Ms Rita Gunther McGrath, a Columbia Business School professor, is one of those business travellers who does not care about delays, cancellations or navigating a new location.

What does concern her is the seeming inability to conquer jet lag and the accompanying symptoms that leave her groggy, unfocused and feeling, she says, "like a dishrag".

"Jet lag has always been an issue for me," says Ms McGrath, who has been a business traveller for more than two decades and has dealt with itineraries that take her from New York to New Zealand to Helsinki to Hong Kong all within a matter of days.

She has scoured the Internet for "jet lag cures" and has tried preventing or dealing with the misery by avoiding alcohol, limiting light exposure or blasting her body with sunlight and "doing just about anything and everything that experts tell you to do", she said.

"Jet lag is not conducive to the corporate environment," she said. "There has to be some kind of help that actually works for those of us that travel a lot, but I sure can't find it."

Although science is closer to understanding the basic biological mechanisms that make many travellers feel so miserable when crossing time zones, research has revealed that, at least for now, there is no one-size-fits-all recommendation for preventing or dealing with the angst of jet lag.

Recommendations to beat jet lag include adjusting sleep schedules, short-term use of medications to sleep or stay awake, melatonin supplements and light exposure timing, among others, said Colonel Ian Wedmore, an emergency medicine specialist for the Army.

These work for many people, "but not all", said Colonel Wedmore, who practices at Madigan Army Medical Center in Tacoma, Washington.

One hope for treatment lies in creating a "personalised" plan, based on an individual's genetic blueprint, said Mr Paolo SassoneCorsi, a scientist at the University of California, Irvine, who studies internal "body clocks", or circadian rhythms - the 24-hour cycles of light and dark that help regulate when people wake up, sleep and eat, among other things.

Scientists now know that about 15 per cent of a human's genes are governed by these biological clocks.

Any disruption to them - whether it is a flight across time zones that leaves travellers in bright light when their bodies crave sleep, or darkness when their bodies are wide-awake, shift work or even stress - can lead to jet lag or, in extreme cases, potentially lead to the development of serious health problems such as obesity and cancer, he said.

"What's new is that we now recognise that we have clocks in every single cell of our bodies and, from a physiological point of view, some people are simply going to be more affected by jet lag because of their genetic or metabolic profile," he said.

"Basically, it's that profile that makes us individuals. But it can also be the reason why someone experiences few problems with jet lag while someone else will say, 'Dude, I'm a wreck'".

One piece of advice for those who travel far, but to the same spots, is to stay in the same hotel. Familiarity will help cut stress and perhaps minimise jet lag.

Experiments on mice performed in Mr Sassone-Corsi's laboratory show that a stressful environment will decrease the ability to adjust to a new time zone.

Quickly shifting meal times and exercise periods to your new locale will help, too, he said.

Doctors do know that heading west is generally easier on the body than travelling east, because it requires a person's internal clock to "set later, not earlier", said Mr R. Robert Auger, a sleep specialist at the Mayo Clinic in Rochester, Minnesota.

But the more time zones crossed, the tougher the jet lag.

The rule of thumb to get your body clocks back in sync is about one day for every time zone change, making it "very difficult for real road warriors to get acclimated", Mr Auger said.

A common aid is melatonin, which has been studied extensively and for many travellers can help symptoms by getting the body in sync with local time more quickly, said Colonel Wedmore, the emergency medicine specialist.

Although it is not a miracle cure, "some studies do show it can help on both eastward and westward flights, and it does seem to help a lot of people with jet lag, including me", he said.

But it has not done much for Ms McGrath. So, for now, she is trying to find the positives.

"What we all need to remember is that we are incredibly privileged to be able to cross time zones so rapidly," she said.

"Plus, when I get home from a business trip and say something stupid, I just blame the jet lag. That's good for about three days."

NEW YORK TIMES