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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
C
Predictions of Daily Water and Sodium Requirements
To generate estimates of water and sodium losses at different energy expenditure levels and thus work rates, the U.S. Army Research Institute of Environmental Medicine (USARIEM) model was adapted for the four levels of energy expenditure identified in the Dietary Reference Intakes report on energy expenditure (IOM, 2002/2005). The USARIEM Heat Strain model is an empirical model that includes an equation to predict sweating rate during work (Moran et al., 1995, Shapiro et al., 1995). This algorithm has been used in the past to prepare military guidance for water needs during training and deployment.
The following is a description of the application of the model:
Variables
Water requirements (L/d)
Sodium requirements (g/d)
Prediction ranges
Four energy expenditure levels (1,900; 2,400; 2,900; and 3,600 kcal/d)
Temperature ranges (15°–40°C)
ANALYSIS
As shown in the example, the environmental, physiological, and individual information was inputted into the model. For any given individual, physiological, or environmental condition, the model predicted expected water losses. These data were then put into an
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
Excel 4.0 spreadsheet and used to generate the dataset of estimated water and sodium requirements at varying energy expenditure levels and temperatures. Environmental and individual assumptions are listed below. These data were then plotted using Sigma Plot 9.0 to generate a graphical display.
ASSUMPTIONS
Individual
70-kg person
Height = 170 cm
Walking velocity = 5 km/h
0% grade
Clothing = 1.0 (cotton)
Environmental
Partly cloudy day
Wind speed = 1 m/sec
Relative humidity = 50%
Outdoor
Water vapor pressure = 19.094 mm Hg
Load = 0 kg
Dry bulb temperature = 30°C
Black globe temperature = 45°C
Physiological
Skin body temperature = 35.0°C
Rectal body temperature = 36.5°C
Initial heart rate = 60 bpm
Rest (N)
Exposure I = 720 min (= 12 h)
Exposure II = 720 min (= 12 h)
Exposure III (min) = 0
Exposure IV (min) = 0
1.0 L/d minimal requirements for survival:
Sodium concentration of sweat (≈ 35 mmol/L), that of a partially acclimated person
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
Example (not used in this analysis):
The version of the program used was MAT version 9/97. Figures C-1a and C-1b describe the approximate daily water (Figure C-1a) and sodium (Figure C-1b) lost due to sweating as a function of dry bulb temperature and level of physical activity derived from modeling data (Table C-1).
*
The screen is an example of the input variable capabilities; however, actual data are not presented in the database.
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
FIGURE C-1 Approximate daily water (Figure C-1a) and sodium (Figure C-1b) lost due to sweating as a function of dry bulb temperature and level of physical activity derived from modeling data (Table C-1). The hatched area indicates ≈ 1 L minimal water requirements. The y-axis represents the predicted water requirements that increase because of increased sweat losses to enable thermoregulation. The x-axis is the average daytime dry bulb temperature. The four lines represent the four levels of energy (in kcal/day) used in the model (1,900 kcal; 2,400 kcal; 2,900 kcal; and 3,600 kcal).
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
REFERENCES
IOM (Institute of Medicine). 2002/2005. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press.
Moran D, Shapiro Y, Epstein Y, Burstein R, Stroschein L, Pandolf KB. 1995. Validation and adjustment of the mathematical prediction model for human rectal temperature responses to outdoor environmental conditions. Ergonomics 38:1011–1018.
Shapiro Y, Moran D, Epstein Y, Stroschein L, Pandolf KB. 1995. Validation and adjustment of the mathematical prediction model for human sweat rate responses to outdoor environmental conditions. Ergonomics 38:981–986.
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
TABLE C-1 Generated Database from the USARIEM Prediction Model
Given:
kcal/h
watts
per 12 h (kcal)
Rest
76
88
912
Light
234
273
2,808
Mod
382
444
4,582
Hard
531
618
6,372
Assumption: 1.0 liter water essential (daily resp water loss and kidney loss)
Predicted Sweating Rates (mL/h)
Air Tdb
Rh
Rest
Light
Mod
Hard
10
50
32
100
355
628
15
50
65
204
456
722
20
50
108
339
618
911
25
50
151
473
763
1,069
30
50
201
629
938
1,263
35
50
265
829
1,168
1,524
40
50
361
1,129
1,524
1,934
12 h Air
Scenario
Rest
Light
Mod
Hard
Kcal
Water Loss
10
0.95
0.05
0
0
1,006.8
425
15
0.95
0.05
0
0
1,006.8
867
20
0.95
0.05
0
0
1,006.8
1,440
25
0.95
0.05
0
0
1,006.8
2,009
30
0.95
0.05
0
0
1,006.8
2,672
35
0.95
0.05
0
0
1,006.8
3,522
40
0.95
0.05
0
0
1,006.8
4,796
WBGT
Rest
Light
Mod
Hard
Kcal
Water Loss
9.9
0.7
0.25
0.05
0
1,570
782
14.2
0.7
0.25
0.05
0
1,570
1,434
18.8
0.7
0.25
0.05
0
1,570
2,299
23.1
0.7
0.25
0.05
0
1,570
3,148
27.4
0.7
0.25
0.05
0
1,570
4,141
31.7
0.7
0.25
0.05
0
1,570
5,416
36.2
0.7
0.25
0.05
0
1,570
7,336
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
Hard
A:J13
khard
A:E7
klight
A:E5
kmod
A:E6
krest
A:E4
light
A:H13
mod
A:I13
Rest
A:G13
sr
A:E13.I20
WBGT
A:F13
ttl kcal
ttl water loss
1,918.8
1.4
35
23
1,147
1,918.8
2.4
35
23
1,905
1,918.8
2.9
35
23
2,367
1,918.8
3.5
35
23
2,825
1,918.8
4.2
35
23
3,358
1,918.8
5.0
35
23
4,042
1,918.8
6.3
35
23
5,068
ttl kcal
ttl water loss
2,481.5
2.3
35
23
1,837
2,481.5
2.9
35
23
2,362
2,481.5
3.8
35
23
3,058
2,481.5
4.6
35
23
3,742
2,481.5
5.6
35
23
4,541
2,481.5
6.9
35
23
5,568
2,481.5
8.8
35
23
7,113
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
WBGT
Rest
Light
Mod
Hard
Kcal
Water Loss
9.9
0.65
0.15
0.15
0.05
2,020
1,445
14.2
0.65
0.15
0.15
0.05
2,020
2,130
18.8
0.65
0.15
0.15
0.05
2,020
3,115
23.1
0.65
0.15
0.15
0.05
2,020
4,047
27.4
0.65
0.15
0.15
0.05
2,020
5,148
31.7
0.65
0.15
0.15
0.05
2,020
6,578
36.2
0.65
0.15
0.15
0.05
2,020
8,754
WBGT
Rest
Light
Mod
Hard
Kcal
Water Loss
9.9
0.45
0.25
0.2
0.1
2,666
2,078
14.2
0.45
0.25
0.2
0.1
2,666
2,925
18.8
0.45
0.25
0.2
0.1
2,666
4,179
23.1
0.45
0.25
0.2
0.1
2,666
5,350
27.4
0.45
0.25
0.2
0.1
2,666
6,741
31.7
0.45
0.25
0.2
0.1
2,666
8,552
36.2
0.45
0.25
0.2
0.1
2,666
11,316
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Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate
ttl kcal
ttl water loss
2,931.9
2.9
35
23
2,371
2,931.9
3.6
35
23
2,922
2,931.9
4.6
35
23
3,715
2,931.9
5.5
35
23
4,465
2,931.9
6.6
35
23
5,352
2,931.9
8.1
35
23
6,503
2,931.9
10.3
35
23
8,254
ttl kcal
ttl water loss
3,578
3.6
35
23
2,881
3,578
4.4
35
23
3,562
3,578
5.7
35
23
4,572
3,578
6.9
35
23
5,515
3,578
8.2
35
23
6,634
3,578
10.1
35
23
8,091
3,578
12.8
35
23
10,317
Representative terms from entire chapter:
bulb temperature
