• Question: what would happen if you drink too much water

    Asked by NIamh 13 Pets!!! to Stephanie, LauraAnne, Katy, Helen, Emilia, Dan, Andrew on 3 Nov 2016.
    • Photo: Helen Hanstock

      Helen Hanstock answered on 3 Nov 2016:

      Hi Niamh!

      This is an interesting question. Actually, drinking too much water can actually be more dangerous than not drinking enough…

      Your body carefully controls the amount of water that you absorb from food and drink. This means that when you drink a lot of water, your urine becomes more dilute, watery and light in colour. However, occasionally during really long running races like marathons, participants might take a drink very regularly and end up drinking more water than their body can deal with. This brings about a state called hyponatremia.

      Hyponatremia is what happens when you drink too much water, and your blood becomes ‘diluted’ by the excess water. This means that the concentration of important salts such as sodium (Na) in the blood falls to dangerously low levels. The symptoms might include nausea, headache, confusion or tiredness, but severe hyponatremia can be very dangerous as it can prevent the nervous system (including the brain) from functioning properly. In extreme cases, if not treated, this could result in coma or death.

      If a person is suspected to have hyponatremia they should avoid drinking any more water or sports drinks until the body has had a chance to get rid of the excess water.

      Hope this answers your question! 🙂

    • Photo: Dan Gordon

      Dan Gordon answered on 4 Nov 2016:

      Hi Niamh, what a great question. When we drink water or any fluid, we do so not so much to keep us hydrated (although this clearly important) but to ensure that we control our ‘core’ temperature. When we exercise or even go into a hot environment we produce hear, in fact about 75% of the energy used to generate a muscle contraction is lost in the form of heat. This heat has to be removed from the body, remember that a high body temperature can be dangerous to human health as this can lead to in very extreme cases death and less extreme sickness.
      Water that you drink is used to keep the core temperature under control (around 37 degrees C). Why is this important. Quite simply the blood is a fantastic vehicle for getting rid of heat from the body. Ever wondered why your skin goes red when exposed to hot climates (no this isn’t sun burn). The blood is directed through circulatory control mechanisms to the skin and through a process using concentration gradients (always moving from high to low concentrations) the heat is dissipated from the body in the form of sweat. The key element here is sodium (Na)
      Now image drinking to much. The same mechanism of re-direction of blood flow would occur, but now because there is more water in the system the blood is in essence more dilute, or to be exact the concentration of sodium becomes more diluted. This means now that the concentration in the circulation is lower than that on the skin (remember that you would be sweating in the heat). SO now it becomes harder to get rid of the heat in the form of sweat and so you start to retain this heat. This is why isotonic solutions are often preferred to just water because these contain the key electrolytes that are need for this concentration gradient.
      This condition is referred to as hyponatremia or water-intoxication

    • Photo: Emilia McAllister-Jepps

      Emilia McAllister-Jepps answered on 6 Nov 2016:

      Hi Niamh, another good question!

      There are some great answers above from the Scientists.

      As Dan has mentioned some people prefer to use isotonic drinks to replenish the sodium lost through sweat during exercise. Whilst there are clear effects on the body in very extreme cases, on a day to day basis if you drink too much water you could find yourself feeling unwell, or less able to make the most of a training session. From personal experience, I find that I feel a bit fuzzy around the edges if I have been too keen to hydrate. This is easy to do on the first few days of a warm weather training camp for example.

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