Posted by kathryn in Q & A Thursday

I’m back from Melbourne. I’ve cleared my inbox and in-tray, so it’s time to continue with Q & A Month.

The next question is from Justine, who asks about water:

I over-indulged over Christmas and the New Year alcohol-wise, so am drinking lots & lots of water now I’m back at work. I’ve heard that too much water can be damaging . . . how much water is too much?

You’ve almost certainly heard how important it is to drink plenty of water and stay hydrated. However, while it’s rare, it is possible to drink too much.

What happens to the water you drink

In a normal situation, water makes up between 40 and 60 percent of your body weight. It’s highly regulated and controlled through a series of mechanisms, governed by hormones, your heart, kidneys and blood vessels. These restrict fluid losses if you’re dehydrated and bump them up when you’re taking in plenty of fluids.

We lose water every day through our lungs, skin and urine. This is replaced by the water we drink and also the water in the foods we eat.

Water intoxication

However, it’s also possible to drink too much water, which causes water intoxication. This happens when you take in more fluid than you can excrete in sweat or urine.

As your water content rises it dilutes the sodium levels in your blood. If your blood becomes less concentrated than the sodium in your cells, your body attempts to re-balance this by moving water from the blood into the cells.

As the cells become full of water, they start to swell. This is a big problem if it’s happening in your brain. There’s not a lot of space available in your skull. If cells start to swell and take up more space areas of your brain become compressed – which affects your brain’s functioning.

The symptoms are similar to those of being drunk – hence the name water intoxication. You become confused, lethargic, nauseous and can have headaches and slurred speech. If you don’t get medical attention, then this can lead to seizures, coma and death.

How much is too much?

But this is rare. The kidneys of a normal healthy adult can process up to fifteen litres of water a day. So you’re unlikely to suffer water intoxication, even if you drink a lot of water.

What is more crucial, is how quickly you drink the water. Water intoxication usually occurs when someone takes in several litres of water at one time, for example this woman involved in a water drinking competition.

How much water do you need?

Under normal conditions we need between 2.5 and 3 litres of water per day. You get this from the water your drink, plus the foods you eat.

For most people 8×250ml glasses (1 cup) will be sufficient. If it’s hot or you’re exercising, you will need more.

What is Q & A Month?

This post is part of Q & A Month. For those of you new to Limes & Lycopene, I usually run a fortnightly question and answer forum, called Q & A Thursday. But for the next four weeks, it’s Q & A Month. If you have a question, or there’s a topic you’d like me to cover, leave a comment below or send me an email. For more information you can take a look at the Q & A Thursday archives.

05 February, 2008