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Boosting your immunity against COVID-19

Advice for patients on improving your immune system in the face of the pandemic

Unplanned learning

This article was correct at time of publishing (April 9). To keep up with the latest information please visit our COVID-19 hub

Patients might ask for advice on how to protect themselves against COVID-19. They will be aware of national advice on handwashing, social distancing and cough etiquette – which are all vital to preventing the spread of the virus – but there are other measures that can be taken to help prevent infection. Patients can be advised on measures that may boost their immunity, keeping them as well as possible during this stressful and uncertain time.

A healthy diet

Maintaining a healthy diet will nourish the body with the vitamins and minerals required to support the immune system. A diet with at least five portions of fruit and vegetables daily will help provide the micronutrients the body needs. Patients should also be advised to reduce intake of sugary, processed and fatty foods, which will help to keep weight within the recommended range. A reduced energy expenditure due to lockdown may lend itself to eating smaller meals, more frequently throughout the day. Being overweight can also reduce the body’s ability to fight infection.(1)

Patients can be referred to the NHS website for further advice on a healthy diet. The British Dietetic Association has also produced advice for the general public during the COVID-19 pandemic.

Vitamin D

Vitamin D is used by the body to help absorb calcium and phosphate from food and is therefore important for musculoskeletal health.(2) Studies have shown that vitamin D deficiency can reduce immunity and the body’s ability to fight infection.(3) Vitamin D receptors are expressed in cells of the immune system such as lymphocytes, macrophages and killer T cells, which would suggest that vitamin D has an immunomodulatory role.(4)

Recent evidence has shown that vitamin D suppresses CD26, a cell surface receptor thought to facilitate entry of the COVID-19 virus into the host cell. Vitamin D also reduces the cytokine storm, an overreaction of the body’s immune system, that can be caused by COVID-19. It does so by reducing the expression of pro-inflammatory cytokines and improving anti-inflammatory cytokines, attenuating the risk of cascading responses in the immune system that may lead to death.(5)

The majority of the body’s vitamin D comes from direct sunlight containing sufficient ultraviolet B (UVB) radiation. Vitamin D is produced by the body from direct sunlight, mostly from late March/early April until September. It can also be obtained to a lesser degree from food and dietary supplements. In 2016, a UK survey found that one in five people are deficient in vitamin D.(4) Vitamin D deficiency can put patients at risk of softening of the bones, resulting in rickets in children and osteomalacia in adults. These conditions can cause pain and weakness in the muscles, leaving patients vulnerable to falls and injuries. Those most susceptible to vitamin D deficiency include:

  • Infants and young children
  • Those aged over 65 years
  • Women who are pregnant or breastfeeding
  • People with very little sun exposure (eg those who wear clothes that cover most of their skin or who are confined indoors)
  • Minority ethnic groups with darker skin.(4)

Patients can give their vitamin D levels a boost by spending short periods of time outdoors (while practicing social distancing and following government guidelines on how often to leave the house), exposing hands, forearms and lower legs. Vitamin D is also found in foods such as oily fish (eg mackerel, herring, salmon and sardines), red meat and eggs.

Vitamin D supplements can be suggested as another way to help strengthen the immune system. The NHS website recommends that a supplement containing 10 micrograms of vitamin D is usually sufficient for those over the age of one.(2) However, research just published (April 2020) in the Irish Medical Journal, has suggested that in Ireland, all older adults, hospital inpatients, nursing home residents and other vulnerable groups will be supplemented with 20–50 micrograms of vitamin D to enhance their resistance to COVID-19, and that this advice may be extended to the general adult population on further research.(5)


There are many benefits of regular exercise, including helping to boost the immune system. Exercise has been shown to reduce inflammatory responses in the body and increase the number of white blood cells that help to fight infection. Moderate to vigorous physical activity lasting less than 60 minutes is now viewed as an important aspect of improving immune function through the exchange of immune cells from the blood to the tissues. Each exercise session improves the function of tissue macrophages – with an enhanced recirculation of immunoglobulins, anti-inflammatory cytokines, neutrophils, natural killer cells, cytotoxic T cells and immature B cells. When exercise is practiced daily, immune defence activity is enhanced.(6)

Stress is a feature of our lives, especially during these uncertain times, and it has been linked to alterations in the immune system. Exercise can help alleviate stress and keep the immune system working optimally.(8)

You can direct patients to home workout resources online, including the NHS website, which features a series of 10-minute workouts that can be done at home and strength and flex exercises.


Adequate sleep is an important immunity booster that is often disregarded. It is essential in keeping the immune system functioning properly: not only does lack of sleep make you more likely to get sick after being exposed to a virus, it can affect recovery rates as well. During sleep the body produces antibodies and proteins which fight off infection. When the time allowed for sleep is reduced to four hours, there is a significant reduction in natural killer T cells and an increase in inflammatory cytokines.(7) Adults should aim for to have about 7-8 hours’ sleep every night. Adolescents need 9-10 hours per night and school children may need 10 hours or more.(9)

You can find more advice for patients in our CPD module Starting the conversation about sleep.

Quitting smoking

Smoking has been linked to more than 24 diseases, including respiratory conditions such as chronic obstructive pulmonary disease and asthma and is a major risk factor for acute respiratory tract infections. Around 7,000 chemicals are released when smoking – including nicotine, formaldehyde, ammonia, carbon monoxide, tar, acetone, and nitrogen oxides. Many of these chemicals not only cause cellular damage and inflammation but can also interfere with the immune system, leaving smokers more susceptible to infection. Tar and nicotine in particular can alter the innate immune response (the body’s initial response when a pathogen is detected) and prevent neutrophils ability to destroy pathogens. Exposure to cigarette smoke causes inflammation, initiating the release of macrophages into the lungs. Overactivation of these macrophages cause the release of cytokines, chemokines and proteases into the mucosal tissue leading to further inflammation.(10,11)

Improvement in smoking-related illness and immunity can been seen just a few hours after quitting smoking. Patients should be advised on the benefits of stopping smoking and given advice on smoking cessation.(10)

Patients can be directed to the NHS website for free advice and tips on giving up smoking.

  1. Myles, I. Nutrition Journal (2014) Fast food fever: reviewing the impacts of the Western diet on immunity.
  2. NHS Health A-Z (2018) How to get vitamin D from sunlight.
  3. Aranow C. (2012) Vitamin D and the immune system. J Investig Med. 2011;59(6):881–886.
  4. Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health.
  5. McCartney D.M & Byrne D.G (2020) Optimisation of vitamin D status for enhanced immuno-protection against COVID-19Ir Med J. Vol 113; 4;58.
  6. Neimen D. C. & Wentz L. M. (2019) The compelling link between physical activity and the body's defence system.
  7. Centers for Disease Control and Prevention (2017) Sleep and the immune system.
  8. Morey J.N. et al (2015) Current directions in stress and human immune function. Curr Opin Psychol. 2015;5:13–17.
  9. Mayo Clinic (2018) Lack of sleep: Can it make you sick?
  10. Centers for Disease Control and Prevention (2020) Smoking and overall health.
  11. Yamaguchi N. H. (2019) Smoking, immunity, and DNA damage.
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