Changing mealtimes 'could help beat jet lag'

2nd June 2017 – Changing meal times may hold a key to overcoming some of the debilitating effects of jet lag, scientists are suggesting.

A team from the University of Surrey say it could also help shift workers cope better too.

Body clocks

The human body keeps time to a roughly 24-hour cycle – known as a circadian rhythm – that is controlled by a so-called 'master' clock in the brain and 'peripheral' clocks in other areas of the body.

A small study in the journal Current Biology has found that at least 1 of these peripheral clocks – which governs the circadian rhythm of sugar in the blood – can be reset according to the time we eat breakfast, lunch and supper.

"The problems that we have when we have jet lag is that our clock system becomes desynchronised," explains Jonathan Johnston, who led the research. "So, you turn up in any time zone and suddenly your body clock is anything between 5 and 10 hours out of synch.

"When you reach that new time zone, we think that the master clock in the brain, which is sensitive to light information, will reset that new time zone quite quickly, but there's a lag between your master clock realigning to the new time zone and your peripheral clocks realigning to that new time zone."

Laboratory tests

To test the effect of changing meal times on the body's clocks, the researchers enrolled 10 healthy young men to take part in a 13-day laboratory experiment.

At the start of the trial, the volunteers were given their first meal half-an-hour after waking. Later meals were provided at 5-hour intervals. In a second phase, the men had to wait 5 hours for food after first waking and subsequent meals were also served up 5 hours later.

Immediately after each phase, blood samples and fat biopsies were taken from each volunteer so that the researchers could measure their bodies' internal circadian rhythms – the 24-hour changes governed by the body's internal clocks.

Blood sugar levels

They found that postponing meal times by 5 hours delayed rhythms of blood sugar by the same amount of time. This allowed the researchers to conclude that mealtimes synchronise internal clocks that control rhythms of blood sugar concentration.

"As we predicted, the master clock wasn't reset by the food," says Jonathan Johnston, who suggests that liver changes may be responsible for the effects seen.

"The liver is of course extremely important in terms of blood sugar control," he says. "It's known from animal studies to be one of the most sensitive clocks to meal timing. So, our speculation would be that the effects we've seen are probably due to the liver clock and possibly with that interacting with other peripheral clocks as well."

Flying east or west

The researchers say that people who struggle with circadian rhythm disorders, including air travellers who take long-haul flights across different time zones, as well as shift workers, might consider timed meals to help resynchronise their body clocks.

"If we can use something like feeding time to help reset these peripheral clocks, then that will hopefully help them to catch up more quickly with the new time zones," says Jonathan Johnston.

The basic principle suggested by the researchers is that air travellers flying westwards, such as passengers heading from the UK to the US, should consider delaying meal times in the run up to their flight, while people flying in the opposite direction should adopt an earlier eating pattern.