=10925&page=186/ Dietary Reference Intakes For Water, Potassium, Sodium, Chloride, and Sulfate] “Potassium” pp. 186-268. The National Academies Press, Washington, D.C.</ref> <ref name=ai-k>[http://www.dietaryguidelines.gov Dietary Guidelines for Americans, 2010]. [http://www.cnpp.usda.gov/Publications/DietaryGuidelines/2010/PolicyDoc/PolicyDoc.pdf PDF (p40]. U.S Dpartment of Agriculture. U.S. Department of Health and Human Services.</ref> recommended that adult humans consume 4700 milligrams (mg) of potassium per day, or more, which, calculated from the atomic mass of potassium (39.1 mg per [[Mole (unit)|mmol)]], corresponds to 120 millimoles (mmol) potassium per day: 4700 mg/39.1 mg/mmol=120 mmol. That recommended intake of potassium substantially exceeds estimates from recent surveys of average intakes by the general population, raising the possibility that a persisting state of suboptimal body potassium content, and rate of throughput of potassium, prevails in the general population. <ref name=03-04K>[http://www.ars.usda.gov/Services/docs.htm?docid=14958 What We Eat in America, NHANES 2003-2004, Tables. 1. Nutrient Intakes: Mean Amounts Consumed per Individual, One Day, 2003-2004 (Downloadable PDF File)]</ref> <ref name=05-06K>[http://www.ars.usda.gov/SP2UserFiles/Place/12355000/pdf/0506/Table_1_NIF_05.pdf Nutrient Intakes: Mean Amounts Consumed per Individual, One Day, 2005-2006.] U.S. Department of Agriculture, Agricultural Research Services, Fast Facts, Reports/Articles, and Tables (2005-2006).</ref> <ref name=eatk2010>[http://www.ars.usda.gov/Services/docs.htm?docid=18349 What We Eat in America, 2009-2010]. USDA. Downladable pdf Tables.</ref>
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| Subsequent sections will discuss potassium intake recommendations for children and special groups, as well as more recent perspectives on the 'optimal' requirements for dietary potassium in humans.
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| ===General considerations=== | |
| Potassium ranks as the most abundant cation (positive ion) inside animal [[Cell (biology)|cells]] (intracellular), and as such contributes critically in numerous important ways to the optimal functioning of cells and therefore to optimal functioning of the organ systems and individuals they compose. Among other metabolic functions, potassium plays a role in the synthesis of proteins and in the biochemical transformations required for carbohydrate metabolism.
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| Potassium plays an esential role in maintaining the electrical potential difference across the cell's plasma membrane, the intra- to extra-cellular electrical potential difference, typically referred to as the 'membrane potential'. That physicochemical regulatory function importantly enables normal transmission of information along nerves (nerve impulse transmission), normal contraction of muscle fibers, and normal functioning of the heart. The concentration of potassium inside cells (the intracellular fluid) exceeds that outside cells (the extracellular fluid) by an order of magnitude (~30 times), whereas the extracellular concentration of sodium exceeds that of its intracellular concentration by an order of magnitude (~10 times), the reverse of the situation with potassium. Those concentration differences between potassium ions and sodium ions generates the membrane potential, the inside potential negative with respect to the outside potential. A protein-based ion-pumping mechanism located within the lipid bilayer of the....
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| By influencing the electrical potential difference across the cell membrane, the ratio of the [[concentration]]s of potassium in intracellular fluid (ICF) to that in the cells' surrounding extracellular fluid (ECF) has important effects on the rate of transmission of electrical activity (pulses) along nerve fibers and skeletal muscle cells, which, among other things, affects the degree of contraction of the smooth muscles of arteries and arterioles (vascular tone).<ref name=moczydlowski2009>Moczydlowski EG. (2009) Electrophysiology of the Cell Membrane. In: Boron WF, Boulpaep EL (editors), Medical Physiology, 2nd ed. Saunders/Elsevier: Philadelphia. ISBN 9781416031154.</ref> Inasmuch as extracellular potassium varies in the 3-6 mmol/L range, while intracellular potassium concentrations average about 145 mmol/L, small changes in extracellular potassium concentration have a greater effect on the ICF-to-ECF potassium concentration ratio than similar small changes in intracellular potassium concentration. Subsequent sections discuss the implication of changes in the ICF-to-ECF potassium concentration ratio in human physiology.
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| ! style="text-align: center;" | [[Potassium in nutrition and human health#References|notes]]
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The Mathare Valley slum near Nairobi, Kenya, in 2009.
Poverty is deprivation based on lack of material resources. The concept is value-based and political. Hence its definition, causes and remedies (and the possibility of remedies) are highly contentious.[1] The word poverty may also be used figuratively to indicate a lack, instead of material goods or money, of any kind of quality, as in a poverty of imagination.
Definitions
Primary and secondary poverty
The use of the terms primary and secondary poverty dates back to Seebohm Rowntree, who conducted the second British survey to calculate the extent of poverty. This was carried out in York and was published in 1899. He defined primary poverty as having insufficient income to “obtain the minimum necessaries for the maintenance of merely physical efficiency”. In secondary poverty, the income “would be sufficient for the maintenance of merely physical efficiency were it not that some portion of it is absorbed by some other expenditure.” Even with these rigorous criteria he found that 9.9% of the population was in primary poverty and a further 17.9% in secondary.[2]
Absolute and comparative poverty
More recent definitions tend to use the terms absolute and comparative poverty. Absolute is in line with Rowntree's primary poverty, but comparative poverty is usually expressed in terms of ability to play a part in the society in which a person lives. Comparative poverty will thus vary from one country to another.[3] The difficulty of definition is illustrated by the fact that a recession can actually reduce "poverty".
Causes of poverty
The causes of poverty most often considered are:
- Character defects
- An established “culture of poverty”, with low expectations handed down from one generation to another
- Unemployment
- Irregular employment, and/or low pay
- Position in the life cycle (see below) and household size
- Disability
- Structural inequality, both within countries and between countries. (R H Tawney: “What thoughtful rich people call the problem of poverty, thoughtful poor people call with equal justice a problem of riches”)[4]
As noted above, most of these, or the extent to which they can be, or should be changed, are matters of heated controversy.
- ↑ Alcock, P. Understanding poverty. Macmillan. 1997. ch 1.
- ↑ Harris, B. The origins of the British welfare state. Palgrave Macmillan. 2004. Also, Oxford Dictionary of National Biography.
- ↑ Alcock, Pt II
- ↑ Alcock, Preface to 1st edition and pt III.
