Water UK

Introduction

Water is one of the most important nutrients for children. It improves physical and mental performance, helps with health problems such as urine infections, bed-wetting, daytime wetting and constipation, and drinking enough water can help to protect the body against chronic diseases such as cardiovascular disease, cancer and urinary tract stones. Water also helps maintain good oral hygiene and healthy skin.(1) (see “Oral health” and “Skin”)

Factors affecting hydration status in children and infants
Children and infants (0-12 months) have a much greater risk of dehydration compared to adults. This is because they have a higher surface area to body mass ratio, which means that they are more likely to lose water by evaporation. For example the average 6 year old child has a surface to body mass ratio about 50% greater than that of the average adult.(2) Children have a higher percentage of body water and a higher rate of daily water turnover which is approximately 15 per cent of total body weight, compared to 5-10 per cent for adults(3) In addition, children have a less developed sweating apparatus and thirst response, and their kidneys have a more limited capacity for handling the large amounts of protein required for growth.(4)

Thirst in children

Children may not recognise the signals of thirst as readily as adults. Depending on age and ability, children and infants may need varying degrees of support in order to maintain an adequate hydration level. They may feel thirsty, but have limited capacity to express their need, or to access drinks.

Voluntary dehydration is a condition in which people, especially children, do not drink appropriately in the presence of adequate fluid availability. Children living in a hot climate are especially susceptible to developing voluntary dehydration. In hot climates the threshold for thirst corresponds to Uosm of about 800 mosm/kg H2O. This means that thirst is only felt when the urine is already highly concentrated and the body is dehydrated. In one study, seventy per cent of school-age children in southern Israel were found to be in a state of chronic dehydration.(5) In another study comparing Jewish children with a Bedouin group, over 80 per cent of the Jewish group were found to be chronically dehydrated (defined as Usom exceeding 800 mosm/kg H2O), compared to only 50 per cent of the Bedouin group. It is possible that the Bedouins, who have lived in a very hot climate of the desert for many generations, may have developed a mechanism that lowers the thirst threshold, or that they are more aware of the importance of drinking water even without feeling thirsty.

Children who are exercising in a hot climate are also susceptible to voluntary dehydration. A group of 10-12 year olds, who were allowed to drink when thirsty, showed a progressively increasing fluid loss of 0.3 per cent of body weight per hour, due to insufficient drinking when exercising in the heat. On average they drank only 72 per cent of the amount required to replace fluid loss.(6)

Children’s drinking habits

Since drinking patterns are established in childhood, children should be encouraged to drink at regular intervals to help them develop healthy drinking habits which will be of benefit throughout their lives.(7)

For 18-month old children in the UK, the most popular non-milk drink is low sugar or low calorie squash. Twenty per cent of all children in one study drank water, whilst a similar number had orange juice, ordinary squash, tea or coffee. Seven percent had fizzy drinks and six per cent consumed commercial baby drinks. The mean volume of water consumed was only 44ml per 24 hours, compared to 452ml of other non-milk drinks.(8)

A survey of 2-7 year olds drinking habits, found that fruit squash was the most frequently consumed drink and had replaced plain drinking water especially among the pre-school age group. Children as young as 2 years had been conditioned to the sweet taste of squash, to the extent that they refuse to drink water as an alternative.(9)
Flavourings, sodium content, palatability and drink composition, have all been shown to influence the volume of fluids voluntarily consumed by children.(10)

Children and young people in the UK eat too much sugar, and more of it comes from fizzy drinks than any other type of food or drink.(11) Reducing the amount of sugary drinks is a good way to reduce sugar intake. Soft drinks not only have minimal nutritional value, but may diminish the appetite so that the child misses out on valuable nutrients provided at mealtimes. Conversely, the high calorific content of soft drinks may lead to excessive energy intake and obesity.(9) (see also Obesity)

The Food Standards Agency recommends that toddlers should not be given sweet drinks, such as fizzy drinks and fruit squash because they cause tooth decay. Between meals, it is better to give water or milk to drink. For all children, water is one of the best drinks to quench thirst, because it is totally calorie free and contains no sugars that damage teeth.(12)

Water requirements in infants and children

After birth the renal system of newborn babies takes several days to adjust to extrauterine life. Daily urine output is about 20ml during the first two days. This increases to a daily output of 200ml by two weeks, at which time milk intake is about 500ml. At three months, urine output is 300ml and daily milk intake has risen to 800-900ml.(13) During the first year of life, more than half of daily water losses occur through urine.(4)

The Food Standards Agency recommends that water is the best alternative drink to milk for babies, but breastfed babies do not need any water until they start eating solid food. For babies under six months old, water from the mains tap can be used. This should be boiled and cooled before giving it to the baby. Some natural mineral waters contain high levels of minerals that are unsuitable for babies. Other bottled waters may be suitable and should include a statement such as ‘suitable for infant feeding’ on the label. These should also be boiled and cooled before being given to a baby.(14) Some bottled waters contain high levels of fluoride and these must contain a warning notice on the label stating that they are not suitable for regular consumption by infants and children under 7 years of age.(15)

The National Academies, Institute of Medicine, Food and Nutrition Board(4) recommends that an adequate water intake for infants aged 0-12 months, based on milk consumption, is as follows:

Table 1: Recommended Adequate Intake for water – infants

In 1989, the US National Research Council estimated that for children aged 1 year and above, the average water requirement was 1.5ml per kcal energy expenditure per day.(16) For an average weight 10 year old boy (31kg) and girl (32.5kg) multiplying the official EAR(17) for calorie intake by these factors gives an average fluid intake requirement of 3 litres and 2.6 litres for 7-10 year old boys and girls respectively. Assuming that approximately one third (1 litre) is derived from solid food, then a conservative estimate is that 7-10 year old children require around 1.5-2 litres per day. These requirements will rise in warm weather and when exercising. This is in accordance with recommendation from the UK Education and Resources for Improving Childhood Continence(18) that children should drink between 1.5 and 2 litres per day, with the proviso that this amount will need to be higher in warm weather and when exercising.

In 2004, the National Academies, Institute of Medicine, Food and Nutrition Board(4) suggested the following water requirements for children, based on US population data.

Table 2: Recommended Adequate Intake for water – children

Other estimates of daily water requirements for children include those based on findings from the German DONALD study of 479 healthy boys and girls aged 4.0-10.9 years. Estimated adequate intake values of total water for German children in this age group ranged from 1.01ml to 1.05ml per kcal energy expenditure.(19)

The World Health Organization advises that a 10 kg child should consume 1 litre per day and a 5 kg infant, 0.75 litres per day under average conditions, but this should be increased depending on conditions, up to 4.5 litres, for example if the child is undertaking manual labour in high temperatures.(20)

Water in schools

The ability to maintain adequate levels of hydration throughout the day is very important for school children. Poor hydration is not only bad for general and dental health, but can also adversely affect children’s mental performance.(21) The extent to which learning ability may be impaired is still unknown, but there are a number of initiatives in the UK to encourage water intake in school-age children in order to promote good health and support learning.(22,23)

In schools, where water is provided throughout the day and where fizzy drinks are banned, there is much anecdotal evidence of improvements in concentration levels, academic performance and pupil behaviour.(24) For example, teachers in schools taking part in the Food in Schools water provision pilot project, reported that “the enhanced water provision contributed to a more settled and productive learning environment, as well as helping instill good habits.” Water reduces tiredness, irritability and distraction from thirst and can have a positive effect on pupils’ concentration throughout the day.(23) An experiment in a Scottish school also found that drinking water contributed to improvements in pupils' test results.(25) Schools who took part in the Sandwell Children’s Fund project to increase hydration amongst school children, reported that since the introduction of project, children showed improved concentration levels and were less tired and lethargic. Children complained less of having headaches and were more aware of the importance of keeping hydrated.(26)

The importance of good hydration for children’s mental performance has received little attention in the scientific literature. Nevertheless, one study of the relationship between voluntary dehydration and cognitive performance in elementary school children aged 10-12 years in southern Israel has found that at the beginning of the day there were no significant differences in cognitive performance between the hydrated and dehydrated groups. At mid-day, however, the hydrated group performed better in four of the five cognitive tests compared to the dehydrated group, especially on a short-term memory task.(27)

A further study found that even moderate heat stress can adversely affect young people’s mental performance. When a group of 17 year olds were exposed to increasing temperatures within a range likely to be found in typical classrooms, moderate heat stress of only a few degrees centigrade above the optimum, had a marked adverse effect on mental performance, particularly on tasks involving concentrating and clear thinking. Sentence comprehension and reading speed were worst at 26-27oC, and boys performed the multiplication task least well at 28 degrees.(28) (see Mental performance and concentration)

Poor hydration can also contribute to bed-wetting, daytime wetting and soiling problems in children.(29) In 2000, ERIC (Education and Resources for Improving Childhood Continence) launched a national “Water is cool in school” campaign(22) to improve children’s access to fresh drinking water in schools. More information is available from the Water is cool in school website.(www.wateriscoolinschool.org.uk)

A questionnaire study of 107 state primary and 20 state secondary schools in Cardiff, South Wales indicated that while primary schools appear largely to restrict the availability of drinks to those conducive to maintenance of good general and dental health, secondary schools appeared to foster the use of vending machines. The authors recommend that guidelines should be developed on the use and content of vending machines in schools in order to promote healthy choices.(30)

Drinking water is now being promoted in schools as part of the National Healthy Schools Standard (NHSS) programmes, sponsored by the Department of Health and the Department for Education and Skills, and managed by the Health Development Agency. More information is available from Wired for Health. (www.wiredforhealth.gov.uk)

Last updated: January 2006

1. As referenced in Water UK, Wise up on water! Kids run on water too! 2005 www.water.org.uk/home/water-for-health/resources/wise-up---children-web.pdf
2. Maughan RJ. Impact of mild dehydration on wellness and on exercise performance. Eur J Clin Nutr 2003;57 (Suppl 2):S19-23
3. Sawka MN, Cheuvront SN and Carter III R. Human water needs. Nutr Rev 2005;63:S30-S39
4. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and Sulfate (2004) Institute of Medicine of the National Academies. Washington DC: The National Academies Press. http://books.nap.edu/catalog/10925.html
5. Bar-David Y, Landau D, Bar-David Z, Pilpel D and Phillip M. Urine osmolality among elementary school children living in a hot climate: implications for dehydration. Amb Child Health 1998;4:393-397
6. Bar-Or O, Dotan R, Inbar O, Rotshtein A, Zonder H. Volluntary hypohydration in 10- to 12-year old boys. J Applied Physiol 1980;48:104-8
7. Brander N. Information for parents. “Water is cool in schools”. http://www.eric.org.uk/infosheets.doc (accessed 13/12/06)
8. Northstone K, Rogers I and Emmett P and the ALSPAC Study Team. Drinks consumed by 18-month-old children: are current recommendations being followed? Eur J Clin Nutr. 2002;56:236-244
9. Petter LPM, Hourihane J O’B and Rolles CJ. Is water out of vogue? A survey of the drinking habits of 2-7 year olds. Arch Dis Child 1995;72:137-140
10. Kenney WL, Chiu P. Influence of age on thirst and fluid intake. Med Sci Sport Exer 2001;33:1524-32
11. Food Standards Agency. Eat well, be well – Water and soft drinks. Accessed 01/02/07 www.eatwell.gov.uk/healthydiet/nutritionessentials/drinks/waterandsoftdrinks/ 12. Food Standards Agency. Eat well, be well - Your Toddler. Accessed 01/02/07 www.eatwell.gov.uk/agesandstages/children/yrtoddler/
13. Principles of Human Nutrition. Ed M Eastwood. Chapter 8: Water, electrolytes, minerals and trace elements. London: Chapman & Hall 1997
14. Food Standards Agency. Eat well, be well - Weaning your baby. Accessed 01/02/07 www.eatwell.gov.uk/agesandstages/baby/weaning/ 15. The Natural Mineral Water, Spring Water and Bottled Drinking Water (Amendment) (England) Regulations 2004, Statutory Instrument 2004 No. 656. London: HMSO 2004. http://www.legislation.hmso.gov.uk/si/si2004/20040656.htm
16. Food and Nutrition Board. Recommended Dietary Allowances. 10th ed. Washington DC: National Academy Press 1989
17. Dietary Reference Values for Food Energy and Nutrients for the UK, Report of the Panel on DRVs of the Committee on the Medical Aspects of Food Policy, Department of Health, 1991
18. Personal communication, Nickie Brander, Campaign Organiser, Education and Resources for Improving Childhood Continence (ERIC) 16/02/04 (http://www.eric.org.uk)
19. Manz F, Wentz A, Sichert-Hellert W. The most essential nutrient: defining the adequate intake of water. J Pediatr 2002;141:587-92
20. WHO. Domestic Water Quantity, Service, Level and Health, WHO/SDE/WSH/03.02. Geneva: World Health Organization 2003 www.who.int/water_sanitation_health/diseases/wsh0302/en/print.html
21. D’Anci KE, Contant F, Rosenberg IH. Hydration and cognitive function in children. Nutr Rev 2006;64:457-64
22. Education and Resources for Improving Childhood Continence (ERIC),. Water is Cool in School Campaign. http://www.wateriscoolinschool.org.uk/
23. Food in Schools: Water provision toolkit. http://foodinschools.datacenta.uk.net/topic%20files/water/water1.asp?idTopic=10&idPage=1
24. IC Cheshire Online – Ban of fizzy drinks boosts pupils’ work. 20 August 2003
25. Water improves school test results. BBC News. http://news.bbc.co.uk/1/hi/education/728017.stm
26. Water In Schools Evaluation, by Joanne Almond, Healthy Schools Co-ordinator, Sandwell Healthy Schools Scheme. March 2004 http://webwell.sandwell.gov.uk/upload/Evaluation_report.doc
27. Bar-David Y, Urkin J and Kozminsky E. The effect of voluntary dehydration on cognitive functions of elementary school children. Acta Paediatr 2005;94:1667-73
28. Wyon DP, Andersen IB, Lundqvist GR. The effects of moderate heat stress on mental performance. Scand J Work Env Hea 1979;5:352-361
29. Haines L, Rogers J and Dobson P. A study of drinking facilities in schools. Nursing Times Plus; 96:40,2-4
30. Hunter ML, Chestnutt IG, Evans SM and Withecombe AC. Fluid for thought: availability of drinks in primary and secondary schools in Cardiff, UK. Int J Ped Dent 2004;14:267-71