Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005) / Chapter Skim
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5 Potassium
5 Potassium
Pages 186-268
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From page 186... ...
The adverse effects of inadequate potassium intake can result from a deficiency of potassium per se, a deficiency of its conjugate anion, or both. In unprocessed foods, the conjugate anions of potassium are mainly organic anions, such as citrate, that are converted in the body to bicarbonate.
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From page 187... ...
In the generally healthy population with normal kidney function, a potassium intake from foods above the AI poses no potential for 2 To convert millimoles (mmol) of potassium to milligrams (mg)
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From page 188... ...
was not set. However, in individuals in whom urinary excretion of potas sium is impaired, a potassium intake below 4.7 g (120 mmol)
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. The correlation between dietary potassium intake and urinary potassium content is high (r = 0.82)
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From page 190... ...
INDICATORS CONSIDERED FOR ESTIMATING THE REQUIREMENT FOR POTASSIUM This section reviews potential physiological indices and pathologic endpoints for adverse effects of insufficient dietary intake of potassium in apparently healthy individuals. Because the demonstrated effects of potassium often depend on the accompanying anion and
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From page 191... ...
The effects on potassium balance of two levels of potassium intake (3.1 g [80 mmol] /day and 11.7 g [300 mmol]
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From page 192... ...
, even marginally, relative to the usual potassium intake in the Western diet. Based on recent diet surveys, the estimated median potassium intakes for adult age groups in the United States (Appendix Table D-5)
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193 POTASSIUM TABLE 5-1 Dietary Potassium and Serum Potassium Concentrations Serum Dietary Potassium Potassium (mmol/L)
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are highly regulated, their plasma concentrations remain normal or little changed despite substantial increases in dietary potassium intake (Lemann et al., 1989, 1991; Morris RC et al., 2001; Schmidlin et al., 1999)
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From page 195... ...
In the African Americans with severe salt sensitivity, increasing dietary potassium to a high-normal intake of 4.7 g (120 mmol) /day reduced the frequency of salt sensitivity to 20 percent, the same percentage as that observed in white subjects when their potassium intake was increased to only 2.7 g (70 mmol)
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From page 196... ...
Furthermore, these trials highlight the potential benefit of increased potassium intake in African Americans, who have a higher prevalence of hypertension and of salt sensitivity and a lower intake of potassium than non-African Americans. Survey data from the Third National Health and Nutrition Examination Survey (NHANES III)
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From page 197... ...
have examined the relationship between blood pressure and dietary potassium intakes, or urinary potassium excretion, used as a proxy of intake (Ascherio et al., 1992; Dai et al., 1984; Dyer et al., 1994; Geleijnse et al., 1996; Hajjar et al., 2001; Khaw and Barrett-Connor, 1984; Langford, 1983; Liu et al., 1988, 1996; Rose et al., 1988; Takemori et al., 1989; Tunstall-Pedoe, 1999; Walker et al., 1979)
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From page 198... ...
198 DIETARY REFERENCE INTAKES TABLE 5-2 Epidemiological Studies on Potassium Intake and Blood Pressure Reference Study Design Walker et al., 1979 Cross-sectional, 574 men and women Khaw and Barrett- Cross-sectional, 685 men and women Connor, 1984 Kok et al., 1986 Cross-sectional, 2,291 men and women in the Netherlands, multivariate analysis Kesteloot and Belgian Interuniversity Research on Nutrition and Health Joossens, 1988 Study, cross-sectional, 8,058 men and women Khaw and Barrett- Cross-sectional, 1,302 men and women Connor, 1988 Liu et al., 1988 Cross-sectional, 3,248 men and women in China Rose et. al., 1988 Intersalt study, cross-sectional, 10,648 men and women Takemori et al., 1989 Cross-sectional, 7,441 women in Japan Witteman et al., 1989 Nurses Health Study, prospective, 4-yr follow up, 58,218 women, multivariate analysis Khaw and Barrett- Cross-sectional, 2,046 men and women Connor, 1990 Ascherio et al., 1992 Health Professionals Follow-Up Study, prospective 4-yr follow-up, 30,681 men, multivariate analysis
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From page 199... ...
1.05 Q5 > 3.2 (82) 1.05 p = 0.26 No independent association with potassium intake and risk of hypertension Age-adjusted SBP and DBP correlated significantly and directly with Na:K ratio Potassium intake g/d (mmol/d)
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From page 200... ...
Although the trials in Tables 5-4 and 5-5 tested the effect of supplemental potassium, their findings are assumed to apply to potassium from foods as well. A few studies have tested the effects of diets rich in potassium (Appel et al., 1997; Sacks et al., 2001)
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From page 201... ...
was associated with a 0.9 mm Hg lower SBP and 0.8 mm Hg lower DBP Potassium intake was significantly and inversely related to blood pressure in white women and African-American men Potassium excretion was significantly and inversely associated with blood pressure, especially SBP in men SBP and DBP were inversely associated with K intake specify the amount of dietary potassium provided by the increased fruit and vegetable diet (John et al., 2002)
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From page 202... ...
and the one by Geleijnse and coworkers (2003) were confined to randomized controlled trials in which the only difference between the intervention and control groups was potassium intake.
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Average net change in urinary potassium excretion for the inter
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7.8 (200) KCl supplement [1.2 (50)
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on Placebo (mm Hg) Potassium Sodium or Control Dietd (K)
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. b Potassium intake from diet unless otherwise indicated.
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. When the analysis was restricted to the 29 trials with a documented intervention-related net change in urinary potassium greater than or equal to 20 mmol (0.8 g)
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KCl supplement Fotherby and 5 men 4-wk crossover Placebo Potter, 1992a 13 women 2.3 (60) KCl supplement Kaplan et al., 6 men 6-wk crossover Placebo 1985a 10 women 2.3 (60)
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(mmol) Control Diet SBP DBP Comments 2.7 (70)
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. b Potassium intake from diet unless otherwise indicated.
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(mmol) Control Diet SBP DBP Comments 2.4 (62)
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. Because virtually all trials used potassium chloride supplements, while observational studies assessed dietary potassium intake from foods (paired with nonchloride anions)
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are difficult to reconcile and therefore preclude firm conclusions. An inverse relationship between dietary potassium intake at baseline and subsequent stroke-associated morbidity and mortality has also been noted in several, but not all, cross-sectional and cohort studies (Table 5-6)
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214 DIETARY REFERENCE INTAKES TABLE 5-6 Epidemiological Studies on Potassium Intake: Stroke and Heart Disease Reference Study Design Stroke Khaw and Barrett- Rancho Bernardo Study, 12-yr follow-up Connor, 1987 n = 859 men and women, not energy adjusted Lee et al., 1988 Honolulu Heart Study, 16-yr follow-up n = 7,591 Japanese men Sasaki et al., 1995 Pearson correlation and multiple regression analysis n = 17 countries Ascherio et al., 1998 Health Professionals Follow-up Study n = 43,738 men, multivariate analysis Iso et al., 1999 Nurses' Health Study, prospective cohort n = 85,764 women, multivariate analysis
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Potassium intake not Urinary potassium correlated reported inversely with incidence of stroke mortality (p < 0.05) RR of stroke Risk for ischemic Q1 2.4 (61)
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216 DIETARY REFERENCE INTAKES TABLE 5-6 Continued Reference Study Design Fang et al., 2000 NHANES I study, 17-yr follow-up n = 9,866 men and women, not energy adjusted Bazzano et al., 2001 NHANES I 19-yr follow-up n = 9,805 men and women, multivariate analysis Green et al., 2002 4–8 yr follow-up 3,595 men and women, > 65 yr Coronary heart disease Tunstall-Pedoe et al., Scottish Heart Health Study, prospective 1997 n = 11,629 men and women, 7.6 yr of follow-up a T = tertile of intake, Q = quartile or quintile of intake. b RR = relative risk, HR = hazard ratio, CHD = coronary heart disease.
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1.66, p = 0.42 dietary African-American men potassium intake n = 595 a predictor of T1 < 1.3 (33) stroke mortality.
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. In a 7-year follow-up report of 5,754 men and 5,875 women who were participants in the Scottish Heart Health Study, an inverse relationship between potassium intake and subsequent death, both from all causes and from coronary heart disease, was found (Tunstall-Pedoe et al., 1997)
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. Pyridinoline excretion, a marker of bone resorption, was negatively associated with energy-adjusted potassium intakes (New et al., 2000)
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In women potassium intake was significantly (p < 0.05) associated with bone mineral density for the trochanter, Ward's area, and radius (cross-sectional)
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Similar results were seen and conclusions drawn in metabolic studies of nonhypertensive young men and women in whom dietary potassium chloride was replaced with potassium bicarbonate, whereupon the urinary excretion of deoxypyridinoline, pyridinoline, and n-telopeptide (markers of bone resorption) promptly decreased (Maurer et al., 2003)
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/day sodium and a concomitant increase in bone resorption, as indicated by biochemical markers, was abolished by supplying 3.5 g (90 mmol) /day of dietary potassium as potassium citrate, a supplement that increased urinary potassium to 141 mmol (5.5 g)
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. The absence of a relationship between dietary sodium and kidney stones should be TABLE 5-8 Epidemiological Studies on Potassium Intake and Risk of Kidney Stone Formation Potassium Relative Risk Intake,a for Kidney Reference Study Design g/d (mmol/d)
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. In a study conducted in Finland where the dietary potassium intake is greater than in the United States, risk for kidney stones appeared to decrease with an increased intake of potassium (3.8 compared with 4.6 g [97 to 118 mmol]
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From page 225... ...
with decreasing urinary potassium excretion (Tribe et al., 1994) , while no relationship was found between potassium intake and bronchial responsiveness or respiratory symptoms in adults in a second study (Zoia et al., 1995)
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/day, which exceeded the potassium intake. Average sweat potassium daily losses of three men who were exposed to 37.8°C (100°F)
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Urinary potassium excretion was significantly lower with the low potassium diet (2.6 versus 1.2 g [67 versus 31 mmol]
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. Interactions with Other Electrolytes The effects of potassium intake depend, in part, on the level of sodium chloride intake (and vice versa)
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The underlined dietary determinants and pathogenic events are those originally hypothesized and depicted. In this scheme, the word "osteoporosis" replaces the term "bone mineralization" specified in the depiction of the original formulation (Modified from MacGregor and Cappuccio [1993]
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. Finally, the hypocalciuric effect of supplemental dietary potassium bicarbonate is also dampened by dietary sodium chloride (Sellmeyer et al., 2002)
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Thus recommended intakes of potassium are based on an Adequate Intake (AI) that reflects a calculated mean potassium intake of infants principally fed human milk, or a combination of human milk and complementary foods.
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. Thus the total potassium intake is estimated to be 0.74 g/day (0.3 g/day + 0.44 g/day)
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Furthermore, given the high energy intake of children relative to their weight and the potential for a high sodium intake as a result of their high energy intake, a greater intake of dietary potassium would be appropriate as a means to mitigate the adverse effects of sodium. The AI is thus derived by extrapolating from the adult AI on the basis of the average of median energy intake levels.
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based on blood pressure, substantial reductions in blood pressure in nonhypertensive individuals were observed at total dietary potassium intakes ranging from around 3.1 to 4.7 g (80 to 120 mmol) /day (Table 5-4)
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are supportive of this level of intake as a means to lower blood pressure. Epidemiological studies also suggest that higher levels of potassium intake from foods are associated with decreased bone loss.
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. However, when potassium intake was high, the efficiency of kaliuretic response to intravenous potassium chloride was impaired in the aging rat; a significantly greater plasma potassium concentration also occurred (Friedman and Friedman, 1957; Rowe et al., 1992)
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Still, the AI does not apply to individuals with medical conditions or who are taking drugs that impair potassium excretion because of the potential for serious adverse effects on the heart from hyperkalemia (see later section, "Special Considerations")
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. Urinary Potassium Excretion.
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. One observational study showed that maternal prenatal potassium intake was inversely related to the infant's diastolic blood pressure at 6 and 12 months of age (McGarvey et al., 1991)
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. In the absence of information to the contrary, it is assumed that the efficiency of conversion of dietary potassium to milk produced is almost 100 percent.
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Predisposition to Hyperkalemia Several relatively common clinical conditions can predispose individuals to hyperkalemia, even at levels of potassium intake that are below the AI. The most common of these conditions are chronic kidney disease, heart failure, and type 1 diabetes, each of which can impair renal excretion of potassium.
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From page 242... ...
; however, data on dietary potassium intake was not collected in this study. Since the 95th percentile estimates of potassium intake for men and women in the United States range from 4.3 to 5.1 g and 2.9 to 3.7 g/day, respectively (Appendix Table D-5)
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From page 243... ...
• Reduced activity of angiotensin-converting enzyme Reduced renal tubular response to aldosterone • Aldosterone-receptor blockers (e.g., spironolactone) • Type 4 renal tubular acidosis Pharmacological inhibitors of distal renal tubular Na+-K+ exchange (e.g., amilioride, triamterene)
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From page 244... ...
While meat, milk, and cereal products contain potassium, their content of bicarbonate precursors does not sufficiently balance the amount of acid-forming precursors, such as sulfur amino acids, found in higher protein foods (Lemann et al., 2003)
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/day for women. The median potassium intakes of white respondents exceeded that of African-American respondents.
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246 DIETARY REFERENCE INTAKES TABLE 5-11 Daily Potassium Intake from a Diet Providing 2,200 kcal Calories Potassium Meal Food/Beverage Consumed (kcal)
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, their intake of potassium intake was substantially greater than their nonpregnant counterparts, with median intakes of 2.8 g (72 mmol) /day and 3.8 g (97 mmol)
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Arrhythmia from Hyperkalemia Cardiac arrhythmias from hyperkalemia are the most serious consequence of excessive potassium intake. The typical sequence of findings is hyperkalemia, followed by conduction abnormalities on electrocardiogram (ECG)
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In contrast, supplemental potassium can lead to acute toxicity in healthy individuals. Also, chronic consumption of a high level of potassium can lead to hyperkalemia in individuals with impaired urinary potassium excretion (see later section, "Special Considerations")
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K 2-wk crossover a SBP = systolic blood pressure, DBP = diastolic blood pressure.
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on high K diet, but still within normal range 161 No other changes noted 58 4 patients withdrew from the study: 1 due to diarrhea from the K supplement; 1 due to ↑ BP when receiving placebo; 139 2 due to taste of K supplement
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Because the renal secreting ability of normal infants is not fully developed, potassium intake should be limited to that contained in formula and complementary foods. Pregnancy.
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From page 253... ...
may make women with undetected renal dysfunction or with a sudden decrease in glomerular filtration rate (as occurs with preeclampsia) more likely to develop hyperkalemia when potassium intake is high.
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• Trials that test the main and interactive effects of potassium and sodium intake on bone mineral density and, if feasible, bone fractures. • Trials testing the main and interactive effects of sodium and potassium intake on the risk of kidney stones.
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2001. Dietary potassium intake and risk of stroke in US men and women.
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1991. Effect of varying potassium intake on atrial natriuretic hormone-induced suppression of aldosterone.
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2000. Dietary potassium intake and stroke mortality.
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1984. Blood pressure in blacks and whites and its relationship to dietary sodium and potassium intake.
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1981. Studies on the hypotensive effect of high potassium intake in patients with essential hypertension.
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1984. Dietary potassium and blood pressure in a popu lation.
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1990. Effect of dietary potassium on blood pressure, renal function, muscle sympathetic nerve activ ity, and forearm vascular resistance and flow in normotensive and borderline hypertensive humans.
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1991. Maternal prenatal dietary potassium, calcium magnesium, and infant blood pressure.
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1999b. Normoten sive salt-sensitivity: Effects of race and dietary potassium.
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1993. Respiratory symptoms and bronchial responsiveness are related to dietary salt intake and urinary potassium excretion in male chil dren.
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1984. Blood-pressure response to moderate sodium restriction and to potassium supplementation in mild essential hypertension.
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1997. Reduced dietary potassium reversibly enhances vasopressor response to stress in African-Americans.
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From page 267... ...
1999. Does dietary potassium lower blood pressure and protect against coronary heart disease and death?
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1995. Chronic respiratory symptoms, bronchial responsiveness and dietary sodium and potassium: A population based study.
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