Water is the main component of our organism. Without it, it’s impossible for us to function properly. What beverages are the most beneficial for our bodies, and how much of them should we drink per day? We asked Prof. Małgorzata Zwolińska-Wcisło, Dr Magdalena Przybylska-Feluś, and Agnieszka Dąbek Department of Clinical Nutrition of the JU MC Faculty of Medicine to give us some advice on these issues.
The percentage of water in the human body varies depending on age, sex, body fat, and muscle tissue. For instance, a new-born baby is 80% water, while an elderly person could be as low as 50% or less. Additionally, the water content of certain tissues changes with age – wrinkles are one of the most common examples of that process. Interestingly enough, non-fat tissue contains around 75% water, as opposed to only 10–20% in fat tissue. This means that percentage content of water in overweight people is lower than in those with a healthy weight.
Water is necessary for a number of biological processes, such as the formation of bolus (or, simply put, the food we put in our mouth), digestion, nutrient distribution, transporting metabolites to our livers and kidneys, and thermal regulation. It’s also a substrate – and the final result – of many biochemical reactions. For our body to work correctly, we need to maintain balance and ingest as much water as our organism excretes.
How much should we drink?
The water requirement of our organisms is defined by a number of factors. These aren’t only physiological differences, such as sex, age, and weight, but also variables like temperature and humidity, recent physical activity, and illness. Generally, we assume that an adult should drink about 1.5 to 2.5 litres of liquids in the span of 24 hours.
The basic water requirement can be calculated using a simplified formula: 10 x 150 ml + [(body mass – 20) x 20 ml]. Another way to look at this is to assume that a healthy adult needs to consume 30 ml of water per 1 kilogram of body weight, although this does not include water lost by our organism due to physical activity or high temperature. It’s very important, since physical exertion in the heat can make us sweat out as much as 4 litres of water a day – enough to fill a small bucket.
Insufficient consumption of water can lead to dehydration. Mild dehydration usually results in increased thirst, drying of mucous membranes, and increased heart rate. Other symptoms include insomnia, impaired concentration, and headaches. Severe dehydration (with a loss of more than 9% of body weight) is a life-threatening medical condition resulting in hypovolemia (blood volume depletion), significant drop in blood pressure, and reduced consciousness.
Water is not always the same
We ingest more than half of our water requirement in the form of liquids (with the rest coming from solid foods and metabolic processes). As we get more and more thirsty, we often find ourselves looking for anything that we can drink, regardless of what it is. We should resist that urge: after all, it’s important to be careful when choosing a beverage, especially during heat waves.
It’s worth mentioning that drinking while eating has not been shown by any scientific study to hamper the stomach’s digestive capabilities.
The best way to hydrate our body is to drink mineral water. Not only does it slake our thirst, but is also rich in minerals that can have a positive effect on our organism. Generally speaking, we can discern three types of mineral water, containing varying levels of minerals – low (<500 mg/l), medium (500–1,500 mg/l), and high (>1,500 mg/l). Mineral water is non-caloric, and contains calcium, sodium, magnesium, iron, potassium, iodine, fluoride, and sulphur, which are very beneficial to our health.
Spring water (often categorised as a sub-type low mineralised water, with no more than 500 mg of minerals per litre), is also worth drinking, since it contributes to proper osmotic balance of our organisms. Osmotic pressure is dependent on the quality and quantity of fluids, and is responsible for maintaining the proper levels of ions in our bodies. Spring water can be ingested without in any quantity without the risk of causing electrolyte imbalance.
We should store our water in containers that can be emptied no more than a couple dozen hours after they’re opened to ensure microbiological purity. Glass bottles are the best for this purpose. When we’re dehydrated, it’s best to drink water in small portions, which allows for steady rehydration. What’s more, it’s worth mentioning that drinking while eating has not been shown by any scientific study to hamper the stomach’s digestive capabilities.
Hypotonic, isotonic, or hypertonic?
Based on molality (the number of carbohydrates in a 100 ml solution), we can distinguish the following:
- hypotonic solutions – liquids that are suitable for rehydrating our organisms, good for people performing low-intensity exercises. They don’t provide sufficient amounts of minerals and electrolytes, so they should be supplemented by a proper diet;
- isotonic solutions – these liquids contain sodium, potassium and carbohydrates that both rehydrate and resupply our bodies with electrolytes and vitamins. They’re good for regeneration during and after mid-intensity workouts. Since their osmotic pressure is similar to that of bodily fluids, they absorb very well;
- hypertonic solutions – they contain much more particles than bodily fluids. They provide a lot of energy, but are not as effective at rehydration. This category includes liquids such as juices and various types of fruit drinks. They are full of vitamins and minerals, and are often the best source of carbohydrates for people who can’t or shouldn’t ingest solid carbohydrates.
On a side note, most popular soft drinks are filled to the brim with sugar, glucose-fructose syrup, and artificial aromas and preservatives absent in natural water. These are not particularly healthy and should be avoided. If a certain type of water is not to our taste, we can always add a slice of lemon, fresh mint, or cucumber.
In conclusion, if we want to slake our thirst, we need to steer clear of sweet fizzy drinks. Due to high content of sugar and other additives, they can have an adverse effect on our health. In addition, our organism will demand an even higher supply of water to dilute the excess sugar.
What about heat waves?
During heat waves, we sweat out not only water, but also minerals like sodium, potassium, chloride, magnesium, and calcium. If we lose too much of them, we risk electrolyte imbalance, which causes feelings of weakness and vertigo. Extended periods of electrolyte imbalance can lead to heart and kidney problems.
Resupplying our organism through proper diet can help mitigate the consequences of excessive sweating. Fruits and vegetables are by far the richest source of minerals that we can consume (some of them, such as watermelons, cucumbers, and broccoli also contain a lot of water, which helps in rehydration). On hot days, it’s good to substitute one meal with a juice or eat soups. For instance, tomato juice contains many valuable ingredients, like potassium, magnesium, phosphorus, and many vitamins as well as a lot of fibre, which ensures that we’ll feel sated after consuming it. Conversely, fatty foods can only make our situation worse, since it takes quite an amount of energy to digest them.
Though hot weather often causes diminished appetite, it’s important to provide sustenance to our bodies. Regardless of temperature, our organism requires a certain amount of macro- and microelements in order to function. Products that are readily available for purchase in every store are sufficient to meet our food and water requirements. We just need to follow a few simple rules.
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Original text: www.nauka.uj.edu.pl