Why drink water, and how much is enough?

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Like a lot of people working in the nutritional field, I believe maintaining hydration is important for peak wellbeing and health. Water makes up about two-thirds of the body, and therefore has the potential to play a critical role in just about any bodily process one cares to mention. Like what? Well, now the benefits of hydration (and the perils of dehydration) have been documented in a review in this month’s edition of the European Journal of Clinical Nutrition [1].

One of the two authors of this review is from the Department of Physiology at the University of Lausanne in Switzerland. The other author’s place of work is listed as ‘Nestle Waters’ in Paris, France. Oddly, though, the fact that one of the authors works for a company selling bottled water is not declared as a conflict of interest. Ho hum, onto the review…

To my mind, the review actually does a very good job of summarising the role that water plays in the structure and function of the body. Here’s a summary:

Water as a building material
Water is present in each and every cell in the body, and acts first as a building material.

Water as a solvent
For nutrients like glucose and amino acids.

Water as a carrier
For the transport of nutrients to cells, and the removal of waste from those cells. Also, for maintenance of blood volume and circulation, which is essential for the function of all organs and tissues of the body.

Water and thermoregulation
To allow sweating, which can dissipate heat from the body.

Water as a lubricant and shock absorber

Water ensures lubrication for joints, as well as parts of the body including the mouth, digestive tract and lungs.

In terms of the effects signs of dehydration, the review lists (for mild-to-moderate dehydration) among other things:

Dry, sticky mouth
Sleepiness or tiredness
Decreased urine output
Muscle weakness
Dizziness or light-headedness

The review goes on to cite official recommendations regarding water requirements (European Food Safety Authority, 2008). These come out at about 1.5 litres a day for adults, with more required during pregnancy and for breast-feeding mums. However, the authors also allude to the fact that making blanket recommendations is not easy, because needs for water will depend on several factors including climate and physical activity.

The authors also write about the assessment of hydration status, and mention urine colour as an indicator. I generally suggest to individuals that this is the most practical way of gauging hydration status. The usual advice I give to individuals is to drink enough water to ensure that the urine is pale yellow throughout the course of the day. I might follow this up with something like “If at any time you notice your urine has straying into darker tones, and has become noticeably odourous, the chances are you are dehydrated and you might think about increasing your water consumption.”

I don’t think anyone’s formally studied this, but my overwhelming experience in practice is that individuals who take steps to improve their hydration almost always feel improvements in terms of their energy and wellbeing. Maintaining hydration easily is generally facilitated by ensuring that you have water by you. So, keep a bottle or jug of water and a glass by you at work, in the garden, when relaxing etc. Most individuals find themselves quite naturally reaching for water as long as it’s in front of them.


1. Jequier E, et al. Water as an essential nutrient: the physiological basis of hydration. Eur J Clin Nutr 2010;64:115-123

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