The critical role and complex functions of the immune system in overall health and protection are often underestimated until the immune system is not working properly. Like an army of soldiers, this system has many vital functions and uses the body’s defenses to guard against damage, disease, and infectious organisms that include bacteria, viruses, fungi, and parasites.1-3 The immune system can also recognize, protect, and destroy abnormal cells derived from host tissues.1,3 

The 2 general functional divisions of the immune system are the innate (also termed “natural”) immune system and the acquired (also termed “specific” or “adaptive”) immune.1 The immune system operates by providing an exclusion barrier, identifying and eliminating pathogens, identifying and tolerating nonthreatening sources of antigens, and maintaining a memory of immunological encounters.1

The immune system comprises various organs, cells, and proteins. The skin, cornea, and mucosa of the respiratory system, gastrointestinal tract, and genitourinary tract form a physical barrier that is the body’s first line of defense.2 Apart from the nervous system, the immune system is considered the most complex and multifaceted system in the human body.4 Its intricate network involves various cells distributed throughout the human body, which move via the lymph stream and the bloodstream.1 In some areas, the cells are classified as primary lymphoid organs, where immune cells appear and mature (bone marrow and thymus), and secondary lymphoid organs (lymph nodes, spleen, and gut-associated lymphoid tissue), where mature immune cells interact and respond to antigens.1 

For the immune system to be effective, it is imperative, however, that it distinguish between self and nonself cells, organisms, and substances and be able to eliminate harmful nonself entities.2,4 When issues arise within the immune system, autoimmune diseases such as rheumatoid arthritis, lupus, multiple sclerosis, and Graves’ disease may occur; these conditions involve problems with the acquired immune system’s reactions. In an autoimmune reaction, antibodies and immune cells target the body’s own healthy tissues by mistake, signaling the body to attack them.2,4 Individuals exhibiting signs of autoimmune diseases, such as fatigue, fever, and inflammation, should always be referred to their primary health care providers for further medical evaluation.

As more individuals become proactive about their overall health, pharmacists are likely to encounter patients seeking guidance about the use of the various nutritional supplements marketed to boost the immune system, especially right before the start of, or during, cold and influenza season. Pharmacists are in a pivotal position to advise and educate patients about the proper use of these nutritional supplements and to provide patients with pertinent information about immune system health. They can also be instrumental in ascertaining whether the use of nutritional supplements is appropriate and in directing patients with medical conditions to discuss the use of these supplements with their primary health care provider.

FACTORS THAT MAY IMPAIR THE IMMUNE SYSTEM

Researchers have discovered certain factors that may affect the immune system, such as poor diet, chronic stress, lack of sleep, specific medical conditions, and the use of certain pharmacological agents such as corticosteroids and immunosuppressive agents used to treat autoimmune disorders, immune-mediated diseases, and transplant patients.5-8 Chronic sleep loss is connected not only to an increase in inflammatory markers but also to immunodeficiency.8 Additionally, research has shown that the aging process can affect the immune system as well and that there appears to be a correlation between nutrition and immunity among elderly patients because older individuals tend to eat less, may have less variety in their diets, and experience loss of appetite due to the use of certain medications or medical conditions.9

Researchers are continually exploring the effects of diet, exercise, age, psychological stress, and other factors on the immune response in both animals and humans.10 Some research has demonstrated that undernourishment with or without having nutritional deficiencies of zinc; selenium; iron; copper; vitamins A, C, E, and B6; and folic acid significantly influence immune system responses.11 Additionally, overeating and being overweight or obese may also diminish the immune response.11

According to the Academy of Nutrition and Dietetics, good nutrition habits such as eating a healthy and balanced diet are crucial to promoting a strong immune system, and the suggested essential nutrients that support immune health include vitamins A, B6, C, and E, as well as folic acid, zinc, selenium, and iron (table 113-23).12 Moreover, the use of probiotics and prebiotics may influence the immune system response.12



NUTRITIONAL SUPPLEMENTS

Many of the products marketed for the overall enhancement of the immune system contain 1 or more of the vitamins A, B6, C, D, and E, along with zinc and selenium. Some of the commonly used products include the line of Airborne products— which contain vitamins, minerals, and various ingredients such as echinacea, ginger, and other herbal ingredients for immune enhancement—and Emergen-C, which contains a combination of vitamin C, B vitamins, and minerals (table 2). Other products marketed for immune support include prebiotics and probiotics, some containing colostrum, which is rich in antibodies; immunoglobulins A and E; and growth factors that may be the components that provide immune-modulating benefits.24 There are also numerous complementary products marketed to enhance the immune system as well as to prevent and manage the symptoms most commonly associated with the common cold and flu virus, which may contain one or more of the following: echinacea, elderberry, and zinc.24



One of the most critical steps in maintaining overall health and building a strong immune system is to incorporate healthy lifestyle habits into a daily routine. During
counseling, pharmacists can suggest and remind patients of nonpharmacological measures that may enhance overall health (table 3).25



CONCLUSION

Ideally, eating a healthy and balanced diet is the optimal approach for building and maintaining a strong immune system. However, many patients elect to use nutritional supplements to ensure that all their nutritional needs are met. Prior to recommending the use of any of these supplements, pharmacists should screen for possible contraindications and drug or nutrient interactions. Patients with medical conditions or those who take other medications should be encouraged to discuss the use of these supplements with their primary health care providers before using them. While counseling patients about the various products marketed for the immune system, remind patients who use these supplements to always adhere to recommended doses and to use products only as directed. Patients should also be cautioned about taking megadoses of vitamins and to always read labels to check for therapeutic duplications, which may lead to toxicities if they are taking other nutritional supplements. Pharmacists can also use this opportunity to remind patients about the importance of obtaining the annual flu vaccine as well as maintaining immunization schedules for other recommended vaccines.
 
Ms. Terrie is a clinical pharmacist and medical writer based in Haymarket, Virginia.

References
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