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Immunity and nutrition

Rohini Diniz 

The human body has an intrinsic inbuilt mechanism that defends it against potentially harmful foreign agents. This system known as the immune system is a complex and integrated system of cells, tissues and organs that have specialised roles in defending against foreign substances and pathogenic

microorganisms including bacteria, viruses and fungi. 

On one hand, the immune system protects the body from foreign invading pathogens while on the other hand, at times it attacks the body’s tissues and cells leading to chronic inflammation and the development of allergic reactions and autoimmune disease. For the immune system to function optimally there has to be a delicate balance between the destruction of invading pathogens and avoidance of self-destruction. 

The cells of the immune system are formed in the bone marrow and circulate through the blood and lymph to the peripheral tissues.

The organs of the immune system include the thymus, spleen and lymph nodes. The immune system is broadly divided into innate immunity and

adaptive immunity. 

Innate immunity involves immediate, non-specific responses to foreign invaders and is the first line of defence against foreign substances and pathogenic microorganisms that do not involve immunologic memory of pathogens. The innate immune system comprises various anatomical barriers such as the skin, the acid in the stomach and the normal gut microflora and also soluble factors and phagocytic cells. The soluble factors include the complement system that consists of a biochemical network of more than 30 proteins in the plasma and on cellular surfaces that are a key component of the innate immunity, acute phase reactant proteins and messenger proteins called cytokines.

Adaptive immunity also known as acquired immunity is the second-line defence against pathogens and takes several days or weeks to develop fully. It is much more complex than innate immunity as it involves antigen-specific responses and immunologic memory. An interaction between the components of both innate and adaptive immunity together protects the body from infection and disease. 

Nutrition has a great impact on the immune system and the science of nutrition and immunology are closely linked. Among the nutrients, energy, protein, iron, copper, zinc, selenium and vitamins A, C, E, B-6; and folic acid – all have important influences on immune responses and deficiencies of these key nutrients results in immunosuppression and dysregulation of an immune response. Malnutrition is the most common cause of immune deficiency in the world, which in turn increases one’s susceptibility to infection and illness. Infections and illnesses, in turn, precipitate malnutrition through the loss of appetite and consequently decreased food intake, impaired nutrient absorption, increased nutrient losses and alteration of the body’s metabolism such that nutrient requirements are increased. 

Proteins provide amino acids which are critical for the formation of antibodies and other immune factors. Deficiencies of protein significantly increase susceptibility to infection by adversely affecting both innate and adaptive immunities. Adequate intake of protein-rich foods – pulses, sprouts, dals, nuts, oilseeds, low-fat milk, lean meats, egg, poultry, fish and shellfish in the daily diet helps keep the immune system strong. 

Research studies have shown that several types of dietary fatty acids can modulate the immune response. Among them are the long-chain polyunsaturated fatty acids of the omega-3 and omega-6 classes. Fatty acids have several functions in immunity including providing energy for the immune cells and as precursors for eicosanoids, which are 20 carbon derivatives that play key roles in inflammatory and immune responses. In the body the omega-3 PUFAs found in soya bean oil and mustard oil as well as foods like wheat, bajra, urad, Bengal gram (chana), cowpea (chawli or lobia), rajma, soya bean, walnuts, mustard seeds, flaxseeds (alsi or sonbiya), chia seeds, fish particularly mackerels, sardines, tuna and

salmon, fish oils and other seafood including algae and krill have a greater anti-inflammatory response as compared to the

omega-6 PUFAs. 

Vitamin A found in foods of animal origin like milk and milk products, butter, ghee, egg yolk, liver and fish liver oils is another immunity-boosting nutrient. Dark green leafy vegetables, yellow-orange fruits and vegetables, red palm oil, spirulina and cow’s milk are rich sources of beta-carotene, a carotenoid that gets converted into vitamin A within the body.

Vitamin A and its metabolites play critical roles in both innate and adaptive immunity. Vitamin A helps maintain the structural and functional integrity of the skin and mucosal cells of the eyes, respiratory, gastrointestinal and

genitourinary tracts which in turn function as a barrier against infections. Vitamin A is also important for the normal functioning of several types of immune cells in

the innate response and is necessary for the generation of antibody responses to

specific antigens.

To be continued . . . 

(Writer is a consultant nutritionist with 20 years of experience, practising at Panaji and can be contacted on

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