Most of us are afraid these days of coronavirus, influenza and tuberculosis like infectious diseases which are caused by pathogenic microorganisms such as bacteria, virus, fungus and protozoa. When these pathogens enter the body our immune system acts immediately to protect us. However for that we should have a strong immune system. Therefore, this week’s health capsule is going to discuss about different kinds of food which contribute to strengthening the immune system.

 

Our immune system largely contains tissues, cells and proteins. Its main function is to defend our body from pathogens, which are disease-causing organisms. When pathogens try to invade our body, as a first step the immune system identifies pathogens. This is done by using antigens which are on the surface of pathogens. Meanwhile these antigens provide a unique sign for the pathogens that enable the immune system cells to recognise different pathogens and distinguish them from the body’s own cells and tissues. As the next step, the immune system responds in 02 ways; namely the innate immune response and the adaptive immune response. 

 

 

A rapid reaction and innate immune cells recognise certain molecules found on many pathogens. They then react to signaling molecules released by the body in response to the infection. Through these actions, innate immune cells quickly begin fighting an infection. These include physical barriers, such as epithelial cell layers that express tight cell-cell contacts, the secreted mucus layer that overlays the epithelium in the respiratory, gastrointestinal and genitourinary tracts, and the epithelial cilia that sweep away this mucus layer permitting it to be constantly refreshed after it has been contaminated with inhaled or ingested particles. This response results in an inflammation. The cells involved in this reaction could kill pathogens and also help activate cells involved in adaptive immunity.

 

 

A slower immune response than the innate response is better able to target specific pathogens. There are 02 main cell types involved in this response such as T cells and B cells. Some T cells kill pathogens and infected cells whereas other T cells help control the adaptive the immune response. The main function of B cells is to make antibodies against specific antigens. Antibodies, also known as immune globulins, are proteins that attach themselves to pathogens. This signals immune cells to destroy the pathogen and make T and B cells to respond to the new antigens when a pathogen causes an infection. Once exposed to the pathogen, these cells develop a memory for the pathogen, so that they are ready for the next infection. As part of the adaptive immune response, some T and B cells change into memory cells. Memory cells mostly remain in the lymph nodes and the spleen and “remember” particular antigens. If a person becomes infected with the same pathogen again, these cells are able to quickly and strongly begin fighting the infection.

 

 

The immune functions are disturbed by several factors such as malnutrition, ageing, physical and mental stress. Studies have proved that the nutritional deficiency can impair immune functions. Normally, foods contain various substances that can control the physiological functions of the body. Modulating immune responses are the most important functions of foods.

Therefore, the ingestion of foods with immune-modulating activities is considered an efficient way to prevent immune functions from declining and reduce the risk of infection.  Growing evidence suggests that for certain nutrients such as omega 3 polyunsaturated fatty acids (PUFA), micronutrients (zinc, vitamins D and E), and functional foods including probiotics and tea components, whose intake is increased above currently recommended levels, may help optimize immune functions. This is done by improving defence function. Thus there is resistance to infection and tolerance is maintained. Many of these nutritive and non-nutritive food components are related in their functions to maintain or improve immune function including inhibition of pro-inflammatory mediators, promotion of anti-inflammatory functions, modulation of cell-mediated immunity, alteration of antigen-presenting cell functions, and communication between the innate and adaptive immune systems. 

Maintaining a healthy lifestyle is a major factor which can strengthen our immune system. Poor nutrition results in increased infection and increase susceptibility to immune system dysfunction. However food is not a major contributor to boost the function of immune system. Other healthy lifestyle practices have a significant effect on the proper function of immune system. These practices are stopping smoking, doing regular exercise, maintaining a healthy weight, getting adequate sleep, trying to minimise stress and following safety precautions to avoid infections. Therefore, we have to pay attention to all of previously mentioned factors in order to protect ourselves from infections.

 

(The writer is a medical laboratory technologist at a private hospital and holds a MSc. Degree in Industrial and Environmental Chemistry from the University of Kelaniya and a BSc. degree in Food Production and Technology Management from the Wayamba University of Sri Lanka)