Are mealtimes the answer to jetlag?

The Daily Telegraph reported today that avoiding airline food during long haul flights, and eating on arrival, could help beat jetlag. The newspaper suggested that although it has long been thought that light was the key to setting our body clocks, with mealtimes having a lesser effect, a new study has found a “‘food-related clock’ that can override the ‘light-based’ master clock when we are hungry”.

Scientists knew before this study that the presence or absence of food could override the effects of light on our body clocks. The study that this report is based on did not discover this phenomenon, but instead identified a specific part of the brain in mice that is involved in the effect of food on circadian rhythms.

Although there is a suggestion that jet lag could be beaten by timing food intake to affect the body clock; the study did not investigate this. Further studies would need to investigate this theory to establish if it were true or not.

Where did the story come from?

Dr Patrick Fuller and colleagues from Harvard Medical School carried out the research. The study did not report sources of funding and was published in the peer-reviewed journal: Science .

What kind of scientific study was this?

This laboratory study looked at how circadian rhythms are controlled in mice. Circadian rhythm is essentially an organism’s pattern of activity and follows a cycle of about 24 hours. One gene known to be involved in this process is Bmal1 , and mice that lack this gene don’t have set circadian rhythms. The light-dark cycle usually has a strong effect on circadian rhythms, with so called “diurnal” animals active in the light and asleep in the dark, and the opposite true of nocturnal animals. However, when food is scarce, animals’ circadian rhythms will be reset so that they are active when food is available, regardless of the light-dark cycle.

The researchers wanted to investigate whether different areas of the brain are involved in these processes, and they did this by reintroducing the Bmal1 gene into different areas of the brain of mice that were lacking Bmal1 . To do this, they first injected the Bmal1 gene into the suprachiasmatic nuclei (SCN) of the hypothalamus; the SCN are known to be involved in synchronising the circadian rhythm with the light-dark cycle.

The other area that the Bmal1 gene was injected into was the dorsomedial hypothalamic nucleus (DMH), an area that has been suggested to be involved in food’s affect on circadian rhythms.

The researchers looked at what effect reintroducing the Bmal1 gene into these different regions had on the mice’s circadian rhythms and whether they responded to the light-dark cycle and food availability.

What were the results of the study?

The researchers found that introducing the Bmal1 gene into the two different areas of the brain appeared to produce opposite effects.

When they introduced the Bmal1 gene only into the SCN of the hypothalamus, the mice regained circadian rhythms that could be set by the light-dark cycle, but not by the presence or absence of food.

Conversely, when they introduced the Bmal1 gene only into the DMH, the mice regained circadian rhythms that could be set by the presence or absence of food, but not by the light-dark cycle.

What interpretations did the researchers draw from these results?

The researchers concluded that they had identified the region of the brain (the dorsomedial hypothalamic nucleus) that was involved in the setting of circadian rhythms in response to food.

What does the NHS Knowledge Service make of this study?

This study furthers understanding of how different areas of the brain are involved in setting the body’s circadian rhythms. Although, the results of this study could be useful in the long term in tackling human problems such as jet lag, they do not immediately suggest any preventative measures.

The fact that the body clock can be affected by timing of food intake does suggest it might be possible to use food to help beat jet lag. However, randomised controlled trials will be needed before it’s possible to draw any firm conclusions about this theory.