By news editor, on 12 June 2013
I usually succumb to three bouts of the common cold a year – once over Christmas, once during exams and the final wild-card infection usually manages to time itself to ruin a holiday.
Is that normal? Hundreds of people who wanted to know the answer attended an event at The Times Cheltenham Science Festival. Vivienne Parry, host of BBC Radio 4’s Am I Normal?, chaired a panel of researchers who investigate immunity.
Imagine, suggested Professor Arne Akbar (UCL Division of Infection and Immunity), that you are a pork chop left out in the sun. You might just smell a little on the first day. But over the course of a few days, you would begin to stink and turn to mush as your tissue broke down.
The difference between humans, who tan (or burn, like myself), and pork chops, which rot, is our living and active immune system. Its mechanisms detect and destroy germs and it keeps our body from degrading.
Microbes, which include viruses and bacteria, give us sniffles, cold sores and even have the ability to make some species suicidal. So it’s understandable that many people are easily convinced of the benefits of Vitamin C supplements, which purport to boost our ability to destroy microbes.
But Dr Joanna Sheldon said that there is no evidence that Vitamin C pills help. We shouldn’t worry about boosting our immune systems at all unless we begin to get serious or rare infections.
Some people, such as teachers and new mothers, are more likely to become ill with an infectious disease simply because they are exposed to more microbes. Even four or five colds a year doesn’t necessarily mean we have an abnormal or weak immune system.
Having a strong immune system doesn’t always act in our favour. As Vivienne Parry noted, many victims of the 1918 flu epidemic were healthy young men. Their immune systems went into overdrive and began to attack their own bodies.
These “cytokine storms”, which occur when the body is unable to tell the immune system to slow down, caused most of the fatalities of the 1918 epidemic.
Similarly, autoimmune diseases are all caused by an overactive immune system.
Coeliac disease and rheumatoid arthritis occur when the immune system doesn’t retire after attacking the alien microbes, but instead continues to mount more and more of an attack. When all of the invading cells have been destroyed, this eventually turns against our own native cells.
Striking a balance between too strong and too weak is like finding the elusive Goldilocks zone, but most of us do it quite easily. Dr Sheldon suggested that getting outside, sleeping well and eating fresh fruit and vegetables are the most important factors in having a healthy immune system.
Professor Rick Maizels of the University of Edinburgh explained that we shouldn’t stress about sterilising those fruit and vegetables.
First, stress damages our immune system’s ability to acquire resources and energy. Second, if we aren’t exposed to enough microbes when our immune system is developing, we might not be able to fend off attacks later in life.
This is the hygiene hypothesis and it may explain why allergies are becoming more common.
But even more importantly, those colds that I get three times a year are probably keeping my immune system nice and normal. Immune systems can get lazy if they don’t have anything to attack.
This could lead to worse reactions when we are eventually exposed to unwelcome microbes. It’s better to have the occasional mild cold than be unable to cope with a more serious strain.
The panellists concluded that there really is no such thing as normality for an immune system. Location, age, environment, diet, sleep and stress levels all affect what counts as normal.
One final bit of reassurance: the peak of infectious disease is in December. So if you, like me, suffer from sniffles on Christmas morning, that’s pretty normal.
Maeve McMahon studies on the MSc Neuroscience promgramme at UCL. She is currently researching the cerebellum in Professor Christopher Yeo’s lab in the Neuroscience, Physiology and Pharmacology Department.