Water balance regulation

The human body uses and loses water every day.

 

How does the body regulate its water balance?

 

The maintenance of a correct water balance
(the net difference between water gain and
water losses) is essential to good health.
It is all the more essential as there is no real
water storage in the body: the water we lose
needs be replaced, and humans cannot survive more
than a few days without water.^1,2

We lose water on a daily basis.

• Through the respiratory tract (by breathing)
• Through the gastro-intestinal tract (faeces)
• Through the skin (perspiration and sweating)
• Through the kidneys (urine excretion)

Lifestyle and environmental conditions have
a significant impact on an individual’s own
level of water loss, but on average, a typical
adult loses about 2.6 litres (L) per day.³

Table: Average daily water loss from different organs in adults³
 

Additional water losses via sweat will be induced by physical exercise and/or a hot environment and could contribute to water losses of up to several litres.
We gain water through fluid and food intake and metabolic water production mainly through food nutrient utilization by the body. Metabolic water production represents 0.3 L per day, on average, and water from foods can vary greatly according to dietary habits. Our remaining requirement needs to be provided by fluids.

References

1. Institute of Medicine (IOM). Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: National Academies Press,2004.
2. EFSA. Scientific Opinion on Dietary Reference Values for water. Available at: http://www.efsa.europa.eu/en/scdocs/scdoc/1459.htm. Accessed April 2010.
3. Shirreffs SM. Markers of hydration status. J Sports Med Phys Fitness 2000;40:80-4.
4. Bouby N, Fernandes S. Mild dehydration, vasopressin and the kidney: animal and human studies. Eur J ClinNutr. 2003;57:S39-46.
5. Armstrong LE. Hydration assessment techniques. Nutr Rev. 2005;63:S40-54.