Staying Hydrated in the Heat

Water is essential and makes up over half of our bodyweight. It helps keep all your organs functioning properly and regulates your body temperature via sweating.

Your body loses water via urine, stools, breathing and sweating. If that water isn't replaced, we can become dehydrated. In hot weather this is more likely, as we lose more water through sweating.

What are the signs of dehydration?

Signs of dehydration include:

• Feeling sleepy
• Headaches
• Fatigue
• Trouble concentrating
• Irritability
• Dry mouth
• Constipation
• Weeing less often

A simple way to keep an eye on your hydration levels is to look at the colour of your wee. If you're drinking enough, your urine should be a straw or pale-yellow colour. If your wee is dark and strong smelling, you probably need to drink up.

How much fluid do we need?

There is no one size fits all recommendation for fluid intake, as our needs can vary according to our body size, activity levels and the climate we live in.

But as a guide, for adults and adolescents 14 and up, EFSA (the European Food Safety Authority) suggest 2.5 litres for men, and around 2 litres for women – but this includes fluid from foods, which accounts for around 20% of our daily intake (so 2 litres and 1.6 litres respectively)

These levels might need to be increased if it's very hot or if you're exercising.

Never drink more than is comfortable though, or to the point where you feel bloated.

If you're wondering about children, the British Nutrition Foundation has guides to healthy hydration for children aged 1-4 here and children aged 5-11 here.

Is it just water that counts?

No! You might be surprised to hear this, but all non-alcoholic drinks really do count towards your daily fluid intake - including tea, milk, squash, soft drinks and even coffee. Although caffeine does increase urine production, the amount of fluid that's consumed with the caffeine outweighs this. And at moderate intakes, caffeine won't dehydrate you.

We also get fluids from foods like soups, high water fruit and veg, smoothies and juices. Drinks provide around 80% of our water needs, with the remaining 20% coming from foods such as soup, stews, some fruits, and vegetables which contain a lot of water.

However, some fluids are a healthier choice than others. Water is great because it is calorie and sugar free and tooth friendly. Try to drink tea and coffee without added sugar too. And pick no added sugar squashes or soft drinks.

Soft drinks, fruit juice and smoothies count as free sugars. These are the ones we need to be consuming less of. Fruit juices and smoothies do also provide some vitamins and minerals, but the advice is to stick to no more than a small glass of 150ml a day.

Who is more vulnerable to dehydration?

Some groups of people are more vulnerable to dehydration.

These include:

• Older adults
• Children
• People exercising a lot or with active jobs – especially in the heat

As we get older, we lose the sense of thirst, and this is why older adults are more at risk of dehydration. The BDA has some helpful advice on older adults and hydration here.

Tips on staying hydrated in the heat

• Keep a water bottle close by at home- and when you're on the move. You're more likely to drink if you have a visible bottle reminding you to drink up, plus it's a helpful guide to how much you've drunk during the day
• Have a glass of water on waking
• Cold drinks can be more palatable – use ice, keep water chilled in the fridge
• Eat more high-water foods like fruits and vegetables (melon, strawberries, cucumber, tomatoes), chilled soup, ice lollies, smoothies
• Dilute 150ml fruit juice with water or fizzy water to make a longer refreshing drink
• If you're exercising or sweating a lot, an electrolyte drink will help to replace lost salts and minerals

Staying cool in the heat

In addition, stay cool and out of the heat. Adjust your routine if you can so you're doing activities like walking the dog in the early morning before it's hottest. Try to stay in the shade between 11 and 3. If you go out, use sunscreen and wear a wide-brimmed hat to protect your face, eyes, head, ears, and neck.

The met office also has advice on staying safe in a heatwave here.