Research at INFS

Evidence-based review on immunity

Since the pandemic broke out, the term ‘immunity’ has garnered a lot of attention. Improving the immune system has become one of the top recommended precautions. Many companies have started advertising their ‘immunity boosting’ products. But have we understood the term to its core?

Boosting immunity is much more than simply consuming a handful of pills. It is a lifestyle change and therefore needs a profound analysis. We need to comprehend the concept by understanding the science behind it.

We bring forth our latest evidence-based review on immunity. Our goal is to decipher the term ‘immunity’ and put forward a holistic approach that is based on long term lifestyle changes.


 Evidence-based Review on Immunity


The whole world, especially our country, is going through a pandemic. Along with safety measures like staying at home, wearing masks, hygiene practices, social distancing and vaccinations, improving immunity is a must. A lot of immune-boosting materials are available without any scientific background.  In this review work, authors have made an effort to conclude that to improve/boost immunity, a holistic approach is required rather than just the addition of some supplements. Immunity is a complex system that has to be finely balanced by focusing on making long-term changes and building positive habits in our lifestyle.          


Immunity is the main mechanism of the host to defend against infectious agents, thus protecting the body from diseases (1). It is the body’s defense system against diseases. Immunity is natural and/or acquired.


This is evidence-based research work. We have reviewed 51 articles and 31 were included based on the criteria. Only human studies were considered and studies published after 2005 were considered. In this article, guidelines for adults were considered.


Immunity is a complex system. The habits weakening immunity were stress, sedentary lifestyle, smoke, processed foods, and alcohol. Immunity is a complex system that has to be finely balanced by focusing on making long-term changes and building positive habits in our lifestyle. there should not be an over-reliance on these supplements. Increasing immunity through physical exercise, consuming balanced nutrition, and taking care of factors like sleep, hydration and stress should be the big picture focus.


“Optimal immune function is dependent on a healthy immune system”

                                                                                                Maggini et al. (2018)


Immunity is the main mechanism of the host to defend against infectious agents, thus protecting the body from diseases (1). It is the body’s defense system against diseases. Immunity is natural and/or acquired. Natural is what you are passed down through vaginal birth, breastfeeding, and genetics whereas, acquired is either through vaccination or by recovering from an illness (infectious disease).  Fig 1 shows a schematic representation of the Classification of Immunity.


Fig 1 Classification of Immunity

Evidence based review on Immunity

The immune system is a delicate balance that is maintained in the body to keep the foreign bodies from invading and taking over our body. This system should be effective in keeping the foreign bodies out and those that invade should be efficiently eliminated. It works through cell signaling and the action of killer/helper cells.

In the lifespan of an individual, immunity will not be the same always. Due to several reasons, immunity will be different. In this article, we will focus on habits that affect immunity.

Habits weakening Immunity

The day-to-day activities will gradually affect immunity. Some activities that will adversely affect your immunity are: 

  • Stress – When a person is stressed, the brain boosts the production of the hormone cortisol. Excess of cortisol hormone impairs the function of infection-fighting T cells. Thus stress can affect immunity (3).  


  • Sedentary Lifestyle – According to a study published in the American Journal of Preventive Medicine, irrespective of age, gender, other habits like smoking and drinking, a sedentary lifestyle is tied to an increased risk for premature death (4). This is because, physical inactivity can gradually lead to a weakened immune system, inflammation, and other chronic diseases thus affecting the overall health.


  • Smoke -Nicotine and other tobacco components have several anti-inflammatory effects, thus contribute to an altered immune set point in smokers (5).  


  • Sleep – Sleep deprivation and weakened immunity are closely associated. Sleep deprivation leads to decreased lymphocyte blastogenesis and natural killer cell activity and upregulates IL-1 and IL-2 (21). However, sleep also increases IL-2 production by T-cells (6). Short habitual sleep (<6 hrs) is associated in humans with reduced life span, increased vulnerability to viral infection, and reduced antibody titers after vaccination (7).


  • Processed Foods – The intake of a diet exorbitantly high in sugar, such as sweetened foods and beverages limits the immune system’s ability to combat disease. It may do this by reducing the effectiveness of white blood cells and increasing inflammation (3). Excessive intake of salted foods inhibits the normal immune function, suppress anti-inflammatory response, alter gut bacteria, and promote the generation of immune cells that are implicated in the pathogenesis of autoimmune diseases (8).


  • Alcohol – Alcohol consumption affects the number, survival, and function of both innate and adaptive immune cells, thereby interfering with immune responses (9). High consumption of alcohol suppresses a wide range of immune responses.

Replacing Bad Habits

All the above-mentioned habits have a direct association with immunity. There are ways and methods to replace bad habits with good ones which will help in improving immunity.

Table 1 shows Replacing Bad Habits to Good Habits.

Bad Habits Replacing to Good Habits
Stress Short-term stress that lasts for a period of minutes to hours activates the immune system by signaling neurotransmitters and stress hormones. However, this is not unique for all (10). Hence manage chronic stress with lifestyle modifications.
Sedentary Lifestyle  As per WHO (2020) (11) adults (18 to 64 yrs) should perform at least 150 to 300 minutes of moderate-intensity aerobic physical activity per week or at least 75 to 150 minutes of vigorous-intensity aerobic physical activity per week, or an equal combination of moderate- and vigorous-intensity activity throughout the week. 
Smoke Cigar smoking behaves like a double-edged sword that affects immunity (12). Always, quitting smoking is beneficial for the immune system. Once the immune system is no longer exposed to tar, nicotine, and all of the other chemicals in cigarettes, the immune system will start to rebound (13).
Sleep There exists a bidirectional association between sleep and immunity.  According to the National Sleep Foundation of US, adults (>18yrs) require 7 to 9 hours of sleep at night for the body and mind to function optimally thereby improving immunity (14).
Processed Foods Processed foods are deleterious to health in multiple ways. It is always safe to consume a balanced diet for maintaining immunity. Details are discussed below in section 4. 
Alcohol As per the Dietary Guidelines for Americans recommends that adults (> 18yrs) can choose not to drink, or to drink in moderation by limiting intake to 2 drinks or less in a day for men or one drink or less in a day for women, on days when alcohol is consumed (15). But avoiding alcohol is always best for immunity as well as health 

How to improve Immunity

To improve immunity, a multifaceted approach is required which includes nutrition, lifestyle, and physical activity.

  • Nutrition

A diet rich in an adequate amount of macro and micronutrients is essential for a healthy immune system. The daily diet should include an adequate amount of foods from all food groups such as vegetables, fruit, nuts, legumes, fish, and healthy dietary fats are associated with a lower risk of chronic non-communicable diseases as well as improved immune function (16). Adequate water intake is a must for immunity.

  • Probiotics

The live microorganisms that can be consumed through fermented foods (curd/buttermilk) or probiotic supplements offer benefits such as improving immunity. Probiotics support a healthy immune system by preventing allergic disease to downregulate inflammation enhancing anti-infection activities (17).

  • Herbs and Spices 

Certain herbs and spices are known for their anti-viral properties. The bioactive compounds of the following herbs and spices have shown promise when it comes to anti-viral activity and immunity – turmeric (curcumin), black pepper (piperine), cinnamon, clove (eugenol), ginger, garlic, basil, giloy, neem (18, 19, 20, 21, 22, 23, 24, 25, 26). Several studies indicate these herbs and spices have properties that will help bolster the body’s defense as well as reduce the effectiveness and spread of the invading microorganism in the body. Herbal compounds are studied extensively across the globe due to their popularity in different cultures and more recently the ability to study their active compounds. The high efficacy in reducing inflammation as well as anti-microbial properties means they can be used therapeutically. In most cultures, these herbs are common ingredients in the kitchen; however, cooking them at high temperatures can destroy the bioactive compounds that bestow them with anti-inflammatory and other benefits. It is recommended to add some of these herbs and spices towards the end of the cooking process and to not subject them to pressure cooking or heat for more than a few minutes. The addition of these herbs/spices regularly in the diet offer health benefits especially improving immunity.

  • Physical activity

Engaging in physical activities regularly decreases the activation of the immune system and improves immunosurveillance and immunocompetence (27). Regular exercising limits or delays inflammation. Also, a physically active lifestyle reduces the risk of contracting a range of communicable diseases including viral and bacterial infections (28).

  • Yoga

Yoga is an ancient Indian practice comprising different techniques such as asanas, breathing techniques, relaxation, meditation, etc. Research on Yoga and its effect on immunity is still in its infancy and there are multiple challenges when creating studies for systematic review. There is no uniformity of Yoga techniques used, and the inflammatory markers or participant backgrounds (healthy vs those suffering from diseases). Of the existing reviews, current research indicates that Yoga has a positive influence on inflammatory markers (salivary cortisol, IgA, leukocytes, and more) as well as the anti-inflammatory response (IL-1ß, IL-6, IL10, CRP, TNF, NF-KB) and hence the immune system (29). Yoga practices give results after 4 weeks and more when it is practiced daily. Sessions lasting atleast 40 minutes that combine asanas, breathing practices, and meditation show more significant differences from the control group. 

Supplements or Immune boosters

There is no denying the fact that deficiency of nutrients such as vitamin A, C, E, K, Zinc, and Vitamin D has been linked to various blunted immune responses in some way or the other. An example is Vitamin A contributes to the production of white blood cells in bone marrow, which in turn can help us fight various infections. However, when we talk about boosting immunity supplements, they are perhaps marketed as something that can make a permanent enhancement or protect against any virus or a specific pathogen/disease. However, as we know from our understanding of the immune system, it is a very complex and multi-layered framework, which is dependent on various processes, nutrients immunity, and functions, and no one pill, supplementation, or drug in isolation can help us boost the overall immunity against the pathogens/specific pathogen that may occur from time to time.   

When a person is purchasing a supplement, always check the nutrition label of these immunity boosters, the overall contents may be below than required ICMR RDA (30) or might not have all the top nutrients required by our body to boost the immunity. 

For example; here are some of the examples of supplements that names themselves as Immunity Boosters, but are just meeting the ICMR RDA of Vitamin C and Zinc, what about the other important vitamins like Vitamin D, Vitamin A, Vitamin E, B complex, etc. and similarly, Folate, Zinc, Iron, Selenium and Copper, etc(31). There is a significant difference between a supplement and a multivitamin. Before purchasing a supplement, one must thoroughly check the nutrition label and try to supplement it accordingly.

Evidence based review on Immunity


Evidence based review on Immunity

So as a takeaway for supplements, get the blood test once or twice a year to check the deficiency or borderline sufficiency, toxicity, and supplement the necessary micronutrient in consultation with your physician and also make dietary changes in consultation with a nutritionist.


Immunity is a complex system that has to be finely balanced by focusing on making long-term changes and building positive habits in our lifestyle. Sometimes compounds consumed to reduce the inflammation markets might do more harm to the body than good when consumed in large quantities. Therefore, there should not be an over-reliance on these supplements. Increasing immunity through physical exercise, consuming balanced nutrition, and taking care of factors like sleep, hydration and stress should be the big picture focus.


Jyoti Dabas, CEO, Institute of Nutrition and Fitness Sciences (

Praveen Budhrani, Faculty, Institute of Nutrition and Fitness Sciences, (

Dr. Shunmukha Priya. S, Research Supervisor and Faculty, Institute of Nutrition and Fitness Sciences,



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