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biscuit (107 versus 67 mL/day, p < 0.01) (Baird et al., 1977). Other studies have also demonstrated increased stool weight due to increased fecal water during periods of increased dietary fiber intake (Cummings et al., 1976; Floch and Fuchs, 1978).

Sodium Intake

The effects of increased sodium intake on urine volume, a proxy of water intake, have been assessed in two experimental studies (He et al., 2001; Luft et al., 1983). In one study, 24 men were given 0.23, 4.6, and 9.2 g (10, 200, and 400 mmol)/day of sodium for 7 days while energy, potassium, and protein intake were maintained at a constant level (Luft et al., 1983). In spite of a 40-fold increase in sodium intake, little change was noted in urine volume (which averaged 2.1 L on the lowest sodium intake level and 2.3 L on the highest). In a second study, 104 hypertensive subjects (48 men and 56 women) were studied after 5 days on approximately 8 g (350 mmol)/day of sodium and again after 5 days on 0.23 to 0.5 g (10 to 20 mmol)/day (He et al., 2001). Twenty-four-hour urine excretion volume was 2.2 L at the higher sodium level, but significantly less, just 1.3 L, on the lower sodium level. In separate analyses of data from the Intersalt study, it was estimated that a 2.3 g (100 mmol)/ day reduction in sodium intake should decrease 24-hour urine volume by 0.38 and 0.40 L in hypertensive and nonhypertensive individuals, respectively (He et al., 2001). Overall, based on these limited data, it is not possible to determine the extent to which sodium intake influences water intake.

Pathophysiologic Factors

Diabetes Mellitus

There is no evidence that increased water intake influences the detection of diabetes mellitus or alters the diagnostic approach to this illness. However, dehydration is clearly associated with worsening of diabetes control. In addition, uncontrolled diabetes mellitus dramatically enhances the development of severe dehydration and volume depletion due to osmotic diuresis. The changes in acid-base balance and increased osmolality of urine from hyperglycemia-induced glycosuria and ketoaciduria increase urine output. In poorly controlled diabetic individuals, reduced water intake can also lead to dehydration as a result of infection or hypotension, which can lead to delirium and impaired ability to seek water.

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