Dietary Potassium RDA, Levels, Benefits and Sources
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What is Dietary Potassium?Potassium, or more specifically dietary potassium is part of the family of minerals, and belongs to the mineral sub-family known as electrolytes. Other examples of mineral electrolytes are sodium and magnesium. They are referred to as electrolytes as they all conduct electricity when dissolved in water. Potassium exists in the body as the potassium cation (element symbol 'K') with a single positive charge (K+).
Potassium Levels in the BodyPotassium is approximately the eighth most common element by mass (0.2%) in the human body. A typical adult weighing 60kg contains about 120g of potassium. Sulfur and chlorine (or more correctly chloride ions) content in the body is almost equivalent to potassium. Calcium and phosphorus are major minerals which are more abundant than potassium in the body. Nearly 98% of the potassium in the body is found in cells. Red blood cells contain about 450 mg of potassium per 100 ml and the blood serum typically will contain 4-5 mg per 100 ml. Therefore red blood cell potassium levels is a good indication of an individuals potassium levels.
It is the main intracellular cation although it does also exist in smaller concentrations as an extracellular cation. The ratio between intracellular and extracellular potassium levels affects muscular contraction, vascular tone, neural transmission and is essential for normal cellular function. Even small changes in the concentration of extracellular potassium can greatly affect the ratio between extracellular and intracellular potassium. The intracellular levels or concentration is approximately 150 mM/L (milli Moles per Litre) while the extracellular concentration in the blood serum at equilibrium is about 5 mM/L (note the blood serum is the component that is neither a blood cell ie neither white nor red blood cells nor a clotting factor; it is the blood plasma not including the fibrinogens). This large concentration difference is not sufficient for net potassium movement as the inside of the cell has a negative membrane potential which balances the diffusion forces which tries to push the potassium out of the cell. The membrane potential which balances the diffusion of the potassium ion is the potassium equilibrium potential and is -92mV.
Low Potassium Levels or HypokalemiaAlthough uncommon in the general population, the main effect of severe potassium deficiency or low potassium levels is known as hypokalemia (reference Mandal AK. Hypokalemia and hyperkalemia. Med Clin North Am. 1997;81(3):611-639). Hypokalemia can cause cardiac arrhythmias, muscle weakness, and glucose intolerance. Moderate potassium deficiency, which typically occurs without hypokalemia, is characterized by elevated blood pressure, increased salt sensitivity, an increased risk of kidney stones, and increased bone turnover.
Causes of HypokalemiaLow potassium levels or hypokalemia can be as a result of a potassium deficient diet although this is not the most common cause of low potassium levels. The most common causes of a fall in potassium levels it typically due to the loss of potassium from either the gastrointestinal (GI) tract or the kidney.
Potassium loss from the GI tract may be caused by vomiting, diarrhea, ileostomy (bowel diversion surgery) or laxative use. These are often associated with heavy fluid losses that "flush" potassium out of the body. People with eating disorders such as anorexia nervosa and bulimia, alcoholics, and those who have had bariatric surgery have a higher incidence of hypokalemia than others. Potassium loss from the kidney may be caused by diuretic medications (water pills) or low body magnesium levels. Low levels of potassium can also be caused by elevated corticosteroid levels, either from medication like prednisone or in many adrenal disorders, such as Cushing syndrome where the adrenal glands produce too much aldosterone, a hormone that causes the kidneys to excrete large amounts of potassium.
Hypokalemia may result in a number of the following complications.
Tiredness or muscle cramps
Fainting or nausea
poor reflexes, tingling or numbness
respiratory failure and or palpitations
cardiac arrest in extreme cases
Hypokalemia or potassium deficiency is defined as serum potassium levels or concentration below 4 mmol/L. Hypokalemia can be further arbitrarily graded by severity.
Relative severity of Hypokalemia
This is defined as potassium levels at 3.5-4mM/L and applies to certain high-risk patient populations with cardiac disease, such as ischemic or scarred myocardium, left ventricular hypertrophy, congestive heart failure, or myocardial infarction.
Moderate severity of Hypokalemia
The levels are defined as: 2.5-3.5mM/L
The levels are defined as: <2.5mM/L
High Potassium Levels or HyperkalemiaThere is no evidence that a high intake of potassium levels from foods has adverse effects in healthy people. However, for individuals whose urinary excretion of potassium is impaired, a potassium intake level below the AI is appropriate because adverse cardiac effects (arrhythmias) can occur as a result of hyperkalemia (markedly elevated serum potassium concentration). Such individuals are typically under medical supervision. Hyperkalemia is defined as a serum potassium concentration higher than 5.0 mM/L, and severe hyperkalemia is defined as a serum potassium concentration higher than 6.5 mmol/L. Hyperkalemia can be asymptomatic, meaning that it causes no symptoms although nausea, fatigue and muscle weakness have been reported. Symptoms are not normally apparent until very high levels of potassium have been reached for example greater than 7mM/L.
Causes of HyperkalemiaAn elevated potassium level occurs when potassium homeostasis is disrupted. Hyperkalaemia has four broad causes:
1) Renal causes for example due to decreased excretion or drugs
2) Increased circulation of potassium which can be exogenous (potassium supplementation) or endogenous (tumour lysis syndrome, rhabdomyolysis, trauma, burns).
3) A shift from the intracellular to the extracellular space eg acidosis in diabetic ketoacidosis (DKA).
4) Pseudohyperkalaemia. Pseudohyperkalemia can occur with thrombocytosis, hemolysis, and extremely high white cell counts.
Specific reasons for hyperkalemia include - poor kidney function, such as acute kidney failure or chronic kidney disease and the use of heart medicines for example angiotensin converting enzyme (ACE) inhibitors and angiotensin 2 receptor blockers (ARBs). Hyperkalemia is also caused by Addison's disease which is adrenal failure, Alcoholism or heavy drug use that causes rhabdomyolysis, a breakdown of muscle fibers that results in the release of potassium into the bloodstream. Destruction of red blood cells due to severe injury or burns or excessive use of potassium supplements or type I diabetes are also potential reasons for elevated potassium levels.
Absorption, Metabolism, Storage, and ExcretionHealthy people absorb more than 85 percent of the potassium they consume. It is absorbed in the body, mostly in the small intestine by moving from the lumen, or central cavity of the intestine, through the junctions between intestinal cells and into the bloodstream. This movement does not require energy and is therefore described as passive. The potassium moves from an area of high potassium concentration, typically in the intestinal lumen, to an area of low potassium concentration, in the blood. Furthermore, the potassium can enter the body through the colon where it can be not only absorbed but secreted as well which is dependent on the concentration in the lumen.
The absorption process in the colon is an active process which requires energy. Potassium is absorbed by a transport enzyme called a hydrogen potassium ATPase pump. It uses adenosine triphosphate, or ATP, as the energy source to pump potassium from the colon lumen into the intestinal cell and hydrogen out of the cell into the lumen. The high intracellular concentration of potassium is maintained by this sodium-potassium-ATPase pump. Because insulin stimulates this pump, changes in the plasma insulin concentration can affect extracellular potassium concentration and thus plasma concentration of potassium. About 77–90 percent of dietary potassium is excreted in the urine. The kidney is the main organ that controls the balance of potassium by removing excess potassium into the urine. This is because, in a steady state, the correlation between dietary potassium intake and urinary potassium content is high. The rest is excreted mainly in the faeces, and much smaller amounts are lost through sweat.
Importance and BenefitsIt is essential for the normal function of the body and for both body growth and maintenance building muscles and transmission of nerve impulses. It is classified as an electrolyte and involved in both electrical and cellular functions. Potassium is particularly important in regulating the activity of muscles and nerves and is often a principal component of hydration drinks used for both pre and post exercise activities. Potassium is lost in excessive sweating and urine and so foods like bananas are important for sports. Furthermore, if you are suffering from vomiting or diarrhea you may require more potassium. Almost one out of five people hospitalized in the United States has a low potassium level.
It preserves proper alkalinity of body fluids and assists in reducing high blood pressure along with promoting healthy skin. Potassium also stimulates the kidneys to eliminate poisonous body wastes. The frequency and degree to which our muscles contract, and the degree to which our nerves become excitable, both depend heavily on the presence of potassium in the right amount. Potassium works with sodium to regulate the body's waste balance and normalize heart rhythms. The FDA has determined that if the potassium content in foods is at least 350 milligrams of potassium, then the following description in the label can be used: "Diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke." Again this shows the importance of not only potassium but sodium as well and the resulting ratio.
Best Ratio of Dietary Potassium to SodiumSodium and potassium are important in the body as they exist in a partnership, and are regulated across the cell membrane by a process which used ATP for hydrolysis. This process which involves an enzyme referred to as Na+/K+-ATPase. The process maintains a large excess of sodium cations outside the cell and a large excess of potassium cations inside the cell. This results in the transport of three sodium ions to the outside of the cell and the transport of two potassium ions to inside the cell. This unbalanced charge transfer contributes to the separation of charge across the membrane. The sodium-potassium pump is an important contributor to action potential produced by nerve cells. Potassium levels will typically change with sodium levels. When sodium levels go up, potassium levels go down, and when sodium levels go down, potassium levels go up. Potassium levels are also affected by a hormone called aldosterone, which is made by the adrenal glands.
Clearly this shows how these two minerals are related and thus the ratio in food is also important to consider to recognise the balance associated with cellular potential and therefore overall cell function. Since sodium and potassium are metabolised very differently and that some people eg atheletes who sweat alot may have different requirements, it is difficult to define the optimal ratio of sodium to potassium in the diet. However it is fair to say that most western diets would benefit from lowering the sodium:potassium ratio by consuming foods high in potassium. Typically the western diet sodium:potassium ratio is about 1:1 although a recommended sodium:potassium would be at least 1:2.
Potassium SupplementsThe US FDA (Food and Drug Administration) only allow up to 99mg of potassium in any dietary supplement that is sold over the counter. Since the recommended daily allowance (or more correctly the adequate intake) is 4700 mg this is approximately 2% of the daily allowance. Extended release tablets are available on prescription and can range from 600 to 750mg and are given for special cases whereby potassium is depleted for example due to diuretics. Since the levels of potassium are tightly regulated by the kidneys, impaired kidney function (for example in the elderly) can give rise to high levels of potassium and therefore heart rhythm problems and in extreme cases cardiac arrest. Drugs can also give an increase in potassium levels which include ACE-inhibitors, nonsteroidal anti-inflammatory drugs, and blood thinning agents such as heparin. Their use with potassium supplements should only be under the guidance of a registered physician.
As previously described potassium usually exists as cation with its associated counterion (or conjugate anion) in supplements the potassium exists in one of the following forms potassium acetate, potassium bicarbonate, potassium citrate, potassium chloride, or potassium gluconate.
Potassum in FoodsAs dietary potassium occurs as positive cation it will be associated with a negative anion (referred to as the conjugate anion). The conjugate anions in unprocessed foods are organic anions such as citrate which are converted in the body to bicarbonate. This bicarbonate acts as a buffer in the human body which means it neutralizes diet derived acids such as sulhpuric acid which is generated from sulphur containing amino acids found in meats and other high protein foods. When the intake of bicarbonate precursors is inadequate, buffers in the bone matrix neutralize excess diet-derived acids. Bone becomes demineralized in the process. The resulting adverse consequences are increased bone turnover and calcium-containing kidney stones. In processed foods to which potassium has been added, and in supplements, the conjugate anion is typically chloride, which does not act as a buffer.
Because the demonstrated effects of potassium often depend on the accompanying anion and because it is difficult to separate the effects of potassium from the effects of its accompanying anion, the data on dietandfitnesstoday.com focuses on non-chloride forms of potassium which is mainly potassium citrate naturally found in fruits, vegetables, and other potassium-rich foods.
Effect of cooking on potassium levelsAlthough food does not lose significant amounts of potassium over time cooking can have a significant impact on potassium levels in food. The way in which food is prepared can have also have an impact on the potassium content (as well as other vitamins and minerals). Boiling foods can result in a loss of potassium therefore steam cooking or brief frying are better cooking methods to retain the potassium in the food and thereby keeping dietary potassium levels high. Taking spinach as an example the levels of potassium are summarised here. In 100g there is 558mg of potassium, however after boiling the spinach the levels of potassium drops to 468mg. Furthermore, freezing the spinach can reduce the potassium levels even further to 346mg.
However, it is worth remembering a balanced diet usually supplies all the potassium you need.
Recommended Daily/Dietary Allowance of PotassiumA dietary survey in the US (reference - Hajjar IM, et al. Impact of diet on blood pressure and age-related changes in blood pressure in the US population: analysis of NHANES III. Arch Intern Med. 2001;161(4):589-593. ) indicated that the average adult dietary potassium intake is about 2,300 mg/day for women and 3,100 mg/day for men. The daily potassium levels needed is defined in several different ways.
Recommended Dietary Allowances (RDAs) are the amount of vitamins and minerals needed to provide for adequate nutrition in most healthy persons. RDAs for a given nutrient may vary depending on a person's age, sex, and physical condition (e.g., pregnancy). Daily Values (DVs) are used on food and dietary supplement labels to indicate the percent of the recommended daily amount of each nutrient that a serving provides. DV replaces the previous designation of United States Recommended Daily Allowances (USRDAs).
Recommended Nutrient Intakes (RNIs) are used to determine the amounts of vitamins, minerals, and protein needed to provide adequate nutrition and lessen the risk of chronic disease.
Because lack of potassium is rare, there is no RDA or RNI for this mineral. However, it is thought that 1600 to 2000 mg (40 to 50 milliequivalents [mEq]) per day for adults is adequate. Since data were inadequate to determine an Estimated Average Requirement (EAR) and thus calculate a Recommended Dietary Allowance (RDA) for potassium, an Adequate Intake (AI) was instead developed. The AIs for potassium are based on a level of dietary intake that should maintain lower blood pressure levels, reduce the adverse effects of sodium chloride intake on blood pressure, reduce the risk of recurrent kidney stones, and possibly decrease bone loss. In healthy people, excess potassium above the AI is readily excreted in the urine; therefore a UL was not set.
The recommended daily allowance ranges from 3g per day for a young baby up to 4.7g for a healthy adult. The complete suggestions for RDA are given below in the RDA section.
Potassium RDA Levels
The RDA for Potassium is actually an Adequate Intake. The difference is explained in the rda section here.
children 1-3 yrs 3.0 g
children 4-8 yrs 3.8 g
children 9-13 yrs 4.5 g
Males 14-70+ yrs 4.7 g
Females 14-70+ yrs 4.7 g
Pregnancy 19-50 yrs 4.7 g
Lactation 19-50 yrs 5.1 g
For further information on nutrients RDA see our complete list for recommended dietary allowance.
Good sources of PotassiumPotassium can be found in most types of fruits, fish and whole grains. As an example a single cup of orange juice (248g) contains 496mg (0.496g) of potassium. Other foods high in potassium include avocados, oranges, bananas, tomatoes and kidney beans.
We have sorted our nutrition database by foods with a high potassium content. You can also search through for foods with Low Potassium content. So you can easily see how much Potassium is contained in different foods. You can also search through our database using the search box below or browse the potassium content by food category.
ReferencesCogswell ME, et al. Sodium and potassium intakes among US adults. Am J Clin Nutr 2012;96:647-57.
Drewnowski A et al. Reducing the sodium-potassium ratio in the US diet: a challenge for public health. Am J Clin Nutr 2012; 96:439-44.
Gennari FJ et al Hyperkalemia: An adaptive response in chronic renal insufficiency.; Kidney Int. 2002 Jul;62(1):1-9.
Drewnowski A et al. Reducing the sodium-potassium ratio in the US diet: a challenge for public health. Am J Clin Nutr. 2012; 96(2):439-44.
He FJ et al. Beneficial effects of potassium on human health. Physiol Plant. 2008;133(4):725-35.
Goyal A et al. Serum potassium levels and mortality in acute myocardial infarction. JAMA. 2012; 307(2):157-64.
Larsson SC et al. Dietary potassium intake and risk of stroke: a dose-response meta-analysis of prospective studies. Stroke. 2011; 42(10): 2746-50.
O'Donnell MJ et al. Urinary sodium and potassium excretion and risk of cardiovascular events. JAMA. 2011; 306(20):2229-38.