What science says about common jet lag cures

First we thought 17- and 18-hour flights on carriers such as Singapore Airlines, Qatar, Qantas and Emirates were extreme. Now Qantas is testing 19-hour flights from Australia’s east coast to London and New York. The aircraft can manage it, but what about the passengers?

If you’re a frequent long-haul flyer you’ll be familiar with the costs of jet lag. It disrupts your whole body, producing indigestion, hormonal changes, irritability, poorer performance, dehydration and fatigue. 

So after a long flight you don’t want to waste your diminished energy on remedies that might not work. Here’s what the science says about these popular jet lag cures.

Exposure to light resets your clock

True. In fact, the highly regarded journal Nature lists light at the very top of your arsenal against jet lag. A 2013 analysis concluded: “Most research suggests that light exposure is by far the most important determinant of rhythms driven by the suprachiasmatic nucleus [your brain’s central timekeeper].”

Going for a walk at your destination and soaking up some sunlight can help keep the fuzzies at bay.

So yes, this is your official reminder to get out in the sunshine at times you’re meant to be awake.

As well as shifting your circadian rhythm or internal clock, it also brings immediate benefits. Daylight will help you think more clearly and feel better during the day, and also sleep better that night. 

The colour of the light is important

True. Modern worries about our exposure to blue light at night are not just a fad. Your body’s light sensors, which influence the timing of your circadian rhythm, are most sensitive to blue light. In contrast, red light is less likely to muck around with your internal sense of time. 

Newer lights like compact fluorescent lightbulbs and LEDs emit more blue light than other fittings. Consider packing a red or orange night light. Switch it on, and the hotel lights off, for two to three hours before bed. 

In the evenings, aim to minimise time in front of digital screens (TVs, laptops, smart phones and tablets). Or at very least, use the device’s night setting, which creates a warmer-coloured screen. You can even buy blue-blocking glasses, which have orange lenses.

Flights of up to 19 hours' duration are set to test the resolve of even the most frequent flyers.

Light on the back of your knees resets your body clock 

False. Exciting research in 1998 suggested light on the back of your knees also affects your sleep-wake cycles. Don’t bother walking around outdoors with your trousers rolled up – these findings have been well and truly debunked.

You should retrain your body clock before you go

Sometimes true. For longer stays of three days or more, prestigious medical journal The Lancetrecommends you switch to the new time zone.

You can start adjusting your schedule beforehand (with the guidance of an app). During the flight, plan your eating and snoozing times accordingly. For shorter visits,stay on home time. You’ll simply do your best to sleep and work at the times you would at home. 

Consider carefully the effects that blue light from a computer or device may have upon your sleep pattern.

Melatonin will make you nod off

True, but you should probably get a prescription. 

In 2002, a rigorous Cochrane review of the research to date found melatonin can be useful for treating jet lag. If you’re crossing five or more time zones, taking 0.5 to 3 milligrams two hours before your desired bedtime can help signal your body that it’s time to sleep.

But be wary if you buy melatonin online. A 2017 Canadian study found huge variability in the quality and purity of over-the-counter melatonin. Shockingly, the content varied from about 80 per cent less to 480 per cent more than what the label said. Melatonin isn’t sold over the counter in Canada any more. Likewise, you’ll need a prescription to buy it from pharmacies in the UK and Australia. 

Jet lag is the main reason you’re so tired

Not necessarily. Messing with your body clock certainly does cause fatigue. But it’s hard to separate jet lag from the other reasons you feel lousy after long flights. Don’t forget garden-variety sleep deprivation, as well as the dehydration, low air pressure and reduced oxygen on board.

Even before you take off, you might be suffering ill effects of chronic “social jet lag” from home. For example, when night owls have 7am meetings then doze to noon on the weekend, it interferes with their natural sleep and wake times. Healthy sleep habits at home help you avoid bringing a pre-existing sleep debt when you travel.

A hot bath helps you sleep

True. Sleep comes with a slight drop in body temperature. About two or three hours before bed, you can try using exercise, a hot bath (rather than a shower), or the sauna to raise your body temperature. Then ensure your room is relatively cool – between 15C and 19C – to facilitate the drop in body temperature.

Also read: Seven expert tips for getting into the inflight work zone

Louise Wedgwood

Louise Wedgwood is a Brisbane-based 'science-savvy' health and lifestyle writer.