By: Nutrition expert- Vidula Kozarekar, Mumbai.
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Immunity is the ability to defend against infection and disease. The immune system is composed of a variety of cells, tissues, and molecules. The immune system is generally classified into 2 main “arms”- innate (nonspecific) and adaptive (specific and acquired) – but all components work synergistically and function in a highly orchestrated manner.
The innate arm (e.g., involving phagocytes, Natural Killer cells) can respond very quickly but lacks specificity (i.e., the same response to all challenges), whereas the adaptive response (e.g., involving T and B lymphocytes) has both antigen specificity and “memory” properties, but takes much longer to develop on initial exposure to an infectious agent, although the speed and magnitude of this response is increased with subsequent exposures (1), (2), (3).
Factors strengthening immunity:
• Good nutritional status
• No stress
• Moderate exercise
• Good sleeping habits
Factors Weakening immunity
• Sedentary lifestyle
• Smoking, alcohol, tobacco abuse
• Frequent traveling
• Crowded places
• Advancing age
• Environmental factors
Importance of nutrition in immune system:
As humans age, the risk and severity of infections vary in line with immune competence according to how the immune system develops, matures, and declines. Several factors influence the immune system and its competence, including nutrition. A bidirectional relationship among nutrition, infection and immunity exists: changes in one component affect the others. For example, distinct immune features present during each life stage may affect the type, prevalence, and severity of infections, while poor nutrition can compromise immune function and increase infection risk. Various micronutrients are essential for immune-competence, particularly vitamins A, C, D, E, B2, B6, B12, folic acid, iron, selenium, and zinc (4).
Malnutrition by itself can cause death; however, epidemiological data reveal that it greatly increases susceptibility to and severity of infections, and is a major cause of illness and death concomitant with numerous diseases. It is the direct cause of about 300,000 deaths per year and indirectly responsible for about half of all deaths in young children. The causal relationship of malnutrition with immune suppression and infection is also aggravated by the profound effect of many infections on nutrition itself. For example, gastrointestinal parasites can lead to diarrhoea, anaemia and nutrient deprivation. It is also well established that Aids, tuberculosis and other chronic infections cause cachexia and anaemia (5).
Among the essential micronutrients required to support a normal immune function, vitamin C, vitamin D and the mineral zinc play a central role. Through their complementary and synergistic effects, they support components of both innate and adaptive immunity which comprise epithelial barriers, cellular defence and antibodies constituting the three main lines of immune defence.
Silvia Maggini et al found in a literature review that; vitamin C, D and zinc are actively used by cells of the immune system engaged in fighting infections like upper respiratory tract infections and a state of micronutrient deficiency can arise during severe infections. They also found that; ensuring adequate levels of micronutrients such as vitamin C, D and zinc may be particularly important in situations putting an extra challenge on the immune system such as when exposed to sudden temperature changes or when spending time in confined spaces (e.g., airplanes, trains, buses, hospitals, schools, or open spaces) where the risk of spreading infectious diseases is high because of close contact and long exposure (6).
Mariangela Rondanelli et al found that; vitamin C, regular supplementation (1 to 2 g/day) may reduce the duration (in adults by 8%, in children by 14%) and the severity of Common Cold. Considering zinc, supplementation may shorten the duration of colds by approximately 33%. Common Cold patients may be instructed to try zinc within 24 hours of onset of symptoms. Regarding vitamin D, the supplementation protected against Common Cold overall. Patients who were deficient in vitamin D experienced the most benefit (7).
Belderbos ME et al concluded that, Vitamin D deficiency in healthy neonates is associated with increased risk of RSV LRTI (Respiratory syncytial virus lower respiratory tract infection) in the first year of life. Intensified routine vitamin D supplementation during pregnancy may be a useful strategy to prevent RSV LRTI during infancy (8).
Vitamin D deficiency is also found to be associated with Increased risk of autoimmune diseases (e.g., type 1 diabetes, multiple sclerosis, systemic lupus erythematous, rheumatoid arthritis) (9), (10).
Upper respiratory tract infections such as the common cold and influenza are among the most common illnesses in humans and despite great advances in medicine, continue to be a great burden on society in terms of human suffering and economic losses.
The intake of a variety of nutrients should be encouraged to promote proper balance among all nutrients. At this crucial time, the best dietary advice to enhance immune function in healthy people is to ensure variety, balance and moderation of the nutrients.
- McArdle, W. D. (2018). Sports and exercise nutrition. Lippincott Williams & Wilkins.
- Walsh, Neil P., et al. (2011). Position statement part one: immune function and exercise.