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Proper nutrition is a must for a strong immune system. Immune-boosting vitamins like zinc, copper, B vitamins, and iron are some of the key micronutrients that help keep immune function running at full strength. In fact, many multivitamins are marketed as “immune system boosters.”
The most important nutrient for optimal immune function, however, may be protein. Studies of malnourished children in developing countries demonstrated the strong link between protein intake and immunocompetence, or the ability to fight off infection and disease. Most components of the immune system defense arsenal are proteins, so it makes sense that the building blocks for these proteins, amino acids, must be in plentiful supply.
The immune system is made up of specialized cells and proteins. Some of these specialized cells include white blood cells such as lymphocytes (B cells and T cells) and phagocytes. Phagocytes such as macrophages and lysosomes are types of cells that engulf and absorb bacteria and other small cells and particles.
The Complement System is a part of the immune system made up of a group of proteins found in the blood that are critical in the defense against infection. Producing these specialized cells and proteins requires an abundant supply of amino acids, some of which must come from the diet. When the immune system can’t keep up with the production of these molecules, we become vulnerable to many health problems and diseases.
While very few people in the United States are “protein-malnourished,” many people may not be consuming enough high-quality proteins to obtain the amount of essential amino acids needed for optimal nutrition.
Dietary protein is broken down to provide amino acids. Essential amino acids are those that cannot be made by the body and therefore must be obtained from the diet. Nonessential amino acids can be synthesized in the body. However, under conditions of stress when the immune system is challenged, the body cannot keep up with the demand for certain amino acids so they are considered conditionally essential in that dietary sources are required to meet the demand.
Like all other cells, the cells that make up the immune system require energy. In fact, you might call immune system cells “energy hogs” because when they are in demand (challenged by a pathogen or disease), they require lots of energy in a hurry.
Mitochondria are the “engines” of cells and produce the energy needed to support all cellular functions. Balanced mixtures of essential amino acids have been shown to increase mitochondrial number and function. Studies show that when essential amino acids are consumed, they stimulate the production of mitochondrial proteins (a process called mitochondrial protein synthesis) including the production of enzymes, chemicals that help in immune system functions. Amino acids help improve mitochondrial function by increasing the available number of enzymes involved in energy production.
If essential amino acids are in short supply, the number of mitochondria and their ability to work at full capacity is compromised. This “energy shortage” limits the ability of the immune system to keep producing all the cells needed to fight off the threat presented by pathogens and disease.
Beyond serving as the fuel source to build up and support the defense system arsenal, mitochondria also get directly involved in killing off infected cells and helping to coordinate signals and messages sent out by the immune system. Nutrients that support mitochondria, therefore, help to improve immune function.
The amino acid glutamine plays a significant central role in maintaining immune function. Glutamine helps to create and mobilize white blood cells and aids in phagocytosis (the ingestion of bacteria or foreign material by specialized immune cells). These processes are influenced by glutamine availability and may run inefficiently if glutamine levels are low.
Immune system cells use glutamine at a high rate, particularly in stressful situations like sepsis, injury, burns, surgery, and endurance exercise. In each of these conditions, the immune system is often suppressed. Supplemental glutamine has been shown to be beneficial in maintaining immune function in these circumstances.
Arginine is also important for white blood cell proliferation and functionality. These cells need certain structures on their surface in order to recognize diseased or damaged cells, and arginine is involved in the formation of the molecules that serve this purpose.
Arginine is also involved in wound repair and is a precursor of nitric oxide. (A precursor is a substance from which another is formed.) Nitric oxide (NO) plays an important role in regulating the dilation of blood vessels, which decreases blood pressure by making it easier for blood to flow. Increased blood flow to an injured area of the body is important because it helps to deliver immune cells along with extra oxygen and nutrients needed to repair the damage.
NO is also important in the activation of inflammation as part of the immune response. Macrophages and a number of other immune system cells can actually make NO, which they then use to neutralize infectious organisms.
The availability of arginine or citrulline may increase levels of NO metabolites. The amino acid citrulline helps elevate arginine levels inside the cell (another example of a precursor), thereby boosting NO.
Glutathione is an antioxidant that is produced in your body. Antioxidants work by donating electrons to free radicals, which neutralizes them before they can cause harm. In addition to its antioxidant properties, glutathione is an important anti-inflammatory and toxin “mop.” It is present in all cells and is believed to help prevent cancer.
Located in the mitochondria of the cell, glutathione is responsible for getting rid of the free radicals that occur naturally from energy-producing reactions in the cell. It prevents damage to important cellular components caused by reactive oxygen species (ROS) including free radicals, peroxides, lipid peroxides, and heavy metals.
In the liver, glutathione binds to and neutralizes toxins by converting them to compounds which can be safely excreted from the body. Glutathione is recycled to some extent, but when free radicals, inflammation, and toxin levels are high, available glutathione levels decrease.
There are nutritional strategies to overcome this deficit but what would seem to be the most obvious, a glutathione supplement, is not the most efficient or effective. The reason is that glutathione is a small protein (called a peptide) made up of three amino acids: cysteine, glycine, and glutamate. If taken orally, the stomach does what it does to proteins, which is to digest it down to its component amino acids such that glutathione itself is not absorbed intact.
Increasing blood levels of the three component amino acids is a starting point to encourage glutathione synthesis. Glycine and glutamate are nonessential amino acids and usually present in good supply. Cysteine is considered semi-essential because it can be produced in the body, but it needs methionine, an essential amino acid, as a starting point. Boosting cysteine in the cell is not an easy task. High doses of supplemental cysteine or its precursor methionine can be toxic or result in homocysteinemia, which is related to early development of heart and blood vessel disease.
Because of its unique chemical structure, N-acetyl-cysteine (NAC) can effectively increase cysteine levels in the cell. NAC is used for treating asthma and in the emergency room to reverse acetaminophen (Tylenol) poisoning. However, NAC is a medicine and therefore presents the potential for side effects including nasal irritation, vomiting, and development of a rash among other problems.
Glutathione and its constituent amino acids are naturally present in many foods, in particular cruciferous vegetables and the alliums and meat and dairy products. Whey protein is particularly rich in cysteine and overall is a very good source of all essential amino acids. These dietary sources at a minimum provide the building blocks for glutathione synthesis.
A balanced essential amino acid supplement containing methionine is an effective approach for improving immune function and glutathione levels since the methionine can be converted to cysteine in the cell, ensuring that intracellular concentrations of cysteine are plentiful.
Glutathione can be replenished more successfully when other vitamins for immune system health, such as vitamins C and E, are available in good supply, as well as folate, B vitamins, and zinc, all of which act as cofactors in the synthesis of glutathione.
A strong immune system is the key to staying healthy, and the key to a strong immune system is proper nutrition with nutrient-dense foods and high-quality proteins and amino acids. So, to answer your question—how can I boost my immune system—eat up!
