als with diuretic-induced hypokalemia did not achieve reduction in cardiovascular events compared with diuretic-treated individuals without hypokalemia (Franse et al., 2000).
Because moderate potassium deficiency and its adverse side effects occur without hypokalemia, hypokalemia is not a sensitive indicator appropriate for use to establish adequacy.
The extent to which blood pressure responds to changes in sodium chloride intake varies among individuals. “Salt-sensitive” blood pressure is that which varies directly with the intake of sodium chloride (Morris et al., 1999b; Weinberger, 1996). Salt sensitivity, even in those who are nonhypertensive, has been found to confer its own cardiovascular risks, including incident hypertension and cardiovascular death (Morimoto et al., 1997; Weinberger et al., 2001). Salt sensitivity occurs with greater frequency and severity in nonhypertensive African Americans than in nonhypertensive whites (Morris et al., 1999b; Price et al., 2002; Weinberger, 1996).
The expression of salt sensitivity is strongly modulated by dietary potassium intake (Morris et al., 1999b; Schmidlin et al., 1999; Luft et al., 1979). In a metabolic study of 38 healthy, nonhypertensive men (24 African Americans and 14 whites) fed a basal diet with low levels of potassium (1.2 g [30 mmol]/day) and sodium (0.7 g [30 mmol]/day), the modulating effect of potassium supplementation on the pressor effect of dietary sodium chloride loading (14.6 g [250 mmol]/day) was investigated (Morris et al., 1999b) (Figure 5-1). Before potassium was supplemented, 79 percent of the African-American men and 26 percent of the white men were termed salt sensitive, as defined by a sodium chloride-induced increase in mean arterial pressure of at least 3 mm Hg. Salt sensitivity was defined as “severe” if sodium chloride induced an increase in mean arterial pressure of 10 mm Hg or more, an increase observed only in African-American men. When dietary potassium was increased with potassium bicarbonate from 1.2 g (30 mmol)/day to 2.7 g (70 mmol)/day, over half of the African-American men, but only one-fifth of the white men, remained salt sensitive. 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)/day. In another metabolic study of 16 mostly nonhypertensive African-American subjects loaded with 14.6 g (250 mmol) of