Topic letter 27

Holiday flu

Did it ever happen to you, falling ill at the onset of your holiday? Just when you reach the moment that you are finally free, your body lets you down. Is this a coincidence or is there a connection between the two? With recent knowledge about stress, we can ascertain that there actually is a relationship. This research and some general issues about stress are the subjects of this topic letter.


Let's start with the question of the impact on our systems of tension and relaxation. In order to fully address this question we have to travel back in time. Our ancestors survived because they could respond adequately to the demands of their environment. If they encountered demanding challenges, their level of readiness increased, allowing them to react immediately at any time. Without any pressing urgent concerns, they would switch back to a comfort zone. A high level of readiness was associated with using a lot of energy and since food was scarce in those days, the fact that our ancestors survived and reproduced themselves, shows that they were able to maintain a constant optimal level of tension. Although we live in a totally different world, we inherited the ability to adjust our level of readiness to the demands of the environment.


This alignment is reflected in many ways. If the perceived demands increase, our brain cells literally start communicating with each other at a higher pace. We experience raised blood pressure and increased heart rate. The level of sugar in our blood increases. The blood vessels in our muscles dilate and ensure that the enriched blood can reach even the smallest capillaries. At the same time, the large blood vessels in our abdomen are pinched. In the heat of battle, food digestion has low priority. That's the reason why we can suffer from stomach problems during periods of prolonged stress.


All these processes are regulated by a series of hormones of which adrenaline and cortisol are the most important. Adrenaline has a longstanding and steady effect; cortisol works only briefly and gives a short-term additional boost. That's why cortisol is sometimes called the stress hormone. What we call stress is actually an indication of operating at the higher end on the scale of readiness. It is a very healthy and necessary tool that allows us to cope with the challenges in our lives.

Bad reputation

Stress has earned a bad reputation due to the fact that it sometimes takes quite some time to normalize the levels of readiness. Long after high demands are met, stress remains. People who suffer from stress, typically say that they no longer are able to organize their lives sufficiently to enable themselves to recover after any exertion. Their minds are already preoccupied with the next challenge and the system never comes to rest. Above all, an excess of cortisol infects and damages the brain. In time this can lead to burnout.

Immune system

This however, does not explain the likelihood of falling ill during a holiday. For that we once more have to go back in time. Our ancestors experienced their greatest stress at moments in which they easily could get injured. A wild beast fighting for its life could rain blows upon them. At such moments, the extra activity of the defense system was no luxury. This principle still stands today. A higher level of readiness is associated with a higher activity of our immune system. That's the reason why people who thrive on dealing with demanding challenges are seldom sick.


And then there is that holiday. We can see it from afar and we change up a gear to complete all the loose ends before we leave. Even if we are infected by some kind of virus or germ, it cannot harm us due to the heightened resistance. But as soon as we arrive at our holiday destination, the whole system, including our immune system, normalizes again. Even before we have unpacked our suitcases, the latent germs grab their chance and strike as hard as they can. They are the only ones who don't take a vacation.

I wish you pleasant and above all, healthy holidays

Juni Daalmans

July 2013

Brain Based Safety


More information on brain based safety can be found on and in the book "Human Behavior in Hazardous Situations. Best Practice Safety Management in the Chemical and Process Industries." 2012 Elsevier

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