Potassium
POTASSIUM
Potassium is one of the principal electrolytes within the body in addition to sodium and chloride. In contrast to sodium and chloride where concern is overconsumption, nutritional concerns with potassium are mainly concerned with the possibility of underconsumption. Absorption and transportation Potassium is the major intracellular electrolyte and exists as the fully water-soluble cation K+. More than 90% of dietary potassium is absorbed from the digestive tract. Potassium is mostly concentrated inside cells. Almost all of the body potassium is exchangeable, intracellular concentration (i.e. within cells) being more than 30 times the concentration of the extracellular fluid (i.e. outside cells). Potassium is distributed within the body in response to energy-dependent sodium redistribution. Various hormonal and other factors regulate potassium homeostasis, both within cells and with the external environment. Hyperkalemia, too much potassium in outside cells, stimulates insulin, aldosterone and epinephrine (adrenaline) secretions, which promote the uptake of potassium by body cells. Aldosterone hormone also stimulates potassium excretion by the kidney and, at the same time, conserves sodium. Hypokalemia, too little potassium in outside cells, has opposite effects, such that more potassium is released from cells. As with sodium, the kidney regulates potassium balance. Urine is the major excretory route in healthy people, with only small amounts lost in the faeces and minimal amounts in sweat.
Roles
1.It is essential component of every cell and is required for cell growth
2. Participates in biochemical reactions especially those involved in energy metabolism from food and in the synthesis of glycogen and proteins.
3. Influence osmotic pressure within cells by controlling water balance
4. Help to maintain acid-base balance by increasing in concentration in fluids that become too acidic and decreasing in concentration in fluids that become too alkaline
5. Crucial participant in the movement of ions across nerve cell membranes that form and sustain nerve impulses
6. Together with magnesium ions, act as muscle relaxant that opposes the muscle-contracting stimulus, of calcium ions Deficiency and Toxicity Deficiency may occur during diarrhoea, excessive vomiting, use of diuretics that enhance potassium loss, chronic renal disease, severe protein-energy malnutrition, starvation or surgery. Hyperkalemia, as a result of either a shift of potassium from inside to outside cells or excessive potassium retention, can be caused by major trauma and infection, metabolic acidosis, aldosterone insufficiency and chronic renal failure. Overuse of potassium supplements can also result in potassium excess. As with potassium depletion, the most important clinical consequence of potassium excess is cardiac arrest. Dietary sources Potassium is naturally widely distributed in foods. Food processing (through leaching) may decrease potassium content as well as increasing salt content. Legumes, nuts, dried fruit and fresh fruit (especially bananas, melons, avocados, kiwi fruit) are rich sources of potassium. Major vegetable sources of potassium are potatoes and spinach. Cereal and dairy products have lower potassium content but are consumed in large quantities. Meat and fish contain appreciable quantities of potassium.
Potassium is one of the principal electrolytes within the body in addition to sodium and chloride. In contrast to sodium and chloride where concern is overconsumption, nutritional concerns with potassium are mainly concerned with the possibility of underconsumption. Absorption and transportation Potassium is the major intracellular electrolyte and exists as the fully water-soluble cation K+. More than 90% of dietary potassium is absorbed from the digestive tract. Potassium is mostly concentrated inside cells. Almost all of the body potassium is exchangeable, intracellular concentration (i.e. within cells) being more than 30 times the concentration of the extracellular fluid (i.e. outside cells). Potassium is distributed within the body in response to energy-dependent sodium redistribution. Various hormonal and other factors regulate potassium homeostasis, both within cells and with the external environment. Hyperkalemia, too much potassium in outside cells, stimulates insulin, aldosterone and epinephrine (adrenaline) secretions, which promote the uptake of potassium by body cells. Aldosterone hormone also stimulates potassium excretion by the kidney and, at the same time, conserves sodium. Hypokalemia, too little potassium in outside cells, has opposite effects, such that more potassium is released from cells. As with sodium, the kidney regulates potassium balance. Urine is the major excretory route in healthy people, with only small amounts lost in the faeces and minimal amounts in sweat.
Roles
1.It is essential component of every cell and is required for cell growth
2. Participates in biochemical reactions especially those involved in energy metabolism from food and in the synthesis of glycogen and proteins.
3. Influence osmotic pressure within cells by controlling water balance
4. Help to maintain acid-base balance by increasing in concentration in fluids that become too acidic and decreasing in concentration in fluids that become too alkaline
5. Crucial participant in the movement of ions across nerve cell membranes that form and sustain nerve impulses
6. Together with magnesium ions, act as muscle relaxant that opposes the muscle-contracting stimulus, of calcium ions Deficiency and Toxicity Deficiency may occur during diarrhoea, excessive vomiting, use of diuretics that enhance potassium loss, chronic renal disease, severe protein-energy malnutrition, starvation or surgery. Hyperkalemia, as a result of either a shift of potassium from inside to outside cells or excessive potassium retention, can be caused by major trauma and infection, metabolic acidosis, aldosterone insufficiency and chronic renal failure. Overuse of potassium supplements can also result in potassium excess. As with potassium depletion, the most important clinical consequence of potassium excess is cardiac arrest. Dietary sources Potassium is naturally widely distributed in foods. Food processing (through leaching) may decrease potassium content as well as increasing salt content. Legumes, nuts, dried fruit and fresh fruit (especially bananas, melons, avocados, kiwi fruit) are rich sources of potassium. Major vegetable sources of potassium are potatoes and spinach. Cereal and dairy products have lower potassium content but are consumed in large quantities. Meat and fish contain appreciable quantities of potassium.
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