5 ways to strengthen your immune system

Tiny living organisms, known as microbes, can affect our health. Some microbes can positively affect our body, for example, by contributing to good digestion or producing vitamin K. However, some microbes can cause problems like disease. These particular microbes are known as pathogens. Small but, in some cases, deadly. 


Our immune system functions as our body’s defence against harmful things, so we need it to work optimally. This amazing system contains specialised cells known as white blood cells (WBCs). These warrior cells recognise harmful intruders and kill pathogens to protect our body.

Why we need a strong and healthy immune system 

At the time of writing this, the United Kingdom and other parts of the world have been in quarantine due to the Coronavirus disease 2019 (COVID-19) pandemic. Coronaviruses are a large family of viruses that were discovered in the 1930s (1). They cause illnesses from the common cold to more severe diseases such as severe acute respiratory syndrome (SARS). COVID-19 exhibits a new Coronavirus strain that has not been previously seen in humans. Symptoms include, but are not limited to, fever, coughing, sore throat, tiredness, loss of appetite and/or difficulty breathing.

In this unprecedented and challenging time, friends, family and others have been reaching out to me in regards to providing sound advice for achieving healthy immune function.

There is no guarantee that a Herculean, strong immune system will provide absolute protection. However, ensuring that this system is functioning optimally lowers the risk of infections from pathogens and helps us recover from illness faster.

So, let’s look at the five essential ways you can potentially strengthen your immune system.

Tip 1. Reduce your sugar intake


Sugar hinders our WBCs’ ability to destroy pathogens. This is because sugar reduces the amount of vitamin C in the immune cells and causes the cells to work less efficiently (2).

Sugar does something else too. Our intestines naturally contain a community of microbes known as gut microbiota. The gut microbiota plays an important role in our immune health. Excess sugar can contribute to small intestinal bacterial overgrowth (SIBO), which is one of the most common causes of bloating. SIBO can give rise to ‘leaky gut’ or, if you prefer the more respected scientific term, ‘intestinal hyperpermeability’.

When the walls in the small intestine become more leaky or permeable, they can allow some naughty substances to pass through gaps in the intestine wall, such as toxins and partially digested foods. When these mischievous substances pass into the bloodstream they can cause inflammation and stress, which puts a strain on our immune system (3-5).

If you are constantly craving sugary foods, gaining weight, have acne or feel tired throughout the day, it could be a sign that you consume too much sugar, so read on.

Practical tips to reduce your sugar intake: 

  • Cut down on adding sugar to tea and cereals etc. Instead, consider using cinnamon or stevia (a plant-based sugar substitute). 
  • Reduce sugar-sweetened drinks, for example, energy drinks, fizzy drinks, and fruit juices with added sugar (always check the ingredients).
  • Dilute your fruit juice with water. Or better yet, jazz up your water with fruit infusions: by adding mint leaves, lemon and/or cucumber to your water. 
  • Exchange refined foods such as white rice, bread and pasta for wholemeal/wholegrain options. 

These are just a few examples. Registered nutritional therapists can help you pinpoint the things that you need to do for yourself.

Be aware that a lot of over-the-counter pastilles and medicines for colds contain sugar. Perhaps some of the pharmaceutical companies were very fond of that old Mary Poppins song?

Our blood sugar control can also affect our sleep and vice versa (6). Higher blood sugar levels can lead to less sleep. But I’ll talk about how sleep affects our immune system later.

Tip 2. Get the sunshine vitamin D


Vitamin D does more than just build strong bones and teeth, it also has a controlling influence over our immune responses. Vitamin D has been shown to activate T cells, which are a type of WBC. T helper cells can help other cells of the immune system and T-killer cells kill virally infected cells and tumours. 

Deficiency in vitamin D is associated with SIBO (7), obesity, increased vulnerability to infections (8) and increased risk of autoimmunity. Autoimmunity is when the immune system wrongly attacks the body’s own healthy cells and tissues. Examples include rheumatoid arthritis, lupus, and multiple sclerosis.

A lot of people tell me they try not to have supplements as they want to obtain their nutrients directly from food. This is admirable but may need to be reconsidered in cases like the following: 

We make vitamin D when our skin is exposed to UV B light from the sun. However, between October and early March we do not make enough vitamin D from sunlight in the UK. Vitamin D can naturally be obtained from certain foods, but in small amounts, such as oily fish, liver and egg yolk. It is worth considering taking vitamin D supplements, especially in the winter months and/or if you have African or Asian heritage. This is because it is difficult to get our recommended amount of 10mcg/ 400 IU from food alone (9). 

However, some research specifies that a higher daily intake of 1000 – 4000 IU (25–100 mcg) is needed and safe to maintain optimal vitamin D blood levels (10, 11).

Practical tips to get the sunshine vitamin D:

  • Reduce or stop smoking. Smoking affects the absorption of vitamin D and other vital nutrients.
  • If supplementing, opt for vitamin D3 instead of vitamin D2, as vitamin D2 is much less effective at maintaining optimal vitamin D blood levels (12, 13). 
  • If supplementing vitamin D3, consider combining vitamin K2 with it. This mixture stops the build-up of calcium in the arteries, thus reducing the risk of the development of heart disease (14). Be aware that vitamin K can interfere with how the medicine warfarin works. 
  • Go outside daily for short periods, with your forearms, hands or lower legs uncovered, between March to September.

Tip 3. Get enough sleep


Sleep has a strong influence on our immune system’s function.

Natural killer (NK) cells are a class of WBCs that fight against infection and cancer. These internal assassins are generated when we are asleep. If we are sleep deprived, they do not work well (15). 

Similarly, sleep loss can upset the balance between pro-inflammatory and anti-inflammatory cytokines. Cytokines are substances produced by certain immune cells and control our response to infections. Sleep deprivation increases pro-inflammatory cytokines, which can make disease worse (16).

Sleep deprivation, especially when it occurs regularly, reduces our ability to fight off infections.

Practical tips to get enough sleep (17)

  • Turn off electronics, visual display units (TV, smart devices) and Wi-Fi at least two hours before bedtime.
  • Go to bed at the same time each day preferably between 8 pm ‐ 1 am. In one study (18), individuals who reported bedtimes between 8 pm ‐ 1 am were shown to have fewer problems with mental health, daytime functioning and sleep problems, than bedtimes outside of this window.
  • Do not consume caffeine after 4 pm.
  • Adults should aim to get 7 - 9 hours per night.

Tip 4. Reduce stress levels


Stress occurs when triggers, which could be psychological, physiological (relating to the body’s functioning), or physical, bring about a known or unknown response.

Short-term stress, such as the psychological stress that helps you pay attention when driving in severe weather, can be protective. Long-term stress, such as the physical stress of regular and excessive exercise without adequate recovery, or the (ironic) physiological stress of smoking, is generally harmful, especially to our indispensable immune systems.

Long-term stress does a lot. High stress changes the balance of our gut microbiota and can decrease the numbers of good bacteria, such as Bifidobacterium and Lactobacilli that possess important health-promoting immune properties (19). 

Stress disrupts our immune responses, causes low-grade chronic inflammation and may also increase vulnerability to some types of cancer. It additionally suppresses numbers, trafficking, and function of immunoprotective cells (20). Like sleep deprivation, any type of stress negatively affects the level of activity of the body’s NK cells (19). 

Long-term stress can cause long-term high blood sugar levels. Hormones, such as cortisol, that are produced by our adrenal glands to combat illness or stress can also cause your blood sugar to rise. As previously explained, high blood sugar levels can weaken our immune system.

If you have found this section stressful, please continue to read below for ways in which you may be able to reduce that stress.

Practical tips to reduce stress levels

  • Re-read the 'Get enough sleep' section. Regular sleeping patterns are a must. Also, re-read the 'Reduce sugar intake' advice. Achieving stable blood sugar, through nutrition, is the first step to alleviating stress through our diet.
  • Integrate at least 15 minutes of relaxation into your day. Go for a stroll, read a book, consider soaking your feet in Epsom salts (magnesium sulphate). Adequate magnesium levels are essential for sleep and stress management, as well as helping relax tired and aching muscles.
    Try relaxation techniques such as meditation/prayer, pilates or progressive muscle relaxation, which may help you cope better.
  • Consider using an adaptogen like reishi mushroom or maca powder. Adaptogens are plants that enhance our response to stress and promote recovery from stress. They also increase resistance to pathogens (21). 

A registered nutritional therapist would be able to advise which adaptogens and other supplements are most appropriate for the individual, providing that there isn’t a health concern or medicine that wouldn’t work well with it.

Tip 5. Eat at least 5-a-day fruit and vegetable portions 


Vegetables and fruits are nutrient-dense. Nutrient-dense means that a food contains an abundance of compounds that are essential to life and health, such as vitamins and fibre, relative to its calorie content.  

Fruit and vegetables are rich in fibre. Fibre can slow the absorption of sugar from food to help improve blood sugar levels and support the gut microbiota. Fibre-rich foods include: wholegrain food options; oats, barley and rye; fruit such as berries, pears, nuts, melon and oranges; vegetables such as potatoes with skin, broccoli, carrots and sweetcorn; as well as, seeds, peas, beans and pulses (22). 

Dietary polyphenols are natural compounds that are found in fruits, nuts, seeds, vegetables, wine, tea, and chocolate. Apologies, but the latter 3 are not a part of your 5-a-day. Polyphenols feed and increase the number of healthy bacteria in our gut, which reduces the risk of developing a ‘leaky gut’ and toxic substances escaping into the bloodstream. 

Polyphenols also possess anti-inflammatory and antioxidant properties. Antioxidants shield our immune cells from harmful substances called free-radicals. Brightly coloured fruits and vegetables tend to contain the most antioxidants (23).

Different fruit and vegetables contain different combinations of minerals, fibre, and other nutrients. Vitamins and minerals such as: zinc, selenium, iron, copper, vitamins A, C (read my previous article about vitamin C for more information), E, and B-6, and folic acid have important influences on immune responses. Eat a wide variety of fruit and vegetables in your 5-a-day to get the most nutritional benefit (24). 

Practical tips to eat at least 5-a-day fruit and vegetable portions

  • For snacks, try having a handful of fruit with unsalted nuts or seeds.
  • Add at least 3-heaped tablespoons of beans and pulses, like kidney beans, lentils or chickpeas to stews, curries and salads.
  • Remember your root vegetables such as: sweet potatoes, parsnips, swedes and turnips. 
  • A portion size is generally 80g or as a rough guide; an amount that fits into the palm of your hand. For example, 3 tablespoons of peas, one tomato, one apple, two broccoli spears or 1/2 an avocado.
  • Always ensure you are eating a balanced diet.


We need strong and healthy immune systems to fight disease. Our immune function is influenced by variables, such as our nutritional status, lifestyle and stress load. 

Vitamin and mineral deficiencies and poor nutritional statuses may make us prone to certain infections and needs to be corrected (24). Ensuring that we get enough vitamin D, at least five portions of fruit and vegetables, reduce sugar, refined and processed foods can help support our immune system.

Lifestyle fundamentals such as achieving quality sleep and reducing stress levels are also needed for our immune system cells to function favourably. Optimal immune function gives us desired and effective responses against pathogens.

How a registered nutritional therapist could help you develop healthy immune function

The nutritional therapy approach for healthy immune systems can consist of:

  • Looking at and modifying the food you eat that may be contributing to imbalances and inflammation.
  • Improving gastro-intestinal health.
  • Decreasing overall chronic inflammation in the body.
  • Supporting the body’s adrenal glands, which affect immune function and inflammation.
  • Tests may be recommended to investigate hidden infections.

Nutritional therapy is specific for each individual. You may receive a bespoke meal plan and diet recommendations, lifestyle changes, and herbal, vitamin and/or mineral supplementation that work together to reduce inflammation, autoimmune flare-ups, and lower future risk for developing infections and additional autoimmune diseases.


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The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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London E18 & E10
Written by Rochelle Logan-Rodgers, Elle Rock Nutrition (BSc PgDIP mBANT mCNHC)
London E18 & E10

Rochelle is a fully Registered Nutritionist MBANT and Registered Nutritional Therapist MBANT & CNHC. Her qualifications include a Postgraduate Diploma in Nutritional Therapy from Middlesex University with the Northern College of Acupuncture. She did also obtain a BSc (Hons) in Molecular Medicine, at the University of Sussex.

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