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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
Forms of Potassium
The anions that accompany potassium have metabolic and physiologic properties that influence health. Plant foods rich in potassium, like fruits and nongrain vegetables, are also rich in bicarbonate-yielding precursors like citrate. In contrast, plants contain little chloride. In fact, chloride, like sodium, is ingested almost entirely as sodium chloride, primarily in processed foods and in discretionary use during cooking for seasoning. In the present Western diet, which dates from the Industrial Revolution some 200 years ago, the content of sodium and chloride is not only much higher than that of previous diets, but the contents of both potassium and bicarbonate-yielding substances are also much lower (Eaton et al., 1999; Morris RC et al., 2001; Sebastian et al., 2002). Thus most dietary deficiencies of potassium are accompanied by a relative lack of bicarbonate precursors. With the advent of the Western diet, both the potassium:sodium ratio and the bicarbonate:chloride ratio have become reversed.
Potassium is also consumed as potassium chloride as a food additive ingredient, a salt substitute, or as pills used therapeutically to treat diuretic-induced hypokalemia. While potassium chloride can correct hypokalemia and reduce blood pressure (see Tables 5-4 and 5-5), it cannot correct the low-grade metabolic acidosis induced by modern diets because chloride, in contrast to bicarbonate precursors, does not titrate diet-derived acids.
In healthy adults, potassium bicarbonate increased excretion of citrate and decreased calcium, whereas potassium chloride did not (Lemann et al., 1991; Sakhaee et al., 1991), suggesting that potassium bicarbonate or citrate is the form most conducive to a reduced risk of kidney stones. Because diet-derived acid can result in bone demineralization (Bushinsky and Frick, 2000; Lemann et al., 1966; New et al., 2000) as illustrated in Figure 5-2, the nonalkaline potassium chloride would not be expected to promote bone health as would be predicted with potassium bicarbonate (Lemann et al., 1991, 1993).
Interactions with Other Electrolytes
The effects of potassium intake depend, in part, on the level of sodium chloride intake (and vice versa). Previous sections have documented that potassium blunts the effect of sodium chloride on blood pressure—that an increased intake of potassium bicarbonate or other bicarbonate-yielding potassium salts mitigates salt sensitiv-