I have recently read that the "conventional wisdom" of drinking 8 glasses of water being good was not substantiated by any medical study, can anyone refute this?

I've heard that also. But it certainly won't hurt you to drink that amount of fluid (unless you have Congestive Heart Failure or similar fluid management illness) and may do you some good.

The Mayo Clinic provides a few guidelines that may be helpful to you.

BTW, Welcome to Answerpool.

This has been a subject of debate for as long as I can remember. Standard concept is 64 ounces of water a day. People who have suffered from kidney stones are told to drink anywhere from 96 to 115 ounces of water a day. However, this is not based on scientific study according to a review in the American Journal of Physiology-Regulatory Integrative and Comparison Physiology. Furthermore, studies show that fluid intake no longer has to be considered specifically from water but can come from any form of beverage as well as foods and fuids with a water content.

Keep in mind, there are factors to consider with regards to what should be considered a healthy water/fluid intake. Climate, exercise, and health conditions that cause dehydrations are 3 key factors that should determine the amount of fluid your body needs.

There are also studies that do tout the benefits of high water intake. Epidemiological studies suggest that drinking 85 ounces of water a day may reduce the risk of developing bladder and colon cancers. Another study found that people who drank up to 45 ounces of water a day reduced their risk of having a fatal heart attack (although I'd like to know how one would go about proving that!). And further studies indicate that increased water intake does reduce the chance of bladder infection, kidney stones, and promotes weight loss.

Of course there are the rare few that experience toxic effects from drinking too much water. I'm not familiar with this but have heard that people who suffer from diabetes insipidus cannot eliminate water appropriately. Also, there have been cases of people dying from water toxicity after taking Ecstasy - a side-effect being the inability to excrete water.