The Influence of Salt Sensitivity Phenotype on Sodium Excretion and Diuresis: A Chrononutrition Pilot Study

Table 3

Time course of changes in diuresis rate, urine osmolality, FWC, and solute/creatinine ratios within the test days (A) and between the test days (B), over 4 hrs after salt and/or water ingestion.

(A) Within the test days
	Control	8 g salt	12 g salt
Diuresis (mL/min)
2 hrs	3.5 (1.4–4.3)	1.1 (0.8–1.5)	1.2 (0.8–1.8)
4 hrs	1.3 (0.8–2.0)	1.2 (0.8–1.5)	1.6 (1.0–1.9)
P value	Baseline vs. 2 hrs: < 0.001a	Baseline vs. 2 hrs: 0.006a	Baseline vs. 2 hrs: 0.006a
	Baseline vs. 4 hrs: 0.026a	Baseline vs. 4 hrs: 0.021a	Baseline vs. 4 hrs: 0.001a
Urine osmolality (mOsm/kg)
2 hrs	260 (166–910)	927 (824–1072)	905 (771–1056)
4 hrs	517 (384–742)	900 (796–982)	849 (764–960)
P value	< 0.001^∗∗	NS	NS
Free water clearance (mL/min)
2 hrs	0.3 (−2.6–1.4)	−2.2 (−3.0–(−1.5))	−2.5 (−3.3–(−1.8))
4 hrs	−1.2 (−1.7–(−0.6))	−2.7 (−2.9–(−1.5))	−2.8 (−3.5–(−1.9))
P value	NS	Baseline vs. 2 hrs: 0.006a	Baseline vs. 2 hrs: <0.001a
		Baseline vs. 4 hrs: 0.021a	Baseline vs. 4 hrs: 0.002a
Sodium/creatinine (mmol/mmol)
2 hrs	7.8 (6.3–12.7)	12.4 (5.8–16.9)	13.1 (11.6–20.5)
4 hrs	10.2 (6.5–16)	23.6 (16.2–31.4)	30.6 (26.3–38.6)
P value	NS	< 0.001^∗∗	< 0.001^∗∗
Potassium/creatinine (mmol/mmol)
2 hrs	5.7 (3.9–8.5)	5.8 (4.1–7.8)	6.2 (3.5–7.7)
4 hrs	9.4 (6.2–11)	13 (9.7–15.1)	12.5 (9.3–17.7)
P value	Baseline vs. 2 hrs: 0.001a	Baseline vs. 4 hrs: <0.001a	Baseline vs. 4 hrs: <0.001a
	Baseline vs. 4 hrs: <0.001a	2 hrs vs. 4 hrs: 0.003a	2 hrs vs. 4 hrs: 0.004a
Urea/creatinine (mmol/mmol)
2 hrs	30 (25–32)	25 (21–32)	28 (20–34)
4 hrs	28 (23–33)	29 (22–36)	28 (24–35)
P value	Baseline vs. 2 hrs: 0.005a	Baseline vs. 4 hrs: 0.018a	Baseline vs. 4 hrs: 0.024a
(B) Between the test days
	Control	8 g salt	12 g salt	P value
Diuresis (mL/min)
2 hrs	3.5 (1.4–4.3)	1.1 (0.8–1.5)	1.2 (0.8–1.8)	0.001^∗ 0.002†
4 hrs	1.3 (0.8–2.0)	1.2 (0.8–1.5)	1.6 (1.0–1.9)	0.010∆
Urine osmolality (mOsm/kg)
2 hrs	260 (166–910)	927 (824–1072)	905 (771–1056)	< 0.001^∗ < 0.001†
4 hrs	517 (384–742)	900 (796–982)	849 (764–960)	0.001^∗ 0.003† 0.026∆
Free water clearance (mL/min)
2 hrs	0.3 (−2.6–1.4)	−2.2 (−3.0–(−1.5))	−2.5 (−3.3–(−1.8))	0.002^∗ 0.002†
4 hrs	−1.2 (−1.7–(−0.6))	−2.7 (−2.9–(−1.5))	−2.8 (−3.5–(−1.9))	0.001^∗ 0.013†
Sodium/creatinine (mmol/mmol)
2 hrs	7.8 (6.3–12.7)	12.4 (5.8–16.9)	13.1 (11.6–20.5)	0.006† 0.027∆
4 hrs	10.2 (6.5–16)	23.6 (16.2–31.4)	30.6 (26.3–38.6)	0.002^∗ < 0.001† 0.006∆
Potassium/creatinine (mmol/mmol)
2 hrs	5.7 (3.9–8.5)	5.8 (4.1–7.8)	6.2 (3.5–7.7)	NS
4 hrs	9.4 (6.2–11)	13 (9.7–15.1)	12.5 (9.3–17.7)	< 0.001^∗ 0.007†
Urea/creatinine (mmol/mmol)
2 hrs	30 (25–32)	25 (21–32)	28 (20–34)	NS
4 hrs	28 (23–33)	29 (22–36)	28 (24–35)	NS

^∗∗ for related-samples Friedman’s Two-Way Analysis of variance and ^a for pairwise comparison with adjusted p values by the Bonferroni correction for multiple tests. NS = not significant. for control vs. 8 g salt, † for control vs. 12 g salt and for 8 g vs. 12 g salt; Wilcoxon signed rank test. NS = not significant.