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In physiological psychology, water intake is an aspect of fluid intake and is necessary for all life on Earth. We are largely composed of water. By weight, mammals are approximately two-thirds water. Humans can survive for several weeks without food, but for only a few days without water. A constant supply is needed to replenish the fluids lost through normal physiological activities, such as respiration, perspiration, defecation and urination and prevent dehydration. Unlike minerals or energy, in adipose tissue, little water is actually stored in the body.

When water use exceeds water intake, the body tries to conserves liquid, mainly by reducing the amount of water excreted from the kidneys. Eventually, physiological conservation can no maintain the balance triggering thirst and the motivation to drink.

The body relies on signals from osmotic and volume pressure baroreceptors in the hypothalamus to inform the brain of body fluid status and to activate the homeostatic process of osmoregulation through specific neurohormonal systems (e.g., the renin-angiotensin system) to restore fluid balance. As with food intake, signals that stimulate drinking behavior, as well as those that terminate drinking, interact to ensure that adequate amounts of both water and electrolytes are consumed. However the signals for water satiety, and how satiety changes the taste and motivation for seeking water are unclear[1].

Requirement[edit | edit source]

The exact amount of water a human needs is highly individual, as it depends on the condition of the subject, the amount of physical exercise, and on the environmental temperature and humidity.[2] In the US, the reference daily intake (RDI) for water is 3.7 litres per day for human males older than 18, and 2.7 litres for human females older than 18[3] including water contained in food, beverages, and drinking water. Food contributes 0.5 to 1 litre, and the metabolism of protein, fat, and carbohydrates produces another 0.25 to 0.4 litres[4], which means that 2 to 3 litres of water for men and 1 to 2 litres of water for women should be taken in as fluid in order to meet the RDI. Because in general, RDI values incorporate a safety margin to account for individual variations, it does not mean that this amount is necessary for every person. The folk wisdom that everyone should drink two litres (68 ounces, or about eight 8-oz glasses) of water per day is not supported by scientific research. Various reviews of all the scientific literature on the topic performed in 2002 and 2008 could not find any solid scientific evidence that recommended drinking eight glasses of water per day.[5] [6] [7] For example, people in hotter climates will require greater water intake than those in cooler climates. An individual's thirst provides a better guide for how much water they require rather than a specific, fixed number. A more flexible guideline is that a normal person should urinate 4 times per day, and the urine should be a light yellow color. [How to reference and link to summary or text] Profuse sweating can increase the need for electrolyte (salt) replacement. Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal[8][9].

The human kidneys will normally adjust to varying levels of water intake. If a person suddenly increases water intake, the kidneys will produce more diluted urine, even if the person did not happen to consume water excessively.[How to reference and link to summary or text] The kidneys will require time to adjust to the new water intake level. This can cause someone who drinks a lot of water to become dehydrated more easily than someone who routinely drinks less. Survival classes recommend that someone who expects to be in an environment with little water (such as a desert), not to drink water excessively, but rather to drink gradually decreasing amounts for several days before their trip to accustom the kidneys to making concentrated urine. Not using this method can, and has been known to be, fatal.[10]

Metabolism[edit | edit source]

Main article: Fluid balance

The cells of animals require water for virtually all metabolic processes. Water acts as a solvent for sodium, chloride, and potassium ions, as well as sugars, amino acids, proteins, vitamins etc, and is therefore essential for the smooth functioning of the nervous system and for other bodily processes

Mineral component[edit | edit source]

In terms of mineral nutrients intake, it is unclear what the drinking water contribution is. However, inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust. Treatment processes also lead to the presence of some mineral nutrients. Examples include fluoride, calcium, zinc, manganese, phosphate, and sodium compounds.[11] Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example sodium, potassium and chloride are common chemicals found in small quantities in most waters, and these elements play a role (not necessarily major) in body metabolism. Other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels. Water is essential for the growth and maintenance of our bodies, as it is involved in a number of biological processes.

Animal water intake[edit | edit source]

Main article: Animal water intake

Like humans animals are largely made up of water and must maintainn their water intake

Birds[edit | edit source]

Water is needed by many birds although their mode of excretion and lack of sweat glands reduces the physiological demands.[12] Some desert birds can obtain their water needs entirely from moisture in their food. They may also have other adaptations such as allowing their body temperature to rise, saving on moisture loss from evaporative cooling or panting.[13] Seabirds can drink seawater and have salt glands inside the head that eliminate excess salt out of the nostrils.[14]

See also[edit | edit source]

References[edit | edit source]

  1. Gallagher, M. & Nelson, R.J. (2003). Handbook of Psychology: Volume 3: Biological psychology. Hoboken NJ:John Wiley
  2. Maton, Anthea bj; Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright (1993). Human Biology and Health, Englewood Cliffs, New Jersey, USA: Prentice Hall.
  3. US daily reference intake values
  4. Swedish DFA (in Swedish)
  5. Research debunks health value of guzzling water. Reuters, April 2008.
  6. H. Valtin, Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 × 8"? Am J Physiol Regul Integr Comp Physiol 283: R993-R1004, 2002.
  7. Dan Negoianu and Stanley Goldfarb. Just add water. J. Am. Soc. Nephrol. 19: 1041-1043, 2008.
  8. Noakes TD, Goodwin N, Rayner BL, et al. (1985). Water intoxication: a possible complication during endurance exercise. Med Sci Sports Exerc 17 (3): 370–375.
  9. Noakes TD, Goodwin N, Rayner BL, Branken T, Taylor RK (2005). Water intoxication: a possible complication during endurance exercise, 1985. Wilderness Environ Med 16 (4): 221–7.
  10. Man Dies of Thirst During Survival Test, San Francisco Chronicle, May 2, 2007
  11. World Health Organization (WHO). Geneva, Switzerland. Joyce Morrissey Donohue, Charles O. Abernathy, Peter Lassovszky, George Hallberg. "The contribution of drinking-water to total dietary intakes of selected trace mineral nutrients in the United States." Draft, August 2004.
  12. Engel, Sophia Barbara (2005). Racing the wind: Water economy and energy expenditure in avian endurance flight, University of Groningen.
  13. Tieleman, B.I. (January 1999). The role of hyperthermia in the water economy of desert birds. Physiol. Biochem. Zool. 72 (1): 87–100.
  14. Schmidt-Nielsen, Knut (1 May 1960). The Salt-Secreting Gland of Marine Birds. Circulation 21 (5): 955–967.

Further reading[edit | edit source]

  • Anderson, W. M., & Dawson, J. (1967). Water Distribution in Affective Disorders: Journal of Psychosomatic Research 11(3) 1967, 291-298.
  • Ashida, S. (1968). The Effects of Water and Food Deprivation on the Heart Rate of Rats: Psychonomic Science Vol 11(7) 1968, 245-246.
  • Bartoshuk, L. M. (1968). Water Taste in Man: Perception & Psychophysics 3(1-B) 1968, 69-72.
  • Beck, R. C. (1967). Clearance of Ingested Sucrose Solutions from the Stomach and Intestine of the Rat: Journal of Comparative and Physiological Psychology Vol 64(2) Oct 1967, 243-249.
  • Beck, R. C., & Brooks, C. I. (1967). Water Preference as a Function of Water Deprivation: Psychological Reports 21(3) 1967, 911-912.
  • Bokert, E. G. (1968). The Effects of Thirst and a Related Verbal Stimulus on Dream Reports: Dissertation Abstracts International.
  • Booth, D. A. (1968). Effects of Intrahypothalamic Glucose Injection on Eating and Drinking Elicited by Insulin: Journal of Comparative and Physiological Psychology Vol 65(1) Feb 1968, 13-16.
  • Boshka, S. C., & Weisman, H. M. (1967). Apparatus Note: on the Preparation of Glass Drinking Tubes for Measurement of Consumed Volume in Animal Research: Psychological Record 17(2) 1967, 249-250.
  • Brookshire, K. H. (1967). Inversion of Discrete Trial Water-Saline Preference as a Function of Prior Drinking Experience: Journal of Comparative and Physiological Psychology Vol 63(1) Feb 1967, 24-27.
  • Brookshire, K. H. (1967). Reinforcement Value of Water and Hypotonic Saline in Discrete Trial Situations: Journal of Comparative and Physiological Psychology Vol 63(1) Feb 1967, 145-148.
  • Bruvold, W. H. (1968). Scales for Rating the Taste of Water: Journal of Applied Psychology Vol 52(3) Jun 1968, 245-253.
  • Burks, C. D. (1967). Drinking Response Distributions Associated with a 4% Sucrose Ffi Food Schedule: Psychonomic Science Vol 8(1) 1967, 13-14.
  • Campbell, B. A., & Lynch, G. S. (1968). Influence of Hunger and Thirst on the Relationship between Spontaneous Activity and Body Temperature: Journal of Comparative and Physiological Psychology Vol 65(3, Pt 1) Jun 1968, 492-498.
  • Capretta, P. J. (1967). Effects of Hunger and Thirst Levels During Sugar and Sugar-Saccharin Consumption on Later Preferences: Psychonomic Science Vol 9(7-B) 1967, 441-442.
  • Clark, R. H., & Bremner, F. J. (1967). Toward an Electro-Physiological Identification of a Primary Drive Factor: Psychonomic Science Vol 8(3) 1967, 113-114.
  • Dillehay, R. C., Bruvold, W. H., & Siegel, J. P. (1967). On the Assessment of Potability: Journal of Applied Psychology Vol 51(2) Apr 1967, 89-95.
  • Donovick, P. J., & Burright, R. G. (1968). Water Consumption of Rats with Septal Lesions Following Two Days of Water Deprivation: Physiology & Behavior 3(2) 1968, 285-288.
  • Dromsky, D. M., Weathersby, P. K., & Fahlman, A. (2003). Prophylactic high dose methylprednisolone fails to treat severe decompression sickness in swine: Aviation, Space, and Environmental Medicine Vol 74(1) Jan 2003, 21-28.
  • Dufort, R. H., & Lawler, J. E. (1968). Food Intake with and without Water after Different Durations of Food Deprivation: Psychological Reports 22(3, PT 1) 1968, 905-908.
  • Evans, T. R. (1967). Experimental Manipulation of an Observer's Criterion in Auditory Detection: Dissertation Abstracts International.
  • Falk, J. L. (1967). Control of Schedule-Induced Polydipsia: Type, Size and Spacing of Meals: Journal of the Experimental Analysis of Behavior 10(2) 1967, 199-206.
  • Feider, A. (1967). Feedback Control of Carbachol-Induced Drinking: Journal of Comparative and Physiological Psychology Vol 64(2) Oct 1967, 336-338.
  • Glover, E. D., Lane, S., & Wang, M. Q. (1995). Relationship of alcohol consumption and recreational boating in Beaufort County, North Carolina: Journal of Drug Education Vol 25(2) 1995, 149-157.
  • Gold, R. M. (1967). Aphagia and Adipsia Following Unilateral and Bilaterally Asymmetrical Lesions in Rats: Physiology & Behavior 2(2) 1967, 211-220.
  • Greene, E. G. (1968). Cholinergic Stimulation of Medial Septum: Psychonomic Science Vol 10(5) 1968, 157-158.
  • Hanumantharao, S., & Grabowski, M. (2006). Effects of introducing collaborative technology on communications in a distributed safety-critical system: International Journal of Human-Computer Studies Vol 64(8) Aug 2006, 714-726.
  • Hunter, D., & Oultram, S. (2008). The challenge of "sperm ships": The need for the global regulation of medical technology: Journal of Medical Ethics Vol 34(7) Jul 2008, 552-556.
  • Huston, J. P. (1968). Extinction under Intracranial and Conventional Reinforcement: Effect of a Correlated Counter: Psychonomic Science Vol 11(1) 1968, 25-26.
  • Kelly, T. L., Neri, D. F., Grill, J. T., Ryman, D., Hunt, P. D., Dijk, D.-J., et al. (1999). Nonentrained circadian rhythms of melatonin in submariners scheduled to an 18-hour day: Journal of Biological Rhythms Vol 14(3) Jun 1999, 190-196.
  • Khavari, K. A. (1967). Suppression of Drinking by Parenteral Administration of Carbachol: Psychonomic Science Vol 9(11) 1967, 599-600.
  • Leiken, S. J., & Caplan, H. (1967). Psychogenic Polydipsia: American Journal of Psychiatry 123(12) 1967, 1573-1576.
  • Levitt, R. A. (1968). Anticholinergic Brain Stimulation and Thirst Induced by 23 Hour Water Deprivation: Psychonomic Science Vol 12(1) 1968, 21-22.
  • Levitt, R. A., Krikstone, B., & Fisher, A. E. (1967). Spreading Depression and Thirst: Psychonomic Bulletin 1(2) 1967, 23.


  • Myers, R. D., & Cicero, T. J. (1968). Are the Cerebral Ventricles Involved in Thirst Produced by a Cholinergic Substance? : Psychonomic Science Vol 10(3) 1968, 93-94.
  • Myznikov, I. L. (1995). Information model of adaptation development: Human Physiology Vol 21(4) Jul-Aug 1995, 352-355.
  • Oatley, K. (1967). Drinking in Response to Salt Injections at Different Times of Day: Psychonomic Science Vol 9(7-B) 1967, 439-440.
  • Rosoff, H., & Von Winterfeldt, D. (2007). Risk and economic analysis of dirty bomb attacks on the ports of Los Angeles and Long Beach: Risk Analysis Vol 27(3) Jun 2007, 533-546.
  • Routtenberg, A. (1968). Dose-Response Problem in Testing the Ventricular Hypothesis: Reply to Myers and Cicero: Psychonomic Science Vol 11(3) 1968, 106.
  • Schaeffer, R. W., & Salzberg, C. L. (1967). Schedule-Induced Polydipsia: an Atypical Case: Psychological Reports 20(3, PT 2) 1967, 1071-1076.
  • Scott, J. C. (2008). Estimating the effects of water supply and sanitation on risk of diarrheal disease. Dissertation Abstracts International: Section B: The Sciences and Engineering.
  • Shelby, B., Whittaker, D., & Danley, M. (1989). Allocation currencies and perceived ability to obtain permits: Leisure Sciences Vol 11(2) 1989, 137-144.
  • Shulman, P., & Pomory, C. M. (2000). The effects of hydrocarbon pollution from a two-stroke outboard engine on the feeding behaviour of Lythrypnus dalli (Perciformes: gobidae): Marine and Freshwater Behaviour and Physiology Vol 33(3) 2000, 213-220.
  • Singer, G. (1967). Modulation of the Functional Circuit for Drinking by the Amygdala: Australian Psychologist 2(1) 1967.
  • Smith, J. C., & Roll, D. L. (1967). Trace Conditioning with X-Rays as an Aversive Stimulus: Psychonomic Science Vol 9(1) 1967, 11-12.
  • Smith, M. H., Jr. (1967). Stimulus Control of the Drinking Response: Psychonomic Bulletin 1(2) 1967, 34.
  • Strouthes, A., & Navarick, D. J. (1967). Saccharine and H2o Consumption as a Function of H2o Deprivation: Psychonomic Science Vol 9(9) 1967, 523-524.
  • Treichler, F. R., & Hoernig, M. J. (1967). Relationships among Age, Deprivational Severity and Intake Behavior of Rats: Psychonomic Science Vol 8(3) 1967, 127-128.
  • Ugolev, A. M., & Roshchina, G. M. (1967). Dialyzing Intraperitoneal Fistula and Its Application in Physiological Experiment: Byulleten' Eksperimental'Noi Biologii i Meditsiny 64(11) 1967, 140-142.
  • Wagenaar, W. A. (1975). Supertankers: Simulators for the study of steering: American Psychologist Vol 30(3) Mar 1975, 440-444.
  • Wayner, M. J. (1967). Hypothalamic and Limbic System Activation During Salt Arousal of Drinking: Psychonomic Science Vol 7(5) 1967, 179-180.
  • Wolfe, J. W., Lubar, J. F., & Ison, J. R. (1967). Effects of Medial Cortical Lesions on Appetitive Instrumental Conditioning: Physiology & Behavior 2(2) 1967, 239-244.
  • Yang, Y., Chen, J., Engel, J., Pandya, S., Chen, N., Tucker, C., et al. (2006). Distant touch hydrodynamic imaging with an artificial lateral line: PNAS Proceedings of the National Academy of Sciences of the United States of America Vol 103(50) Dec 2006, 18891-18895.
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