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General Preventive Maintenance of the Immune System:
A Brief Overview from
a Behavioral and Nutritional Perspective
Stephen Behr, Ph.D.
There is more and more information indicating that dysfunction of the immune system should be included in the category of degenerative conditions that require prevention and maintenance, rather than reacting strictly after the fact by means of symptomatic treatments or antibiotics. After all, we understand the importance of staying fit. We exercise to maintain muscle, heart and lung function. We stop smoking to prevent lung cancer. We eat more fruits and vegetables to avoid cancer. We watch our weight to help prevent hypertension and diabetes. We should treat our immune system with the same dedication.
Although he did not express it in exactly these terms, the use of vitamin C to boost the immune system, and thereby avoid the common cold, was advocated 25 years ago by Linus Pauling. It is really only within the last ten years that the notion that the immune system could be maintained or modulated has become somewhat popular among health care providers and the public. One of the barriers in developing simple preventive approaches for complete immune health is the tremendous complexity of the immune system. Such a complex system can be affected, negatively or positively, in many ways.
The immune system is a diffuse interacting whole-body network, rather than a discrete organ or body part. the heart or brain, and can be divided into three sub-systems as show in Fig. 1: phagocytic cells that "ingest" and "digest" parasitic invaders, t-lymphocytes that destroy foreign or infected cells by "cell-mediated" immunity, and B-lymphocytes that produce antibodies.
Fig. 1 also indicates the interactions between these three sub-systems as follows:
- Phagocytes "present" antigens to lymphocytes.
- T-lymphocytes stimulate macrophages and B-lymphocytes by secreting cytokines.
- Antibodies mark parasites for destruction.
The failure of any one of the sub-systems seriously impedes the other two.
While we are born with phagocytic cells, which are part of what is called "innate immunity," lymphocytic immunity is "acquired" after birth. The maturation of t-lymphocytes is shown in Fig. 2. Bone stem cells are shuttled to the thymus where they become mature T-cells which are then seeded into the secondary lymphoid organs. As do all physiological systems of the body, the immune system deteriorates with age. The "involution" of the thymus described in Fig. 3 decreases the capacity to generate new T-cells. Furthermore, as a result of continuous turnover throughout life, the existing T-cells in the body gradually lose their capacity to proliferate. The overall result is the gradual loss of the body's ability to mount an immune response.
Immune System Stressors
Part of this aging process is undoubtedly programmed into our genes. But, a large part is also the result of personal habits and our surrounding environment. There are three general categories of stressors to the immune system:
- Personal habits or lifestyle, such as nutrition, sleep, exercise, alcohol consumption, smoking or drug use.
- Environmental stresses we encounter everyday such as contaminants, toxins, allergens and extreme weather.
- Traumatic or disease states such as trauma, burns, cancer, renal disease, chronic fatigue, and AIDS; and/or various procedures or treatments which address the trauma or disease including surgery, chemotherapy, radiation, corticosteroids, etc.
Some habits and activities are so routine that we may think nothing of their effects on our immune sytsem, such as:
Sleep deprivation, especially when accompanied with jet lag and the resulting changes in circadian rhythm, depresses immune function (Irwin et al 1996).
Exercise, which many people assume can do only good, can have deleterious effects on the immune system when overdone (Nieman, 2000).
Cold weather can set off an asthma attack and can also depress cell-mediated immunity.
Excessive alcohol intake can cause deficiencies in host defense, particularly in T-cell function (Szabo 1999).
Cigarette smoking is immunosuppressive, and has been associated with various autoimmune conditions (Sopori et al 1998; George et al 1997).
The Role of Nutrition
Nutrition affects immunity in many fundamental and subtle ways. Protein-energy malnutrition and iron have the largest impact, with more impact on cell-mediated and non-specific immunity than on humoral immunity (Scrimshaw and San Giovanni 1997). Protein-calorie malnutrition is part of the problem of immune deficiency and parasitic infections in developing countries, but is rare in North America. However, slight deficiencies in zinc, copper, selenium, and/or vitamins A, C, E, B6 and folate can be linked with immunological deficiencies, especially in children (Chandra 1999) and in the elderly (Lesourd 1997). Although supplementation is generally helpful in assuring an adequate intake of these vitamins and trace elements, care is required in order to achieve the proper balance. For example, excess zinc intake can cause deficiencies in copper nutriture (Greger 1978).
Glutamine, normally a non-essential amino acid, may become "conditionally essential" in certain situations of catabolism, such |