The human body is really one large water storage tank with entry and exit valves. Water makes up about 60% of our bodies. Each litre of water weighs 1 kilogram, so in a person who weighs 60 kilograms, 36 kilograms is water.

Nearly one third of our daily water supply comes from what we eat.

On average we excrete at least 1.5 litres (six and a half glasses) of water a day to function properly, especially to keep our kidneys working.  The World Health Organization (WHO) has adopted 2 litres as the standard quantity of daily consumption of drinking water for adults,

Depending on how much we drink, we produce 4 to 9 glasses of urine a day. Other systems in the body also excrete water. For example, our skin, which is our biggest organ, is responsible for a large amount of water excretion in the form of sweat. We can sweat out water to a maximum of 9 glasses per hour). In reality, our daily water loss in sweat is quite variable: from half a glass to 32 glasses per day. The air we breathe is also quite “wet”. The amount of water we breathe out is roughly 1 to 2 glasses per day.

With such a large and diverse water egress system, it is difficult to replace all our excreted water through drinking. Something else is happening. It’s food. Nearly one third of our daily water supply comes from what we eat.  In the EU the average water content of food is 30%. In the USA it is less (19%) and in China it is more (40%).

This water, called virtual water, is incorporated into the cells of our food chain, is largely unregulated. In Finland, for example, only half of the water consumed is drinking water, the rest is virtual water.  Even our most protected organic produce contains a large amount of unregulated water, for example, organic carrots and lettuces have over 90% water.

Water related outbreaks of infectious diseases and the discovery of harmful substances in drinking water such as arsenic during recent years have driven us to drink bottled water.

Our drinking water is regulated and will never counter the unregulated water we consume in our food products. So next time you buy bottled or filtered water remember you are controlling, at best, the quality of two thirds of the water that is going into your body.