mmol/L for all three trials, and averaged about 4.9 mmol/L for all three trials postexercise (Wells et al., 1985). Hence, under these three conditions, a potassium deficit was not evident.

The effects of two diets and exercise on potassium losses were evaluated in eight men during two 4-day exercise-dietary regimens (Costill et al., 1982). The control diet contained 3.1 g (80 mmol)/day of potassium, while the experimental diet contained only 0.98 g (25 mmol)/day of potassium. Urinary potassium excretion was significantly lower with the low potassium diet (2.6 versus 1.2 g [67 versus 31 mmol]/day) on day 5 of the study for each dietary period. Sweat potassium also significantly decreased from 12.3 to 10.9 mmol/day (measured on day 1 of the study for each dietary period). When fed 3.1 g (80 mmol)/day, the individuals were in balance, whereas a negative potassium balance was observed (−0.5 g [−14 mmol]/day) when fed the low potassium diet. Still, the authors did not detect diminished total body potassium content with a combination of heavy exercise and the lower potassium diet. However, this dietary and exercise regimen was brief; the long-term effects are uncertain.

Diuretics, which are often prescribed for the treatment of hypertension and congestive heart failure, result in increased urinary excretion of potassium and can lead to hypokalemia. However, the response is highly dose-dependent. Continual loss of potassium, if sustained, can result in clinical signs and symptoms of potassium deficiency, including arrhythmias (Robertson, 1984). For this reason, potassium supplements are often prescribed. In a recently completed trial (Furberg et al., 2002), approximately 8 percent of individuals assigned to the thiazide diuretic, chlorthalidone (12.5 to 25 mg/day), required a potassium supplement as treatment for diuretic-induced hypokalemia. Alternatively, potassium-sparing diuretics (e.g., amiloride, triamterene, and spirolactones) are frequently used concurrently with thiazide-type diuretics, which increase urinary potassium excretion. Triamterene has been shown to prevent diuretic-induced potassium loss comparable to 3.1 to 4.7 g (80 to 120 mmol)/day of supplemental potassium. While diuretics can cause hypokalemia, the amount of additional potassium required to prevent hypokalemia is uncertain and highly variable. Accordingly, in individuals taking diuretics, serum potassium should be regularly checked by their health care provider.