It seems like every celebrity puts their good skin or toned physique down to ‘drinking plenty of water’. But water isn’t the latest food fad – it performs a range of vital functions in our body.
But do we really need eight glasses a day to stay healthy? And is anything else apart from H2O a no-go?
Why our bodies need water
Water makes up about 60% of our body weight, and it’s involved in every single process in our body.1 We need it to:
• help regulate our temperature
• keep our joints, eyes and muscles lubricated
• get rid of waste via sweat, urine or bowel movements
Water is essential for life. Without it, we would only be able to survive for a few days.2
What happens if you don’t drink enough water?
Dehydration can affect your body and brain in a number of ways. You may feel tired, find it hard to concentrate, experience mild memory problems, lack motivation – especially when it comes to exercise – or find it takes more effort during a run or gym session.3
You can tell if you’re drinking enough by checking the colour of your wee. It should be a pale-yellow colour.4 Dark, cloudy or strong-smelling urine is a sign you’re dehydrated, so start upping your fluid intake as soon as possible.
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How much water should you drink?
The rule that we should drink eight glasses of water a day is not technically true.
Research published in the British Medical Journal in 2007 explored where the idea that we need eight glasses every day for hydration comes from.5 Researchers found that this figure is based on 1945 study, which stated we need 2.5 litres of water a day – but that most of this could be found in our food.
It’s this last bit of information (that most water can be found in our food) that has been forgotten over the years and so the study has been misinterpreted as claiming we need eight glasses of water a day
The NHS says we should drink six to eight glasses of fluid a day, about 1.2 litres.6 This includes water, lower-fat milks, tea and coffee. And don’t worry that tea and coffee can cause dehydration.
Although they are diuretics, which make you wee more often, a 2003 study by the School of Sport and Exercise Sciences at Loughborough University found there was no evidence that coffee led to dehydration.7 The study concluded that coffee actually had ‘similar hydrating qualities’ to water.
When you might need more water
Most of us will only need six to eight glasses of fluid a day, but there are times you may need more. These include after exercise – especially if you get sweaty – if you’ve been ill with vomiting and diarrhoea, or are in a hot climate.8
Don’t glug back loads of water straight after a workout. This can stimulate urine production, which in turn means your body will retain less water. The American College of Sports Medicine9 recommends drinking 2 litres of water in 500ml amounts, every 20 to 30 minutes, instead.
If you’re pregnant or breastfeeding, you may also need to increase your fluids.
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Easy ways to stay hydrated
Bored of plain water? Try drinking herbal teas, coconut water, or adding slices of fruit for flavour to your water bottle instead.
Around 25% of the water we consume comes from our food10, so include more foods with a high water-content. The US Department of Agriculture11 says these are:
• strawberries, watermelons, spinach (90 – 99% water)
• apples, grapes, broccoli (80 – 89% water)
• bananas, avocado, baked potato (70 – 79%)
• pasta, salmon, chicken breast (60 – 69%)
Can you drink too much water?
Don’t force yourself to drink if you don’t feel thirsty. This could lead to hyponatremia,12 a dangerous condition where excess water dilutes the electrolytes in your blood.
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.
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1. Mayo Clinic. Water: how much should you drink every day? Available from: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/water/art-20044256
2. Popkin BM, D’Anci KE, Rosenburg IH. Water, hydration and health. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908954/
3. As above
4. Mayo Clinic. Urine color. Available from: https://www.mayoclinic.org/diseases-conditions/urine-color/symptoms-causes/syc-20367333
5. Vreeman RC, Carroll AE. Medical Myths. Available from: http://www.bmj.com/content/335/7633/1288
6. NHS Choices. Water, drinks and your health. Available from: https://www.nhs.uk/Livewell/Goodfood/Pages/water-drinks.aspx
7. Killer SC, Blannin AK, Jeukendrup AE. No Evidence of Dehydration with Moderate Daily Coffee Intake: A Counterbalanced Cross-Over Study in a Free-Living Population. Available from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084154
8. NHS Choices. Dehydration. Available from: https://www.nhs.uk/conditions/dehydration/
9. American College of Sports Medicine. Roundtable on Hydration and Physical Activity: Consensus Statements. Available from: 500
10. Guelinckx I, et al. Contribution of Water from Food and Fluids to Total Water Intake: Analysis of a French and UK Population Survey. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5084017/
11. As Source 2 – see Table 1
12. Healthline. How much water you need to drink. Available from: https://www.healthline.com/health/how-much-water-should-I-drink#risks