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. 2017 Nov 17;5(22):e13356. doi: 10.14814/phy2.13356

Table 3.

Estimated mean changea in indices of total body water volume associated with unit changes in indices of total water intake and body water flux, regulation, and distribution over 4 weeks of higher water intake

Indices of total body water volume
Body weight change, % of Baseline Saliva osmolality, mmol/kg Height‐squared BIA resistance, Hz
Change P R‐squared Change P R‐squared Change P R‐squared
β  ±  SE W B β  ±  SE W B β  ±  SE W B
Total water intake
L/dayb 1.0 ± 0.3 0.004 0.38 0.00 −13 ± 4 0.005 0.36 0.08 0.7 ± 0.2 0.01 0.37 0.04
mL/kcal intake 0.8 ± 0.3 0.03 0.23 0.00 −8 ± 5 0.1 0.14 0.05 0.2 ± 0.3 0.4 0.05 0.02
mL/kg body weight 0.07 ± 0.02 0.006 0.35 0.00 −0.9 ± 0.3 0.006 0.35 0.05 0.05 ± 0.02 0.01 0.37 0.01
% Change vs Week 2 0.03 ± 0.01 0.008 0.33 0.10 −0.4 ± 0.1 0.02 0.26 0.01 0.02 ± 0.008 0.008 0.40 0.04
Body water flux
Half‐life of water in the body, % Changec −0.04 ± 0.01 0.002 0.32 0.15 0.2 ± 0.2 0.2 0.06 0.62 0.001 ± 0.01 0.9 0.00 0.27
Half‐life of water in the body, days −0.2 ± 0.08 0.005 0.28 0.07 1 ± 1 0.3 0.04 0.16 0.02 ± 0.08 0.8 0.00 0.39
Body water regulation
Thirst, mmd −0.001 ± 0.02 1.0 0.00 0.12 −0.2 ± 0.3 0.6 0.02 0.08 0.02 ± 0.01 0.09 0.16 0.02
Serum osmolality, mmol/kge −0.06 ± 0.08 0.5 0.02 0.01 2 ± 1 0.1 0.10 0.03 −0.07 ± 0.07 0.3 0.06 0.25
Urine ADH, pmol/Lf −0.1 ± 0.03 0.03 0.18 0.52 1.0 ± 0.5 0.046 0.16 0.00 −0.02 ± 0.03 0.50 0.02 0.32
Plasma aldosterone, pg/mLe 0.01 ± 0.006 0.08 0.13 0.65 −0.08 ± 0.1 0.4 0.03 0.09 0.01 ± 0.006 0.1 0.15 0.23
Vitamin D 1,25, pg/mLe 0.02 ± 0.02 0.2 0.06 0.46 −0.5 ± 0.2 0.04 0.17 0.24 0.004 ± 0.01 0.8 0.01 0.02
Serum Na, mmol/Le 0.3 ± 0.2 0.1 0.10 0.27 −0.1 ± 3 1.0 0.00 0.16 −0.1 ± 0.2 0.6 0.01 0.04
Serum K, mmol/Le −1.9 ± 1.2 0.1 0.10 0.15 −16 ± 19 0.4 0.03 0.03 1.1 ± 1.3 0.4 0.04 0.56
RBC K:Nae −0.3 ± 0.2 0.1 0.10 0.02 2 ± 3 0.5 0.02 0.16 −0.2 ± 0.2 0.2 0.08 0.00
Fasting RMR, kcal/dayg −0.0009 ± 0.0007 0.3 0.05 0.14 0.03 ± 0.009 0.005 0.29 0.09 −0.001 ± 0.0005 0.02 0.27 0.27
Urine Na, mmol/Lh −0.005 ± 0.004 0.3 0.05 0.99 0.1 ± 0.1 0.1 0.09 0.12 −0.002 ± 0.005 0.7 0.00 0.81
Urine K, mmol/Lh −0.02 ± 0.007 0.005 0.28 0.46 0.3 ± 0.1 0.02 0.21 0.44 −0.003 ± 0.009 0.7 0.01 0.24
Urine osmolality, mmol/kgh −0.002 ± 0.008 0.02 0.23 0.68 0.03 ± 0.01 0.01 0.24 0.50 −0.002 ± 0.0008 0.8 0.00 0.21
Urine norepinephrine, ug/g crtf −0.007 ± 0.01 0.6 0.01 0.12 0.2 ± 0.2 0.4 0.03 0.19 −0.01 ± 0.01 0.4 0.03 0.64
Systolic blood pressure, mmHge −0.03 ± 0.03 0.4 0.02 0.04 −0.1 ± 0.5 0.9 0.00 0.45 0.006 ± 0.03 0.8 0.00 0.54
Diastolic blood pressure, mmHge −0.1 ± 0.06 0.05 0.16 0.06 −0.4 ± 0.8 0.6 0.01 0.13 0.06 ± 0.05 0.2 0.10 0.82
Body water distribution
BIA height‐squared/reactance, cm2/Ωg 0.4 ± 0.2 0.01 0.30 0.99 −4 ± 3 0.3 0.06 0.07 0.1 ± 0.2 0.5 0.03 0.87
Manual hematocrit, %e −0.2 ± 0.1 0.1 0.10 0.19 3 ± 2 0.2 0.08 0.02 −0.1 ± 0.1 0.4 0.04 0.77
Automated hematocrit, % −0.1 ± 0.1 0.3 0.04 0.37 3 ± 2 0.1 0.09 0.00 0.01 ± 0.1 0.9 0.00 0.93
Body water volume
Saliva osmolality, mmol/kgd −0.02 ± 0.01 0.1 0.09 0.09 −0.03 ± 0.009 0.007 0.32 0.01
BIA height squared/resistance, cm2/Ωg 0.4 ± 0.3 0.2 0.10 0.88 −12 ± 4 0.007 0.32 0.01
Body weight, kgi 1.5 ± 0.01 <0.001 0.99 0.00 −7 ± 4 0.1 0.09 0.33 0.4 ± 0.3 0.2 0.10 0.35
Body weight, % of Baseline −4 ± 3 0.1 0.09 0.09 0.3 ± 0.2 0.2 0.10 0.88
a

Data presented are estimates from within‐person fixed effects models that include all data from Week 1 to Week 6, n = 5. The β  ±  SE β represent the estimated mean change in each index of total body water (percent body weight change, saliva osmolality, and height‐squared reactance) associated with a unit change in indices of total water intake and body water flux, regulation, and distribution. The W and B represent the within and between R‐squares for each bivariate relationship, respectively.

b

The weekly mean intake was estimated from 7 24 h records.

c

The half‐life of water in the body was estimated by deuterium elimination rate in Periods 1, 2, and 3.

d

Thirst and overnight, water restricted, fasting saliva osmolality was assessed on arrival at the clinic.

e

Blood pressure was measured and fasting blood collected 90 min after a 750 mL water bolus.

f

Urine ADH and norepinephrine were determined on urine collected after the first morning void until 11 pm on the day before the clinic visit.

g

Fasting, recumbent RMR and bioimpedance reactance were determined 60 min after the 750 mL water bolus.

h

Urine sodium, potassium, and osmolality were determined on first morning specimen collected at home before the clinic visit.

i

Fasting body weight was measured when participants arrived at the clinic.