While the body changes with the passing years, seniors have basically the same water needs as adults younger than themselves.
Change at a cellular level
Muscles atrophy with age and seniors consequently have less water in the body than younger adults. On average, from infancy to old age, the body’s water content diminishes from 75% to 50% water. The kidneys’ ability to reabsorb water decreases with age, so water is lost from the body in greater amounts.
Taking special care
Since the sensation of thirst diminishes as they grow older, seniors need to pay close attention to their water intake, to avoid dehydration(1). By the same token, elderly people feel less hungry and eating less food reduces hydration from this source.
Infants and young children are at risk both of not drinking enough fluid for their specific physiological needs and of drinking liquids of unsuitable quality.
The bodies of infants and young children contain more water (75%) than those of adults and are more vulnerable to dehydration(1). They have a larger surface area in relation to weight (surface-to-volume ratio) than do adult bodies, which allows for greater water loss through the skin. By the same token, since their kidneys are not fully mature, children excrete more diluted urine, which means they lose more water than they retain.
Furthermore, infants and young children have a higher risk of illness than adults. Fever, vomiting and/or diarrhea can rapidly result in dehydration. Young children also have more difficulty recognizing and communicating their need for water and rely on their caregivers to supply sufficient water to protect their health.
The message is simple: whatever the circumstances, get children to drink regularly throughout the day.
Hydration and exercise
Children often fail to voluntarily drink enough fluid during vigorous physical activity and can therefore dehydrate. Parents, caregivers and coaches should ensure that young children receive appropriate hydration during and after exercise(2) (particularly in a hot climate). Drinking water should be provided whenever children are physically active.
Quantity of fluids
Authoritative publications report that, in countries such as Lebanon, the US, Mexico, the UK and France the daily water intake of a high proportion of children does not meet recommended levels. Another study highlights that this is so for a third or more of European children and adolescents. Moreover, children in the US, Italy, France, the UK and Egypt are not adequately hydrated when they go to school in the morning.
Quality of fluids
Children everywhere in the world are over-consuming sugar-sweetened beverages(SSB). Medical evidence overwhelmingly shows that overconsumption of sugary drinks is a key contributor to the increase in childhood obesity and cardio-metabolic problems (WHO Guidelines on Sugar Intake, 2015).
Children should clearly be helped and encouraged to drink pure water – it has zero undesirable effects and is the best possible source of hydration.
Did you know
WHO-Europe reports that sugary drinks are often the main source of added sugars in the diets of European children and adolescents. In the UK, for example, nearly 30% of people’s total dietary energy comes from sugar-sweetened drinks and fruit juices (Public Health England, 2015).
Water balance for children
Less than a third of the water we consume comes from food. Most comes from what we drink. This table gives the recommended daily water amounts for children, across different age groups, established by the Institute of Medicine and the European Food Safety Agency.
Sources: (1) Jéquier et al. Water as an essential nutrient: the physiological basis of hydration. EJCN 2010, 64: 115-23; (2) Naughton et al. Reducing the risk of heat-related decrements to physical activity in young people. Journal of Science and Medicine in Sport 2008, 11: 58-65