How to keep your immune system strong

Wellness Article

Your immune system is your body's defense system. When a harmful invader like a cold or a flu virus, or the novel coronavirus (SARS-CoV-2) that causes COVID-19 gets into your body, your immune system mounts an attack. Known as an immune response, this attack is a sequence of events that involves various cells and unfolds over time.

We recommend you prioritise these basic steps for protecting and improving your health and strengthen your immune system.

Proper handwashing: 
The novel coronavirus is killed by proper handwashing for 20 seconds with soap or using hand sanitiser that contains greater than 60% alcohol. 1

Don’t smoke: 
Smokers have an increased risk of catching infections and suffering severe complications from those infections.2

Get adequate sleep:
Sleep is important for health in general, and as a bonus, it may also benefit our immune function. For instance, one study showed those with insomnia had, on average, less immune response to the influenza vaccine.3

In another study, 153 volunteers were inoculated with the rhinovirus (the virus that can cause the common cold). They found those who slept less than seven hours were three times more likely to develop symptoms than those who slept more than eight hours.4

The right amount of exercise: 
Observational studies show that those who exercise tend to suffer fewer infections than those who do not.5

The general consensus is that exercise overall is likely to be beneficial. There is evidence that frequent exercise enhances, rather than lower the immune system. Additionally, vaccination studies show heightened responses to bacterial and viral antigens following rounds of exercise.

Regular physical activity and frequent exercise might also limit or delay aging of the immune system.6

Stress management: 
While acute stressors (stress suffered for a short period of time) may temporarily increase immune functions, chronic stressors (stress over long period of time) will likely diminish the immune function.7

Worrying about the stock market, stressing about losing your job, and focusing on the uncertainties of the future can raise cortisol levels, which may negatively impact our immune function.

Researches who observed volunteers who were exposed to the cold virus (using nose drops) found that people who reported lower levels of stress in their lives were less likely to develop cold symptoms.8

Researchers also found that marital conflict is especially taxing to the immune system.9

Reduce or cease your alcohol intake:
In times of stress, some people turn to alcohol as a coping mechanism.

However, studies show a relationship between chronic heavy alcohol consumption and increased susceptibility to infections.10 Notably, a number of these studies showed an increased risk among heavy drinkers of acute respiratory distress syndrome (ARDS), which is the lung complication responsible for most of the COVID-19 related deaths.

Alcohol disrupts the ciliary function in the upper airways of the lungs (responsible for removing foreign invaders), impairs the function of immune cells and weakens the barrier function of the cell lining in the lower airways of the lungs.10

Eat a healthy diet:
Eating whole-food, plant-based diet may help give the immune system a boost. The immune system relies on white blood cells that produce antibodies to combat bacteria, viruses, and other invaders. Vegetarians' data-id='32' data-target='#glossaryModal' data-string='People who consume a plant-based diet with no meat, fish or seafood, but may include eggs and animal products such as dairy.' data-image=''>Vegetarians have been shown to have more effective white blood cells when compared to nonvegetarians, due to a high intake of vitamins and low intake of fat.11

Eating a low-fat diet may also be protective. Studies have shown that limiting dietary fat helps strengthen immune defenses. Research also shows that oil may impair white blood cell function and that high-fat diets may alter the gut bacteria flora that aid in immunity.12,13
Maintaining a healthy weight can also benefit the immune system. Obesity has been linked to increased risk for influenza and other infections such as pneumonia.14

Plant-based diets are effective for weight loss because they are rich in fibre, which helps fill you up, without adding extra calories. Fibre can also lower the Body Mass Index ' data-id='20' data-target='#glossaryModal' data-string='An indication of body size based on height and weight and used to estimate whether a person is underweight, overweight or within a healthy weight range. The healthy weight range is a BMI of 18.5 to 24.9 kg/m2. Overweight range is a BMI of 25 to 29.9 kg/m2. Obese range is a BMI of 30 kg/m2 or higher.' data-image=''>BMI' data-id='21' data-target='#glossaryModal' data-string='An indication of body size based on height and weight and used to estimate whether a person is underweight, overweight or within a healthy weight range. The healthy weight range is a BMI of 18.5 to 24.9 kg/m2. Overweight range is a BMI of 25 to 29.9 kg/m2. Obese range is a BMI of 30 kg/m2 or higher. ' data-image=''>BMI, which is linked to improved immunity.15

Reduce refined carbs and sugars:
A landmark laboratory study suggested that sugar may impair white blood cell function, but no credible evidence shows that eating it makes you get more infections.16 However, other evidence suggests an acute increase in blood sugar may increase the risk of infections and complications.17

Furthermore, an increase in sugary food or drinks increases inflammation internally which creates further stress to the body.18 

Therefore, it would make sense that we limit these blood sugar elevations. Refined carbohydrates and simple sugars are two of the biggest offenders for blood sugar spikes and therefore should be avoided.

Make sure your vitamin D level is normal:
Increased vitamin D in the blood has been linked to the prevention of other chronic diseases including tuberculosis, hepatitis, and cardiovascular disease. Food sources of vitamin D include fortified cereals and plant-based milks and supplements.19,20

Getting adequate sunlight is the best way to elevate vitamin D levels without supplementation. Around 10 minutes in summer and 45 minutes in winter, in the middle of the day, between 10 am and 2pm, is ideal.21 

Research shows vitamin D supplementation may reduce the risk for viral infections, including respiratory tract infections, by reducing the production of pro-inflammatory compounds in the body.22 

In short, COVID-19 is spreading so rapidly and having such a significant impact on people around the world because it is new to humans and we don’t have immunity to it. Take the above steps to strengthen your immune system. The more actions we take to keep ourselves generally healthy, the better we will be.



1.        Siddharta A, Pfaender S, Vielle NJ, et al. Virucidal activity of world health organization-recommended formulations against enveloped viruses, including zika, ebola, and emerging coronaviruses. J Infect Dis. 2017;215(6):902-906. doi:10.1093/infdis/jix046

2.        Strzelak A, Ratajczak A, Adamiec A, Feleszko W. Tobacco smoke induces and alters immune responses in the lung triggering inflammation, allergy, asthma and other lung diseases: A mechanistic review. Int J Environ Res Public Health. 2018;15(5). doi:10.3390/ijerph15051033

3.        Taylor DJ, Kelly K, Kohut ML, Song KS. Is Insomnia a Risk Factor for Decreased Influenza Vaccine Response? Behav Sleep Med. 2017;15(4):270-287. doi:10.1080/15402002.2015.1126596

4.        Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009;169(1):62-67. doi:10.1001/archinternmed.2008.505

5.        Campbell JP, Turner JE. Debunking the myth of exercise-induced immune suppression: Redefining the impact of exercise on immunological health across the lifespan. Front Immunol. 2018;9(APR). doi:10.3389/fimmu.2018.00648

6.        Nieman DC, Wentz LM. The compelling link between physical activity and the body’s defense system. J Sport Heal Sci. 2019;8(3):201-217. doi:10.1016/j.jshs.2018.09.009

7.        Dhabhar FS. Enhancing versus suppressive effects of stress on immune function: Implications for immunoprotection and immunopathology. Neuroimmunomodulation. 2009;16(5):300-317. doi:10.1159/000216188

8.        Cohen S. The Pittsburgh common cold studies: Psychosocial predictors of susceptibility to respiratory infectious illness. Int J Behav Med. 2005;12(3):123-131. doi:10.1207/s15327558ijbm1203_1

9.        Kiecolt-Glaser JK. Marriage, divorce, and the immune system. Am Psychol. 2018;73(9):1098-1108. doi:10.1037/amp0000388

10.      Dunne FJ. Alcohol and the immune system. A causative agent in altering host defence mechanisms. Br Med J. 1989;298(6673):543-544. doi:10.1136/bmj.298.6673.543

11.      Berenbaum F, van den Berg WB. Inflammation in osteoarthritis: Changing views. Osteoarthr Cartil. 2015;23(11):1823-1824. doi:10.1016/j.joca.2015.09.012

12.      McAnulty LS, Nieman DC, Dumke CL, et al. Effect of blueberry ingestion on natural killer cell counts, oxidative stress, and inflammation prior to and after 2.5 h of running. Appl Physiol Nutr Metab. 2011;36(6):976-984. doi:10.1139/H11-120

13.      Hutchison AT, Flieller EB, Dillon KJ, Leverett BD. Black Currant Nectar Reduces Muscle Damage and Inflammation Following a Bout of High-Intensity Eccentric Contractions. J Diet Suppl. 2016;13(1):1-15. doi:10.3109/19390211.2014.952864

14.      Alwarawrah Y, Kiernan K, MacIver NJ. Changes in nutritional status impact immune cell metabolism and function. Front Immunol. 2018;9(MAY). doi:10.3389/fimmu.2018.01055

15.      Haddad EH, Berk LS, Kettering JD, Hubbard RW, Peters WR. Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr. 1999;70(3 SUPPL.). doi:10.1093/ajcn/70.3.586s

16.      Sanchez A, Reeser JL, Lau HS, et al. Role of sugars in human neutrophilic phagocytosis. Am J Clin Nutr. 1973;26(11):1180-1184. doi:10.1093/ajcn/26.11.1180

17.      Atamna A, Ayada G, Akirov A, Shochat T, Bishara J, Elis A. High blood glucose variability is associated with bacteremia and mortality in patients hospitalized with acute infection. QJM. 2019;112(2):101-106. doi:10.1093/qjmed/hcy235

18.      Aeberli I, Gerber PA, Hochuli M, et al. Low to moderate sugar-sweetened beverage consumption impairs glucose and lipid metabolism and promotes inflammation in healthy young men: A randomized controlled trial. Am J Clin Nutr. 2011;94(2):479-485. doi:10.3945/ajcn.111.013540

19.      Grant WB, Lahore H, McDonnell SL, et al. Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths. Nutrients. 2020;12(4):988. doi:10.3390/nu12040988

20.      Chung C, Silwal P, Kim I, Modlin R, Jo E. Vitamin D-cathelicidin axis: at the crossroads between protective immunity and pathological inflammation during infection. Immune Netw. 2020;20:e-12-38. Accessed March 17, 2020.

21.      Samanek AJ, Croager EJ, Gies P, et al. Estimates of beneficial and harmful sun exposure times during the year for major Australian population centres. Med J Aust. 2006;184(7):338-341. doi:10.5694/j.1326-5377.2006.tb00267.x

22.      Gunville CF, Mourani PM, Ginde AA. The role of vitamin D in prevention and treatment of infection. Inflamm Allergy - Drug Targets. 2013;12(4):239-245. doi:10.2174/18715281113129990046

We recommend you prioritise these basic steps for protecting and improving your immune system

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