Thursday, 30th August, 2018

Staying hydrated: how much water should I drink?

A recent survey carried out by the Royal National Lifeboat Institution (RNLI) revealed that 89 per cent of people in the UK are not drinking enough water to maintain healthy hydration levels.

The survey found that women are more hydrated than men: while 13% of women don’t drink any water during the day, the figure for men is an alarming 20%. Age also seems to play a role, with a staggering 25% of over 55s admitting to drinking no water during the day. For 25 to 34 year olds, the figure is a low as 7%.

These statistics are cause for concern, and it’s clear that collectively we need to be drinking more water. But what is the optimum daily amount we should all be drinking? Before we answer that question, we need to explore why drinking enough water is important.

You are what you drink


60% of the human body is water. Yes, that’s a lot of water, and it’s water that regularly needs topping up. Water helps regulate our body temperature and maintains vital bodily functions. Our brains alone are 73&% water, and unsurprisingly poor hydration can seriously impact your brain’s functions.

We naturally lose water through breathing, sweating and digestion. If this fluid loss is left unchecked, however, you’ll end up getting dehydration.

What is dehydration and why is it bad?

Dehydration occurs when your body is losing more water than it is taking in. When you body does not take in enough water, you will become dehydrated. Symptoms of the dehydration include:

  • thirst
  • dizziness and lightheadedness
  • dark-coloured and strong-smelling urine
  • tiredness
  • dry mouth, lips and eyes

Dehydration can also slow down your metabolism, and not drinking enough water therefore makes weight loss difficult.

A study by the European Journal of Clinical Nutrition found that even mild dehydration (or 1% to 2% body weight loss) can cause impairments in alertness, concentration and short-term memory, as well as physical performance like endurance or sport skills.

To reiterate, that’s just from mild dehydration. As such, it’s certainly worth being aware of your thirst impulse.

How much water should I drink a day?

The NHS advise on drinking 1-2 litres of water daily in the UK. That’s roughly 6-8 glasses a day.

For those of you who would admit to being under-hydrated, this may sound like a large amount of water to aim to drink. Look at it this way: the average time a Brit spends awake during a given day is between 15 and 16 hours (940 minutes to be precise). By following NHS advice, that means you’ll be having a glass of water roughly every 2 hours. On a busy working day, that’s hardly over the top.

In hotter climates the body produces more sweat, so you’ll need to drink more water to address the balance if you’re in a balmier country or there’s hot weather at home. The European Food Safety Authority (EFSA) recommends a water intake of 2.5 litres a day for men and 2 litres a day for women per day from both food and drink. They also recommend that around 70-80% of your daily water intake should come from drinks.

The health benefits of drinking water


Water acts as a detoxer, hydrater and refresher. Given that more than half of the human body consists of the stuff, it’s hardly surprising that the benefits of drinking H20 are legion.

Drinking more water allows you to produce more sweat, so staying hydrated can help you maintain athletic performance and prevent excessive fluid loss during spells of intense sporting activity.

Getting enough water can also improve your digestive health and relieve constipation. When you are dehydrated, your large intestine soaks up water from food waste which hardens stools and makes it difficult for them to pass.

By maintaining the recommended level of water consumption, you’ll also keep your urine diluted. This will stone waste products getting too concentrated and drastically reduce your chances of getting kidney stones. Good news indeed.

Based on age, gender, weight and height, this water intake calculator is a useful tool for working out your ideal daily water intake. It also factors in the type of exercise you regularly do, as well as the current temperature in your location.

What happens if I drink too much water?

While many of us should be drinking more water, it's still possible to overdo it.

Although most healthy people who drink too water will urinate much more frequently, certain people will be at a high risk of hyponatremia. This can happen when an excessive intake of water causes causes sodium levels to fall dangerously low. Athletes who perform in endurance sports and drink lots of fluids may be at risk of developing this condition.

Contact your GP if you are worried about excessive water intake and its effect on your sodium levels.

Further information

For more on the health benefits of water, check out the NHS Live Well page.

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