Everybody knows that the best moisturizer you can use comes free. Right? Everyone from your mother to famous dermatologists tell you to drink six to eight glasses of water a day to maintain that dewy youthful look. And if that's what She Who Must Be Obeyed and the medical experts say, then it must be right. Right?

Actually, it could be wrong.

Or at the very least unproven.

There is hardly any scientific data to corroborate the claim that drinking plenty of water keeps wrinkles at bay.  Earlier this year, the International Journal of Cosmetic Science admitted: "It is generally stated that drinking plenty of water has a positive impact on skin condition. However there is no published scientific study that has investigated this matter."

In April this year, two studies appeared and for the first time promised to shed some empirical light on the subject. Guess what? Yep, they don't agree.

The first took 93 healthy adults and required that they drink 2.5 liters of water a day for four weeks. They divided the group into tap water drinkers and mineral water drinkers. The mineral water group showed a "significant decrease in skin density", while the tap water group showed an increase in skin density.

The second paper, published in Skin Med in April 2007, says bluntly: "There is no scientific proof that drinking habits have any influence on the water content of the skin." Even if it did, it would not be visible on outer layers of the dermis. It concludes: "Drinking water is excellent for general health. Drinking water expressly to enhance the skin is a myth."