Just when you master the saintly habit of drinking eight glasses of water a day or more, the media tells us not to. Could we be drinking too much of it? Jacquie Dale reports on the benefits of water and how much you need to drink every day for health.

Nutrition rules come and go, first we are told not to eat too many eggs, then we are told that eggs are healthy, in fact the more we read about food or nutrition for health the more confused we can become, and now some health experts are questioning our "eight glass a day" rule for water. Many nutritionists have been banging home the message, drink two litres of water a day every day. Perhaps it's time we had a re-think. When it comes to healthy eating one size does not fit all and this also applies to how much water we should all be drinking.

In an article published in the American Journal of Physiology, kidney specialist Heinz Valtin examines scientific evidence to support drinking eight glasses of water a day. His conclusions have surprised some people, in fact in healthy sedentary populations he could find no scientific proof that eight glasses every day improved health, further more the bottled water trend could be leading some of us to over do it. Too much of any substance can kill us, people can and do drink themselves to death and I'm not just talking about alcohol related deaths. Hyponatremia is a condition where there is insufficient salt in the blood, in the body our kidneys control the amount of water and salts that leave the body. When a person drinks too much water over a short period of time the kidneys cannot cope, in extreme cases this can lead to brain swelling, coma and respiratory arrest. Most cases of Hyponatremia occur when a person is consuming more than a litre of water an hour.

The standard recommendation for fluid intake is 1 millilitre per calorie of food consumed per day or 2.5 litres a day, this includes fluid from fruit, beverages, and other food. It seems that somewhere along the way, probably coinciding with the bottled water boom we have mistakenly presumed that the 2 litres a day rule applies to water and not total fluid intake. This highlights the fact that individual fluid needs can vary among us all.

Before you toss the water bottle aside take note, water is by far our most important nutrient. We can go for about a month without food but try going without water and you'll be dead within seven to ten days. Water makes up around 60 percent of the human body, it plays a vital role in helping the body to function and stay healthy. A lack of water, even mild dehydration can drain your energy and make you feel tired. If you are active or living in a hot or dry climate you will need to drink more.

So how much do we need for good health?

The eight-glass rule is still a good guide, some people may need to drink more for health conditions or to replace the sweat losses from exercise. You can safely include fluid from other beverages and food throughout the day, green tea and coffee still count as part of your fluid intake. You know you are drinking enough water if you are rarely thirsty, produce more than 1.4 litres of urine a day and your urine is pale and odourless. By all means use the eight-glass rule as a guideline, drink more if you are active but apparently there's no need to over do it.