Hydration is a key part of a healthy lifestyle, but what do we mean when we say staying hydrated? Here Dr Pippa Gibson discusses the role of fluids in health, how to spot when you could be at risk of dehydration and Pippa shares her top tips for staying hydrated throughout the day, come rain or shine!

The importance of hydration

Hydration status is something that can quite easily be overlooked, but is very important. Over half of your body is made up of water, and therefore it is essential that you stay hydrated for your body to work at its best. Dehydration occurs when at least 3% of your bodyweight is lost due to a lack of fluid, although effects are seen with a loss as little as 1-2% on mood and performance in adults and children. If we don’t stay hydrated, in the short term it could lead to some unpleasant symptoms including:

• Lack of concentration

• Tiredness

• Dizziness/ light headedness/ fainting

• Confusion

• Headaches

• Constipation

If we have poor hydration status and are repeatedly dehydrated, this can cause longer term consequences including:

• Kidney stones

• Urinary tract infections

• Chronic renal disease

How do I know if I am drinking enough?

If you feel thirsty it is important to have a drink as this is your body’s way of telling you that you need fluid. However, once we feel thirsty we can already be mildly dehydrated. Therefore, we should try not to let ourselves get into this situation. You can also check the colour of the urine you pass, to assess your level of hydration; the more dehydrated you are, the darker your urine will be (colours 4-8 on the urine chart). Aim for a pale straw or pale coloured urine (colours 1-3) for optimal hydration. Clear urine is a sign of good hydration, but consistently clear urine could be a sign of overhydration.

 

How much do I need to drink?

While this is a rather individual answer, it also varies with the seasons, as well as your lifestyle choices, for example, on a hot summers day you may need to drink more, and if you participate in a lot of exercise and sweat a lot you may also need to drink more. Typically, the average adult needs to drink between 1.5-2.5 litres of fluids a day, or around 6-10 glasses. For children these values will be slightly lower (see the below table), but you can always check if you are hydrated enough by checking the colour of your urine.

The British Dietetic Association (BDA) also states that certain groups need to take extra care of their hydration status:

• Children, who are often too busy to notice or recognise thirst

• Pregnant and breastfeeding women who have higher requirements

• Older people, who often don’t drink enough or forget

• Athletes, who have higher losses of water through sweat

The table below shows fluid requirements set out by the BDA for different population groups

Population Group	Adequate Intake per day, from drinks
Infants aged 0-6 months	500ml as milk
Infants aged 7-12 months	640-800ml
Infants aged 1-2 years	880-960ml
Infants aged 2-3 years	1040ml
Children aged 4-8 years	1280ml
Over 14 years	As adults
Adults including the elderly
Men	2000ml
Women	1600ml
Pregnant women	As adults + 300ml per day
Lactating women	As adults + 600-700ml per day

It is also worth being aware of the fluid requirements set out in 2010 by the Scientific Opinion on Dietary Reference Values for Water by the European Food Safety Authority (EFSA) where the values differ to the BDA recommendations. The differences are due to the fact that the EFSA assume that 70-80% of fluid in the diet comes from drinks (20-30% from food).

What counts as fluids?

Many drinks count towards your fluid intake:

• Water

• Flavoured drinks

• Fizzy drinks

• Hot drinks such as teas and coffees

• Fruit and vegetable juices, and smoothies (limited to 150ml per day)

• Milk and plant-based milk alternatives

However, the UK public health advice includes limiting the intake of sugary drinks such as fizzy drinks, squashes and juice drinks, particularly in children. They can have high amounts of free sugars (which should be limited in the diet as per government advice) and minimal nutritional benefits.

Although fruit juices and smoothies can contribute to one portion of 5-a-day (never more), they should be limited to one 150ml glass per day. This is because the sugars in fruit and vegetables are released when they’re juiced or blended, making them a source of free sugars.

Did you know, many foods will also contribute to your fluid intakes? It is estimated that up to 20-30% of your fluid intake will come from foods such as:

• Fruits and vegetables

• Soups, stews and casseroles

• Yoghurt

• Jelly

• Ice cream

Do alcoholic drinks count towards my fluid intakes?

There is conflicting evidence surrounding alcoholic beverages and hydration. Alcohol is a diuretic, meaning it can make us pass more urine and cause us to become more dehydrated, especially when consumed in large quantities. Alcohol is also not recommended daily or in large amounts due to the variety of health risks associated with consuming it. MyNutriWeb have a webinar on alcohol and cancer risk which highlights the detrimental effects alcohol can have on cancer development, again supporting limiting intakes.

In an interesting recent systematic review, researchers concluded that low alcoholic beers, with a little added sodium, were an effective way to rehydrate post exercise. However, for stronger drinks (>4% ABV), rehydration results were better if paired with a non-alcoholic beverage to mitigate the alcohol-induced diuresis. While I wouldn’t advise complete rehydration with alcoholic beverages, a celebratory drink post event might not be as harmful as previously thought, if consumed appropriately and responsibly. Though it should be noted that more well-designed studies are needed to draw robust conclusions.

Is it possible to overhydrate?

Excess of anything can be bad, and the same is true for too much water. Consuming excess water can lead to overhydration and can have some side effects such as restlessness, lethargy, polyuria, diarrhoea, nausea, vomiting, and in severe cases, death. This is because you could end up diluting your sodium levels in your blood known as hyponatremia. People at higher risk of a fluid-electrolyte imbalance include athletes performing in endurance training where prolonged periods of sweating need to be carefully counteracted with fluids containing electrolytes. If you are exercising for an hour or less, water is a good hydration fluid, but for those doing moderate to high intensity exercise lasting longer than an hour, an electrolyte containing isotonic drink should be used to replace fluids lost through sweat. This can easily be made cheaply at home by using sugar containing squash, water and a pinch of salt.

What are the best ways to stay hydrated?

Here are my top tips for helping keep your body hydrated throughout the day:

• Monitor your output – First of all let’s check if you need to hydrate any more than you currently do.  If you notice your urine is a darker colour, or if you are passing urine less than 4 times a day then you need to start drinking more fluids

• Use a refillable bottle, and always keep it on you – If you use a reusable bottle, you can monitor the volume of fluid you are consuming. For example, if your bottle is 500ml you know you should be aiming to fill it up around 3 times during the day

• Little and often – Sometimes we can get carried away with a task at hand and forgetting to take a drink. Try to get into the habit of drinking a little fluid throughout the day. Again, using a refillable bottle can help you achieve this as you can set targets to refill your bottle once during the morning and once during the afternoon to ensure you are drinking throughout the day

• Eat your 5-a-day! Many fruits and vegetables contain a high percentage or water, and therefore make a large contribution towards your fluid intakes. Fruits such as cucumber, tomatoes, melons, strawberries, and vegetables such as lettuce, courgettes, celery and peppers are all over 90% water.

• Cool it down when the temperature rises – Just because it’s hot doesn’t mean you can’t enjoy your favourite caffeinated beverages – these drinks still count towards your fluid intake. Why not try turning them into the cool counterparts with iced coffees and iced teas to help keep you cool*. Just watch out for any hidden added sugars these may contain, or try making them at home yourself so you know exactly what goes into them.

Nectarine Iced Tea Recipe

Here is one of my favourite ways to stay hydrated during the summer.

Serves 1

Ingredients

• 1 teabag of choice
• 1 tsp of honey, or to taste
• Juice of 1 lemon, or to taste
• Ice
• 1 nectarine, cubed
• Sprig of mint (optional)

Method

• Start by brewing the tea bag in around 100ml of boiling water for 2 minutes

• Remove the tea bag and add honey to taste followed by the lemon juice

• Fill a large glass with ice and top with the chopped nectarine

• Pour the tea mixture over the top and top up with cold water if needed

• Stir and garnish with mint

• No nectarines? Use peaches instead – flat peaches would be delicious in this drink and would still give the same flavour!

Cheers!

*Pregnant women should limit caffeine intakes to 200mg/day, and caffeinated drinks are not suitable for babies and toddlers.

References

Armstrong et al. Urinary Indices of Hydration Status. International J of Sport Nutr, 1994, 4; 265-279

BDA Alcohol Fact Sheet. 2019 Available at https://www.bda.uk.com/resource/alcohol-facts.html (accessed July 2022)

BDA Fluid Fact Sheet. 2017 Available at https://www.bda.uk.com/uploads/assets/337cfde9-13c5-4685-a484a38fbc3e187b/Fluidfood-fact-sheet.pdf (accessed July 2022)

BDA Sport and Exercise Food Fact Sheet. 2020 Available at https://www.bda.uk.com/resource/sport-exercise-nutrition.html (accessed June 2022)

BDA The importance of hydration 2019 available at https://www.bda.uk.com/resource/the-importance-of-hydration.html (accessed July2022)

Benton & Young. Do small differences in hydration status affect mood and metal performance? Nutrition Reviews 2015 73(suppl_2); 83-96

Collins & Claros. Recognising the face of dehydration. Nursing 2020, 2011 41(8); 26-31

Drozdowska et al. Water consumption during a school day and children’s short-term cognitive performance: the cogniDROP randomized intervention trial. Nutrients 2020 12(5); 1297

EFSA Scientific Opinion on Dietary Reference Values for Water. EFSA Journal 2010 8(3): 1459

Hew-Butler et al. Of mice and men – the physiology, psychology and pathology of overhydration. Nutrients 2019 11; 1539

Kavouras et al. Validation of a urinary color scle for assessment of urine osmolarity in healthy children. Eur J Nutr, 2016, 55; 907-915

NHS Website. Water, drinks and your health. 2021 Available at https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/water-drinks-nutrition/ (accessed July 2022)

Perry et al. Hydration status moderated the effects of drinking water on cildren’s cognitive performance. Appetite 2015 95; 520-527

Polhuis et al. The diuretic action of weak and strong alcoholic beverages in elderly men: A randomized diet-controlled crossover trial. Nutrients 2017 9(7); 660

Public Health England, 2016. The Eatwell Guide. Available at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/528193/Eatwell_guide_colour.pdf (accessed June 2022)

Rehm. The risks associated with alcohol and alcoholism. Alcohol Research & Health 2011 34(2); 135-43

Riebl and Davy. The Hydration Equation: Update on Water Balance and Cognitive Performance. ACSMs Health Fit J. 2013, 17(6); 21-28

Wynne and Wilson. Got Beer? A systematic review of beer and exercise. International J of Sport Nutr and Exercise Metabolism 2021 31; 438-450