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Can you drink too much?

15 April 2016
Man drinking water

The past two posts in this blog have discussed what's in your tap water and why it is your best choice for hydration - a timely point considering today's announcement from the Local Governments Association (LGA) on the rise in tooth decay in the UK.

But now that the basics on water quality have been covered, it makes sense to consider quantity. Recommendations on how much you need to drink can often vary, with experts disagreeing over exact levels. Zuzana Cabejskova, on behalf of Water UK, researched the role of drinking water in society and created a full literature review, published on our website. This post will briefly consider the main points of the review.

How much water should you drink in a day?

Clear question, unclear answer: it depends.

The British Nutrition Foundation states that 'it is not meaningful to give a specific recommendation regarding water requirements, as these vary widely.' Put simply: there's no one-volume-fits-all guideline.

It all comes down to how much water leaves your body. The logic is straight-forward, you have to maintain a water balance: what goes out must come in, otherwise you will be dehydrated. How much water you excrete depends on many factors: age, gender, health, body mass, environmental conditions and physical activity all play a role. There are two main paths in which your body gets rid of water: urinating and sweating. The volumes depend on intake, diet, activity level, temperature and clothing.

A vague answer to the question is that you should drink enough to prevent dehydration. Read on to find out how to control that.

What are the symptoms of dehydration?

When you are running on a negative water balance, your body will start to function improperly. Depending on how severe the disbalance is, you will notice different symptoms. The more dehydrated you are, the more you suffer and the worse your body performs. Think of your dehydrated self as a printer running out of ink: colour starts fading away and if the cartridge isn't replaced, you could stop printing completely. But let's not get too pessimistic!

Dehydration is measured in percentage points that say what proportion of water is missing in your body. Here's what generally happens as the levels increase (in reality, the thresholds aren't this clear and symptoms can occur at different levels):

  • >1% dehydration: you feel thirsty
  • >2% dehydration: reductions in exercise performance, in thermoregulation and in appetite
  • >3% dehydration: dry mouth, poor concentration, headaches, irritability and sleepiness
  • >4% dehydration: increases in body temperature and heart and respiratory rates
  • Dehydration of more than 10% at high ambient temperatures brings serious risk of a life-threatening heat stroke
  • Chronic dehydration can increase the risk of infection, especially of the urinary tract

How to avoid dehydration

Many people only drink when they are thirsty. Although thirst is one of the body's primary feedback mechanisms, it is activated by dehydration. Therefore, if you only drink when you are thirsty, you are allowing your body to get dehydrated.

To combat dehydration, you may wish to consider some new tactics in your water regime. Try setting yourself specific goals to ensure you are drinking as much as you should. Carrying a reusable bottle with you, or keeping a glass of water on your desk could be helpful in striking the right balance. There are also multiple smartphone apps that allow you to track your daily water intake.

It is important to note that the elderly, children and the ill are at a higher risk of dehydration as their thirst sensation isn't as reliable. If you are caring for someone in these parts of society, try to offer them a drink whenever you have one.

How much water do we drink a day?

In the large part, the UK tends to drink enough liquids. However, we should drink more water instead of some less healthy alternatives.

Let's have a look at some of the numbers. The below infographic outlines some basic stats on liquids and water consumption in the UK. It shows that men drink more liquids overall, but women drink more water.

Infographic on drinking water

What can be calculated from the numbers is that on average, people drink 1967 ml of liquids a day and 66% of tap water.

Note: This data comes from a 2008 DWI survey that defined tap water as plain water, as well as other drinks made from tap water.

So, the UK largely drinks enough, but we need to work to give our intake a health kick by switching to tap water.

LGA announcement on tooth decay

The Natural Hydration Council fact sheet

British Nutrition Foundation - Hydration and health