A global review of the physiology of hydration in adults, detailing the water distribution in the human body, the water balance and the main recommendations for water intake.

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Water and Hydration:
Physiological Basis in Adults

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3. Water in the human body
Water absorption and distribution in the body
Body water balance
Body fluid losses
Focus on urine production
Body water inputs
Regulation and maintenance of body water balance
Body water balance impairment: dehydration
Guidelines for daily water intake
Key facts
References – References are sorted by slide, at the end of the presentation
Content
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4. Extracellular fluid
35% of total body water, 14L
Intracellular fluid
65% of total body water, 28L
Interstitial fluid
28% of total body
water, 11L
Plasma fluid
7% of total body
water, 3L
Two thirds of the body
water is intracellular
Total body water
60% of body weight, 42L
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Water in the human body
Body water content www.h4hinitiative.com

5. Most of the organs and tissue contain more than 70% water:
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Water represents on average 60% of body weight in adult men (50-55% in women).
Water in the human body
Body water content
Blood 83%
Liver 68%
Kidney 83%
Adipose
tissue 10%
Muscle 76%
Skin 72%
Heart 79%
Lungs 79%
Spleen 76%
Intestine 75%
Skeleton (bones) 22%
Brain 75%
As lean body mass increases, so does body water content.
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6. Water appears
in the blood
as soon as
5 minutes
after ingestion
Water in the human body
Water absorption & distribution in the body
Ingested water is absorbed mainly in the small intestine
* For a man drinking 2L of water per day.
The more a person drinks, the faster body water is renewed.
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99% of the body water pool
is renewed within 50 days*
A molecule of water stays in
the body on average 10 days*
INTERSTITIAL LIQUID
CELLS
PLASMA AND BLOOD CELLS
GASTRO-INTESTINAL TRACT
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7. INPUTS LOSSES
Body water balance
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Urine
Faeces
Sweat
Insensible
water losses
Water from fluids
Water from
food
Metabolic
water
Body water balance = (sum of water inputs) – (sum of water losses)
Body water balance is tightly regulated, to ensure homeostasis and to respond
to changes in consumption and losses.
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8. 7
Body water balance
Body fluid losses
The main sources of water losses from the body are urine and sweat, but water
is also lost through stools and insensibly through skin and breathing.
≈ 750mL
skin evaporation & breathing
(usually not perceived by the subject)
≈ 200mL
Adaptable
Minimum 500mL;
Desirable urine osmolarity = 500 mOsm/L (EFSA)
> 1600 – 2000 mL
Highly variable
Adapted to maintain body core temperature
LOSSES
Urine
Faeces
Sweat
Insensible
water losses
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9. Body water balance
Body fluid losses: urine production
Urine is produced from blood filtration in the nephrons
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Kidney
1 Filtration 2 Reabsorption
(water, solutes)
3 Secretion
of additional wastes
4 Excretion
Peritubular capillaryArtery
Corpuscule
(glomerulus + Bowman’s
capsule)
Tubule
Blood flow
Nephron
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10. 9
Body water balance
Body water input
Drinking water and beverages represent 70 - 80% of total water intake,
and therefore are the largest source to compensate body water losses.
≈ 300mL
approximates respiratory losses
Variable
≈ 20 - 30% of total water intake
depends on diet
Highly variable
≈ 70 - 80% of total water intake
varies between individuals & countries
INPUTS
Water from fluids
Water from
food
Metabolic
water
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11. 10
Body water balance
Variable fluid intake, adaptable urine volume
The adjustment of urine volume is critical to regulate body water balance.
PHYSICAL EFFORT HOT ENVIRONMENT
SWEAT
INPUTS LOSSES
LOW URINE
VOLUME
Athlete / hot environment
LOW URINE
VOLUME
INPUTS LOSSES
Sedentary
HIGH URINE
VOLUME
INPUTS LOSSES
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12. Regulation & maintenance of body water balance
Body water is regulated by the balance between water intake on one hand,
and renal excretion of water on the other hand.
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Thirst
-+
AVP
Stimulation of
Osmoreceptors in hypothalamus
-
-+
Pituitary gland
Water intake
Permeability
to water
Kidneys
Water deficit Water excessPLASMA OSMOLALITY
Small volume of
concentrated urine Water reabsorption Water reabsorption
Larger volume of
diluted urine
-
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13. 12
Body water balance impairment
Cognitive impairment
memory
motor skills
mood
Physical performance
body temperature
heart rate
perceived effort
Health implications:
risk of kidney stones
recurrence
Dehydration and/or low fluid intake
may impact
Possible impacts of dehydration www.h4hinitiative.com

14. Guidelines for daily water intake
Reference values for Total Water Intake*
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*Total water intake: includes both water from food and from beverages of all kinds
Individual water needs vary considerably, therefore there is no single adequate
intake that is suitable for everyone.
Most of the guidelines for total water intake
are based on median population intake
EFSA: first to introduce a physiological parameter:
desirable urine osmolarity of 500mOsm/L.
Country
(references)
Europe
(EFSA, 2010)
Australia & New Zealand
(NHMRC, 2006)
USA & Canada
(IoM, 2004)
World
(WHO, 2003)
Men 2,5L/d 3,4L/d 3,7L/d
Sedentary 2,9L/d
Active 4,5L/d
Women
2,0L/d 2,8L/d 2,7L/d
Sedentary 2,2L/d
Active 4,5L/d
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15. Key facts
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Water balance is tightly regulated
Adaptable
urine volume
An adequate fluid intake
contributes to
Urine volume varies with fluid intake
The maintenance of normal
physical & cognitive functions
Reducing the risk of kidney stones recurrence
Variable
fluid intake
INPUTS LOSSES
Reference values, Europe (EFSA) From 14 to adulthood
Total water intake (fluid + food) Women 2.0L/d Men 2.5L/d
Water from fluids (estimated at 80% of TWI) Women 1.6L/d Men 2.0L/d
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16. Perronet F, Mignault D, du Souich P, Vergne S, Le Bellego L, Jimenez L, Rabasa-Lhoret R (2012). Pharmacokinetic analysis of
absorption, distribution anddisappearance of ingested water labeled with D(2)O in humans. Eur J Appl Physiol 112:2213-2222.
Sawka MN, Cheuvront SN, Carter R, III (2005). Human water needs. Nutr Rev 63:S30-S39.
Wang Z, Deurenberg P, Wang W, Pietrobelli A, Baumgartner RN, Heymsfield SB (1999). Hydration of fat-free body mass: review
and critique of a classic body-composition constant. The American Journal of Clinical Nutrition 33:27-39.
Pivarnik JM and Palmer RA (1994). Water and electrolytes during exercise. In: Hickson, J.F and Wolinski, I., ed. Water and
electrolyte balance during rest and exercise. Boca Raton; CRC Press, 245-262.
Marieb EN and Hoehn K (2007). Fluid, electrolyte, and acid-base balance. In: Human Anatomy and Physiology. 7th ed. San
Francisco: Benjamin-Cummings Publishing Company, 1036-1048.
Watson PE, Watson ID, Batt RD (1980). Total body water volumes for adult males and females estimated from simple
anthropometric measurements. The American Journal of Clinical Nutrition 33:27-29.
EFSA Panel on Dietetic Products Nutrition and Allergies (NDA) (2010). Scientific Opinion on Dietary Reference Values for water.
EFSA Journal 8(3):1459-1507.
IOM (Institute of Medicine of the National Academies) (2004). Dietary reference intakes for water, potassium, sodium, chloride
and sulfate. 4:73-185. National Academies Press, Washington, DC.
Bibliographic references
Slide 3 – Body water content
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17. Armstrong LE (2005). Hydration assessment techniques. Nutr Rev. 63:S40-S54.
Marieb EN and Hoehn K (2007). Fluid, electrolyte, and acid-base balance. In: Human Anatomy and Physiology. 7th ed. San
Francisco: Benjamin-Cummings Publishing Company, 1036-1048.
Bibliographic references
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Shaffer EA and Thomson ABR (1994). First principles of gastroenterology: the basis of disease and an approach to
management. Canadian Association of Gastroenterology; Astra Pharma Inc.
Perronet F, Mignault D, du Souich P, Vergne S, Le Bellego L, Jimenez L, Rabasa-Lhoret R (2012). Pharmacokinetic analysis of
absorption, distribution anddisappearance of ingested water labeled with D(2)O in humans. Eur J Appl Physiol 112:2213-2222.
Slide 5 – Water absorption and distribution in the body
Slide 4 – Water content in the human body
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18. Grandjean A and Campbell S (2004). Hydration: Fluids for Life. A monograph by the North American Branch of the International
Life Science Institute. Washington DC: ILSI North America.
EFSA Panel on Dietetic Products Nutrition and Allergies (NDA) (2010). Scientific Opinion on Dietary Reference Values for water.
EFSA Journal 8(3):1459-1507.
Bibliographic references
Slide 6 – Body water balance
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19. Sherwood L (2010). Human Physiology: From Cells to Systems. 7th ed. Belmont: Brooks/Cole, Cengage Learning.
Grandjean AC, Reimers KJ,Buyckx ME (2003). Hydration: issues for the 21st century. Nutr Rev 61:261-271.
Hoyt RW (1996). Environmental influences on body fluid balance during exercise: altitude. In: Buskirk, E.R. and Puhl, S.M., ed.
Body fluid balance: exercise and sport. Boca Raton: CRC PressINC, 183-196.
EFSA Panel on Dietetic Products Nutrition and Allergies (NDA) (2010). Scientific Opinion on Dietary Reference Values for water.
EFSA Journal 8(3):1459-1507.
Powers SK and Howley ET (1997). Exercise Physiology. Theory and Application to Fitness and Performance. 3rd ed. Colombus:
WCB/McGraw-Hill.
Montain SJ, Cheuvront SN, Lukaski HC (2007). Sweat mineral-element responses during 7 h of exercise-heat stress. Int J
Sport.Nutr Exerc Metab 17:574-582.
Bibliographic references
Slide 7 – Body fluid losses
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20. Brenner BM and Rector FC (2008). The Kidney. 8th. Philadelphia: Saunders Elsevier.
Valtin H and Schafer JA (1995). Renal function. 3rd ed. Boston: Little, Brown, and Co.
Guyton AC and Hall JE (2006). Textbook of medical physiology. 11th ed. Philadelphia: Elsevier Saunders.
Bibliographic references
Slide 8 – Body fluid losses: urine production
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21. EFSA Panel on Dietetic Products Nutrition and Allergies (NDA) (2010). Scientific Opinion on Dietary Reference Values for water.
EFSA Journal 8(3):1459-1507.
Hoyt RW (1996). Environmental influences on body fluid balance during exercise: altitude. In: Buskirk, E.R. and Puhl, S.M., ed.
Body fluid balance: exercise and sport. Boca Raton: CRC PressINC, 183-196.
Food Standard Agency (2002). McCance; Widdowson’s The Composition of Foods. 6th ed. Cambridge; The Royal Society of
Chemistry.
Sontrop JM, Dixon SN, Garg AX, Buendia-Jimenez I, Dohein O, Huang SH, Clark WF (2013). Association between water intake,
chronic kidney disease, and cardiovascular disease: a cross-sectional analysis of NHANES data. Am. J Nephrol. 37:434-442.
Ma G, Zhang Q, Liu A, Zuo J, Zhang W, Zou S, Li X, Lu L, Pan H, Hu X (2012). Fluid intake of adults in four Chinese cities.
Nutr.Rev. 70:Suppl 2, S105-S110.
EFSA (2008). The EFSA Concise European Food Consumption Database.
http://www.efsa.europa.eu/en/datexfoodcdb/datexfooddb.htm. Accessed July 2013.
Bibliographic references
Slide 9 – Body water inputs
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22. Perrier E, Vergne S, Klein A, Poupin M, Rondeau P, Le Bellego L, Armstrong LE, Lang F, Stookey J, Tack I (2012). Hydration
biomarkers in free-living adults with different levels of habitual fluid consumption. Br J Nut, 109(9), 1678-1687.
Perrier E, Rondeau P, Poupin M, Le Bellego L, Armstrong LE, Land F, Stookey J, Tack I, Vergne S, Klein A (2013). Relation
between urinary hydration biomarkers and total fluid intake in healthy adults. European Journal of Clinical Nutrition, 67(9),
939-943.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Stachenfeld NS (2007). American College of Sports Medicine position stand.
Exercise and fluid replacement. Med Sci Sports Exerc, 39:377-390.
Bibliographic references
Slide 10 – Variable fluid intake, adaptable urine volume
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Guyton AC and Hall JE (2006). Textbook of medical physiology. 11th ed. Philadelphia: Elsevier Saunders.
Slide 11 – Regulation & maintenance of body water balance
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23. Armstrong LE, Ganio MS, Casa DJ, Lee EC, McDermott BP, Klau JF, Jimenez L, Le Bellego L, Chevillotte E, Lieberman HR (2012).
Mild dehydration affects mood in healthy young women. J Nutr 142:382-8.
Ganio MS, Armstrong LE, Casa DJ, McDermott BP, Lee EC, Yamamoto LM, Marzano S, Lopez RM, Jimenez L, Le Bellego L,
Chevillotte E, Lieberman HR (2011). Mild dehydration impairs cognitive performance and mood of men. Br J Nutr 106:1535-43.
Pross N, Demazières A, Girard N, Barnouin R, Santoro1 F, Chevillotte E, Klein A, Le Bellego L (2012). Influence of progressive
fluid restriction on mood and physiological markers of dehydration in women. Br J Nutr 13:1-9.
Sawka MN, Coyle EF (1999). Influence of body water and blood volume on thermoregulation and exercise performance in the
heat. Exerc Sport Sci Rev 27:167-218.
Curhan GC. (2007) Epidemiology of stone disease. Urol.Clin North Am 34:287-293.
Trinchieri A, Cappoli S, Esposito N, Acquati P. (2008) Epidemiology of renal colic in a district general hospital. Arch.Ital.Urol.
Androl. 80:1-4.
Irving RA, Noakes TD, Rodgers AL, Swartz L. (1986) Crystalluria in marathon runners. 1. Standard marathon--males. Urol. Res
14:289-294.
Bibliographic references
Slide 12 – Possible impacts of dehydration
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24. EFSA Panel on Dietetic Products Nutrition and Allergies (NDA) (2010). Scientific Opinion on Dietary Reference Values for water.
EFSA Journal 8(3):1459-1507.
IOM (Institute of Medicine of the National Academies) (2004). Dietary reference intakes for water, potassium, sodium, chloride
and sulfate. 4:73-185. National Academies Press, Washington, DC.
NHMRC (National Health and Medical Research Council) (2006). Nutrient Reference Values for Australia and New Zealand
Including Recommended Dietary Intakes. Commonwealth of Australia, Canberra.
WHO (World Health Organization) (2003). Domestic water quantity, service level and health. WHO/SDE/WSH/3.02.
Bibliographic references
Slide 13 – Guidelines for daily water intake
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25. Access Adults Monograph online
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26. Developed by for the Hydration for Health Initiative