Water and Hydration

Removing waste: water carries waste products out of the body in urine. The kidneys help control how much water is lost this way. When fluid intake is low, they conserve water by producing more concentrated urine, which is usually darker.

Cooling: sweating helps regulate body temperature. As sweat evaporates from the skin, it takes heat away from the body. This is useful during exercise or hot weather, but the water lost must be replaced.

Digestion: water forms part of saliva, which mixes with food during chewing. It helps nutrients to be digested and absorbed and acts as a lubricant, helping food move through the digestive tract. Enough water also helps keep stools soft and easier to pass. Too little fluid can contribute to constipation.

How water leaves the body

Water is lost throughout the day, even when we are not noticeably sweating:

• Urine: water leaves with dissolved waste products.
• Faeces: stools contain some water, although the large intestine absorbs water before they leave the body.
• Skin: water is lost through sweating and evaporation from the skin.
• Lungs: breathed-out air contains water vapour.

If these losses are not replaced, dehydration develops. It can cause tiredness, headaches and poor concentration. Thirst is a signal to drink. Pale-yellow urine generally suggests adequate hydration; darker urine can suggest that more fluid is needed, although foods, medicines and supplements can also affect its colour.

How much fluid is needed?

The general UK recommendation is 6–8 cups or glasses of fluid each day, alongside the water supplied by food. This is a guide rather than an identical requirement for everyone: needs vary with age, body size, activity and weather.

Plain water is a useful everyday choice, but other non-alcoholic drinks also contribute. Milk, tea and coffee count towards fluid intake. Alcohol should not be counted towards the daily fluid target.

Fruit juice and smoothies provide fluid, but they also contain free sugars. Keep their combined intake to no more than 150 ml a day rather than using them as the main way to stay hydrated.

When extra fluid is needed

In hot weather and during physical activity, increased sweating means more water needs replacing. Drinking before, during and after activity helps maintain hydration; water is suitable for moderate exercise.

Extra fluid may also be needed during illness involving fever, vomiting or diarrhoea. Fever can increase sweating, while vomiting and diarrhoea cause additional fluid loss. Pregnancy and breastfeeding also increase fluid requirements.

Young children and older adults may need encouragement or help to drink regularly. Children may not communicate thirst, and older adults may have a weaker thirst response. This is a need for support with hydration, not a reason to assume that everyone in these groups needs the same extra amount.

Preparing water-rich foods and drinks

Soup, juice and smoothies offer ways to practise fruit and vegetable preparation. Wash produce and use clean equipment before starting.

For a vegetable soup, peel a carrot with a vegetable peeler, working away from your hand. Grate it with a stable grater, keeping fingertips clear of the sharp surface. Crush peeled garlic with a garlic press and scissor-snip washed herbs into small pieces. These techniques prepare ingredients for cooking in water or stock: the vegetables contribute water too, and the cooking liquid remains part of the finished dish.

For juice, wash and prepare fruit before squeezing or using a juicer. For a smoothie, prepare fruit by removing unsuitable peel, stones or cores, then blend the edible parts with a suitable liquid. Use blending equipment according to its safety instructions and keep hands away from blades. These drinks can contribute to fluid intake, but the 150 ml combined daily limit still applies.

Losses exceeding replacement cause dehydration: possible signs include thirst, tiredness, headache, poor concentration and darker urine.

Intake and extra needs

• General guide: 6–8 cups or glasses of fluid daily, plus water from food.
• Non-alcoholic drinks count; plain water is a useful everyday choice.
• Fruit juice and smoothies: no more than 150 ml combined per day.
• Extra needs: hot weather, exercise, fever, vomiting, diarrhoea, pregnancy and breastfeeding.
• Young children and older adults may need support to drink regularly.

Food preparation links

Practise peeling, grating, crushing and scissor-snipping when preparing fruit and vegetables. Soups retain the cooking liquid; juices and smoothies also supply fluid.