Does going on holiday help boost the immune system?
"Prescribing holidays 'could help fight infections'," BBC News reports, while the Mail Online claims holidays can "turbo-boost" the immune system. But the news isn't quite as conclusive as it sounds.
It comes from a study where two groups of mice were housed for two weeks in two different types of housing: standard housing consisting of a cage with sawdust and nesting material, or an "enhanced environment".
The enhanced environment saw better bedding, wheels, toys and activity tunnels added to the cage. According to the lead researcher, this was akin to "put[ting the mice] in their equivalent of a holiday resort".
The researchers wanted to investigate whether an enhanced environment resulted in changes in mouse behaviour and the composition of white blood cells used to fight off infection.
No differences were seen in the behaviour of the mice – and no major changes were seen in their immune cells.
More in-depth analysis revealed differences in certain inflammatory molecules, suggesting a possible effect on T helper cells, which regulate other immune cells.
But we're not biologically identical to mice – even if the arguably modest effects on immunity were the same in humans, we can't say these changes would result in an improved ability to fight infections.
You're unlikely to get two weeks in the Caribbean on an NHS prescription any time soon.
But you can take steps to enhance your own environment and boost your mood, which could help you cope better with the coming winter months.
Get tips on five ways to stay healthy this winter.
Where did the story come from?
The study was carried out by researchers from the Barts and The London School of Medicine and Dentistry at Queen Mary University of London, and Imperial College of Science, Technology and Medicine at the University of London.
The study did not receive any grant funding.
It was published in the peer-reviewed journal Frontiers in Immunology on an open access basis, so it is freely available to access online.
Both BBC News and the Mail Online provided balanced coverage of the study. However, both talk about the prospect of doctors "prescribing holidays" to help people recover from illness.
This seems a jump too far just based on this research, which is in its early stages and only provides rather inconclusive findings in mice.
What kind of research was this?
This animal study in mice aimed to see whether changes in their housing conditions would alter their T immune cells, a core part of the human immune system.
This builds on recent research, which suggests immune cells alter their form and function in response to environmental changes, such as pollution, geographical location and social status.
Animal research is a useful starting point for understanding biological processes that may be similar in humans.
However, we are not identical to mice, and the experimental scenarios may not be representative of real life in humans.
What did the research involve?
The study involved six-week-old male mice, who were housed for two weeks in groups of five in either standard housing conditions or an enhanced environment.
The enhanced environment was intended to provide an enriched multisensory environment for the animal, rather than just the standard lab cage.
The mice were provided with various nesting materials rather than just sawdust, as well as a nest box and a tunnel, wheel and swing. This equipment was replaced with new toys after one week.
The mice were weighed weekly and had a series of behavioural tests every second day. This included assessing their exploration and anxiety in an open field test, and their repetition and perseverance in a marble-burying test.
Mice that spend much of their time digging for marbles are thought to be displaying obsessive compulsive-type behaviour, which could be caused by underlying anxiety.
The researchers also obtained samples of immune tissue from the lymph nodes, spleen and thymus gland to assess the composition of T immune cells.
What were the basic results?
The researchers found no significant differences in mouse behaviour on either the open field or marble tests.
Also, despite expectations, they found no major changes in the composition of the T cells. There were no changes in the total number of lymph node or thymus cells.
There was a very minor 5-10% increase in the number of a particular T cell (CD3) in mice in the enhanced environment, but no changes in other T cells.
The researchers then stimulated the T cells in the laboratory by culturing them with antibodies.
They found no differences in any of the inflammatory molecules, with the exception of interferon-gamma.
Levels of this inflammatory molecule were about two times lower in those from the enhanced environment.
This suggested a possible effect on the production of T helper cells, which regulate other immune cells.
Further analysis of T helper cells – again, stimulated with antibodies – confirmed that samples from the enhanced environment produced lower levels of interferon-gamma and higher levels of two other molecules: one possible inflammatory (interleukin 10) and one anti-inflammatory (interleukin 17).
Further genetic analysis showed changes in the gene activity of the different groups of mice, with immune signalling pathways being modified.
How did the researchers interpret the results?
The researchers said their results "provide first evidence for a specific effect of [enhanced environments] on T cell differentiation and its associated changes in gene expression profile.
"In addition, our study sheds new light on the possible mechanisms by which changes in environmental factors can significantly influence the immune response of the host and favour the resolution of the inflammatory response."
Conclusion
Though an interesting experiment, this mouse study has limited applicability to humans. It certainly doesn't prove that going on holiday will boost your immunity and make you better if you're unwell.
There are a number of points to consider. For one thing, even in mice the results weren't demonstrative. The enhanced environment had no effect on mouse behaviour and there were no major changes to their immune cells.
It was only on further analysis that the researchers found differences in specific inflammatory molecules.
This means we don't know whether this would translate into real differences in the mice – for example, differences in their lifespan or propensity for certain illnesses, inflammatory conditions or cancers.
We also don't know whether these effects would be sustained if the mice stayed in the enhanced environment, or if they would be reversed if they switched back.
Although we have some similarities to mice, human biology is not identical – we can't conclude that exactly the same effects on T helper cells would be seen if we lived in "standard" or "enhanced" stimulatory environments.
And spending time in an enhanced environment with wheels, toys and better bedding doesn't automatically translate into the equivalent of a couple of weeks' holiday for a human being.
Even if a holiday did temporarily alter specific inflammatory molecules in the same way for us, we don't know if this would make any difference to our ability to fight illness or chronic disease.
The study also only included male mice – do the findings extend to females, whether they're mouse or human?
Nevertheless, most of us know that a break can do us good. It is certainly possible that the effects of relaxation and improved wellbeing could extend to effects on our immune system as well, but this hasn't been proved by this study.
Read more about how to improve your sense of wellbeing.
