Nutrition 4: Water

Posted on 26 April, 2011 by Chris Beardsley

This post is part of a series describing my adventures into my personal training nutrition module course notes.  They were sometimes boring, occasionally interesting, mostly infuriating and often misleading.

In this instalment about water, they talk purely about hydration levels, the importance of drinking plenty of water and the potential hazards with consuming diuretics such as tea and coffee.  Given that my mother taught me all about that when I was five, I don’t propose to discuss this in any detail but rather to talk about more interesting things instead…

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My course notes

My course notes make the following points about water:

  • Functions of water: water performs several key functions as follows:
    • Transportation – it moves everything around in the bloodstream
    • Temperature regulation – it distributes heat around the body
    • Medium of chemical reaction – it provides the medium for every chemical reaction in the body
  • Daily requirement: our daily requirement of water is as follows:
    • Sedentary – 2.5L
    • Active – 3.5 – 4.0L
    • Active in hot climates –  4.0 – 5.0L
  • Consequences of dehydration: the consequences of dehydration are as follows:
    • A loss of 3% causes a reduction of blood volume and blood flow, inefficient kidney function and a reduction in exercise performance
    • A loss of 4% causes a reduction in exercise performance by 20 – 30%
    • A loss of 5%, heat exhaustion occurs
    • A loss of 7% leads to hallucinations
    • A loss of 10% causes heat stroke, circulatory collapse and death
  • Assessing hydration levels: a prosaic but effective way of assessing hydration levels is to look at the colour of your urine.  Clear and pale yelow urine implies that you are hydrated but darker yellow alerts you to the fact that you are becoming dehydrated.
  • Diuretics: diuretics are substances that encourage water loss in the body.  Common examples are caffeine and alcohol.

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So what are the real issues?

Leaving aside the elementary material, when it comes to water, I figure that the real issues are:

  • Is drinking a lot of water necessary for good health?  If so, why?
  • Is drinking tap water any different from drinking bottled water?

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Is drinking a lot of water necessary for good health?  If so, why?

I haven’t delved into any research about the requirements of water for health but I was aware of two great articles by two of my favourite fitness writers, Charles Poliquin and Mark Sisson.  Strangely, they have completely differing opinions.

  • In a two part article (part one and part two), Charles Poliquin is definitive in rejecting the idea that eight glasses of water (c. 2.4L) is a sufficient quantity of water in today’s day and age.
    • In part one of this article, Charles explains that our bodies need extra water compared with previous generations in order to deal with the pollutants in our food and surroundings.  He suggests that an appropriate calculation for adequate hydration is bodyweight (lbs) /2 in fl. oz or bodyweight x 1.5 in litres.  So a 200lb person would need 3L of water for adequate hydration.
    • Charles also gives a formula for optimum hydration as an additional 20% on top of this.  So this would be (bodyweight (lbs) /2) x 1.2 in fl. oz or bodyweight x 1.5 x 1.2 in litres.  So a 200lb athlete would need 3.6L.
    • In part two of his article, Charles goes into more of the details of why dehydration is disadvantageous for athletes.
  • Mark Sisson again believes that eight glasses of water might not be the best protocol.
    • Mark points out that much of the water we need should be obtained from the foods we eat.  After all, he suggests, would the Palaeolithic human have carried a water bottle around with him?
    • Mark suggests that the whole “eight glasses a day” or 2.5L idea probably came from a similar arbitrary calculation as the food pyramid and it’s hard to argue.  Many of these maxims seem to have little grounding.

So who is right?

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Is drinking tap water any different from drinking bottled water?

Breaking this issue down, I guess that the two main points are:

  • How bad for you is fluoride in tap water?
  • Are there other unpleasant things in tap water, like hormones?
  • How bad are the carcinogens in plastic bottles?

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How bad for you is fluoride (in tap water)?

I found the following studies relating to fluoride (thanks again to Healthy Diets and Science):

I am not enough of a scientist to tell whether these studies suggest that it is a serious concern for us in drinking tap water with fluoride in it.

However, we put fluoride in our water simply because of our tendency to get dental caries.  And we only get dental caries because we eat grains and sugar.  After all, caries did not exist in Palaeolithic populations.  So it would seem to me that we have traded better dental health for the problems that fluoride causes.

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Are there other unpleasant things in tap water, like hormones?

Well, that’s a slightly less difficult question to answer:

  • Scientific American reports that in 2008, the US Geological Survey reported that there were 85 man-made chemicals in the water supply, including birth control hormones (mainly oestrogen) and pharmaceuticals.  The recommendation is that we use reverse-osmosis filters to remove such contaminants to protect our health.
  • And SprintStrong reports that the oestrogen in rivers is so significant that it is causing male fish to become female.
  • The Sunday Times notes that the increasing incidence of men seeking breast reductions is being blamed on oestrogen in the drinking water and in fast food.  Apparently, the increase has been noticeable even over a couple of years.
  • And the National Geographic reports that there may well be other things as well as oestrogen in the water supply, including basic products such as sunscreen and more dangerous substances including cocaine.
  • And the Huffington Post gives details of an Associated Press investigation into the same issues and their similar findings.

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How bad are the carcinogens in plastic bottles?

  • Mark Sisson did a round up of various issues surrounding why you shouldn’t drink out of plastic bottles, including this article at Science Daily, which discusses recent research into the effects of BPA, or bisphenol.
  • However, Cancer Research have a page designed to help answer questions about the possible dangers of plastic bottles.  They note that there was a false scare in Japan in 2002 that led to a number of articles without scientific grounding doing the rounds on the internet about the dangers of drinking out of bottles that had been frozen.  They note that there is no research to suggest that there is any danger in eating or drinking foods that have come into contact with plastic that has been heated or frozen.  They don’t mention BPA by name, however.

So who is right?  I may need to get into the research on this one…

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Other interesting links

  • Freakonomics discusses the strange economics of water.
  • World of Psychology investigates why bottled water tastes better than tap water.  It’s the expectation, you see.
  • Conditioning Research notes that apparently washing your face in cold water after exercise helps you to recover faster.
  • The Frugal Girl reports on why bottled water is an outrage and shouldn’t be allowed anyway.  It’s hard to disagree once you read her reportage.

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I never would have believed water could be so interesting!  There are so many issues surrounding such a basic element of our health.  I think I will return to these fertile grounds again in the future.  There is much to discover here…

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