Learning Aims:
    • Students explain why each individual has a different fluid intake, which can differ from the values ​​given in literature.
    • Think about the impact of the lack of fluid on the human organism and explain the general relation between the availability of beverages and water.
    • Create the rules for proper fluid intake.
    • Worksheet.
    Suggestions for use:

    First the students will be asked the following questions.

    • Why is it important to drink?

    Fluids must be continuously supplied. Enough water ensures the metabolism and excretion of harmful substances arising in the body. The water in our body is in every cell and all biochemical processes are bound to water. Water ensures the absorption of nutrients, their transport to the cells, dissolves and eliminates superfluous products of metabolism, moistens the air we breathe; by evaporation through perspiration it helps the body thermoregulation, regulates the level of the electron and proton in the cells (osmoregulation).

    Source: http://www.rajec.com/cz/zdravi/voda-a-lidske-telo/voda-v-lidskem-tele

    • Why is it necessary to continuously supply fluids?

    In order to function properly, an adult human body must excrete every day approximately 2.5 litters of water. The body eliminates water in three ways - in the urine (1 - 1.5 litters per day), in faeces (100-200 ml per day; during diarrhoea there occurs up to 1.5 - 5 litre loss), by respiration (in the form of small droplets in the exhaled air the body loses 250 to 300 ml per day) and through skin (normally we sweat out 500 to 700 ml per day). Therefore we have to supply fluid to compensate for water balance (Suchánek, 1999).

    • What would happen if we did not supply water?

    Lack of water or dehydration causes both acute and chronic problems. Acute dehydration represents the loss of 2% of body weight. This acute dehydration is manifested by headache, fatigue, malaise, decline of physical and mental condition. The loss of such amount causes a performance decrease of 20%. Children during this acute dehydration may have reduced ability to concentrate on teaching, and this may affect their school results.

    Long-term lack of water can cause headaches, constipation as well as serious diseases such as renal disorders, formation of kidney and urinary stones. It also increases the risk of urinary tract inflammation, in the worst cases, occurrence of cancer (rectum or bladder), and cardiovascular diseases (Kožíšek, 2005).

    • How much fluid should we daily take?

    Every day we should get into the body 2 to 3 litres of fluid, but we must not forget that the water entering our body is bound in food, i.e. approximately 900 ml per day. This means that the rest, about 1.5 litres, we have to insert into the body in the form of fluid. This amount should not be drunk at once, but gradually during the day. The need for fluid is an individual matter and depends on many factors, both internal (body weight, activity, composition of food, current health status) and external (temperature and humidity of the ambient environment, the type of clothes ...) (Kožíšek, 2005).

    • How do I know when to drink?

    We are reminded of a lack of fluid by thirst, but do you think that thirst in time points to the need for water? Thirst is a sign that we have already been dehydrated. So to prevent dehydration, we should not follow the sense of thirst. Furthermore, the sense of thirst decreases with age. Another symptom of a lack of fluid is a dry mouth and stale lips (Kožíšek, 2005).

    On the basis of discussion, the students create the rules for proper fluid intake:

    • It is necessary to drink evenly throughout the day, starting in the morning.
    • Every day we should drink at least 1.5 litres of fluid.
    • We should not wait for thirst, which is already a manifestation of moderate dehydration.
    • Consider which water will be the basis of your fluid intake (it should be tap water or still spring water, the suitability of other beverages vary in relation to the needs of a particular organism, the ongoing activity, health problems, weather, etc.).
    • Limit a consumption of larger amount of highly carbonated water.
    • If we drink mineral waters, we should try to change them and limit their number.
    • Limit the consumption of sweetened soft drinks and Cola drinks.
  • Increased load needs also increased consumption of fluids.
  • Possible questions:
    • How long can we endure without fluids?

    Two – three days. Everything depends on the actual conditions.

    • Which beverages are the most suitable?

    The best drink is, of course, clean tap water from waterpipes or a well but also bottled infant and spring water. The appropriate drinks include also fruit and vegetable juice (preferably made ​​from your own fruit and vegetables using a juice extractor) and sugar-free tea, especially green. These stimulate the activities of salivary glands and thus excellently quench thirst, promote secretion of digestive glands and metabolism. Medium and highly mineralized waters are not an appropriate basis for fluid intake and cannot be drunk in worsened state of health, such as kidney stones or high blood pressure. Daily intake of mineral water should not exceed 0.5 litres. It is appropriate to alternate the mineral water. The fluid intake cannot include milk and cocoa; these are rather liquid nutrition (Kožíšek, 2005; Slavíková, 2002).

    • Which beverages are inappropriate?

    Lemonade, Cola drinks, flavoured mineral waters, energy drinks, etc. The reason for this inappropriateness is the sugar content, which on the contrary increases the sense of thirst. Another undesirable substance is carbone dioxide, which along with organic acids (flavours) damages tooth enamel, causes stomach and digestive disorders, but the recommended dosage stimulates urine production and encourages the digestive system (such as sipped ice cola helps for nausea). Moreover, cola drinks contain caffeine as coffee does. Caffeine increases urine production, so it takes away even more fluid from the body than we are trying to get by drinking. In addition, caffeine promotes children’s tendency to hyperactivity, because it encourages the organism. Inappropriate fluids are definitely alcoholic beverages, which do not belong among fluids suitable for water intake. They can only be a tasty supplement of food and their daily consumption should not exceed 0.5 litre of beer or 0.2 litre of wine (Kožíšek, 2005).