Immune System Strengthening

Age, stress, and poor nutrition can sap our immune system of its effectiveness. Influenza provides one example. During young adulthood, when the body can mount a robust immune response to this common virus, influenza is rarely fatal. Among the elderly, however, the virus is associated with significant rates of death and hospitalization (Nichol KL 2005).

The impact of aging on the immune system is profound. As people age, a number of critical immune system components are reduced or slowed, including cellular response, response to vaccines, and antibody production. At the same time, susceptibilities to infection and cancer are increased. Some of this increased susceptibility to disease is linked to chronic inflammation, which is associated with many disorders of aging (Ershler WB et al 2000; Hamerman D 1999; Taaffe DR et al 2000).

Age, however, isn't the sole culprit in reduced immune function. There is no question that exercise, stress, and nutritional status play an important role in maintaining a healthy immune system. Consider just a few of the research findings:

• Dietary deficiencies and malabsorption alter metabolism and exacerbate chronic disorders (Kaput J et al 2004). An imbalance in the intake of dietary fat, carbohydrate, and protein can contribute to the development of diseases (Kaput J et al 2004). On the other hand, there is overwhelming evidence of the benefits of a good diet on reducing the risk of many chronic diseases (Ames BN 2001; Kaput J et al 2004).
• Malnutrition causes a decline in immune function and increased susceptibility to infection (Brussow H et al 1995; Lotfy O et al 1998; delaFuente M et al 1998). Likewise, a vitamin or mineral deficiency can suppress immune system function (delaFuente M et al 1998). Correct choices of supplements, vitamins, minerals, fatty acids, probiotics, and botanicals have been shown to boost immunity and may also reduce the risk of diseases in healthy Individuals (Kaminogawa S et al 2004).
• Psychological health influences the immune system and the course of many diseases (Kiecolt-Glaser J et al 2000). Depression, stress, and anxiety increase the production of pro-inflammatory chemicals in the blood, which in turn can compromise, depress, or suppress the immune system (Appels A et al 2000; Dentino AN et al 1999; Maes M et al 1997; Maes M et al 1998; Maes M et al 1999; Boscarino JA et al 1999; Lutgendorf SK et al 1999; Zhou D et al 1993; Papanicolaou DA et al 1998).
• High levels of anxiety are associated with decreased immune function (Ironson G et al 1990; Koh KB et al 1998; Boscarino JA et al 1999; Kiecolt-Glaser J et al 2000).
• Chronic stress can provoke long-term increases in pro-inflammatory chemicals. For example, caregiving for a relative with a serious medical condition results in long-term immune suppression among women (Lutgendorf SK et al 1999).
• Chronic stress from persistent marital problems, burnout at work (Lerman Y et al 1999), and lengthy unemployment (Arnetz BB et al 1991) can also lead to immune alterations that persist for years (Boscarino JA et al 1999; Kiecolt-Glaser JK et al 1987; Kiecolt-Glaser JK et al 1997; Kiecolt-Glaser JK et al 1988; Kiecolt-Glaser JK et al 1993).

Life Extension believes that all aging people should take prospective action to bolster their immune systems. This means reducing negative psychological stress; following a physician-approved, moderate, long-term exercise program; and following a diet and consuming nutrients that have been shown to enhance the immune response and promote health.

The Immune System: How It Works

The immune system is an elegant and complex set of components that combine to fight disease, infections, and various pathogens. A healthy immune system distinguishes organisms in the body as “self” or “non-self.” An intact immune response identifies pathogens as “non-self” and rapidly destroys them. A depressed immune system, by contrast, will allow invading organisms to flourish.

Furthermore, when the immune system mistakenly recognizes a “self” cell as “non-self” and mounts an immune response, the result is an autoimmune disorder such as rheumatoid arthritis.

In general, the body has two primary defense mechanisms: natural immunity and acquired immunity. Natural immunity is the “first responder” to an attack. The natural immune response relies on various white blood cells and physical barriers to block or immediately attack any foreign invader and attempt to destroy it.

Acquired immunity, on the other hand, involves antibodies that are created in response to specific foreign antigens. This sort of response requires a few days for the body to recognize the invader and manufacture antibodies against it. Once the body has manufactured a particular antibody for a specific invader, the immune system response is faster and more effective the next time that invader appears (Janeway CA et al 1999; Beers MB 2004).

The natural immune system relies on a host of weapons to protect the body, including various kinds of white blood cells (see Table 1). These natural defenses include the following organs, chemicals, and processes:

Physical and chemical barriers. The body's first lines of defense are the skin and mucous membranes, which prevent the entrance of many pathogens. There are many secondary barriers. For example, tears, sweat, and saliva combat some bacteria, and the hydrochloric acid and protein-digesting enzymes secreted by the stomach are lethal to many, but not all, pathogens (Janeway CA et al 1999; Beers MB 2004).

Inflammation and fever. Inflammation is a nonspecific response to infection or tissue injury. The four signs of the inflammatory response are redness, swelling, heat, and pain. Inflammation begins when cells release certain cytokines, including interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha (TNF-alpha ) (Janeway CA et al 1999; Beers MB 2004).

Phagocytic cells. Phagocytic cells engulf foreign cells and destroy them. The phagocytic cells are white blood cells and include neutrophils, eosinophils, and macrophages; they have short lives and must be continually replenished by the body. Neutrophils and macrophages are a very important aspect of the innate defenses of the body (Janeway CA et al 1999; Beers MB 2004).

Natural killer cells. Natural killer cells destroy certain cancer cells and a variety of pathogens. Killer cells are active secretors of interferon, an important and potent protein. Natural killer cells attach directly to the surfaces of infected cells and cause them to burst. They can also kill a pathogen by making its outer membrane leak (Janeway CA et al 1999; Beers MB 2004).

Antimicrobial proteins. Infected immune cells produce interferon, which causes healthy cells to produce antiviral proteins. There are more than 30 distinct antiviral proteins. When an individual complement (immune system) protein is activated by infecting organisms, it triggers a cascade that activates other complement proteins. Activated proteins can destroy bacteria while sparing host cells or cause the infected cells to become engulfed by phagocytic cells (Janeway CA et al 1999; Beers MB 2004).

Cytokines. To communicate and share information, cells use chemicals. Each chemical sends a different message to other cells. These chemical messengers are called cytokines. Cytokines regulate immunity, inflammation, and the production of white blood cells. There are dozens of cytokines; each performs a specific set of activities against specific target cells. They can act in concert or in opposition. Cytokines are often produced in a cascade; in other words, a cytokine stimulates its target cells to make additional cytokines. TNF-alpha, IL-1, IL-6, and type I interferon are important cytokines in the regulation of natural immunity.

Acute-phase proteins. The acute-phase response is activated during critical illnesses. When phagocytic cells bind pathogens, they release pro-inflammatory cytokines. This response enables the body to recognize invaders before the immune responses have been fully activated. Acute-phase proteins promote inflammation and stimulate phagocytes to move where they are needed.

Inflammation, Free Radicals, and Cytokines

Although acute inflammation is an important immune system response, chronic inflammation has also been linked to many diseases, including heart disease. Besides the pro-inflammatory cytokines, inflammation may be related to the overproduction of free radicals (Janeway CA et al 1999).

A free radical is an atom or group of atoms (i.e., a molecule) with unpaired electrons. Free radicals are extremely unstable and react easily with other molecules, thereby changing their chemical composition. Oxygen is especially susceptible to free radical formation. The free radicals derived from oxygen are known as reactive oxygen species, or oxidants.

When the body has increased levels of reactive oxygen species (i.e., when it is experiencing oxidative stress), widespread damage may result. At high concentrations free radicals can damage fats, proteins, and nucleic acids. They can also cause cell death, gene mutations, and cancer ( Moslen MT 1994). Several diseases may be the result of cellular and genetic damage caused by free radicals, including several immune disorders ( Moslen MT 1994).

In order to reduce the damage caused by elevated free radicals and cytokines (which are both part of the natural immune system), the body fights back by producing antioxidants and hormones such as cortisol to suppress the immune system (Grimble RF 1996). Antioxidants are valuable because they pair with unstable free radicals, thereby limiting the damage free radicals can inflict on other cells.

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.

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 J et al 2000) deplete glutathione. Glutathione is also involved in one of the major liver detoxification pathways.

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

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

Glutamine depletion slows wound healing and increases the risk of organ failure under certain conditions (Wilmore DW 1991). Endurance athletes whose muscles do not fully recover between workouts have decreased glutamine levels (Shephard RJ et al 1998; Castell LM et al 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 E 1994).

SAMe. 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 E et al 1993) and is intrinsically related to the synthesis of glutathione.

NAC. NAC acts as an antioxidant and is recommended for conditions that increase oxidative stress or decrease glutathione levels (Burgunder JM et al 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 JM et al 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 JE et al 1996). It has also demonstrated an ability to inhibit cell growth and proliferation in cancer cell lines (Chiao JW et al 2000) and prevent the transformation of carcinogens into more toxic compounds (De Flora S 1984; Wilpart M et al 1986).