How does nutrition affect the immune system?
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In times of COVID-19 pandemic.

The on-going COVID-19 pandemic is a major shock to the modern day civilization disrupting economy and livelihood throughout the world. It has been estimated that COVID-19 and malnutrition go hand-in-hand as evidences suggest that undernutrition may make populations more susceptible to COVID-19.

On the other hand, the presence of obesity and other non-communicable diseases as co-morbidities have been linked to more severe and adverse outcomes in COVID-19 patients. However, in the absence of targeted medicinal therapy, immunity is said to be the key player in the fight against COVID-19. Immunity is intrinsically related to nutrition and therefore it is high time to revisit and consider the existing knowledge to hone our tool to combat COVID-19.[1,2,3,4]

How does nutrition affect the immune system? 1

What does the immune system do for your body?

The immune system is the body’s line of defense against all the invading agents which may enter our body to produce illnesses. There are different types of immunity – innate, i.e., the one we are born with an adaptive, i.e., the one we acquire throughout life. Also, immunity can be conferred by immunization through vaccines.

Whenever a substance from the environment enters into our body the cells of the immune system identify them as “foreign”. These substances may range from different chemicals to pathogenic or non-pathogenic organisms like bacteria and viruses. Any substance that can trigger the production of infectious or communicable diseases upon entering our body is termed as “antigen”. The immune system of our body starts to produce fighter molecules known as “antibody” against these antigens as soon as they are recognized.

The antibodies react violently with the antigens to destroy them by engulfing (phagocytosis) in order to protect us from diseases. Whenever the antibodies are able to overcome the antigens in this battle we remain safe from illnesses. However, at other times we may fall prey to the pathogenic reactions initiated by the antigens and suffer from diseases.

Interestingly, the immune system can also boast of some specialized memory cells which remember the pathway to produce particular antibodies targeted against specific antigens, such that we remain safe from the concerned disease for a longer period of time. The success of the immune system to prevent diseases depends on the dose-response and time-response pattern of the antigen-antibody reactions as well as the strength of our immune system. Therefore, it is needless to say that the stronger the immune system the safer we are from various diseases.[5]

How does nutrition affect the immune system?2

What is the relationship of the immune system with nutrition?

Like any other system, the immune system of the body completely depends on the nutritional status of an individual. Since we are exposed to a multitude of disease-causing agents every day the immune system needs to work continuously to recognize the antigenic substances and to protect against them. Most of the fighter molecules produced by the immune system are immunogenic proteins like immunoglobulins and antibodies. Also, many specialized cells need to be produced continuously to help in the recognition and presentation of antigens, protection against them, and memorizing of the pathways involved. All these events call for the involvement of a large number of macro and micronutrients. So, the immune system relies heavily on daily nutrient supply to afford better protection against diseases.[6,7]

Which nutrients are most important for immune function?

The immune system depends on a number of nutrients for its proper function. The following are the most important in this regard:[8-16]

NutrientFunctions regarding ImmunityEffects of Deficiency
ProteinProliferation of immune cellsProduction of immunoglobulins and antibodiesMaintenance of the amino acid pool of the body needed for the cellular turnover of immune cellsBreakdown of muscle proteinProtein malnutritionGeneralised diminished immune response
CalorieMaintenance functions, cytokine synthesis, phagocytosis and antigen recognitionInactive immune system requires about 380Kcal of energy/day which increase to about 480Kcal/day during mild infections and inflammationOccurs along with protein deficiencyFunctions of T-cells are hampered impairing immunogenic memory response among othersChances of opportunistic infections, morbidity and mortality all increase in protein energy malnutrition (PEM)  
Vitamin A  Regulation of innate and adaptive immunityMaintenance of integrity of mucosal epithelial cells and skin to protect against harmful invasionsStimulation of resistance to infectionsSusceptibility to invading pathogens increase
Vitamin B complexRegulation of cell division, cell growth and DNA/RNA metabolism, particularly by vitamins B6, B12 and folateDecreased immunocompetenceImpaired response to pneumonia
Vitamin CSynthesis of defensive biomolecules of cellIncreased synthesis of immunoglobulins and cytokines as well as proliferation of T-cellsBoost to overall immune functionIncreased susceptibility to infectionsImpaired immune function
Vitamin DPolarisation of the immune system towards anti-inflammatory responsesStimulation of the proliferation of immune cells and phagocytosisIncreased susceptibility to infectionsIncreased autoimmunity
Vitamin EPositive modulation of different parameters of immunityDeficiency is rare but it can impair normal immune function
ZincInhibition of the virus binding on target cellsInhibition of the antigenic protein synthesis and enzymatic machinery of the virusesIncrease in pro-inflammatory responseImmuno-suppresion and decreased  resistance to infections
CopperProduction of anti-inflammatory biomoleculesCellular proliferationReduced immunityDecreased white blood cell production
IronProliferation and maturation immune cell Immune response to infectionsFrequent infections
How does nutrition affect the immune system?3

Is malnutrition a cause for a weak immune response?

            Malnutrition is a major cause of the weak immune response. Malnutrition is a multi-faceted problem and the spectrum of malnutrition ranges from undernutrition, e.g. protein-calorie malnutrition to overnutrition, e.g. obesity. Both the extremes of malnutrition are detrimental to effective immune response.

How great is the concern for undernutrition at present?

            The world is reeling under the looming threat of unprecedented hunger and undernutrition in the near future as food production and supply is disrupted due to the COVID-19 pandemic. It is a vicious cycle as poor immunity due to undernutrition may result in a surge of COVID-19 infection among the undernourished. Data suggests that, at present, globally about 820mn people are already food insecure. By the end of 2020, an additional 130mn is estimated to fall into this category. Particularly, women and children will suffer from the consequences of food insecurity to a great extent. Therefore, it is needless to say that the post-COVID era will call for urgent action and integration between different sectors of food production and supply to combat the impending threat of hunger pandemic.[17]

How is overnutrition or obesity-related to poor immunity?

            It must be remembered that good nutrition depends on the quality of food rather than quantity. Therefore, people belonging to affluent sections of society may also suffer from malnutrition in the form of overnutrition or obesity due to unhealthy food habits. Dependence on high calorie, high sugar, high-fat junk foods result in positive energy balance, and obesity. Obesity can increase the pro-inflammatory responses in our body and inhibit the immune cells thereby interfere with the body’s response to infections. Thus obese people have suppressed immune responses and antigen-killing abilities and fall ill more often than others.[18,19]

What foods should we eat to strengthen our immune system?

There is no one wonder food so as to say to strengthen our immune system. Therefore, we must eat a balanced diet comprising of fresh seasonal and locally available fruits and vegetables to get good nutrition. The immunity-boosting diet should include the following foods:

FoodstuffImmunity Nutrients Obtained
Fresh fruits & vegetables, preferably, coloured fruits and vegetables, citrus fruitsVit. C, Vit. E, Iron, Vit. A, Folate
lean meat, fish, eggs, poultry, milkProtein, Zn, Vit. B6, Iron, Vit. D, ω-3 fatty acids
Sprouts, nuts & seeds like rajmah, black gram, soybean, flax seeds, chia seeds, sesame seeds, walnuts, peanuts, almonds etc.Zn, Vit. E, Iron, ω-3 fatty acids
Berries like cranberry, gooseberry, elderberry, blueberry, blackberry etc.Energy, Vit. C, antioxidant and anti-inflammatory agents  
Herbs like coriander, basil, curry leaves, fenugreek leaves, celery etc.Antioxidant, anti-inflammatory, anti-infective agents
spices like cumin, saffron, cinnamon, turmeric, ginger, garlic, licorice, nutmeg, fenugreek etc.Antioxidant, anti-inflammatory, anti-infective agents  
  Mushrooms like shiitake mushroomsEnergy, Protein, Vit. B1, B2, B3, B6, Folate, B12, Copper, Zinc
  Prebiotics like banana, onion, garlic, radishes, cucumber, oatmeal, various seeds and berries  Functional foodSupply variety of nutrientsMaintains gut healthGood for immunity  
  Probiotics like yogurt, buttermilk, cheese, curd, fermented foods  Functional foodSupply  variety of nutrientsMaintains gut healthGood for immunity  

Can nutrition supplements prevent COVID 19?

No amount of supplement can prevent COVID 19. In most cases high dosage of vitamins does not get absorbed rather excess water soluble vitamins (vitamin B complex, Vitamin C) flush out from your system or fat soluble vitamin (Vitamin A,D,E,K) may create toxicity if taken without consulting the expert.

You must understand there is a Recommended Dietary Allowance per day for each micro-nutrient recommended by ICMR. Even if you consume extra, it will not be utilized in your body.

Please note, deficiency of vitamin D, B12, and iron is very common in India. It is advised to check these nutrient levels and in case of deficiency, one must take supplements as well as proper dietary support to ensure enough supply.

Elderly people above 60, also should consider taking multivitamin tablets after expert’s consultation.

It is best to consume a clean wholesome diet on a daily basis to ensure all the nutrients. [21]

How does nutrition affect the immune system? 5

How to ensure proper absorption of the nutrients?

More than 50% of Indians are suffering from acidity, bloating, flatulence, etc which are an indication of poor gut health. Consuming a clean diet is necessary not only to supply the necessary nutrients for immunity but also to improve the health of your gut. Good gut health is essential for the absorption, utilization of the nutrients, the formation of immunity-boosting cells, and fine-tuning of the overall immune system.

Constant consumption of refined cereal, refined sugar, refined oil, etc are toxic for gut health which enhances the growth of bad bacteria in the gut microbiome and finally overpowers the good bacteria in the gut. This can cause leaky gut and various inflammatory diseases in the due course. Therefore avoiding the consumption of such food (mainly ultra-processed foods) is mandatory to maintain gut health.

How can we boost our immunity?

There are various ways to boost the immune system of our body. The most important among these are[20]:

  • Eating a healthy diet high in fresh fruits and vegetables
  • Exercising regularly
  • Abstinence from smoking and alcoholism
  • Sleeping adequately (Regular sleeping hours to maintain biological rhythm )
  • Staying hydrated
  • Avoiding junk foods
  • Maintaining a desirable body weight
  • Minimizing stress


There are multiple factors you should consider to boost immunity. Consuming only nutrient supplements may not help much. Adopt a sustainable lifestyle with a healthy diet, deep sleep, sufficient activity & exercise, and control stress to get the actual benefit. All the best.


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  3. Ahmed M. Abbas AM, FAthy SK, Fawzy AT, Salem AS, Shawky MS. The mutual effects of COVID-19 and obesity. Obesity Medicine. May, 2020 doi: 10.1016/j.obmed.2020.100250
  4. Jayawardena R, Sooriyaarachchi P, Chourdakis M, Jeewandara C, Ranasinghe P. Enhancing immunity in viral infections, with special emphasis on COVID-19: A review. Diabetes & Metabolic Syndrome: Clinical Research & Reviews. July–August 2020.
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  6. Chandra RK. Nutrition and the immune system: an introduction. The American journal of clinical nutrition. August, 1997. doi: 10.1093/ajcn/66.2.460S.
  7. Malnutrition and the Immune System. In: Pediatric Allergy, Asthma and Immunology. Springer, Berlin, Heidelberg. 2008
  8. Wintergerst ES, Maggini S, Hornig DH. Contribution of selected vitamins and trace elements to immune function. Annals of nutrition & metabolism. August, 2007. doi: 10.1159/000107673.
  9. Karacabey K, Ozdemir N. The Effect of Nutritional Elements on the Immune System. Journal of Obesity & Weight Loss Therapy.November, 2012. doi:10.4172/2165-7904.1000152
  10. Childs CE, Calder PC, Miles EA. Diet and Immune Function. Nutrients. August 2019. doi: 10.3390/nu11081933
  11. Mora JR, Iwata M, von Andrian UH. Vitamin effects on the immune system: vitamins A and D take centre stage. Nature reviews. Immunology. September, 2008. doi: 10.1038/nri2378
  12. Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. November, 2017. doi: 10.3390/nu9111211
  13. Axelrod AE. Role of the B Vitamins in the Immune Response. In: Phillips M., Baetz A. (eds) Diet and Resistance to Disease. Springer, Boston, MA. 1981.
  14. Wessels I, Maywald M, Rink L. Zinc as a Gatekeeper of Immune Function. Nutrients. December, 2017. doi: 10.3390/nu9121286
  15. Keen CL, Uriu-Adams JY, Ensunsa JL, Gershwin ME. Trace Elements/Minerals and Immunity. In: Gershwin M.E., Nestel P., Keen C.L. (eds) Handbook of Nutrition and Immunity. Humana Press, Totowa, NJ. 2004.
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  18. França TGD, Ishikawa LLW, Zorzella-Pezavento SFG, ChiusoMinicucci F, da Cunha MLRS, Sartori A. Impact of malnutrition on immunity and infection. Journal of Venomous Animals and Toxins including Tropical Diseases. June, 2009.
  19. Butler MJ, Barrientos RM. The impact of nutrition on COVID-19 susceptibility and long-term consequences. Brain, Behavior, and Immunity. July, 2020.
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