Does Running Strengthen Your Immune System?

Everywhere we go, we’re surrounded by viruses, bacteria and fungi that could do us harm. Fortunately, our immune systems are continually scanning for these potential threats, and they spring into action the moment they encounter a pathogen (something that can cause disease). 

If you run regularly or are just thinking of getting into the sport, you may have heard mixed messages about what running can do to your body’s natural defences. Does running strengthen your immune system, or could it in fact weaken it? Let’s look at what the evidence says. 

What is your immune system?

Your immune system is your body’s protection against microbes that could do you harm. 

Your first line of defence is your skin. For anything you eat, the strong acids in your stomach help prevent germs getting into your bloodstream. In your nose and mouth, there are mucous membranes which also trap bacteria and stop them getting further. 

If a pathogen manages to get past these defences and enters your blood, the next layer of your immune system comes into play. This consists of several different kinds of white blood cells which are constantly circulating through your veins and organs. If they encounter a virus or bacteria, they ‘swallow’ them up and destroy them with chemicals. There are also numerous other kinds of immune system cells which are produced in different parts of your body. 

There is, of course, much more to how the immune system works. For an in-depth overview, the Patient.Info website provides further detail. 

Does running help your immune system? 

Yes, there is an enormous amount of evidence that running - and other kinds of exercise - is beneficial for the immune system. 

For example, a study in the United States compared active people versus sedentary people for 12 weeks. The active people had 43% fewer days with an upper respiratory tract infection (that is, a cold) than people who weren’t active. That’s fairly compelling evidence that doing aerobic exercise like running seems to boost your immune system. 

Looking at the cellular level, one study found that elderly people who had cycled regularly for  most of their lives had much higher levels of naive T cells (part of the immune system) than people who hadn’t regularly exercised. What’s particularly interesting, is that the immune systems of the cyclists were found to be as healthy as inactive people who were 20 years younger than them. 

More broadly, a study of life expectancy in Finland found that former professional athletes lived almost six years longer than other people. There’s several reasons why this might be the case (such as healthier hearts or avoiding diabetes), but it suggests that their immune systems were also in good working order thanks to all the exercise they’d done.  

Generally speaking, studies that find a positive link between exercise and an improved immune system function have looked at people who do moderate exercise and for shorter times (generally 90 minutes or less). There is debate among experts about whether longer and more intense exercise can temporarily make the immune system weaker (more on this below). 

Why does running boost your immune system?

There’s clearly plenty of evidence that exercise like running can improve your immune system. But why does working out make your body’s natural defences stronger? There’s no single explanation, and it’s probably a combination of factors coming together. 

Exercise increases blood flow

When you lace up your running shoes and start your workout, your heart rate will increase and blood starts to flow faster around your body. As your blood is circulating more rapidly, your white blood cells may therefore discover pathogens sooner and neutralise them before they can multiply. 

Short and long term immune system cell production

Studies have found that even short, 10 minute bouts of exercise seem to ‘trigger’ the body to produce immune system cells such as T cells (which help combat pathogens) for up to 30 minutes after exercise. Over the long term, regular exercise seems to ‘train’ your immune system to be better at spotting germs and responding to them too. 

Stress management

Scientists have found strong evidence of a link between stress and poor immune response. People who experience acute and long term stress have higher levels of proteins called cytokines in their bodies. The good news is that dozens of studies have found that people who run regularly have lower levels of stress.

Vitamin D

Vitamin D plays an important role in supporting a healthy immune system. And one of the best places to get Vitamin D is by getting outdoors. Our bodies naturally produce Vitamin D when we’re exposed to sunlight, and so running outdoors means you may have higher levels of Vitamin D in your body. 

Does running weaken the immune system of distance runners?

For many years, there has been debate among scientists (as well as coaches and runners) about whether running extremely long distances could temporarily weaken the immune system. 

Experts and runners have long observed that people who regularly participate in marathons and similar distance races seem to get colds more often than others. 

An important study in 2007 found that in the days after a marathon, runners’ immune systems seem to become suppressed. Several key immune system cells are found in lower numbers in the blood for up to 72 hours after a long distance race. The researchers hypothesised that this leaves an ‘open window’ for pathogens to enter the body and cause colds and other illnesses which might otherwise be caught earlier by the immune system. 

However, a more recent study from 2018 countered this ‘open window’ theory. The researchers argued that while it’s true that immune system cell blood levels seem to go down after lengthy exercise, they don’t actually disappear. Instead, they move to our peripheral tissues (such as our mucous membranes) where pathogens usually enter our bodies. This suggests that these immune system cells are in fact being extra vigilant after long distance running - and they’re not being suppressed. 

There could be other explanations for the correlation between catching a cold and running in a marathon:

• Exposure: People running in marathons and similar races are surrounded by thousands of other people while breathing hard. This could increase their chance of exposure to viruses. Similarly, if you are often travelling by bus, train or plane to marathons, there’s more chance of exposure to other people’s coughs and sneezes. 

• Poor sleep: It’s not uncommon to sleep badly both before and after a marathon. A combination of nerves, anxiety and adrenaline can make it harder to nod off - but quality sleep is vital for a strong immune system. 

• Nutrition: Our immune systems rely on good nutrition. But during long distance races, we use up far more energy than usual. This could leave the immune system struggling to keep up. 
  

What does this all mean for running and immune system health?

There is a pretty clear consensus among scientists that moderate exercise such as running benefits the immune system. Even a short, one-off jog can help, but the real benefits come from regular, long term exercise. 

And, while some researchers suspect that long distance running could possibly suppress the immune system, this would still only be a temporary issue (up to 72 hours after the event). 

As the Finnish study mentioned above shows, former elite athletes - many of whom would have taken part in endurance events like marathons - live significantly longer than other people on average. This would suggest that taking part in long distance races isn’t a serious cause for concern when it comes to a healthy immune system.

Tips for running and immune system health

While most research shows that running does boost your immune system, there are several things you can do to help your body stay in top form and avoid the risk of unwanted colds. 

Rest between runs

Your body needs time to rest between runs in order to repair small amounts of damage in your muscles, tendons and ligaments. Depending on your running routine or training schedule, you should have at least two or three rest days per week where you do little or no exercise. This gives your body the time to recover and means your immune system will be ready to handle any threats. 

Focus on your sleep

Poor sleep can lead to a run down immune system. Everyone’s different, but aim to get between seven and eight hours of sleep per night. Follow good sleep hygiene practices, such as:

• Not looking at your phone in bed. 

• Going to sleep around the same time most days. 

• Making your bedroom quiet, dark and peaceful. 

• Avoid drinking stimulants like tea or coffee for at least four hours before bed (but preferably longer). 

• Reduce alcohol intake. 
  

Avoid pathogens

It’s not always possible to avoid catching a cold - you could be waiting in the starting zone of a half marathon and someone near you sneezes. All the same, simple hygiene best practice can reduce your risk of exposure. Wash your hands with soap regularly, avoid rubbing your eyes, and don’t share cups, cutlery or bottles with people who have a cold. 

Eat well

Eating a nutritious, balanced diet is important for normal immune system function. But it’s particularly important if you run regularly or take part in endurance races. For runners in particular, experts recommend that you have an effective nutritional strategy and increase your intake of carbohydrates and vegetables. 

Stay warm

Becoming too cold can reduce your immune system’s ability to respond to threats. If you exercise in cooler weather, it’s a good idea to wear appropriate clothing. Choose specially-designed cold weather running clothes that provide adequate insulation, while allowing air to circulate so you don’t get too hot. Staying dry when running in the rain will also prevent you from getting too cold. A water resistant rain jacket is essential, while water resistant shoes can also help avoid discomfort. 

Should you run if you’re ill?

When you’re ill, your immune system is working hard to fight off the pathogen and using energy to do so. So, as a rule of thumb, it’s best not to do exercise when you feel sick. You’ll use up lots of energy when running, and that could slow down your recovery. 

That being said, it may be OK to run with a cold after doing the ‘neck check’. If the symptoms are in your neck or above, then it’s normally fine to do some light exercise. But if they’re below the neck, rest in bed instead:

• Above the nex: If you have a blocked nose, runny nose or sore throat, going for a run is OK.

• Below the neck: If you have a tight chest, high temperature or aching muscles, stay in bed and rest. 

Read more:Advice for running with a cold

For other kinds of illness - from heart conditions to cancer to high blood pressure - it’s best to seek out medical advice before going running. 

Can you run if you’re immunocompromised?

Many people have weakened immune systems due to a variety of conditions. If you are immunocompromised, always speak with your doctor before starting a new exercise regime. 

That being said, running in and of itself shouldn’t pose a problem to many people. The sport is often done outdoors and can be done alone. This reduces your chances of exposure to pathogens. If you prefer to run on a treadmill at a gym, you may want to wear a face mask, visit at quieter times, and take care to wash your hands with sanitizer after finishing your workout. 

So, does running strengthen your immune system?

For most people, running does appear to boost their immune systems. And the more you do it, the greater the long term benefits for your body’s defences seem to be. 

It’s true that there is some evidence that long distance running may temporarily suppress the immune system, but other experts dispute this theory. In any case, the potential negative effects are short term in nature. 

And it gets better. Not only does running boost your immune system, it’s also been shown to have plenty of other benefits too. From improving mental health to boosting physical fitness, running is undoubtedly a positive activity for most people. 

Want to experience all these benefits of running, but aren’t sure where to start? Read our introduction to running to take your first steps.