When the body is in a state of dehydration, many substrates and neurotransmitters
are influenced by circulating vasopressin
(antidiuretic hormone) and angiotensin II (1,2).
Dehydration can increase levels of cortisol (3).
Interestingly, even a decrease in cell volume caused by hypohydration
promotes insulin resistance
(4,5,6).
Conditions dehydrating insulin target tissues such as hyperosmolarity or
amino acid deprivation are associated with insulin resistance;
blockage of the cell volume response to insulin may be the common denominator
in dehydration-induced insulin resistance (4).
As a consequence of dehydration, the
blood–brain barrier permeability is altered by serotonergic and dopaminergic
systems, potentially causing central nervous
system dysfunction if dehydration is prolonged (7).
Chronic dehydration influence inhibitory and excitatory activities of the brain by increasing aminobutyric acid and glutamate levels (8), by stimulating γ-aminobutyric acid and N-methyl-D-aspartate receptors, to synthesize and release antidiuretic hormone (9).
Chronic dehydration influence inhibitory and excitatory activities of the brain by increasing aminobutyric acid and glutamate levels (8), by stimulating γ-aminobutyric acid and N-methyl-D-aspartate receptors, to synthesize and release antidiuretic hormone (9).
Even mild dehydration produces significant changes at the neural level:
total brain volume shrinkage and over-recruitment of specific brain areas
during cognitively demanding tasks (10).
Overhydration
Hyperhydrating means drinking more water than you could possibly need,
so much fluid that you dilute the amount of sodium in your blood. The low
sodium level can cause a cerebral edema, swelling of the brain, leading to
death. Sodium
and potassium
are essential electrolytes. An inadequate amount of sodium in the blood is defined as
"hyponatremia” (11).
Women’s menstrual cycle phase
influences body water, during the luteal phase total body water can increase up
to 2 kg (12,13).
Water intoxication
Water intoxication can lead to life-threatening hyponatremia,
which can result in central nervous system edema, lung congestion, and muscle
weakness (14). Hyponatremia can also occur from excessive fluid intake, underreplacement
of sodium, or both during or after prolonged endurance athletic events. This is
common during marathon events (15). For example 13% of the athletes who
finished the 2002 Boston Marathon were in a hyponatremic state (16).
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1. Wilson MM & Morley JE (2003) Impaired cognitive function and
mental performance in mild dehydration. Eur J Clin Nutr 57, S24–S29.
2. Bourque CW (2008) Central mechanisms of osmosensation and systemic
osmoregulation. Nat Rev Neurosci 9, 519–531.
3. Daniel A. Judelson , Carl M. Maresh , Linda M. Yamamoto , Mark J.
Farrell , Lawrence E. Armstrong , William J. Kraemer , Jeff S. Volek , Barry A.
Spiering , Douglas J. Casa , Jeffrey M. Anderson. Effect of hydration state on
resistance exercise-induced endocrine markers of anabolism, catabolism, and
metabolism. Journal of Applied Physiology Published 1 September 2008Vol. 105no.
3, 816-824
4. Schliess F, Haussinger D. Cell hydration and insulin signalling. Cell
Physiol Biochem 10: 403–408, 2000.
5. Schliess F, Haussinger D. Cell volume and insulin signaling. Int
Rev Cytol 225: 187–228, 2003.
6. Schliess F, von Dahl S, Haussinger D. Insulin resistance induced by
loop diuretics and hyperosmolarity in perfused rat liver. Biol Chem 382:1063–1069,
2001.
7. Maughan R, Shirreffs S & Watson P (2007). Exercise, heat,
hydration and the brain. J Am Coll Nutr 26, 604S–612S.
8. Di S & Tasker J (2004) Dehydration-induced synaptic plasticity in
magnocellular neurons of the hypothalamus supraoptic nucleus. Endocrinology
145, 5141–5149.
9. Babar, S. (October 2013). "SIADH Associated With
Ciprofloxacin.". The Annals of Pharmacotherapy 47 (10): 1359–1363.
10. Kempton MJ, Ettinger U, Foster R, et al. (2011) Dehydration affects
brain structure and function in healthy adolescents.Hum Brain Mapp 32, 71–79.
11. Reynolds, R. M; Padfield, PL; Seckl, JR (2006). Disorders of sodium
balance. BMJ. Mar 25, 2006; 332(7543): 702–705.
12. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld
NS. American College of Sports Medicine position stand. Exercise and fluid
replacement. American College of Sports Medicine. Med Sci Sports Exerc. 2007
Feb;39(2):377-90.
13. Sawka M, Burke LM, Eicher ER, et al. Exercise and fluid replacement.
Med Sci Sports Exerc. 39:377–390.
14. Institute of medicine. Water. In: Dietary Reference Intakes for
Water, Sodium, Chloride, Potassium and Sulfate, Washington, D.C: National
Academy Press, pp. 73–185, 2005
15. Rosner, M. H.; Kirven, J. (2006). "Exercise-Associated
Hyponatremia". Clinical Journal of the American Society of Nephrology
2 (1): 151–61
16. Almond, Christopher; Shin, Andrew (2005). Hyponatremia among runners
in the Boston Marathon. N Engl J Med 352 (15): 1550
