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Immune System Strengthening

Supporting a Healthy Immune System

A healthy immune system grows ever more important as we age, and immune status is closely associated with nutrition, exercise, and stress reduction. Older people and people with compromised immune systems should talk to their physician about exercising, reducing stress, and designing an active, immune-boosting nutritional program.

Vitamin D. Adults (and children) with higher vitamin D levels contract substantially fewer cold, flu, and other viral infections (Ginde 2009; Karatekin 2007; Cannell 2006). Vitamin D downregulates the expression of pro-inflammatory cytokines while upregulating the expression of antimicrobial peptides in immune cells (Schauber 2007). This biological mechanism explains why Vitamin D confers such dramatic protection against common illnesses.

Glutathione boosters. Glutathione is probably the body's most important cellular defense against free radical damage. It is a free radical scavenger and major antioxidant.

Low levels of glutathione are linked to many diseases. Malnutrition and aging (Cai 2000) deplete glutathione. Glutathione is also involved in one of the major liver detoxification pathways.

Glutathione is produced in the body, but not easily absorbed when taken orally. Instead, glutathione precursors may be used by the body to increase glutathione (Bounous 2000). Glutathione precursors include glutamine, N-acetylcysteine (NAC), and S-adenosyl-L-methionine (SAMe) (Devlin 2002). It can also be upregulated by lipoic acid as well as vitamins C and E.

Glutamine. Glutamine is the most abundant amino acid in the body (Roth 2002). Glutamine depletion causes downregulation of glutathione levels in the body (Roth 2002), and dietary supplementation increases these levels (Roth 2002). Glutamine has immunoregulative activities (Roth 2002; Li 1995). Lymphocytes and macrophages use glutamine at a very high rate (Newsholme 1994). Glutamine stimulates lymphocyte production and killer immune cell activity (Rohde 1995, 1998, 1996; Jurectic 1994).

Glutamine depletion slows wound healing and increases the risk of organ failure under certain conditions (Wilmore 1991). Endurance athletes whose muscles do not fully recover between workouts have decreased glutamine levels (Shephard 1998; Castell 1998). Some scientists believe that intense physical exercise or stress due to trauma, burns, or sepsis (blood infection) forces the body into glutamine debt, which temporarily compromises immune function (Newsholme 1994).

S-adenosyl-L-methionine. S-adenosyl-L-methionine (SAMe) is a natural amino acid present throughout the body. It is crucially important because it is involved in dozens of chemical reactions, including the synthesis of DNA and RNA, proteins, melatonin, creatine, and many others. SAMe is an important energy source (Osman 1993) and intrinsically related to the synthesis of glutathione.

N-acetylcysteine. N-acetylcysteine (NAC) acts as an antioxidant and is recommended for conditions that increase oxidative stress or decrease glutathione levels (Burgunder 1989). NAC has a protective effect on DNA and is a powerful free radical scavenger. It increases the synthesis of glutathione only when there is a demand, and is thought to concentrate only in tissues where it is required (Burgunder 1989). NAC can modulate the concentrations of certain cytokines. In laboratory studies, it has increased IL-1 and IL-2 levels when they are at low concentrations and decreased these cytokines at higher concentrations (Baier 1996). It also demonstrated an ability to inhibit cell growth and proliferation in cancer cell lines (Chiao 2000), and prevent the transformation of carcinogens into more toxic compounds (De Flora 1984; Wilpart 1986).

Antioxidants and Coenzyme Q10

Because of their ability to scavenge free radicals, antioxidants are important immune-system boosters. Supplementation with antioxidants like vitamins C, E, and B vitamins may improve immune function (Grimble 1997), and supplementation with vitamin A stimulates antibody-mediated immune responses (Cantorna 1995).

Vitamin E is a powerful fat-soluble antioxidant. It protects cellular membranes of the immune system and other cells by trapping free radicals, and enhances the effectiveness of lymphocytes (Kaminogawa 2004).

Vitamin C (ascorbic acid) is a key component of the immune system and antioxidant defense (Kagan 1991, 1992; Peters 1993). It prevents the production of free radicals and reduces DNA damage in immune cells. Moreover, vitamin C downregulates the production of pro-inflammatory cytokines and participates in recycling vitamin E (Schwager 1998).

B vitamins indirectly contribute to antioxidant defenses and have considerable influence on immune function. Vitamins B12 and B6 are cofactors in the creation of cysteine, a key component in glutathione synthesis. Deficiencies in B vitamins and vitamin E create abnormalities in immune response (Murrary 2000).

Lipoic acid is a potent antioxidant with antiviral, free-radical-quenching, and immune-boosting qualities. It is unusual because it is soluble in both fat and water (Kagan 1992), and is active in both its oxidized and reduced forms (Bustamante 1998). Lipoic acid is able to regenerate other antioxidants (eg, vitamins C and E) and raise glutathione levels significantly (Packer 1995, 1997; Scholich 1989; Fuchs 1993).

Coenzyme Q10 (CoQ10), synthesized from the amino acid tyrosine, is present in high quantities in the heart muscle. CoQ10 has shown a wide range of benefits. It is an essential cofactor in the production of adenosine triphosphate (ATP), which is the primary source of energy for all the body's cells. Levels of CoQ10 decline naturally as humans age, which may be related to increased lipid peroxidation. CoQ10 is a powerful antioxidant and scavenger of free radicals. It inhibits lipid peroxidation and works synergistically with vitamin E (Alleva 1995). CoQ10 has an important role in the stimulation of the immune system and improves several parameters of immune function (Folkers 1985).

Whey protein. Whey protein is isolated from milk. Proteins in whey are highly available to the body, and whey protein contains potent antioxidants. Its antioxidant activity is due to its high concentrations of glutamate and cysteine, which are precursors to glutathione (Walzem 2002). Whey also contains several substances that enhance the immune system, including the following:

  • Beta-lactoglobulin, which modulates lymphatic responses (Guimont 1997)
  • Alpha-lactalbumin, which has a direct effect on B and T lymphocytes and has the ability to reduce oxidative stress
  • Lactoperoxidase, which reduces toxic hydrogen peroxide (Sundberg 1991; Ha 2003)

Lactoferrin, a major component of whey protein, also acts as an antioxidant (Steijns 2000). It can inhibit the absorption of bacteria through the intestinal wall. Whey protein can activate natural killer cells (Nishiya 1982). In the laboratory, lactoferrin inhibited metastasis of cancer cells in mice (Marshall 2004) and increased IL-2 and natural killer activity (Watanabe 2000).


Metallic micronutrients such as copper, zinc (Prasad 2000), and selenium influence the activity of antioxidant enzymes and can reduce oxidative stress. Among children, deficiencies of zinc, copper, and selenium have been linked to immune deficiency and infection (Cunningham-Rundles 2005).

Selenium is involved in several key metabolic pathways (Rotruck 1973; McKenzie 1998, 2000). Glutathione peroxidase, the enzyme that recycles glutathione, depends on the presence of selenium for its antioxidant activity (Arthur 2003). Although plant food is a major dietary source of selenium (eg, garlic is rich in selenium), the highest concentration of dietary selenium occurs in meat.

Zinc deficiency is linked to impaired immune function, partly because of decreased T lymphocyte and B lymphocyte function. Zinc has shown the ability to decrease inflammation and the production of IL-2 (Tanaka 2005). Copper and zinc together have been shown to stimulate internally produced antioxidants such as glutathione and superoxide dismutase (SOD) (Kuppusamy 2005).

DHEA and Immune Function

Dehydroepiandrosterone (DHEA) is produced by the adrenal glands. DHEA has over 100 metabolites and is used by the body for estrogen and testosterone production.

Blood levels of DHEA rise until they peak in the third decade of life, then rapidly decline. Endocrinologists and anti-aging researchers have been focusing on this decrease in DHEA, which in turn produces a decline in other steroidal hormones.

Animal experiments suggest that DHEA has many biological effects, including anticancer, immune-enhancing, neurotrophic, and general anti-aging effects (Bovenberg 2005). A recently published review article of DHEA supplementation in men found convincing research showing positive effects of DHEA on the cardiovascular system, body composition, skin, central nervous system, sexual function, and immune system (Saad 2005).

On the cellular level, DHEA exerts its actions on peripheral target tissues either indirectly (following its conversion to androgens, estrogens, or both) or directly, as a steroid hormone (Perrini 2005). Lower DHEA levels are associated with decreased production of IL-2 and an increase in the presence of IL-6, which is a pro-inflammatory cytokine (Hammer 2005). A study was performed on younger and older men to compare DHEA blood levels and peripheral blood mononuclear cells (PBMCs) in populations of varying ages. The results showed significant changes in sex steroid metabolism by human PBMCs with aging, which may represent a link to age-associated changes in the immune system (Hammer 2005).

Immunomodulatory effects of DHEA in various autoimmune diseases have been studied. Relative reductions in DHEA have been noted in patients with rheumatoid arthritis, systemic lupus erythematosus, HIV and AIDS, sepsis, and trauma (Chen 2004). Overall, DHEA blood levels have been used as diagnostic factors in evaluating the impact of aging on the immune system. Supplemental DHEA has been clinically valuable when used to restore youthful hormonal blood levels in aging, stressed, and immune-compromised individuals (Valenti 2004).

One of DHEA's metabolites, 7-keto DHEA, has also been studied for its ability to support the immune system. A study found that four weeks of 7-keto DHEA supplementation improved immune function in elderly men and women (Zenk 2004). In this randomized, double-blind, placebo-controlled study, 22 women and 20 men over the age of 65 took either 100 mg of 7-keto twice daily or a placebo. The 7-keto group had a significant decrease in immune suppressor cells and a significant increase in immune helper cells. The 7-keto group also saw reductions in diastolic blood pressure and an increase in neutrophils, the first white blood cells to respond to infection.

Polyunsaturated Fatty Acids

Polyunsaturated fatty acids, such as the omega-3 fatty acids found in fish oil and flaxseed oil, have been studied for their anti-inflammatory action (Kaminogawa 2004). Polyunsaturated fatty acid reduces the inflammatory response caused by TNF-α (Johnson 1993; Pedersen 2000).

Most people in the United States have an imbalance in the ratio of omega-3 to omega-6 fatty acids because of diets high in animal fat and vegetable oils high in omega-6 (eg, corn oil). This imbalance has been associated with inflammation (Calder 1997). The ratio can be improved by taking supplemental omega-3 fatty acids. Omega-3 fatty acids have also been shown to:

  • Counteract suppression of the cellular immune system (Pedersen 2000)
  • Suppress TNF-α production and have an anti-inflammatory effect (Grimble 2002)


The gastrointestinal tract relies on live bacteria (microflora) to help support a robust immune response. These probiotic bacteria help prevent foreign bacteria and allergens from passing through the intestinal wall and are important to the overall health of the intestinal immune system (Marteau 2001; Conway 1987; Robins-Brown 1981). Probiotics are found in foods such as yogurt and kefir, which enhance the microflora in the gut by providing additional probiotic bacteria (Fuller 1991; Isolauri 2001). The most commonly used probiotic bacteria are lactobacillus and bifidobacterium, found in yogurts.

Probiotics also strengthen the intestinal immunological barrier. Lactobacillus stimulates natural immunity by improving phagocytic and natural killer immune cell activity (Kaminogawa 2004).

Grape Seed Extract

Chemicals in grape seeds known as proanthocyanidins have potent antioxidant and immune-boosting properties (Ashraf-Khorassani 2004; Bagchi 1997; Bagchi 1998). They increase the activity of internal antioxidants such as glutathione and SOD (Peng 2000).

The antioxidants in grape seed extract are twice as potent as vitamin E and four times as potent as vitamin C (Bagchi 1997; Bagchi 1998). In laboratory studies, proanthocyanidins increased the power of natural killer cells, enhanced the production of IL-2, and decreased production of IL-6 (Cheshier 1996).

Green Tea Extract

Green tea extract, which contains a class of compounds known as catechins, has become increasingly popular as scientists learn more about its antioxidant and free radical–scavenging abilities. One of the most potent catechins in green tea is epigallocatechin-3-gallate (Chen 2002). Green tea extract is also rich in vitamins C and B (Hasegawa 2002; Hasegawa 1998).

Green tea has a positive influence on lipid metabolism and exerts anticancer effects. Green tea modulates the inflammatory processes and protects against DNA damage (Lin 1998). The catechins from green tea demonstrate considerable antioxidant activity (Chen 2002) and are potent free radical scavengers (Zhong 2003; Jimenez-Lopez 2004).

Hyperimmune Egg Extract

Hyperimmune egg extracts provide unique immune protection. Long ago, agricultural scientists discovered that they could immunize hens against germs that threaten humans. This immunity was then passed on by the hen to her egg (Dias da Silva 2010; Dean 2000; Cama 1991). Concentrated protein extracts from those so-called “hyperimmune eggs” confer some immunity to humans who consume them (Fujibayashi 2009; Sarker 2001).


Healers in Asia and India have long prescribed the bitter herb Andrographis paniculata for the treatment of ailments ranging from infections and inflammation to colds and fevers (Ji 2005). Researchers have isolated a number of the herb’s active ingredients. Chief among these are andrographolides, which are phytochemicals believed to exert their effects, in part, on tissues of the blood cell-producing bone marrow and/or spleen. One such compound, andrographanin, enhances the ability of certain white blood cells to recognize and neutralize foreign cells (eg, tumor cells and viruses) (Ji 2005).

Beta Glucan

Beta glucans can naturally boost the immune system by optimizing its response to diseases and infections. Because the body does not produce beta glucans naturally, the only way to get them is through outside sources. Studies have shown that beta glucans act as immunomodulator agents, meaning they trigger a cascade of events that help regulate the immune system, making it more efficient. Specifically, beta glucans stimulate the activity of macrophages, which are versatile immune cells that ingest and demolish invading pathogens and stimulate other immune cells to attack (National Institute of Allergy and Infectious Diseases 2012). Macrophages also release cytokines, chemicals that when secreted enable immune cells to communicate with one another. In addition, beta glucans stimulate lethal white blood cells (lymphocytes) that bind to tumors or viruses, and release chemicals to destroy it.