In clinical trials, potassium chloride has been shown to reduce blood pressure (Cappuccio and MacGregor, 1991; Geleijnse et al., 2003; Whelton et al., 1997); potassium bicarbonate has been shown to reduce the rise in blood pressure in response to increased sodium chloride intake (salt sensitivity) (Morris et al., 1999b); and potassium citrate has been shown to reduce the risk of kidney stones (Barcelo et al., 1993) (see earlier section, “Indicators Considered for Estimating the Requirement for Potassium”). Observational studies suggest that diets rich in potassium may also prevent bone disease and cardiovascular disease, particularly stroke.

Dose-response trials that test the effect of at least three levels of potassium are not available. While such studies would be useful in trying to estimate an average requirement (an EAR) 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). One dose-response trial tested the effect of potassium on salt sensitivity; in this study, an intake of 4.7 g (120 mmol)/day of potassium as potassium bicarbonate abolished severe sodium sensitivity in most nonhypertensive African-American men, a degree of salt sensitivity not observed in white men also tested (Morris et al., 1999b) (see Figure 5-1). In white men enrolled in this trial, salt sensitivity was reduced at a potassium intake of 2.7 g (70 mmol)/day compared with a potassium intake of 1.2 g (30 mmol)/day. Finally, three epidemiological studies suggest that increasing potassium intakes may reduce the risk of kidney stones (Table 5-8) (Curhan et al., 1993, 1997; Hirvonen et al., 1999). At the highest quintile of potassium intake in two studies conducted in the United States (4.0 and 4.7 g [102 and 120 mmol]/day), the lowest relative risk of kidney stones was observed (RR 0.49 and 0.65) (Curhan et al., 1993, 1997). In Finland where potassium intakes are greater than in the United States or Canada (Rose et al., 1988), at the second quartile of intake (4.6 g [118 mmol]/day), there was a reduced relative risk of kidney stones (0.76) that was not further reduced at higher potassium intakes (Hirvonen et al., 1999).