How can you improve your immune system? On the whole, your immune system does a remarkable job of defending you against disease-causing microorganisms. But sometimes it fails: A germ invades successfully and makes you sick. Is it possible to intervene in this process and boost your immune system? What if you improve your diet? Take certain vitamins or herbal preparations? Make other lifestyle changes in the hope of producing a near-perfect immune response?
Here in this scientific review, you will find the answers to several questions about our immune system and how to boost it using some natural supplementation.
The two arms of the immune system, humoral and cell-mediated immunity, work together as an integrated defensive system. Normally, antibodies are produced in response to a foreign material (acquired immunity). Immune complexes form between antibodies and antigens and are scavenged from the circulation or mucosal surfaces. Cell- mediated immunity relies on T and B lymphocytes, mast cells, macrophages and others. T-cells regulate other defensive cells, including macrophages and killer cells. Cells of the immune system, turn over rapidly, hence, their nutrient requirements are high.
In addition, phagocytic cells generate free radicals and other reactive species to attack invaders. These oxidants contribute to the oxidative burden of organs which, if unchecked by the body’s antioxidant defenses, can damage membrane lipids, diminish T-cell function and injure mucosal cells. Membranes damaged by lipid peroxidation may offer less resistance to infection. The production of radicals from endogenous and exogenous sources consumes antioxidants. Consequently, a variety of nutrients and factors support immune function.
Vitamin A has long been known to support mucosal cell surfaces and the immune system.(1) Vitamin A helps maintain the integrity of lymphatic tissues, antibody levels (especially sIgA), and responses of cellular immunity to challenge by exogenous stimulatory substances. However, the effects are selective. Possibly a metabolite of retinol regulates lymphocytes.(1) In vitamin A deficient rates, phagocytic activity of circulating polymorphonuclear lymphocytes declined.(2) The integrity of epithelial cells and production of protective agents, such as mucus secretions, are essential for healthy mucosa. In vitamin A deficiency, the mucosa, glands and ducts are susceptible to disease. Vitamin A requirements appear to be only partially met by the consumption of dark, green, leafy vegetables.(3)
Vitamin C scavenges free radicals and is essential for the function of many systems, including the immune system. Vitamin C is required for eicosanoids that regulate inflammation and it combats the effects of oxidative stress. Vitamin C is a major antioxidant in the blood and it works together with vitamin E.
For example, supplemental vitamin C and vitamin E decreased the production of reactive oxygen species and of lipid peroxidation in patients with myocardial infarction.(4) During periods of stress, urinary excretion of vitamin C increased.(5) Vitamin C supplemented volunteers exhibited increased natural killer cell activity.(6)
B vitamin deficiency is characterized by reduced phagocytic activity. Vitamin B2, B6 and pantothenic acid have specifically shown an ability to enhance antibody production. Lack of vitamin B1 reduces the spleen’s ability to produce antigens.(7) Vitamin B2 is necessary for proper thymic function.(7)
Vitamin B6 as pyridoxal phosphate, the coenzyme form of the vitamin, is required by transaminases and amino acid decarboxylases in the breakdown of amino acids. As such, vitamin B6 plays a critical role in all rapidly dividing cell types. Human studies, as well as animal experiments, link vitamin B6 deficiency to reduced lymphocyte differentiation, reduced delayed hypersensitivity responses and impaired antibody production.(8) Other research suggests that suboptimal vitamin B6 intake may play a role in a defective immune response in hemodialysis patients.(9)
Pantothenate deficiencies are associated with infections of the upper respiratory tract and pharyngitis.(10) Pantothenic acid is necessary for immunoglobulin production. Proper adrenal function requires pantothenic acid, ascorbic acid and zinc.(11) These water soluble nutrients are necessary during stress.
Mixed natural carotenoids, isolated from plants, include alpha and beta carotenes and oxy-carotenoids, such as zeaxanthin, lutein and cryptoxanthin. Carotenoids complement vitamin E as lipid-soluble antioxidants.
The natural mixed carotenoids are better absorbed and are more effective antioxidants than synthetic beta carotene in vivo.(12)
By acting as antioxidants, carotenoids can limit lipid peroxidation.(13) As example, beta carotene supplementation reduced lipid peroxidation in smokers(14) beta carotene has long been known to have a protective impact on the immune system. Healthy male nonsmokers supplemented with beta carotene revealed increased CD4-CD5 ratio after 9 months compared to controls who had taken a placebo.(15) After supplementation with beta carotene, there were significant increases in monocytes expressing major histocompatibility complex molecules, adhesion molecules and TNF secretion in a similar group of subjects.(16)
Coenzyme-Q10 functions both as an essential mitochondrial electron carrier for energy production and as a lipid-soluble antioxidant,(17) and dietary coenzyme-Q10 can decrease plasma production of lipid peroxides.(18) Although coenzyme-Q10 can be synthesized by the body, the levels in membranes of mitochondrial and other structures may be lower than needed for optimal function. Thymic coenzyme-Q10 levels declined in mice with increasing age.(19)
Coenzyme-Q10 together with vitamin B6 supported the production of T4-lymphocytes and immunoglobulins.(20)
Selenium is a trace mineral that is converted to selenocysteine, which plays a catalytic role in glutathione peroxidase production. In this sense, selenium can be considered an antioxidant. Selenium has a major impact on the immune system. Selenium deficiency can lead to depressed immunity and reduced T-cells.(21) Glutathione peroxidase activity was significantly higher in younger people than in elderly subjects.(22)
Copper, Manganese and Zinc: Superoxide dismutase (SOD) is the only family of enzymes that specifically inactivate free radicals, namely, the superoxide radical. Excessive superoxide production, as well as excessive amounts of other oxidants, is linked to chronic, oxidative stress.
Mitochondrial SOD requires manganese as an essential cofactor, while the cytoplasmic form of SOD requires both copper and zinc. Manganese SOD and copper-zinc SOD activities in lymphocytes and neutrophils were not inducible by cytokines in elderly subjects, although these activities were readily inducible in nonaged subjects.(22) These results suggested an age related alteration in the regulation of these defensive enzymes. Erythrocyte copper-zinc SOD activity tends to reflect copper status, and this has been used in laboratory assessment.(23) In addition, supplementation with superoxide dismutase vegetable culture may increase erythrocyte superoxide dismutase activity in vivo.(24)
Zinc plays an important role in maintaining the health of the immune system. It is a required cofactor for DNA polymerase and RNA polymerase, essential for cell proliferation. Rapidly dividing cells, including mucosal cells and immune cells, require zinc. Zinc deficiency leads to atrophy of lymphatic tissues, decreased skin delayed hypersensitivity response, impaired phagocytes, decreased T-cell function and lowered IgA and decreased thymic hormone activity.(25,26) Zinc supports granulocyte chemotaxis in vitro.(27)
Lactobacillus acidophilus, a member of the normal gut flora, which produce vitamins, stimulate the immune system, and produce factors that inhibit growth of less desirable organisms. By occupying an ecological niche in the intestine, they further limit the growth of opportunistic organisms.(32)
Lactobacillus can be depleted by an imbalanced diet and the long term usage of broad-spectrum antibiotics. The effectiveness of supplemental Lactobacillus acidophilus in normalizing GI function has been demonstrated.(33) DDS-1 strain developed at the University of Nebraska, has proven to be a superior strain in terms of its compatibility with the human GI tract and its stability.
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