How does nutrition affect the immune system?

10 Apr 2020

Before I get into this blog I’d like to first just remind those of us lucky enough to have a fully functioning immune system how privileged we are. There are plenty of vulnerable people out there who do not have the luxury of proper immune function; these people are facing an even more challenging time in this pandemic we're all currently stuck in. So let's take a second to be grateful for the miracles that are our bodies, shall we?

What is the immune system?

Now this is a BIG question and I’m not afraid to admit that I don’t fully understand it (people dedicate their whole lives to understanding it!). Lessons on the immune system at school and university always daunted me as it's so ridiculously complicated, incorporating cells with cool names like natural killer cells, macrophages and neutrophils, as well as proteins which you might be familiar with like antibodies and cytokines. 

Our immune system is working all the time to help keep our body in balance. We tend to only think about it though when the complicated components come together to orchestrate a response to pathogens like the SARS-CoV-2 virus we find ourselves confronted with now.


There are two lines of defence to the immune system:

Non-specific immune response – this is the first line of defence and includes both physical barriers (like skin or hairs in the nose and windpipe) and chemical barriers (like stomach acid or tears). These barriers can’t distinguish between different threats so just provide a general barrier to invading pathogens. The non-specific response also includes white blood cells (e.g. phagocytes, neutrophils, basophils etc) which again mounts the same attack on any pathogen and also doesn’t hold any ‘memory’ of the response.


Specific immune response – if pathogens pass through this first line defence they can then cause an infection. This is where the body’s highly tuned and complex immune response comes in to play and can organise what’s called acquired immunity. This system uses B cells produced in the bone marrow and T cells developed in the thymus gland which produce specific antibodies in response to antigens (proteins) found on pathogens. This is actually how vaccines work as these cells remember the pathogen so next time they see it they can mount a better, speedier response.


We don’t want to ‘boost’ our immune system

Even though the term ‘boosting our immune system' is everywhere, as a concept it's actually scientifically flawed. This is because our immune system exists in a balance, so that it’s ready to respond to incoming infections but isn’t overly active which causes other issues. Inflammation, allergy symptoms and autoimmune conditions are all associated with an overactive (or in other words boosted) immune system. It’s therefore much more useful to talk about how we can support our immune system to function normally or ideally.

What can we do to support our immune system?

Eat a wide variety of different foods across time

This will ensure you’re getting the right balance and amount of nutrients important for supporting overall health and your immune system. It’s also critical to make sure you’re eating enough food as being under-fed and under-nourished can mean your body doesn’t fight back as it should. There’s no one specific nutrient or food that’s most important in supporting your immune system.

Nutrients that play a role in immune function include…

Vitamin A – helps certain white blood cells to develop properly and also helps T cells involved in the specific immune response. This is found as retinol in animal products (liver, whole milk, cheese) and as carotenoids in (dark green leafy veg and orange-coloured foods like carrots and sweet potato).

B vitamins (6 & 12) – these help with production of new immune cells and allows them to communicate effectively. Vitamin B6 is found in a wide range of different foods whereas B12 is mostly found in animal products (meat, fish, dairy and eggs) but also fortified yeast extract and other foods.

Vitamin C – helps to clear away old immune sites from the site of infection, supports immune cells to attack pathogens and also supports the structure of the skin as a physical barrier. Vitamin C is found in many fruit and veg such as citrus fruits, berries, peppers, tomatoes and green veg.

Vitamin D – vitamin D deficiency is associated with reduced immune response but beyond that we don’t really know how it’s involved in the immune system. Sources of vitamin D include oily fish, eggs, fortified foods (e.g. cereals and spreads). But it’s hard to get enough from our diet so during autumn/winter (or when we can’t get outside much) we’re all advised to take a 10mcg supplement.


Zinc – helps with the production of new immune cells and helps those badass natural killer cells to function properly. It’s found in shellfish, meat, eggs, nuts, seeds and wholegrains.

Selenium – can also help to produce new immune cells and mount a sufficient response to infection. Selenium is found in nuts and seeds, eggs, offal, fish and shellfish.

Iron -  is important for maintaining the health of immune cells and is found in red meat, offal, pulses (peas, beans and lentils), nuts, seeds, quoin and dried fruit.

Lifestyle factors can play a huge role in the proper functioning of the immune system too…

Sleep – prioritising sleep and rest, so having some sort of routine around sleep, can be really helpful.

Stress – worry about whether we’re eating the ‘right things’ can itself cause stress which is detrimental to our immune system.

Activity – although rest is important, we should also stay active by making the most of our one form of outside activity, trying out new at-home work outs or just getting busy with the cleaning.

Booze – although it’s so easy to get in the habit of treating every day as a weekend day, try and be mindful of how much you’re knocking back..

Smoking – this is particularly important right now as many of us are facing the possibility of being struck down by this respiratory illness. Taking care of our lungs now and always should be a top priority.

Personal hygiene – we’ve all seen the messages from Government about how important proper hand washing is right now so making special care to wash them thoroughly for 20 seconds (I find singing to be pretty helpful).

Do we need supplements?

As of right now we have no good evidence that any supplement will help to protect from coronavirus or help reduce its severity. It’s a brand new virus so we just don’t have any evidence specifically about it. There's some research to suggest that vitamin C and zinc supplements might help reduce the severity and durations of the common cold, but that’s caused by a totally different virus to the current coronavirus (1,2).

If you’re otherwise healthy with no nutrient deficiencies taking supplements at best isn’t going to give you any benefit and at worst could come with nasty side effects. Certain supplements can also interfere with medications.


So although we can’t actually boost our immune system, we can give ours the best chance we can by remembering...

Balanced diet (with enough food!) = Balanced immune system

The same for our lives in general as we have a balance of awake and sleep, rest and activity, stress and calm. This can be hard to achieve, particularly now, so if you feel like you could benefit from a one-off consultation to have a chat about your particular concerns I'm offering them at a discounted rate while we're still under lock down. 

Get in touch at or on 07403896800.

For sources of professional, evidence-based information regarding the coronavirus and our health check out the sources below:

British Nutrition Foundation 

British Dietetic Association



Hemilä & Chalker (2013) “Vitamin C for preventing and treating the common cold” .DOI: 10.3390/jcm7090258

National Institute of Health “Zinc”