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What happens to your body in cold weather?

Dr Adam Simon photo

Created: 3 November, 2016

Updated: 30 August, 2018

Autumn’s here, which means it's going to startMan running along pathway in autumn getting colder. It won't be long till you're scraping ice off your windscreen and wrapping the kids in 5 layers for their walk to school.

And while there’s plenty you can do to dodge the chilly conditions outside, did you know that your body has its own defence mechanisms too?

Many of them are designed to keep you healthy and functioning, even as your thermometer dips towards zero.

We’ll assume that most of you aren’t planning a trip to the Arctic Circle any time soon, so we can leave the frostbite and hypothermia to the explorers. Instead, let's just focus on what happens to you when it gets a bit nippy outside. You may want to invest in a woolly hat and gloves after this.

You start shivering

Shivering occurs even if your body falls as little as one degree below its usual core temperature, which is normally around 98 degrees. When this happens, a part of your brain called the hypothalamus lets your muscles know that they need to start moving in order to generate heat.

It’s essentially your body’s way of trying to warm you up. The colder your surrounding environment, the more energy your body needs to generate and the more vigorously you’ll start to shake.

So, while it can be tempting to try and suppress your shivering, it would actually be much better to let your body do its thing. Or buy a warmer coat. It’s up to you!

You’re more likely to get a virus

Let’s get this out of the way right now. Going out in cold weather is not going to give you a virus, like the common cold, even if you have wet hair.

However, research suggests that the viruses which cause colds and flu prefer chillier temperatures. A Yale University study found that animal test subject were much less able to fight off a virus if their core body temperatures was a few degrees cooler than normal. Indeed, it appears that when this happens, the body may not even notice that a virus is present.

On a much more basic level, when it’s cold outside, you’re more likely to spend time inside, where there are lots of other people. These people could easily be sneezing, coughing and generally doing all the things that can allow a virus to pass between people. As we know, protecting yourself in this situation is easier said than done.

Your joints and muscles ache

When your blood vessels constrict which causes that achy feeling, it means that blood isn’t getting to your muscles and tendons as quickly as normal. This is bad news if you’re sporty or regularly go jogging, as it affects your flexibility and increases your risk of suffering a sprain or pulled muscle.

Exercising indoors is one way to avoid this, but if you don’t want to give up your usual routine, you’ll just need to be extra careful with your warm-up to ensure your body is ready for the challenge ahead.

Cold weather also makes the fluid around your joints thicker, which could be one reason why arthritis sufferers may notice their symptoms more in colder months. There are lots of ongoing studies investigating whether the cold can increase arthritic pain, but none have reached a concrete conclusion as yet.

You get goosebumps

Goosebumps are a defence mechanism thatTwo people sat in front of a cosy fireplace humans have evolved over thousands of years to protect themselves against the cold.

When you get goosebumps, it causes the hairs on your body to stand on end. Many generations ago, when humans were much hairier than they are now, goosebumps helped to trap a layer of air around our bodies and form a protective insulating layer over the skin.

Of course, these days most humans have much thinner hair on their arms and legs, so while the goosebump reflex remains, it’s not really that useful any more.

Your blood rushes to your internal organs

As your surroundings get colder, your blood vessels narrow in order to keep as much warm blood as possible near the centre of your body. This helps your vital organs continue to function and, by moving blood away from the surface of your skin, your body loses less heat.

However, it also means that blood stops getting to your extremities, such as your fingers and toes. This is what causes them to turn white, a condition known as Raynaud’s Syndrome.

You can protect yourself against this by wearing gloves and warm socks, while you can also cut back on habits that affect your circulation, such as smoking. Even if you’ve left your gloves at home, you’ll soon return to normal once you’re back indoors.

You burn calories

Did you know that your body contains two types of fat?

You’re probably most familiar with white fat, which provides insulation for the body and a protective cushion for your organs. While it’s necessary for your health, we all know that too much of it can be harmful.

On the other hand, brown fat exists solely to burn calories and generate heat, a process that’ll start naturally if the weather turns chilly. You’ll be pleased to hear that it’s possible to turn white fat into brown fat by exercising.

Your brain chemistry is affected

As well as the cold, a feature of autumnal evenings is, of course, the sun clocking off early. Many of us will know the disappointment of leaving work in the dark, but did you know that this feeling is actually caused by a chemical shift in your brain? To find out what’s going on, we need to focus on two chemicals - melatonin and serotonin.

Melatonin is produced by your brain’s pineal gland, which is triggered by the onset of darkness. It’s designed to prepare you for sleep by making you feel less alert, allowing you to gently drift off when you need to.

During the colder months, when it’s dark before you even get home, your melatonin levels are high and it’s not unusual to feel a little sluggish even when there are still plenty of hours left in the day.

In contrast, serotonin is a neurotransmitter in the brain that has been widely linked to an improved mood and increased alertness. When the sun goes down, serotonin production decreases, meaning you’re more likely to experience a low mood and feel sleepy.

People who develop depression and become more irritable during autumn and winter may be suffering from a condition known as Seasonal Affective Disorder (SAD). If you notice any symptoms of depression, you should talk to a doctor about it, as there are plenty of treatment options available.

Need help looking after your health this autumn?

Whether you’ve caught a virus, are experiencing joint pain or worried about mental health issues such as SAD, our doctors are here to help. You can book an online consultation 7 days a week, and ask our experienced GPs as many questions as you like.

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Topics: Health and Wellbeing, Winter Health