Water as an essential nutrient: the physiological basis of hydration
There are many times when the decision to say we need ‘8 glasses of water’ a day just pops out. But what is the evidence for this, do we need more or less? Obviously climate, activity, age and availability of fluids are all going to have an effect, and what about if we drink too much and suffer hyperhydration leading to hyponatraemia (a disturbance of the salts in the blood) in which the sodium (Natrium in Latin) concentration in the plasma is lower than normal (hypo in Greek), specifically below 135 mEq/L)?
Often ridiculed, the minimum volume per day has been contentious, with many commentators settling on 8 full 8oz glasses of water, and other suggesting that any fluid intake that hydrates will suffice.
Water is your body’s principal chemical component and makes up about 60 percent of your body weight. Every system in your body depends on water. For example, water flushes toxins out of vital organs, carries nutrients to your cells and provides a moist environment for ear, nose and throat tissues.[1]
Lack of water can lead to dehydration, a condition that occurs when you don’t have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.
This month’s European Journal of Clinical Nutrition publishes an article[2] asking that very question and start by saying:
How much water we really need depends on water functions and the mechanisms of daily water balance regulation.
They go onto qualify the typical sources of water for humans by defining three major sources:
- The water we drink,
- The water we eat and
- The water we produce.
The water we drink is essentially composed of water and other liquids with a high water content (85 to 490%). The water we eat comes from various foods with a wide range of water content (40 to 480%). The water we produce results from the oxidation of macronutrients (endogenous or metabolic water).
Conclusion
The regulation of water balance is essential for the maintenance of health and life. On an average, a sedentary adult should drink 1.5l (6 x 8oz glasses) of water per day, as water is the only liquid nutrient that is really essential for body hydration.
So that’s all clear then….
References
[1] Häussinger D. The role of cellular hydration in the regulation of cell function. Biochem J. 1996 Feb 1;313 ( Pt 3):697-710. Review. View Full Paper
[2] Jéquier E, & Constant F (2010). Water as an essential nutrient: the physiological basis of hydration. European journal of clinical nutrition, 64 (2), 115-23 PMID: 19724292
