For our 'Children and Babies' water FAQ's go here.
Q. How much water should I drink?
A. We know there’s no such thing as ‘average’ but the answer is that the average adult in average circumstances (that is in moderate temperatures and not undertaking prolonged strenuous exercise) should drink around 1.5 – 2 litres of water a day (that’s around 8 x 250ml glasses). As a simple rule drink 35ml of water for every kilogram of body weight.
The World Health Organisations and the British Dietetic Association recommends that the average 60kg adult should drink 1.5-2 litres (6-8 x 250ml glasses) of fluid, plenty of which should be water. This quantity should of course be increased in hot weather or during periods of sustained physical activity in order to replace the water lost through perspiration. By drinking 1.5-2 litres as fluid, and gaining the rest of the fluid we need through foods, we replenish the 2.5 litres we lose daily (see chart below):
The body loses water through:
Normal output (approximate average)
Nutritionist, Fiona Hunter, says: “Most people would benefit from drinking more water so if you want to hydrate healthily make water part of your daily regime. Drink a glass on waking, one just before bedtime and the rest with meals or just before and in between meals”.
Q. Isn’t tap water better regulated than bottled water?
A. No. Both tap water and bottled waters are governed by strict Regulations to ensure they are safe to drink. Tap water is subject to certain treatments such as the addition of chlorine to make it safe to drink. We are fortunate in the UK to have high quality mains water. However, for those people who prefer their foods and drinks as natural as possible, bottled waters are ideal as, especially if they are Natural Mineral Water or Spring Water, they must be microbiologically safe as they emerge from the ground. Bottled water is governed by DEFRA and overseen by the relevant local authority. . See section on The law governing bottled water.
Q. What serious health problems can I help avoid by drinking enough water?
A. Dr John Briffa writes: “There is also evidence that a good intake of water is associated with a reduced risk of chronic health conditions. For instance, studies have found that drinking water is associated with a substantial reduction in risk in certain cancers, including those of the bladder (Radosavljevic V, et al. Fluid intake and bladder cancer. A case control study. Neoplasma 2003 50(3):234-238) and colon (Shannon J, et al. Relationship of food groups and water intake to colon cancer risk. Cancer Epidemiol Biomarkers Prev 1996 5:495-502).
“Research has also found that higher water consumption is associated with very significant reduction in risk of heart attack (Chan J, et al. Water, other fluids, and fatal coronary heart disease: the Adventist Health Study. American Journal of Epidemiology 2002 155(9):827-833).”
Dr John Bradley, Director of Renal Medicine at Addenbrooke’s Hospital and Senior Medical Advisor to The National Kidney Research Fund, says: “Although the kidneys can function if people drink less than one litre a day, this would produce concentrated urine and is far from ideal. There are huge advantages to drinking a higher level of fluid. A high fluid intake can reduce the risk of kidney stones, bladder cancer and urinary infections. Kidney stones are common: one in ten men and one in twenty women suffer from them at some point in their lives. They cause great pain and can compromise the kidney function.”
Q. What does water do for the human body?
A. Water is essential to life - it is needed - directly or indirectly - for every physical and chemical process that takes place in our bodies. It acts as a transport system and delivery service taking oxygen, nutrients and other essentials around the body and into and out of our cells. At the same time it acts as a removal service helping to clear the body of all of the waste and toxins that our body produces. It helps regulate our temperature and produce the energy vital for the body's daily workings and is involved in our immune systems and in lubricating our joints. Some experts believe that if your fluid levels are low, muscle cramps can develop during exercise. Constipation often results from dehydration. It is also increasingly believed that water has a vital role to play in keeping our skin moisturised and in regulating our emotions but it can also help prevent serious ailments. Other fluids also hydrate, of course, but water comes with the benefits of being calorie-free and tooth-kind.
Q. Is it possible to drink too much fluid?
A. The problem for most people in the UK appears to be the health effects of drinking too little, not too much, water. However, there are rare cases where excessive water intake in individuals has been recorded. In normal circumstances, the daily intake for a healthy person in a temperate climate should be 30-35ml per kilogram of body weight (that’s around 1.5-2 litres daily). According to Dr Wagg clinical director at London’s Middlesex Hospital, the rate of consumption should be limited to less than one litre over two or three hours. However, this intake should be increased during periods of hot weather or when doing strenuous exercise.
In the rare cases where people drink copious quantities of water, this excessive intake can result in water intoxication, which occurs when too much water causes the blood to become over-diluted and the cells swell. Severe problems occur when too much water is retained in the brain. Hyponatraemia has been identified in scientific studies in athletes who took in excessive fluid during exercise.
Water intoxication is a condition which, according to Professor Steven Sacks, head of renal medicine at Guy’s, King’s and Thomas’ School of Medicine, is not very common because “the rate at which you take in the water is important. It [drinking too much water] is really quite hard to do”. If too much water is drunk the sodium level in the body is diluted and this results in cell swelling all over the body. When this happens in the brain it causes nausea, headaches, confusion and, in extreme cases, convulsions and coma (cerebral oedema). Medical help should be sought immediately. If anyone has sufficient thirst to drink 6-8 litres of water a day this could indicate a potential serious medical or other problem and they should take advice from a doctor.
Q. To stay hydrated won’t any fluid be as good as water?
A. Other fluids will, of course, hydrate you but bottled water is the perfect means of staying hydrated as it is calorie-free and contains no unwanted chemicals. Alcohol and coffee for example, whilst fine in moderation, can act as diuretics reducing the level of fluid in the body and brain. That’s why it is so important to drink large amounts of fluid – preferably plain water - to ease a hang-over.
Q. How do I tell if I’m dehydrated?
A. The easiest means of judging whether you are dehydrated is to check the colour or your urine. It should be pale lemon or straw-coloured. If it is dark yellow or brown, the urine is concentrated and is a sign of dehydration. As we get older, the thirst mechanism is poor and by the time you feel thirsty you are probably already dehydrated. So, drink water regularly.
Q. Should I drink more water when travelling?
A. When driving a car, it is important to maintain fluid levels as dehydration can lead to road rage and loss of concentration. But NEVER drink while driving (not even water)! Pull over somewhere safe and take a drink instead.
When travelling by plane, water is the best fluid to choose. Take a bottle with you as this, combined with leg and ankle exercises and frequent walking, are some of the best means of avoiding Deep Vein Thrombosis (DVT) on long haul flights.
Q. How should I store bottled water?
A. Like any food-stuffs, bottled water should be stored in a cool, dark place away from noxious chemicals or even strong-smelling foods such as curry powder. In some instances it is possible for odour to permeate plastic (PET) packaging and whilst this is unlikely to cause health problems it can affect the taste of the water. Of course, such tainting can occur with any PET packaged product (such as soft drinks) but is more obvious in water due to its normally neutral taste.