Why we get ill in winter

Why do we tend to get ill in winter?

Dr Jenny Goodman: Partly, the answer is simply because it’s cold, and when it’s very cold that makes us more vulnerable. And we are going from very warm heated houses out into the freezing cold. When our grandmothers said ‘be careful you’ll catch your death of cold’ - they were actually not wrong. But there are two other very important reasons.

One is that we’re not living as though it is winter. When its winter, normally people go out and about just as much as they do in the summer, but actually the way we’re programmed is to play and party outdoors in the summer and to hibernate in the winter. And what we need to be doing is staying at home, hiding under the duvet, building a fire, hunkering down and doing about ¼ as much activity.

It’s partly that winter is inherently riskier because it’s cold and damp, but it’s more because we ignore that. I’m not only talking about ignoring the temperature, I’m talking about day and night and light and dark. We have a pineal gland in our brain that registers light, and when it sees blue light it thinks ‘that’s the summer light go out and play’, of course a blue screen simulates that. When it’s dark we make melatonin, so when it’s 5pm in the middle of January we should already be at home and getting ready for bed really as it's dark, and that's what our bodies are designed to do.

So, we’re going against that rhythm all the time because of the way post-industrial life is organised. And we have limited choice about that - but we have some. We can at least be aware that when its dark, nature is telling us to stay home and rest, and when its light, nature is telling us to go outside and party.

Dr Jenna Macchioci: Another reason is the lack of sunlight (UV light influences the survivability of many viruses). And a lack of sunlight makes us more likely to be vitamin D deficient which is a key immune nourishing hormone-vitamin, reducing our capacity to fight infections.

The lifestyles we lead in winter tend to mean that we huddle closer together (easier for viruses to pass from one person to another), and stay indoors more which means potentially we get less exercise, sunlight, exposure to green space and vitamin D.

What causes winter blues and Seasonal Affective Disorder?

Dr Jenny Goodman: We get winter blues and Seasonal Affective Disorder, for two reasons.

One is a lack of Vitamin D - because even if you got plenty from the sunshine over the summer, it will have run out by November.

And the other is lack of light to the pineal gland, and we need to get that light through our eyes (and if you wear glasses you have to take them off because it doesn’t get through glass!). What I would say is that in the depth of winter when there's only 6-8 hours of daylight, you must get outside during that time of day and get some light.

Are colds caused by the cold weather?

Dr Jenna Macchioci: Even the word influenza holds a clue since it means influence of the cold ('influenza di freddo'). It's a common misconception that colds and flu are caused by colder weather. This is not quite true. These seasonal illnesses are caused by viruses. Cold temperatures simply create the conditions that make it easier for these viruses to spread. Survivability and transmission of many seasonal viruses occurs easier in cooler temperatures (we still don't know if this is true for Covid).

Key takeaways

1. Get outdoors during the day for your exercise and sunlight
2. Eat plenty of nutritious fruit and veg, and also supplement with Vitamin D
3. Pay attention to when it’s light and dark and adapt your behaviour accordingly.