Immunity and building your defences

This blog comes from Charlotte Lucas, our nutritional advisor. Charlotte is a qualified pharmacist with over 25 years experience and is completing her MSc in Nutritional Medicine. Passionate about lifestyle medicine and empowering individuals to take charge of their health, Charlotte is our guest blogger this month to help our visitors gain an insight into how gut microbiota (GM) can help build your immunity.

When it comes to maintaining good health, the immune system is our most precious asset; Incredibly sophisticated and astonishingly complex.


In these challenging COVID-19 days one thing’s become very apparent. We need a resilient immune system to protect us from infective organisms like viruses and bacteria but it's important to understand we also rely on this complex network to protect us from the malfunctioning of our own cells. Here, in an introduction to the fascinating world of immunity, I hope I’m going to convince you that the greatest opportunity to impact your health is in your hands.


Like fingerprints, immunity varies from person to person. We all inherit a unique set of immunity genes and while genetic code can’t be changed, it can be interpreted in many different ways. We can help train and maintain immunity by manipulating genetic code through lifestyle factors. The gut microbiota, diet, sleep, stress and physical activity, all play a part.

For this blog, I am going to focus on gut microbiota.

Immunity and the gut microbiota

Over 70% of our immune system is located in the gut and the link between diet and immune response is driven by the trillions of microbes known as the gut microbiota which I’ll call GM for short. Our gut is our entire digestive tract running from mouth to bowel and it is a barrier between the body and the environment. The majority of our GM live in the small section of the bowel called the large intestine.

So what do these trillions of bugs actually do? The GM are responsible for many things including digesting food, releasing vitamins from ingredients and maintaining the integrity of the gut lining. This lining is only one cell thick to allow all the products of digestion and the products made by our GM to pass through to the bloodstream for transport around the body. However, it is also a route for harmful microbes and products to pass into our blood, which leads to damage. Therefore our immune cells need to be constantly assessing and recognising friend or foe. It’s relentless work keeping human cells in harmony with foreign microbes.

Having a robust and well functioning GM protects us and bolsters our ability to fight infection on several levels.

  • Specific microbes maintain the integrity of the gut lining preventing harmful pathogens or materials from entering the bloodstream. Diversity is key.

  • They secrete their own antibiotic and antifungal chemicals that attack harmful microbes, preventing colonization of the gut

  • Beneficial microbes support an anti-inflammatory environment

  • Microbes themselves produce and release micronutrients that support our immune cells

So keeping your GM in shape really improves immune health.

How to keep your GM healthy

Think of your GM as a garden that needs feeding. Just like your immune system, your GM is unique to you and pretty much remains the same from the age of about 3. But which of these good or bad microbes flourish depends on diet and lifestyle. An easy way to imagine this is by thinking of your GM as an orchestra with food and lifestyle being the conductor. Harmony depends on how the conductor encourages you to play.

Prebiotic is a term to describe the foods the microbes like to feed on. GM food if you like. These are the key to gut health. Another term you may hear is probiotics, which refers to the helpful bacteria found in fermented foods and also in supplemental form. At the moment the jury is out on how useful probiotics are as there is little evidence to suggest these microbes colonize once they reach your gut. Plus we all have very different GMs so the bacteria which may be useful to you, for example, may be absolutely useless to me. Saying that however, they can be a good way to assist gut health during periods of illness, stress episodes of poor diet or antibiotic use and in those who struggle to tolerate high fibre diets. Until research tells us more I try to include live yoghurt or Kefir in my daily diet because I know it’ll do no harm and may be beneficial.

So how can you help your immunity? The best thing you can do to support your immunity is feed yourself and your good gut microbes. So what are their favourite foods? Complex fibres readily found in fruits, vegetables, grains and legumes, nuts and seeds.

Let COVID-19’s legacy be a refocusing on health and until next time here are my top tips on what to eat to support your GM.

  1. Eat whole foods. Avoid all processed foods. Think natural state, brown, wholemeal and you get the picture

  2. Eat variety. Diversity of foods is the goal. Aim for at least 5 different vegetables/salads portions a day, with additional fruit. 8-9 portions in total daily if possible.

  3. Eat a rainbow. Coloured fruits and r vegetables contain different nutrients.

  4. Eat seasonally if possible as foods tend to be richer in nutrients

  5. Avoid processed foods, As a rule of thumb, if a food label has more the 5 ingredients listed, avoid it! Avoid snacking too unless its whole fruit.

  6. Reduce stress. Raised stress hormones negatively affect the GM which in turn damages the integrity of the gut lining. Find ways to relax via exercise, yoga and meditation for example.

  7. Sleep. Good quality sleep is linked to reduced stress hormones so sleep too is essential for your GM

Stay safe and stay well



Nutritionist, pharmacist and health coach


Nutrition and Lifestyle Medicine

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