because it is difficult to separate the effects of potassium from the effects of its accompanying anion, this report focuses primarily on research pertaining to nonchloride forms of potassium—the forms found naturally in foods.
As previously mentioned, urinary potassium excretion reflects dietary potassium intake. The effects on potassium balance of two levels of potassium intake (3.1 g [80 mmol]/day and 11.7 g [300 mmol]/day) were examined in six healthy men about 24 years of age (Hene et al., 1986). After 18 days on the high potassium diet, urinary potassium excretion increased from 2.0 to 9.1 g (50 to 233 mmol)/day. In a separate study, daily fecal potassium loss ranged from 0.11 to 0.85 g (2.8 to 22 mmol)/day on dietary intakes approximating 2.6 to 2.9 g (66 to 74 mmol)/day (Holbrook et al., 1984). Losses of potassium in sweat vary; under conditions in which sweat volume is minimal, the reported values range from 2.3 to 16 mmol (90 to 626 mg)/L (Consolazio et al., 1963).
A number of dietary factors, including dietary fiber and sodium, can affect potassium balance. The effects of increased wheat fiber intake on fecal potassium loss were examined in six healthy men, 21 to 25 years of age, who consumed 45 g/day of wheat fiber for 3 weeks; their previous average intake was 17 g/day. Potassium intake was held constant at 3.1 g (80 mmol)/day (Cummings et al., 1976). Fecal weight increased significantly from about 79 g/day to about 228 g/day with the increased fiber intake. Fecal potassium loss also significantly increased from a prestudy level of 0.3 g to a final value of 1.1 g (8.6 to 28.5 mmol)/day (Cummings et al., 1976).
The level of sodium intake does not appear to influence potassium excretion (Bruun et al., 1990; Castenmiller et al., 1985; Overlack et al., 1993; Sharma et al., 1990; Sullivan et al., 1980) except at levels of sodium intake above 6.9 g (300 mmol)/day, at which point net loss of potassium has been demonstrated (Kirkendall et al., 1976; Luft et al., 1982). At dietary sodium intakes greater than 6.9 g (300 mmol)/day, there was a net loss of potassium—urinary potassium excretion exceeded dietary intake, at least during the 3-day periods in this trial (Luft et al., 1982). Over the long term, net potassium losses do not occur at lower levels of sodium intake. At three levels of dietary sodium, 1.5, 2.4, and 3.2 g (65, 104, and 140 mmol)/day, each provided for 28 days, urinary potassium excretion did not exceed intake and urinary potassium excretion was similar at each sodium level (Sacks et al., 2001).