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What weakens the immune system: 5 important factors

24 September 2021|3 min read

Key points on what may weaken the immune system

  • Vaping can have a negative effect on the immune defences of the upper respiratory tract
  • Excessive alcohol consumption may leave you more susceptible to illness
  • The immune system relies on adequate nutrition to function properly  
  • Chronic stress may weaken the immune system
  • Too much exercise may negatively impact the immune system

If you’ve ever wondered what weakens the immune system – whether it's genetics, lifestyle or other factors – we may have the answers you’re looking for. It does seem like some people get sick quite a lot, whereas others manage to escape all the lurgies that go around.

GP, Dr Jill Gamberg, says that while there are some genetic immunodeficiencies, they aren’t actually all that common. 

“I’ll often see patients who are wondering why they get sick all the time. They want to know if there’s something wrong with them. But the reality is if you’re exposed to a virus and if, for whatever reason, your immune defences are low, it’s normal that you may get sick,’ Dr Jill says. 

So, what weakens your immune system? Dr Jill shares her insights into five common factors that may play a role in your immune health. Get ready for some interesting facts about the immune system!

1. Can smoking weaken your immune system?

It’s probably no surprise that being a non-smoker is better for your health. Smoking puts you at risk for a range of health issues, including respiratory conditions, heart disease and diabetes. 

Research has also shown that smoking tobacco may have negative impacts on your immune health. 

“I think it’s quite clear that smoking is bad for us,” says Dr Jill, “But one other thing that we should be talking about is vaping. Many people think that vaping is better than smoking but there is more and more research coming out to show that this isn’t the case. Vaping can lead to various lung conditions, many serious.”

In fact, research shows that vaping and e-cigarettes can also have a negative effect on the immune defences of the upper respiratory tract. 

2. Does alcohol weaken the immune system?

While the evidence on smoking is more clear-cut, it’s not as straightforward for alcohol. 

“Everyone is different but the first thing to say about alcohol is that you should certainly follow the Australian alcohol guidelines. That is, for adults aged 18 and over you should have no more than ten standard drinks a week and no more than four standard drinks on any one day. People who are pregnant or breastfeeding should not drink any alcohol, according to the guidelines,” Dr Jill advises.

The reality is if you’re exposed to a virus and if, for whatever reason, your immune defences are low, it’s normal that you may get sick

- Dr Jill Gamberg, GP

Dr Jill also notes that it’s important for people to consider how alcohol makes them feel. If alcohol is negatively affecting you, that’s not ideal.

Of the impact of alcohol on the immune system, the research says that excessive alcohol consumption may have a negative effect and leave you more susceptible to respiratory illness, infections and impair your recovery when you are trying to get well. 

So, if you’re worried about alcohol potentially weakening your immune system, think about reducing your intake.

3. How does diet affect your immune system?

The immune system relies on adequate nutrition to function properly. According to Dr Jill, this means eating a balanced diet of whole foods. 

“If you eat too much food, it’s probably not good for you. Likewise, if you eat too little, it’s also probably not good for you,” explains Dr Jill, “Anything that’s extreme is probably not good for us. You should be aiming for a varied, whole food, plant rich diet with less processed foods and only occasional discretionary (sometimes) foods and drinks. This is the best thing you can do is be kind to yourself and your body.”

4. How stress may weaken the immune system

On the subject of mental health and the immune system, Dr Jill says we should try to manage our stress effectively with physical activity, rest, mindfulness and meditation.

That’s not always possible, and in these cases, it’s important to reach out for help from your healthcare provider. 

However, Dr Jill wants you to know that not all stress is bad. When it’s acute stress related to our body’s natural fight or flight response, it’s actually a good thing. 

“The fight or flight response is a natural bodily response to danger. It’s a protective mechanism and it’s not a bad thing. When it becomes a problem is when you’re in fight or flight mode all day, for many days in a row without reprieve. That’s chronic stress, otherwise known as distress or negative stress. 

“When you’re experiencing chronic stress, that’s when you will start to see the physical, mental and emotional side effects of stress.”

There are two terms you should understand that relate to stress and the immune system – cortisol and cytokines. Cortisol is a hormone that is released when your body is under stress. Cortisol is what helps your body in its fight or flight response.

Cytokines are immunomodulating proteins. At a fundamental level, their role in the immune system and the body’s immune response is to carry messages that tell cells how to adapt or grow.

So how do cortisol, cytokines, stress and immunity all work together? Both cortisol and cytokines are a normal part of immune health. What may weaken your immune system is when you have an excess of either. And that excess can be caused by stress. 

Here’s how it goes. When you are under chronic stress, your body may start to release more and more cortisol. Usually, that’s ok… but too much cortisol is a problem. Why? When you have an overproduction of cortisol, it can cause havoc on your immune system and the response of cytokines. 


5. Can too much exercise weaken your immune system?

According to the Australian Bureau of Statistics, 44% of adults (aged 18-64 years) spend the majority of their workday sitting. At the same time, more than half of Australian adults don’t meet the Federal Government’s physical activity guidelines.

However, Dr Jill says that while moderate exercise may strengthen our immune system, too much exercise could possibly have the opposite effect.

It’s thought that extremely strenuous or prolonged exercise may induce immune changes associated with decreased resistance to the viruses in the days after that strenuous exercise. Conversely, moderate exercise may offer protection against infections.

“Does exercise increase white blood cells that play an important role in the immune system? The science suggests that it does. Can overtraining cause low white blood cells? It appears that strenuous exercise may have this deleterious effect. Moderation and consistency are key,” says Dr Jill.

Treat your body kindly and reap the benefits

Yes, there are absolutely factors that can weaken your immune system. But a large part of it comes down to how you treat your body and what you put into it.

By making healthier lifestyle choices and seeking help where you need it, you may be doing the best thing you can for your immune health.

Be sure to consult your GP or health practitioner if you have any questions or concerns about your immune system.


Dr Jill Gamberg is a General Practitioner and one of the first Australian Lifestyle Medicine Physicians whose goal is to help prevent disease and maintain wellness with evidence-based practice, and to passionately improve health literacy.

Reviewed by the healthylife Advisory Board September 2021.


This article is for informational purposes only and does not provide medical advice, diagnosis, or treatment. Any information published on this website or by this brand is not intended as a substitute for medical advice. If you have any concerns or questions about your health you should consult with a health professional.