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How you CAN stop jet lag wrecking your holiday

More of us are getting too little sleep, with surveys suggesting that around a third of the UK working population wants more.

Our 24/7 culture and the move towards even more night-shift work is partly to blame — one in eight UK workers now works nights, that’s more than three million people (more than the combined populations of Birmingham, Liverpool and Nottingham).

Research shows night-shift workers’ body clocks don’t adapt to their work patterns —and, as a result, they experience a chronic lack of sleep and disruption to their body clocks. Meanwhile, the rest of us try to squeeze more into our daily schedules, sacrificing relaxation time and sleep.

Research shows night-shift workers’ body clocks don’t adapt to their work patterns 

At the same time, and because we live most of our lives indoors, we have also become increasingly detached from the natural cycle of light and dark, leading to a mismatch between our body clocks and environmental time so that our bodies are not doing the right thing at the right time.

This misalignment is having important consequences for our physical health, raising the risk of type 2 diabetes and other conditions, but also our mental wellbeing — and, as I explain today, it is associated with the rise of depressive illnesses such as the so-called ‘winter blues’.

All of this is a relatively recent problem in human history. In 1800, most people in Europe and the U.S. worked outside and were exposed to the natural cycle of light and dark.

Today, in the UK, just 1 per cent of the working population works in agriculture and fishing, which means most of us have become profoundly detached from environmental light.

And as a result, we have lost one of the most important signals that regulates our sleep and wake cycle.

The move indoors, and increased exposure to dim artificial light, particularly since the Fifties, is correlated with a rise in seasonal affective disorder, or SAD.

The symptoms of SAD, and its milder cousin the ‘winter blues’, are persistent low mood, loss of pleasure or interest in normal everyday life, weight gain, feeling irritable, low self-esteem and feeling stressed or anxious.

In most cases, SAD can be treated effectively with travel to a sunnier clime, or bright artificial light delivered by light boxes (available to buy online). It is worth emphasising that the artificial light needed to reduce the symptoms of SAD are high, requiring approximately 10,000 lux for at least 30 minutes in the morning on a daily basis.

As to how light might help, it’s still not clear.

It could act by stopping the body clock ‘drifting off’ schedule during the winter when there is less environmental light to set it (this is a particular problem for those who commute in the dark during the winter).

The light may also trigger the release of brain hormones such as serotonin that improve mood.

A more benign and common version of this mismatch between our internal clocks and the day and night cycle is jet lag.


The problem of long-distance travel affecting our body clocks and sleep is not just a very modern phenomenon.

There is some evidence that ‘boat’ lag used to affect transatlantic passengers in the days of the large ocean liners.

But the faster you cross time zones, the worse it is for most people, because our biological clocks cannot cope quickly enough with the change.

Indeed, almost everyone who has flown across a few time zones has felt at least some of the symptoms of jet lag: fatigue, an inability to fall asleep in the new time zone, body aches, digestive problems and disorientation.

It can easily spoil the enjoyment of a holiday during the first few days — and make a work trip difficult — but it’s also potentially dangerous. A number of airlines warn passengers that the effects can be severe, with the ability to make decisions reduced by up to 50 per cent; communication skills by 30 per cent; memory by 20 per cent; and attention by a huge 75 per cent.

There is little doubt this is down to the effects of both a misaligned body clock and a lack of sleep. If you need to make important decisions after crossing multiple time zones, try to go a few days early so your body clock can at least partially adapt to the new time zone. On average, it takes about a day to adjust for each time zone crossed: in general, the body takes around ten days to adjust from the jet-lagging effects of crossing ten time zones (from the UK to Australia, for example), but there are differences between individuals in response to jet lag.

However, there are ways to speed up your adaptation to a new time zone.


While there are no guarantees, a truly effective way of minimising the problems caused by travelling across time zones is to use light to ‘shift’ the clock.

As I have explained throughout this series, light exposure at different times of the day shifts our body clocks differently. Light around sunrise advances the clock so that we start our sleep earlier and go to bed earlier the next day. Light around sunset delays the clock, so we go to sleep and get up later the next night.

When travelling across time zones, the principle is simple: in the new time zone, work out when it’s dawn and dusk in the UK, then for the first few days after arrival, seek out or avoid light, either to delay or advance the body clock.

The rule of thumb is that when travelling west you seek out light as soon as possible upon arrival in the new time zone to delay the clock. For instance, if you’re flying from the UK to New York (five hours behind us), and arrive at 7pm UK time, that’s 2pm New York time. So take a stroll outside in daylight when you arrive.

When travelling east from the UK, you need to drag your body clock forward in time. To adjust quickly, you want to avoid morning light and seek out late afternoon light for the first few days.

For instance, if you’re flying to Sydney (11 hours ahead of the UK) and arrive at 5am to 7am, that’s 6pm to 8pm in the UK — if you’ve got light exposure then, it would delay your body clock and not advance it to the new time zone. But if you arrive later in the day in Sydney, say 4pm to 6pm, it will be will be 5am to 7am in the UK, and light exposure at this time will advance your body clock and help you adjust to the new advanced time zone. (There are also plenty of apps to help you work out when to seek out and when to avoid light.)

A pair of dark sunglasses is the simplest means of dealing with the problem of inappropriate light exposure.

If you fly across multiple time zones and have to function as soon as you arrive, then avoid alcohol on the flight and keep fully hydrated. Then, before the meeting, if you are able, take a short nap (no more than 20 minutes) and drink a strong coffee (to get the caffeine).

During the meeting make sure the room is as brightly lit as possible, or sit by a window. All this will increase alertness.

But be very careful: your brain will still be tired, less able to process information, be more impulsive, less reflective and less empathetic. So pause, and delay making any important decisions until you have had chance to sleep on the problem.


Melatonin has been used extensively as a treatment for jet lag. However, for most people it brings only a minor or no improvement (I don’t use melatonin myself).

So why has it become so popular? Melatonin is often termed the ‘sleep hormone’, but this is misleading. In fact, this hormone doesn’t so much trigger sleep as act as a marker for the body that it’s night-time.

What not to eat when you’re tired 

People who are tired are more likely to seek out fatty, sugary foods. This is because a lack of sleep can affect both the way our bodies deal with sugar and our metabolism.

Studies suggest it raises levels of the ‘hunger’ hormone ghrelin and causes a decline in levels of leptin, a hormone that inhibits hunger signals to the brain.

These changes may help to explain why shift workers have a higher risk of weight gain, obesity and type 2 diabetes — and, to a lesser extent, why, when we’re all tired, we seek out the same sorts of high-sugar foods.

But it is important to avoid these foods, and if you do feel hungry, make sure you choose protein-rich snacks (which help you feel full and don’t cause spikes in blood sugar).

This is especially true if you work night shifts. Sugar-rich foods or sugary beverages at the beginning of a night shift will produce a ‘sugar rush’, followed by a crash and increased tiredness.

In addition, sugar consumed in the evening is not as easily absorbed by the cells of the body and remains in the blood for longer, increasing the risk of type 2 diabetes.

Ideally, work canteens should help by providing snacks and easy-to-digest foods, with lots of protein available. This means soups, nuts and seeds, peanut butter, boiled eggs, chicken, and tuna.

When I am tired, I tend to eat cashew nuts, and have a small ‘emergency’ bag in the drawer.

As discussed previously, if you are tired you should avoid too much caffeine on a routine basis, because this will increase your blood pressure and heart rate and can give you the ‘caffeine jitters’, making you anxious and irritable.

Because caffeine causes sleeplessness, it may encourage you to use sedatives (e.g. alcohol and sleeping tablets) after work to reverse the alerting effects.

This can lead to a cycle of increased caffeine use to drive alertness, followed by more sedatives to induce a state of unconsciousness, which prevents many of the benefits of natural sleep.


Melatonin is made mainly in the pineal gland, which is located in the centre of the brain and was considered by René Descartes, the French philosopher and scientist, to be the anatomical location for the soul.

The pineal gland is regulated by the body clock to produce melatonin; levels rise at dusk, peaking in the blood at around 2am to 4am, and then declining around dawn. Bright light, detected by the eyes, acts to stop melatonin production.

It’s significant that while in animals that are active in the day such as humans, melatonin production occurs at night during sleep, nocturnal animals (e.g. mice and rats) also produce melatonin at night when they are active.

And humans who do not produce melatonin — for instance, because they take beta-blocker pills for heart conditions — still have normal sleep and wake rhythms with only minor changes in sleep. So if melatonin is not a ‘sleep hormone’, what does it do?

The master body clock, the suprachiasmatic nuclei in the brain, has receptors that detect melatonin and so the night-time rise in melatonin may provide an additional signal to set the clock that’s already adjusted by light via the eyes (which detect sunrise and sunset).

Melatonin seems to tell the brain how long it has been dark, reinforcing signals from the eyes. However, the melatonin signal is not very strong, and the body clock will always respond to light in preference to melatonin, which may explain why the pills have little impact.

There are studies suggesting melatonin may help to reduce the time it takes to get to sleep and increase total sleep time, which is why it is sometimes prescribed on the NHS for sleep problems.

Yet while these effects on sleep are significantly better than a placebo (or dummy pill), in the majority of studies the effects were relatively minor, reducing the time it takes to fall asleep by around seven minutes and increasing the time spent asleep by around eight minutes.

And, of course, melatonin has been used as a treatment for jet lag. In most studies, but not all, melatonin was found to reduce the symptoms of jet lag in people crossing five or more time zones when it was taken close to the bedtime at the destination.

As with sleep, the overall effects were moderate, possibly due to individual differences in both the sensitivity to melatonin and the effects of jet lag.

The point is, for some people, melatonin is probably useful for jet lag and for others not at all.

For this reason, and because melatonin can cause sleepiness in some sensitive individuals, the general advice is not to drive or operate heavy or dangerous machinery for four to five hours after taking it. There are other important caveats: you need to be very careful about when you take it as doing so at the wrong time may confuse the body clock even more.

Potential difficulties with timing the dose is why long-haul pilots and crew (and others crossing multiple time zones repeatedly) are not advised to use melatonin.

In addition, if you or a close relative suffers from a psychiatric condition or migraine, you’re advised not to use melatonin as it may interfere with the mood centres of the brain and either exacerbate or trigger a mental health problem.