THE CLAIM

The tongue is mapped into four areas of taste.

THE FACTS

High school textbooks call it the tongue map—that colourful illustration that neatly divides the human tongue into sections according to taste receptors. There is the tip of the tongue for sweet, the sides for sour and salty, and the back for bitter. But recent studies show that while scientists still have much to learn about receptors, the map at least is wrong.

A study published in the journal Nature in 2006 reported that receptors for the basic tastes are found in distinct cells, and that these cells are not localized but spread throughout the tongue. That said, other studies suggest some parts may be more sensitive to certain flavours and there may be differences in the way men and women detect sour, salty and bitter flavours.

THE BOTTOM LINE

Receptors for different tastes are not confined to certain parts of the tongue.

THE CLAIM

Drinking lots of water is good for your skin.

THE FACTS

The old saw about drinking eight glasses of water a day has been debunked. But a similar adage about water and healthy skin persists. However, there is no evidence that drinking anything more than the recommended amounts is particularly beneficial to skin.

A 2007 study on the effects of water consumption did show that drinking 500ml water, about 2 cups, increased blood flow to the skin. But there was no evidence that that reduced wrinkles or improved complexion. Other studies hinted that vitamin C might prevent wrinkles, or that oestrogen use in postmenopausal women might reduce dry skin and slow skin ageing. But the evidence for each is limited, and oestrogen therapy can have side effects.

Margaret E. Parsons, a spokeswoman for the American Academy of Dermatology, says excess water does not help the skin but “if dehydrated, fine wrinkles certainly seem to show up a bit more". Her advice? Always wear sunscreen, avoid cigarettes and eat well.

THE BOTTOM LINE

There is little evidence that excess water helps skin.

THE CLAIM

Coffee eases headaches from epidural injections.

THE FACTS

Headaches can be an excruciating side effect of routine procedures that involve puncturing the middle and lower back, including spinal taps and anaesthetic injections such as epidurals.

Doctors have long advocated a cup of Joe. One theory is that caffeine narrows cerebral blood vessels, which helps reverse the vasodilation that occurs when a puncture causes cerebrospinal fluid to leak. Research, however, suggests it does not help. In 2007, researchers at the Mayo Clinic, Arizona, reviewed several studies on caffeine as a treatment for postdural puncture headache, and found no evidence it worked. That echoed the findings of a separate study at the University of California, Los Angeles, and Cedars-Sinai Medical Center in Los Angeles, which found slim evidence for caffeine or another popular antidote, more fluids. Other studies suggest the most effective treatment is epidural blood patching. It can be invasive, but relieves headaches in 85-98% patients. It also helps when smaller needles are used.

THE BOTTOM LINE

Studies suggest caffeine is not effective treatment for headaches caused by lumbar puncture procedures.

©2008/ The New York Times

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