Michael Mosley
Is it possible to beat jet lag?
This summer, lots of people will be jetting off to exotic countries and passing through multiple time zones. I’ll be one of them. The trouble is, I spend far too much of my life doing this, mainly while making documentaries. So I am, naturally, obsessed with jet lag.
Jet lag is caused by a mismatch between external time cues (the Sun is rising, it must be morning) and our internal, circadian clock. The circadian clock plays a vital role in regulating a range of things, such as your sleep/ wake cycles, and which hormones get secreted and when. Jet lag, which messes with your circadian rhythm, can do some pretty awful things to your body and your brain. It not only makes you feel knackered, but lots of long-distance travel can trigger sleep disorders and encourage obesity.
New research suggests that one way it does this is via the microbiome, the one to two kilograms of microbes that live in your gut. To demonstrate the impact that jet lag can have on the microbiome, Dr Eran Elinav and Dr Eran Segal from the Weizmann Institute asked some of their students to fly across multiple time zones. They were asked to collect a faeces sample before they got on the plane, another when their jet lag was particularly bad and a final one two weeks after that.
The researchers cultivated these samples and transferred the microbes into mice, specially raised to have bacteria-free guts. The impact was dramatic. As Elinav enthusiastically informed me, “the mice that received the microbes from jet-lagged students grew obese and developed diabetes. Those that were given bacteria from samples taken before or after the jet lag set in were unaffected.”
The moral is, try to avoid flying across lots of time zones. But if you can’t, what should you do? Well, since your gut bacteria seem to play a role in regulating your circadian rhythm, you could try, before you fly, changing mealtimes so they fit in with your new destination. If you are flying to the US, consider having breakfast five hours later than normal.
A University of Surrey team recently did this with 10 volunteers. They found that some of their circadian rhythms were delayed by roughly five hours, suggesting that altering mealtimes had partially reset their body clocks.
Then there’s melatonin. This hormone, produced by the pineal gland, helps prepare the body for sleep. While it’s only available on prescription in the UK, you can buy it at any pharmacy in the US as a supplement. A Cochrane study (when it comes to evidence-based medicine they don’t come much better) said: “Melatonin is remarkably effective in preventing or reducing jet lag, and occasional short-term use appears to be safe. It should be recommended to adult travellers flying across five or more time zones, particularly in an easterly direction, and especially if they have experienced jet lag on previous journeys.” I find it helpful, particularly on overnight flights and for the first few days in a new time zone.
I use light to adjust my internal clock, too. When I arrive at my destination after flying east, I avoid early morning light and seek out afternoon light for a couple of days. This is known as ‘phase advancing’. When going west, I do the reverse. Anything to keep my microbiome happy!
The microbiome seems to return to normal two weeks after a long-haul flight, but frequent flyers could find the disruptions become chronic.