HEALTH / Common Complaints: Jet lag

THIS SUMMER most travel companies are offering lots of last-minute bargains, some to exotic locations in unfamiliar places. People may, indeed, find that they have booked to go somewhere with only a hazy idea of its geographical location. The travel agent will readily say something about the weather to be expected - usually unremitting sunshine and warm water - but may be less willing to offer information about drawbacks. One important factor for the holiday traveller, who is unlikely to be spending more than two weeks away, is jet lag.

Anyone aged 60 or more will remember the surprise with which people discovered that travel by jet had disadvantages. Until the 1950s, intercontinental travel was a slow business: crossing the Atlantic by even the fastest of the great passenger liners took four or five days, with the ship's clock being put back one hour each day. Flying to Australia involved several overnight stops. Jet aircraft transformed schedules, enabling executives to leave London at breakfast time and arrive in New York or Boston in time for lunch while colleagues at home were catching the evening train home. Soon, however, these travellers began to find that this rapid transition upset their bodies and their minds. For the first few days after arrival, not only does the body want to sleep at its normal bedtime; it wants to eat at home mealtimes, empty its bowel and bladder at the usual times, and do its thinking while the sun is out at home - not in the middle of the night.

The severity of the symptoms of jet lag depends on location, not on distance. Someone who flies from London to Cape Town may cover twice the distance of a trip to the United States, but Cape Town is only two hours away on the international clock, whereas the Caribbean and Florida are five or six hours off. Most of us can adjust with little difficulty to a shift of two hours; but anything over five becomes more uncomfortable. Travel eastwards, when the day of travel is shortened, seems to be more upsetting than in the opposite direction. This may need to be taken into account when choosing a holiday destination.

People vary enormously in the extent to which jet lag upsets them. Those who need little sleep seem to do better than those who need their eight or nine hours every night. Standard advice is to reset your watch and to try to eat, sleep and socialise at local times from day one. If possible, bank some sleep before travelling and sleep on the plane. Alcohol makes things worse - few experienced travellers drink much on cross-

Atlantic flights. Research workers have established that a brain hormone, melatonin, helps the readjustment process, but attempts to use this hormone as a treatment to hasten adjustment have proved disappointing.

What does seem to help is exposure to sunlight. Having arrived at your destination, spend as many of the daylight hours as possible out of doors, and awake - sleeping on the beach is no good. If your idea of a good holiday is sleepy sunbathing by day (medically inadvisable because of the harmful effects of strong sun on the skin) and lots of activity at night, choose your location with care. Pick one within two or at most three time zones of Greenwich and jet lag will be no problem.