Article by the Drummond team
Water is a life-essential, and its very important to get the right amount of fluid to stay healthy. However, there are lots of mixed messages about how much, and exactly what to drink – and this can be confusing.
So why do we need water?
Water makes up a large proportion of the body – on average 60% of body weight in men and 50-55% in women (because women have a higher percentage of body fat). Water has many functions in the body including regulating temperature, transporting nutrients and compounds in blood, removing waste products that are passed in the urine and acting as a lubricant and shock absorber in joints. Water is lost in urine and in sweat and is also being lost throughout the day when you breathe and when small amounts of water evaporate through the skin. To avoid dehydration you need to replace this fluid regularly with fluids from food and drinks. ‘Fluid’ includes not only water from the tap or in a bottle, but also other drinks that provide water such as tea, coffee, milk, fruit juices and soft drinks. You get water from the food you eat as well – on average it’s estimated that food provides about 20% of your total fluid intake.
What happens when we get dehydrated?
If you don’t consume enough fluids, over time the body will become dehydrated. Studies have shown that at about 1% dehydration (equivalent of 1% of body weight water loss) there are negative effects on mental and physical function and these become more severe as dehydration gets worse. Symptoms of mild dehydration include a dry mouth, headaches and poor concentration. When the body detects that more water is needed the first thing that happens is that the kidneys reduce the amount of water lost in the urine. This means that the colour of the urine becomes darker and you can use the colour of your urine to tell if you are well hydrated – if you are drinking enough your urine should be a straw or pale yellow colour. If it’s darker then you probably need more fluid. Thirst kicks in when the body is already a little dehydrated, so it is important to drink when you are thirsty.
How much do we need?
The amount of fluid you need depends on many things including the weather, how much physical activity you do and your age, but the Eatwell Guide suggests 6-8 glasses of fluid per day. If the weather is hot or you are exercising you may need to drink more fluid. You can get water from nearly all fluid that you drink, apart from stronger alcoholic drinks such as wine and spirits.
Can we drink too much?
It is possible, although very rare, to drink so much water the body cannot get rid of the excess quickly enough and sodium levels in the blood become dangerously low. This can have serious health consequences and is unlikely under normal conditions but has happened in individuals following a very extreme detox programme.
Do we need sports drinks when exercising?
Physical activity also increases the amount of fluid you need to consume in order to replace the water you lose as sweat and the amount lost depends on how long you are active, how intense the activity is and whether it’s hot and humid . It’s a good idea to start any physical activity well hydrated and to drink at intervals during activity. Water is fine for rehydrating after the kind of moderate exercise that most active people choose, and the majority of active people do not need special sports drinks to stay hydrated. However, for high intensity exercise that lasts more than 1 hour or so, drinks that contain some sugars and sodium (salt), such as sports drinks or homemade versions, may be better at replacing the extra fluid lost as sweat.
Does it matter which drinks we choose?
All non-alcoholic drinks can contribute to hydration and some also contain essential vitamins and minerals. However, many drinks, such as soft drinks and fruit juices are high in sugars and so contain energy (calories). These calories contribute to your daily intake in the same way as those from the foods you eat and higher consumption of sugary drinks has been associated with risk of type 2 diabetes and with weight gain in children. It is also important to look after your teeth, and consuming sugar-containing drinks too often can potentially harm your teeth, especially if you don’t brush teeth regularly with fluoride toothpaste. It is also important to be aware that some drinks are acidic (e.g. fruit juice and carbonated drinks) and that this may cause dental erosion (damage to tooth enamel) if they are consumed frequently.
- Drinking water is a great choice because it delivers fluid without calories or the sugars that can potentially damage teeth.
- Tea or coffee can also count towards your fluid intake although the caffeine found in tea and coffee can make you produce more urine, consuming moderate amounts does not appear to affect hydration. Pregnant women are advised to consume no more than 200mg or caffeine a day. This is equivalent to about two mugs of instant coffee or about two and a half mugs of tea. Other hot drinks such as herbal teas, hot chocolates and malted drinks can provide water butiIf these drinks are sweetened with sugar it increases their calorie content. Sugar in hot drinks also increases their potential to damage teeth if good dental hygiene is not practiced.
- Milk contains lots of essential nutrients such as protein, some B vitamins, iodine and calcium, as well as being a source of water. However, it can also contain saturated fat and so it’s a good idea for adults and older children to choose semi-skimmed (less than 2% fat), 1% or skimmed milks. For children between the ages of one and two years, the recommended milk is whole milk. From two years onwards semi-skimmed milk can be introduced gradually. Skimmed and 1% milks are not suitable for children until they are at least five years old because they have less vitamin A and are lower in calories.
- Fruit juices and smoothies give you water plus some vitamins and minerals…. But fruit juices and smoothies contain sugar (and therefore calories) and can be acidic, so they can potentially harm teeth. Fruit juices and smoothies should be kept to a combined total of 150ml per day – this can count as a maximum of one portion of your 5 A DAY but not more than this. This is because they don’t contain the fibre that is found in whole fruits and vegetables.
- Sugary drinks, such as fizzy drinks, squashes, juice drinks and flavoured waters can contain a lot of sugar and generally provide few nutrients – this adds to your calorie intake and the sugar can potentially damage teeth if the drinks are consumed frequently. It’s a good idea to limit or avoid consumption of sugary drinks and swap them for diet, sugar free or no added sugar versions.
- Sports drinks typically contain some carbohydrate and electrolytes (generally sodium but sometimes others). Adding these elements can help the fluid from the drink be absorbed into the body more quickly, replace some of the sodium that may be lost when sweating and will also provide some energy (calories). However, these are only really necessary when you are training at a high level, e.g. in endurance sports where sweat losses are higher and you may need some extra energy. If training at a lower level then water is likely to be sufficient to replace fluid losses and any sodium lost in sweat will be replaced when foods are eaten. The carbohydrate in the drink will add calories, which may not be needed and will be counterproductive if part of the reason for being active is for weight control. The sugars in sports drinks can also increase the risk of tooth decay.
- Energy drinks can be high in sugars and also contain caffeine and other stimulants. They can contain high levels of caffeine and so are not suitable for children.
- Alcoholic drinks have a diuretic effect, that is, the cause you to lose more water in urine, so drinking alcohol may lead to dehydration. . It is important to keep alcohol consumption within the recommended limits (no more than 14 units per week for both men and women). Alcoholic drinks contain calories so it’s important to be aware that these will contribute to your calorie intake, for example, a standard (175ml) glass of 12% wine contains about 126kcal and a pint of 5% lager contains about 215kcal.
- Food – it may be a surprise to learn that we get on average 20% of our total water intake from food! Some foods have a high water content, especially fruits and vegetables, which are usually more than 80% water. Foods like soups and stews, which have lots of water added during preparation, also are a source of water. So food can provide extra water, on top of the 6-8 glasses of fluid you should drink a day.
Do some people need more water than others?
Needs vary from one person to the next, but there are certain population groups who may need to pay particular attention to hydration.
- Children need plenty of fluid, despite their smaller body size, and they should be encouraged to drink regularly, especially if they are very active.
- Infants get their fluids from breast or formula milk, but will start to get some fluids from food when they move onto solids.
- Older adults may have a weaker sense of thirst and, if necessary, should be helped and encouraged to drink regularly.
Source: British Nutrition Foundation