The body of an adult consists for 55-60% of water. Through breath, urine, defecation and sweat, it loses water. Drinking enough water is very important, because it enables our body to continue to function properly (Campbell, 2004):

• Water is the truck and highway in our body: it transports nutrients to cells, waste material from cells, and hormones, proteins, platelets and blood cells to where they need to be. In this way, cell metabolism and chemical cell processes keep running smoothly.
• Water is a good solvent and degradent. It absorpts waste materials, so we can excrete them through urine and poop.
• It enables particles to form connections, like lubricant for joints and for food.
• Water absorpts heat without changing much in temperature. Water helps you to control your body temperature by producing sweat that can evaporate.
• Water works as a shock absorber. It retains cell form, makes up an important part of cell membrane, protects our organs and bone structure.

Dehydration takes place when you lose more water than the body can replace. There are actually two ways of dehydration:

• Hypertonc dehydration: Because of fever, vomiting, diarrhoea or drinking too little water, you lose water. Because of osmotic pressure, the remaining water leaves your cells, so your blood can borrow the water. Cells shrink, the degree of electrolytes increase, osmotic receptors pick this up, and you get thirsty.
• Hypotonic dehydration: Because of excessive sweating or eating too little, you lose electrolytes, such as salt. Water moves from outside into your cells.

• First signs of dehydratation are less energy, focus and concentration. Your reaction times slow down.*
• You feel tense, restless and irritated.
• Je krijgt hoofdpijn.
• You feel dizzy (for instance when standing up) and you risk falling down.
• You feel nauseous and don’t feel like drinking.
• Your muscles are more tense when relaxing and can twitch. There is more muscle loss.
• You risk urinary infections and respiratory infections.
• In a further stage, you risk a heart attack.
• You have less brainpower, you feel anxious and afraid, you are delusional.
• In the last stage, your bodily functions stop one by one and you die.

Because a large group of people benefits from simple advice, the National Food Centre advises to drink 1.5-2L of fluid per day. However, our stage of life, our characterists and our behaviour impact our individual need for water. Babies exist of 75% water, adult men approximately of 60%, and adult women approximately of 55% water(KU Leuven, 2011).
Acoording to Westerterp, Plasqui & Goris their study (2005) the season and the outside temperature in the Netherlands, don’t influence water loss in men, but physical activy does. The more they move, the more they lose. For women, physical activity does not influence water loss much, but the season does. And they already experience more water loss than men. Logically, the more both groups eat and drink, the less water loss they experience. Hence, how much litres of water per day is enough, is different for everyone.

There is a trick that allows you to calculate how much water you should drink on an average day: 0.03 times your body weight. This forms your basic number of litres, but science shows that there are some things that you should take also into account.
You need to drink more water per day than you just calculated, if:

• You’re a woman.
• You’re more physically than normal (goes especially for men).
• It’s your day for doing sports (no.. fishing and darts don’t count!).
• It’s hot outside (goes especially for women).
• You’re exposed to heat, for instance in a sauna, a subtropical swimming pool or a subtropical zoohouse;
• You’re sick or don’t feel so good.
• You have a fever, diarrhoea, or you need to vomit.
• You’re drinking alcohol.
• You consume a lot of sugar.
• You’re experiencing mental stress.
• You are getting or having your period.
• You’re on pills that increase urination or other medicin that influence your digestion.

According to Thomas et al. (2008) you first can sense dehydration through a dry mouth, a dry skin, absense of sweat, headache, fast heartbeat or dizziness. In the next stage, confusion, less desire to drink and deep-set eyes indicate dehydration. You should then drink more water. Even if your urine looks dark yellow or brown, you should drink more, although the first pee after you wake up does not count. There is no single symptom that predicts fluid loss, but the urine check is the closest for all people who don’t have a kidney problem.
Take notice: thirst receptors and temperature receptors of older people no longer work properly. Older people experience less thirst and feel less hot. This means they have a much bigger risk of dehydation. It’s also the reason that dehydration isn’t a reliable sign of bad health care in a nursing home. The only way to make sure older people drink enough, is to always be able to serve their favourite drink and to frequently remember them to drink between meals (Thomas et al., 2008).

You can basically count all fluids from your diet. Tap water, coffee, cola, yogurt, cucumber and soup all count. What you have to take into account is that caffeine and alcohol cause you to urinate more and water leaves your body faster. And note that the above calculation is only based on how much you drink: water from solid food does not count.

I would like to conclude this blog with a subject that is discussed very much in the Netherlands; tap water. Dutch tap water belongs to the best of the world because of great waterworks maintainance and sustainable water puration techniques. There are five reasons why you should prefer (Dutch) tap water over mineral water from a bottle (source:Voedingscentrum):

• Tap water is much cheaper than bottled mineral water. For just 1 euro per year, you can tap 1.5 litres of tap water every day! Bottled water is 150-500 times more expensive.
• Tap water is a much more sustainable choice than bottled mineral water. For the production of those second option, they waste 1.5 liters water per 1L bottled water and use up so much fossil fuels to source the material and produce the plastic bottles. Although mineral water doesn’t travel that far from the source than other food products, it still needs storage and distribution. And although much of the bottles are being recycled, the nano particles of the plastic pollute the ground water and eventually also the mineral water.
• (Dutch) tap water is healthier than bottled mineralwater. In the Netherlands, there are very strong rules for the quality of the tap water, but there aren’t for mineral water. Combined with the fact that filtering costs money, this means that some mineral water contain more minerals and some contain less than tap water, but at least much more filth.
• Tap water contains less (mineral) salt than bottled water. Limiting salt consumption is good for your heart and blood vessels.
• Tap water contains no sugar, while mineral water sometimes (a lot) of sugar. Especially true for mineral water with added flavour.
• Bottled water sometimes contains carbon dioxide. Normally, this does no harm, but 5-20% of people do experience unpleasantness. People with irritable bowel syndrome can experience bloating, intestinal cramps, formation of gas or diarrhea when they drink carbonated drinks.