Water makes up a significant proportion of the body, so ensuring adequate hydration is essential for all of us, as water maintains normal bodily functions. However, it is not always straightforward to achieve.

Whilst this varies from person to person, a recent study looked at the amount of water in different aged children and also compared ‘normal’ and ‘overweight’ subjects. They found that total body water (TBW) was similar in boys and girls aged 3-10 years of age (62%).

In males, this remained the same until age 61 plus, when it decreased to 57% in ‘normal’ weight males and was significantly lower in ‘overweight’ males. In females, the TBW decreased to 55% in the 11-20 year-old group and then remained stable until age 61 plus, when it decreased to 50% in ‘normal’ weight individuals.

The ‘overweight’ females also had significantly lower TBW than the ‘normal weight’ females.(1) EFSA Journal data(2) found ages 3-10 varied between 64.8 and 66.0% in boys and 6.2 and 64.3% in girls, with percentages going up and down in those age ranges but did not compare ‘normal’ with ‘overweight’. This gives further evidence of the large proportion of the body which is made up of water.

The human body loses water largely through urine, faeces, sweat and tears. It needs to replace this fluid in order to maintain equilibrium and the percentage water discussed above. Without good hydration, the body does not function properly.

Symptoms of dehydration

When discussing the symptoms of dehydration, it is important to note that good hydration is not just the absence of dehydration. Good hydration is positive beyond prevention of the NHS symptoms found in Table 1.(3) Good hydration supports health in a wide range of ways, too many to discuss the research in depth in this article.

Symptoms of dehydration in adults and children include:

• Feeling thirsty
• Dark yellow, strong-smelling pee
• Peeing less often than usual
• Feeling dizzy or lightheaded
• Feeling tired
• A dry mouth, lips and tongue
• Sunken eyes

Signs of dehydration in a baby may include:

• A sunken soft spot (fontanelle) on top of their head
• Not having many wet nappies
• Being drowsy or irritable
• Few or no tears when they cry
• Sunken eyes

Recommendations vary within the UK. Table 2 below shows different recommendations given to children from organisations within the UK, as well as the EFSA adequate intakes. Notice the American guidance quoted in the NICE constipation guidlines outlining both total water intake from food and drinks, as well as the recommendations from drinks separately.

Also note the sometimes-significant difference in recommendations for children at different ages between the bodies. All three organisations recognise that requirements will vary including with exercise and climate. When advising families on adequate hydration this variation of requirements must be considered and discussed with them.

Recommendations vary within the UK. Table 2 below shows different recommendations given to children from organisations within the UK, as well as the EFSA adequate intakes. Notice the American guidance quoted in the NICE constipation guidlines outlining both total water intake from food and drinks, as well as the recommendations from drinks separately.

Also note the sometimes-significant difference in recommendations for children at different ages between the bodies. All three organisations recognise that requirements will vary including with exercise and climate. When advising families on adequate hydration this variation of requirements must be considered and discussed with them.

Sugar-sweetened beverages are not recommended for children. The NDNS data shows that in the 11 years since 2008 intakes in children have been reducing. However, for 2016 to 2019, children aged 1.5-3 years were still consuming 19g/day and 11-18 year-olds 142g/day. (7) There is a way to go in reducing these beverages.

According to SACN, children aged 1-5 should have mainly milk (whole or semi-skimmed milk) and water (in addition to breast milk). Older children are encouraged to have water, milk (skimmed or semi-skimmed) or fruit juice (the latter limited to 150ml per day). (8) Two campaigns by Food Active seek to support this. Kind to Teeth (9) is a campaign aimed at the early years and Give Up Loving Pop (GULP)(10) is aimed at older children. Food Active has several free resources available to support this work.

The infographic below could be a helpful tool to use with families to support them in increasing their children’s water intake.

When talking about hydration two other issues must also be considered:

1. Culture. Being culturally sensitive to the families to whom the messages are directed is key. For some cultures, consuming sweetened tea from a very young age is normal and a healthcare professional saying it is bad could make the family feel pushed out. Open discussions are
   important here.
2. Safety. Whilst most children will struggle to consume enough water, care should be taken when delivering these messages, so that children don’t have too much. Discussing the amounts and how to spread drinks throughout the day is also essential.

References

1. Lu H, Ayers E, Patel P, Mattoo TK. Body water percentage from childhood to old age. Kidney Res Clin Pract. 2023 May;42(3):340-348. doi: 10.23876/j.krcp.22.062. Epub 2023 May 16. PMID: 37313612; PMCID: PMC10265208. Accessed 4th Jun 2024 from https://pubmed.ncbi.nlm.nih.gov/37313612/

    

    

2. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA) (2010) Scientific Opinion on Dietary reference values for water. EFSA Journal 2010; 8(3):1459. [48 pp.]. Page 10 doi:10.2903/j.efsa.2010.1459. Accessed on 2nd July 2024 at https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2010.1459

3. NHS (2022) Dehydration. Accessed 2nd July 2024 https://www.nhs.uk/conditions/dehydration/
4. Popkin, B. M., D'Anci, K. E., & Rosenberg, I. H. (2010). Water, hydration, and health. Nutrition reviews, 68(8), 439–458. https://doi.org/10.1111/j.1753-4887.2010.00304.x Accessed 2nd July 2024 at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908954/

5. British Dietetic Association (2023) Fluid (water and drinks) and hydration. Accessed 4th June 2024 at: https://www.bda.uk.com/resource/fluid-water-drinks.html BDA (2023)

6.  

    

   EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA) (2010) Scientific Opinion on Dietary reference values for water. EFSA Journal 2010; 8(3):1459. [48 pp.]. Page 1 doi:10.2903/j.efsa.2010.1459. Accessed on 2nd July 2024 at https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2010.1459

    

    

7. PHE and FSA (2020) National Diet and Nutrition Survey Rolling programme Years 9 to 11 (2016/2017 to 2018/2019). Accessed on 2nd July 2024 at: https://assets.publishing.service.gov.uk/media/5fd23324e90e07662b09d91a/NDNS_UK_Y9-11_report.pdf

    

    

8. Office of Health Improvement and Disparities (2024) Feeding young children aged 1 to 5 years - summary report. Accessed 2nd July 2024 at: https://www.gov.uk/government/publications/sacn-report-feeding-young-children-aged-1-to-5-years/feeding-young-children-aged-1-to-5-years-summary-report#

9. Food Active (2018) Kind to Teeth. Accessed 2nd July 2024 at: https://foodactive.org.uk/what-we-do/campaigns-and-interventions/kind-to-teeth/

    

    

10. Food Active (2015) Kind to Teeth. Accessed 2nd July 2024 at: https://foodactive.org.uk/what-we-do/campaigns-and-interventions/give-up-loving-pop/