British Nutrition Foundation Hydration and health British Nutrition Foundation Earlier in the year, BNF undertook some research on hydration and health and published a review in our journal, the Nutrition Bulletin. The work was steered by a panel of experts in the topic, and the report written by my colleagues, Bridget and Laura. The full article is freely available online with additional information which you may find useful. Today we will have a look at the main findings from the report, which include the importance of hydration, the problem of drinking too little or too much fluids, have a look at different types of drinks, how to make healthy drink choices and drink enough. We will also have a look at some resources available for use in the classroom.

Hydration and health review Benelam B and Wyness L (2010) Hydration and health Nutrition Bulletin 35 (1):3-25. Presentation based on Hydration and health review by Benelam and Wyness (2010). Available as a free download. http://onlinelibrary.wiley.com/doi/10.1111/j.1467-3010.2009.01795.x/abstract www.nutrition.org.uk/nutritioninthenews/hydration/

Healthy hydration Water is essential for life. The body is nearly two-thirds water. Poor fluid intake can lead to dehydration. All drinks count to fluid intake except stronger alcoholic drinks such as spirits and wine. Water is also provided from food (about 20%). We cannot live without water. Water makes up a large proportion of our body weight (almost two-thirds of our body is made up of water), and is distributed throughout our body. Water is the major component of body fluids, e.g. blood, saliva and urine, which all perform different important functions in the body. In general, our body has a tightly controlled mechanism to regulate the concentration of solutes in body fluids, and is sensitive to even very small changes. The amount of water in our body is adjusted to make sure the concentration of solutes in our body fluid is more or less constant.

How much are we drinking? Data on current water consumption in the British population are not available. Most recent National Dietary and Nutrition Survey (2000/01) estimated average fluid intake from drinks: British men: 1988ml/day. British women: 1585ml/day. There is currently no data on water available for the British population, however, the most recent National Dietary and Nutrition Survey shows the estimated average fluid intake from drinks are around 2 L/day for men and 1.6L/day for women.

How much water does a person need? The amount needed depends on: age; climate; physical activity. It is generally accepted to drink around 1.2 litres (6-8 glasses) per day. This is on top of the water provided by food. The FSA recommends us to drink around 6 to 8 glasses each day, that is approximately 1.2 litres, the amounts should be on top of the water provided by food. We have to drink more when the weather is hot, or if we have been active because we lose water through breathing and sweating.

Dehydration Being dehydrated can affect physical performance and cognitive ability (e.g. concentration and alertness). Even slight dehydration (2%) can affect physical performance by 20% - this is not enough to feel thirsty. By the time you feel thirsty you are already dehydrated. It is important to keep well hydrated. Slight hydration, even as little as 2%, can affect physical performance by 20%, and sometimes this is not even enough to make you feel thirsty. Also, some people ignore their feelings of thirst, which can lead to serious consequences, because thirst is a physiological response and a mechanism of survival.

Signs of dehydration feeling thirsty; having a headache; passing dark-coloured urine; feeling sleepy; being unable to concentrate. People may not recognise the symptoms of dehydration, which include thirst, headaches, passing dark-coloured urine (of course you have to exclude the first pee in the morning because you are likely to be dehydrated without drinking water overnight), feeling sleepy and a lack of concentration.

Excess intake Drinking excessive amount of fluids is not helpful to health and wellbeing, and in rare cases may be dangerous, leading to low levels of solutes in blood. An example is hyponatraemia, which means low levels of sodium in the blood. Signs of excessive intake are passing urine frequently and urine that is very pale in colour. Drinking too much fluid is not helpful to the wellbeing. In very rare cases drinking too much water within a short period of time can even be dangerous, causing hyponatraemia, meaning low levels of sodium in the blood. This may lead to lung congestion, brain swelling, headache, fatigue, lethargy, confusion, vomiting, seizures, coma and death, which has happened a few times in the UK, often sensationalised by the media. Signs of excessive fluid intake, include passing urine frequently and urine that is very pale in colour. Consequences of prolonged over consumption of fluid include.

Urine test The simplest way to tell if you are drinking enough is to check the colour of your urine. If your urine is very dark you need to drink more fluids. Once it is pale, you are well hydrated again. May not be a good take-home assignment, but a useful way to monitor levels of hydration.

What should I drink? When choosing drinks be aware of their energy content and other nutrients they may provide. Choose drinks that will complement your diet. To make a healthy drink choice, we should be aware that different drinks may provide energy and nutrients. The most recent nutrition survey in the UK found that drinks provided 10% of the energy intake of adults, mainly by alcoholic drinks. We should try to go for the ones which complement our diet. This is The eatwell plate, UK’s food selection guide. You can see some drinks, e.g. fruit juice, milk and soft drinks on The eatwell plate, but other common drinks such as water, tea and coffee are not. In the following slides, we are going to have a closer look at a few commonly consumed fluids.

Water Delivers fluid without adding energy or potentially damaging teeth. Does not contribute to energy intake. First up, water. Water has the advantage of fulfilling hydration requirements, without providing extra energy or adversely affecting dental health. From a nutritional point of view, bottled and tap water are not significantly different. Some waters flavoured with fruit extracts and flavourings, in combination with sugar or energy-free sweeteners may provide energy, depending on their sugar content. And this may also encourage consumption.

Tea and coffee Delivers water. Moderate intakes of caffeine do not affect hydration. Pregnant women are advised to consume no more than 200mg caffeine a day. This is equivalent to 2 mugs of instant coffee or 3 cups of tea. Tea is the second most commonly consumed beverage in the world after water. According to the latest nutrition survey, the average consumption of tea by an adult in the UK is 540ml per day (and that’s almost 3 mugs of tea), which is quite significant. Black tea infusions contain some micronutrients, e.g. potassium, magnesium, and if consumed with milk, provide some other additional nutrients, e.g. B vitamins and energy. Similarly, coffee is also widely consumed in the UK and it contains small amounts of micronutrients, e.g. potassium, calcium and phosphorus. Both tea and coffee contain a number of polyphenols, including caffeine. Moderate intakes of caffeine do not affect hydration although caffeine is a mild diuretic, which means it tends to make you go to the toilet more often. In general, fluid in a caffeinated beverage compensates for the short-term diuretic effects. Pregnant women are advised not to consume more than 200mg caffeine a day, which equals to 2 mugs of instant coffee, or 3 mugs of tea. Remember, some other drinks, e.g. cola, or foods, e.g. chocolate, also contain caffeine.

Milk Provides protein, calcium and B vitamins. Wholemilk contains saturated fat, it is advisable for adults to choose lower fat milks: semi-skimmed (2% fat), 1% or skimmed (less than 0.1% fat). For children aged 1 to 2 years, wholemilk is recommended. From 2 years onwards, semi-skimmed milk can be introduced. 1% or skimmed milks are not suitable for children until they are at least 5 years old. Milk provides protein, calcium and B vitamins including vitamin B12. Wholemilk contains saturated fat, it is advisable for adults to choose lower fat milks; semi-skimmed (2% fat) or skimmed (1% fat). For children between the ages of one to two years, wholemilk is recommended for the extra energy and nutrients, e.g. fat and fat-soluble vitamin A. From two years onwards, semi-skimmed milk can be introduced if they are having a healthy, varied diet. Lower fat milks are not suitable for children until they are at least 5 years old because they have less vitamin A and are lower in energy.

Fruit juices and smoothies Provide vitamins and minerals and natural plant substances. Smoothies may contain puréed fruit, which adds fibre. Juices (150ml) count towards one portion of 5 A DAY. Smoothies (150ml juice and 80g crushed fruit) count as two portions. Sugars and acidity can be harmful to teeth. 150ml of fruit juice can only be counted as one portion, because the pulp has been extracted, losing the fibre. Fruit juice can also contain non-milk extrinsic sugars which, when consumed between meals, can increase the risk of dental erosion.

Soft drinks Provide water and sugar, which consumed in between meals, can be harmful to teeth. Diet drihnks or sugar free versions may be a better choice. Some people may wish to avoid artificial sweeteners. Soft drinks provide water and sugar, which consumed in between meals, can be harmful to teeth Sugar free versions may be a better choice. Some people may wish to avoid artificial sweeteners due to various reasons, such as personal choice, or aftertaste.

What is the most popular drink in the UK? Tea ... Coffee … Tap water … Bottle water … Soft drinks … Fruit juice … Alcoholic drinks … What is the most popular drink in the UK?

What is the most popular drink in the UK? Tea ... Coffee … Tap water … Bottle water … Soft drinks … Fruit juice … Alcoholic drinks … 536 ml/person/day 536 ml/person/day 744 ml/person/day 744 ml/person/day 333 ml/person/day 333 ml/person/day 229 ml/person/day 229 ml/person/day 211 ml ‘regular’ & 240ml low calorie/person/day 211 ml ‘regular’ & 240ml low calorie/person/day 106 ml/person/day 106 ml/person/day 425 ml/person/day

Alcohol Weak alcoholic drinks (e.g. a shandy) contribute to fluid intake. Stronger alcoholic drinks cause diuresis. Alcohol recommendations: Men - no more than 3-4 units per day. Women - no more than 2-3 units per day. Over consumption of alcohol, or binge drinking, should be avoided. Weak alcoholic drinks (e.g. a shandy) contribute to fluid intake. Stronger alcoholic drinks cause diuresis, which makes you go to the toilet more frequently, making you more likely to be dehydrated. Alcohol recommendations: Men - no more than 3-4 units per day. Women - no more than 2-3 units per day. Over consumption of alcohol, or binge drinking, should be avoided. If you have over-consumed, allow your body at least 48 hours to recuperate. 18

Units of alcohol One unit of alcohol is: half a pint of standard strength (3 to 5% ABV) beer, lager or cider; a pub measure of spirit; half a glass of wine; two thirds of an Alcopops. The units of alcohol are set out as shown: 19

The effect of alcohol on water balance Drink Serving Loss of water in urine (ml) Net gain of water (ml) Beer, larger and cider 568ml (1 pint) 170 398 Alcopops 330ml (1 bottle) 165 Spirits 25ml (small) 50ml (double) 100 140 -75 -105 Wine and champagne 175ml (standard) 210 -35 This table compare the hydrating and diuretic effects of different alcoholic drinks. 20

Contribution from food Water is also provided from food (about 20%). The amount of water in food varies from less than 10% in savoury snacks, less than 40% in cereal products to 80% or more in some fruit and vegetables. Foods, such as soups, stews, yogurts have a high water content. It is important to recognise that food provides water, and on average is around 20% of our fluid intake. Different foods contain different amounts of water: dry foods, e.g. savoury snacks only contain less than 10% of water and cereal products less than 40%, but fruit and vegetables contain a high proportion of water (around 80% or more), which keeps the energy content of the food low. Foods which are high in water content, e.g. fruit and vegetables, soups, stews and yogurts, tend to have a lower energy density, can help you feel fuller for longer, thus helping you maintain a healthy weight.

Some people need to drink more Children Lactating women Older adults Children Children need plenty of fluid. They should be encouraged to drink regularly and establish a good drinking pattern. They should drink more when they are being active. Lactating women Lactating women require extra fluid for the production of breastmilk. Older adults Older people can avoid drinking for physical and social reasons, such as avoiding trips to the toilet. They may also have a weakened sense of thirst. They should be encouraged to drink regularly.

Physical activity Even slight dehydration has been shown to affect sporting performance, so drink before, during and after you train or play a match. Being dehydrated may mean that: running pace is slower; unable to cover as much distance; reaction time is slower; experience lack of power. When you are physically active, your body loses water through breathing and sweating.

Keeping hydrated during exercise To keep hydrated: drink lots before exercise; don’t wait until you feel thirsty; drink small, regular sips of water during exercise; drink plenty when you have finished. The fluid needed for activity is in addition to the 6 to 8 glasses or 1.2 litres needed every day. It is also important to drink more when the weather is hot. The fluid needed for activity is more than the daily recommendation of 6 to 8 glasses (1.2 litres) each day. So try to keep hydrated during exercise by drinking a lot beforehand, continue to drink small, regular sips during exercise, drink plenty when you have finished; and remember not to wait until you feel thirsty. Bear in mind also to drink more when the weather is hot.

Sports drinks Sports drinks are designed to provide water and carbohydrate. Some types are very quickly absorbed. They can help you recover quickly after a hard match or training session. Sports drinks are designed to provide a source of carbohydrate for energy, and to promote hydration, before, during and after exercise, replacing fluids and electrolytes lost as a result of sweating. Depending on the ingredients used in a sports drink and their concentration, different types of sports drinks are absorbed differently. Evidence suggests that sodium is that only electrolyte to be added.

Sports drinks It is easy to make your own sports drinks at home and cheaper too! Per 100ml water: 5-8g glucose powder. 0.5g salt. Any sugar free flavouring. There are many different types of sports drinks available in the market, but making your own sports drink is absolutely doable! Try following this simple recipe:

Drinking schedule A large glass one hour before you start. A smaller glass 15 minutes before start. Small sips during the event. A glass at half time. A large glass immediately afterwards. A drinking schedule for physical activity could be like this: Keep yourself hydrated before the training, then have small sips during, some more during break/half-time, then go for a big one immediately afterwards to make sure you replenish the fluid content in your body. It’s a good habit to drink before, during and after playing sport. It may be uncomfortable at first, but you’ll get used to it.

Healthy hydration guide To complement the review, we have published a few online resources on hydration. One of these is the Healthy hydration guide, to help consumers choose a good balance of drinks. The .pdf is available online and could be downloaded as a classroom resource as well. www.nutrition.org.uk/nutritioninthenews/hydration/healthy-hydration-guide

Getting the balance right: every day examples On our website, there is also a section on some everyday examples which look at case studies of different people, to see if they have their fluid balance right. www.nutrition.org.uk/nutritioninthenews/hydration/getting-the-balance-right-everyday-examples

Are you drinking plenty? poster This is the poster inside our latest Education news. Aimed at younger students, this ‘Are you drinking plenty?’ poster provides a good way to record how much water the class is drinking, over a week and teach about the messages on the importance of hydration.

For more information visit www.nutrition.org.uk www.foodafactoflife.org.uk