Potassium neodecanoate

Endpoint summary

Additional information

1        Introduction

Unless otherwise stated, the information contained in this section was taken from the EFSA Scientific opinion on dietary reference values for potassium, 2016.

1.1      Chemistry

Potassium (K) is an abundant and highly reactive alkali metal which makes up 2.4 mass % of the Earth’s crust. Potassium is present in only one oxidation state (+ 1). It is a powerful reducing agent that is easily oxidized. Because of its high reactivity, potassium is not found free in nature but only as salts. Potassium compounds have good water solubility.

1.2      Biochemical functions

Potassium is an essential mineral in the human diet [and] predominant osmotically active element inside cells. Together with sodium and chloride, which are characteristic of the extracellularfluid, potassium contributes to osmolarity and plays a major role in the distribution offluids inside and outside cells. In addition, potassium participates in the regulation of the acid–base balance. Differences in potassium and sodium concentrations across cell membranes are maintained by the specific permeability of membranes to each of these ions and by Na⁺/K⁺-ATPase activity, which pumps sodium out of and potassium into the cells (Bailey et al., 2014; Gumz et al., 2015). The enzyme Na⁺/K⁺-ATPase plays an important role in the strict homeostatic control of plasma potassium concentrations. As a result, the intracellular potassium concentration is about 30 times higher than that of plasma and interstitialfluid. This concentration gradient (largely responsible for driving the membrane potential) is important for the transmission of electrical activity in nervefibres and muscle cells. Small changes in the ratio of extracellular to intracellular potassium concentration have large effects on neural transmission, muscle contraction and vascular tone (Bailey et al., 2014; Gumz et al., 2015). Potassium transport across the membranes of the endothelial and vascular smooth muscle cells has important effects on their contractile state, which can, in turn, influence endothelial function, bloodflow and blood pressure (Haddy et al., 2006). The concentration of potassium in cells of the collecting duct system of the kidney is important for the excretion of sodium. Maintenance of the transmembrane gradient is the key element for electrolytes andfluid homeostasis, a critical factor in blood pressure regulation (Bailey et al., 2014; Gumz et al., 2015). Different types of potassium channels have been implicated in functions such as salivary secretion, bile and gastric acid secretion, protein digestion and absorption, insulin secretion, carbohydrate digestion and absorption, and taste transduction. Potassium has a role in cell metabolism, participating in energy transduction, hormone secretion and the regulation of protein and glycogen synthesis. Potassium is a cofactor for a number of enzymes including glycerol dehydrogenase, mitochondrial pyruvate carboxylase, pyruvate kinase, L-threonine dehydratase, ATPases and aminoacyl transferase (Page and Di Cera, 2006; Toraya et al., 2010).

1.3      Dietary sources and intake data

1.3.1       Dietary sources

Potassium is present in all natural foods, in particular starchy roots or tubers, vegetables, fruits, whole grains, dairy products and coffee. Substantial potassium losses may occur during food processing. Drinking water and many food additives also contain potassium; however, it is unlikely that they represent major sources. The addition of potassium to food and food supplements is strictly regulated.

·        Food: Regulation No 1925/2006

·        Food supplements: Directive 2002/46/EC

·        Infant and follow-on formulae: Commission Directive 2006/141/EC

·        Processed cereal-based foods: Commission Directive 2006/125/EC

·        Baby foods for infants and young children: Commission Directive 2006/125/EC

Although a balanced diet usually supplies all the potassium a person needs, potassium supplements may be needed by patients who do not have enough potassium in their regular diet or have lost too much potassium because of illness or treatment with certain medicines. However, additional potassium application needs supervision due to possible health issues in case of potassium excess.

1.3.2       Recommended dietary intake

	D-A-C-H 2015 (b)	NCM 2014 (a)	WHO 2012 (c)	IOM 2005 (d)
Age (years)	≥ 19	≥ 18	≥ 16	≥ 19
DRV men (mg/day)	2000	3500	≥3510	4700
DRV women (mg/day)	2000	3100	≥3510	4700
Infants, age (months)	4-12	6-11	-	7-12
DRV (mg/day)	650	1100	-	700
Children, age (years)	1-4	2-5	-	1-3
DRV (mg/day)	1000	1800	-	3000
Children, age (years)	4-7	6-9	-	4-8
DRV (mg/day)	1400	2000	-	3800
Children, age (years)	7-10	10-13	-	9-13
DRV (mg/day)	1600	2900-3300	-	4500
Children, age (years)	10-13	14-17	-	14-18
DRV (mg/day)	1700	3100-3500	-	4700
Children, age (years)	13-15	-	-	-
DRV (mg/day)	1900	-	-	-
Children, age (years)	15-19	-	-	-
DRV (mg/day)	2000	-	-	-

DRV: dietary reference value; D-A-CH: Deutschland-Austria-Confoederatio Helvetica; IOM: US Institute of Medicine of the National Academy of Sciences; NCM: Nordic Council of Ministers; WHO: World Health Organization

(a): Population reference intake, (b): Adequate minimal intake, (c): Suggested intake, (d): Adequate intake

 

1.4      Toxicokinetics

1.4.1       Intestinal absorption

About 90 % of dietary potassium is absorbed, mainly in the small intestine, mostly through passive mechanisms in response to electrochemical gradients (Agarwal et al., 1994; Bailey et al., 2014). In the proximal small intestine, water absorption provides a driving force for the movement (solute drag) of potassium across the intestinal mucosa. In the ileum, the transepithelial electrical potential difference strongly influences its movement. It has been hypothesised that potassium may also be actively absorbed in the small intestine due to the presence of an H⁺/K⁺-ATPase in the apical membrane (Heitzmann and Warth, 2008). In surface cells of the distal colon, potassium is excreted through apical potassium channels in exchange for sodium which is reabsorbed through epithelial sodium channels. Potassium may also be reabsorbed in the colon through the action of luminal H⁺/K⁺-ATPases (colonic type), which can be of importance during potassium deprivation (Meneton et al., 1998).

1.4.2       Distribution

In healthy individuals, serum potassium concentrations range between 3.5 and 5.5 mmol/L, whereas plasma concentrations are lower by about 0.3–0.4 mmol/L. This difference is due to a release of potassium during clot formation (Nijsten et al., 1991; Sevastos et al., 2008). Homeostatic mechanisms act to maintain blood potassium concentration within a narrow range, even in the presence of wide variations in dietary potassium intake (Giebisch, 1998, 2004; Palmer, 2014; Gumz et al., 2015). In plasma, most potassium is present as free ions and 10–20 % is bound to proteins (Ifudu et al., 1992).

Around 98 % of systemic potassium is within the cells, making potassium the major intracellular cation, whereas the remaining potassium (2 %) is present in extracellular fluids. 

·        About 70 % of body potassium is located in the muscle and

·        About 30 % in the bone, liver, skin and red blood cells (Weiner et al., 2010).

Most of the body potassium (about 85 %) is rapidly exchangeable (half time of less than 7 h), while exchanges with red blood cells and brain pools are slower (Jasani and Edmonds, 1971). Intra- and extracellular concentrations of potassium are maintained within narrow limits.

After a meal, potassium is absorbed and rapidly enters the extracellular fluid. The subsequent rise in plasma potassium concentration is quickly attenuated by cellular uptake (Giebisch, 1998; Palmer, 2014). Na⁺/K⁺-ATPase is responsible for the active transport of potassium into the cells and for the maintenance of the extra- and intracellular sodium and potassium concentrations against electrochemical gradients. This ATPase is found in the cytoplasmic membrane of virtually all cells (McDonough and Nguyen, 2012). Potassium is also actively transported into some gastrointestinal cells and renal tubules by H⁺/K⁺-ATPase. Various Na⁺-K⁺-Cl^-cotransporters, which carry Na⁺, K⁺and Cl^-into the cell and are driven by the force of ion gradients, have been identified in the salivary glands, gastrointestinal tract and renal tubules. The K⁺-Cl^-cotransporter plays an important role for erythrocytes to maintain a specific shape and mediates potassium efflux (Lote, 2007).

Potassium transfer between the extra- and intracellular milieus is influenced by a variety of endogenous and exogenous factors (Gumz et al., 2015). Cellular potassium uptake by the muscle, liver, bone and red blood cells is promoted by the increase in plasma potassium concentration, by insulin, epinephrine and aldosterone, by metabolic alkalosis, and by drugs activating β-2 adrenergic receptors. Conversely, a decrease in plasma potassium concentration, metabolic acidosis, hyperosmolarity of the extracellular fluid, and α-antagonist drugs induce potassium transport from cells to the extracellular fluid.

1.4.1       Storage and liberation

The total body content of potassium is about 40–55 mmol/kg body weight (Rastegar, 1990; Agarwal et al., 1994; Crook, 2012; Bailey et al., 2014), which corresponds to 3–4 moles (110–150 g) for a 70 kg adult. Similar potassium body contents (expressed per kg body weight) have been reported in infants and children (Fomon et al., 1982; Butte et al., 2000). Based on 462 US children (232 boys and 230 girls) aged 3–18 years, no differences in total body potassium were observed for boys and girls between 12 and 30 kg of weight and 100 and 135 cm of height (about 10 years of age) (Flynn et al., 1972). Above these values, girls had less potassium per centimeter of height and per kilogram of weight than boys. In a sample of 116 US children (66 boys and 50 girls, aged 5–17 years), males had larger skeletal muscle (SM) and total body potassium (TBK) compared to females, while the SM: TBK ratio did not differ between both sexes (Wang et al., 2007). SM: TBK was positively correlated with age, weight and height (r = 0.62, r= 0.63, r = 0.86, respectively; all p < 0.001). The total body potassium accumulation during growth appears to reflect patterns of skeletal muscle gain.

1.4.2       Metabolism

Potassium as cation is absorbed, stored and eliminated in human physiology, but no further metabolism is known to occur.

1.4.3       Elimination

Body potassium content is regulated by the balance between dietary intake and renal excretion. In addition to urinary excretion, small quantities of potassium are excreted in the faeces and through the skin.

1.4.3.1      Urine

The kidney is the main route of potassium excretion. Studies in humans reported average urinary excretion of potassium between 77 % and 92 % of total dietary intake (Mickelsen et al., 1977; Pietinen, 1982; Holbrook et al., 1984; Tasevska et al., 2006; Yoshida et al., 2012). Urinary excretion of potassium varies with dietary intake. According to results published by the Intersalt Cooperative Research Group in late 1980s (Intersalt Cooperative Research Group, 1988), a typical range observed with a mixed Western diet was 46–77 mmol/day. Potassium is freely filtered by the glomerulus. In healthy adults, the rate of potassium filtration by the glomerular capillaries is 756 mmol/day, considering a glomerular filtration rate of 180 L/day multiplied by a plasma potassium concentration of 4.2 mmol/L (Guyton and Hall, 2006). The renal tubules are capable of reabsorbing and secreting potassium in response to various stimuli (Rodenburg et al., 2014). The human kidney efficiently excretes potassium in response to high dietary intakes, but is less capable of sparing potassium when dietary intake is low (Kee et al., 2010). The majority of filtered potassium is reabsorbed in the proximal tubule and loop of Henle, so that less than 10 % of the filtered load reaches the distal nephron.

The major factors regulating potassium excretion include dietary potassium, distal nephron flow rate and sodium delivery, mineralocorticoids (including aldosterone), and acid–base balance (Palmer, 2014; Gumz et al., 2015). Renal potassium excretion has also a circadian rhythm independent of food intake (Gumz et al., 2015). The circadian rhythm, which originates from the brain, is transmitted to circadian clocks in the tubule cells responsible for variations in potassium excretion. As a result, potassium excretion is enhanced during the daylight phase and reduced during the night time phase (Gumz et al., 2015).

1.4.3.2      Faeces

Potassium concentration in faeces is highly variable (ranging from 20 to 200 mmol/L). Distal ileum and the colon can actively secrete potassium (Sorensen et al., 2010). Net absorption only takes place when large gradients of concentration between the colon and the blood are present (Devroede and Phillips, 1969). Faecal potassium excretion is about 10–25 mmol/day, constituting 10–20 % of total potassium elimination from the body (Holbrook et al., 1984; Agarwal et al., 1994; Tasevska et al., 2006). Faecal potassium excretion increases with fibre intake (Cummings et al., 1976; Tasevska et al., 2006). Potassium losses in faeces may considerably increase in pathological situations, especially in cases of diarrhoea (Sandle and Hunter, 2010; West and von Saint Andre-von Arnim, 2014) or renal insufficiency (Sandle et al., 1986). In a study on four adult men in which dietary potassium intake was severely restricted (less than 39 mg (1 mmol)/day) for 2–7 days, faecal potassium loss decreased and was 2.5–7.6 mmol/day at the end of the depletion period (Squires and Huth, 1959). This is presumed to represent obligatory potassium losses related to digestive secretions (salivary, gastric, biliary and pancreatic), cell desquamation, and mucus secretion (Agarwal et al., 1994; Sorensen et al., 2010).

1.4.3.3      Sweat

The concentration of potassium in the sweat is relatively low; typical values range from 3 to 7 mmol/L (Costill, 1977; Montain et al., 2007; Penney, 2008; Baker et al., 2009; Kilding et al., 2009; Maughan et al., 2009). In various studies, the concentration of potassium in the sweat was not or only minimally affected by physical exercise (Montain et al., 2007), heat stress (Malhotra et al., 1976) or dietary sodium intake or ethnicity (Palacios et al., 2010), including conditions of dietary potassium restriction (Malhotra et al., 1981; Costill et al., 1982). Sweat potassium concentration stays relatively constant, regardless of sweat rate, level of acclimatisation or an individual’s sodium concentration in the sweat (Weschler, 2008). When sweat losses are several litres a day, as under heat or physical exercise stress conditions, potassium sweat losses may be up to 10–25 mmol/day (Consolazio et al., 1963; Malhotra et al., 1976, 1981). It is considered that potassium losses through the sweat at moderate physical activity performed around thermoneutrality are likely to be in the range of 2–3.5 mmol/day, assuming a daily sweat volume of around 0.5 L/day (Shirreffs and Maughan, 2005; Subudhi et al., 2005).

 

 

 

 

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