Woman with healthy support for respiratory immune system smelling flower

Nutrients to Support Respiratory Immune Health

Nutrients to Support Respiratory Immune Health

Last Section Update: 04/2021

1 Nutrients to Support Respiratory Immune Health

  • Zinc. Zinc has demonstrated antiviral effects against several respiratory viruses, promoting their clearance from the airway surfaces, preventing their entry into cells, and suppressing viral replication. Using zinc in the form of a lozenge within 24 hours of symptom onset may reduce the duration and severity of a cold.1,2
  • Elderberry. Clinical research indicates elderberry extract, rich in anti-inflammatory and antioxidant polyphenols, may reduce influenza symptoms and shorten duration of illness when started within 48 hours of symptom onset.3
  • Probiotics. Multiple randomized controlled trials and several meta-analyses have shown probiotics reduce the risk of acute respiratory tract infections. Species of Lactobacillus and Bifidobacterium have been found to reduce the incidence and severity of upper respiratory viral infections, including the flu.4
  • Lactoferrin (as apolactoferrin). Lactoferrin, an immune modulator capable of enhancing antimicrobial immune activity while reducing inflammation, has exhibited a broad spectrum of activity against bacteria, fungi, protozoa, and viruses.5,6
  • Vitamin D. Numerous studies around the world have found correlations between low vitamin D status and increased risk of respiratory viral infections and poor outcomes.7
  • Curcumin. Numerous preclinical studies indicate curcumin may activate antiviral immunity, and it has demonstrated antiviral effects against a range of respiratory viruses. Curcumin also helps mitigate inflammation associated with the immune response to infection.8-12
  • Melatonin. In addition to its role in promoting healthy sleep, melatonin is an antioxidant with anti-inflammatory activity. Some researchers have suggested taking 3–10 mg of melatonin at bedtime for respiratory immune health.13,14
  • N-Acetylcysteine (NAC). NAC inhibits cellular entry and replication of some respiratory viruses, assists in clearing thickened mucous from the airways, and suppresses inflammatory signaling.15
  • Vitamin C. When initiated soon after symptom onset, vitamin C may reduce the duration of influenza-like respiratory illness symptoms such as fever, chills, and body pain.16-19
  • Selenium. Selenium has been shown in preclinical studies to reduce infectivity, replication, and virulence of several respiratory viruses.20-22
  • Licorice. Active constituents of licorice have demonstrated antiviral effects against viral causes of respiratory infection as well as other viruses. 23-25
  • Garlic. Garlic compounds have demonstrated antiviral activity against respiratory viruses, such as rhinoviruses and influenza viruses, and have broad antimicrobial activity against bacterial and fungal causes of illness.26
  • Andrographis. Multiple randomized controlled trials and two meta-analyses have found andrographis extract, alone and in herbal combinations, reduced symptoms of upper respiratory tract infections and may be especially helpful in alleviating cough and sore throat.31-36
  • Green Tea. Green tea catechins have demonstrated antiviral actions against influenza and other respiratory viruses. Green tea may help prevent viral respiratory infections and may decrease flu-like symptoms by reducing inflammation.37,38
  • Ginseng. Ginseng extracts have been shown to activate the antiviral immune response while reducing the inflammatory response, and clinical trials suggest it may lower risk of the flu and improve immune response to the flu vaccine.39,40
  • Echinacea. Echinacea may reduce the incidence of colds and sick days, as well as reducing the risk of recurrent infections.41,42
  • Beta-glucans. These prebiotic fibers may stimulate the body’s antimicrobial defense and prevent infection as well as decrease upper respiratory tract infection symptoms.43

The nutrients listed here may generally support respiratory immune health. Additional details are available in Life Extension’s protocols on Influenza, Common Cold, Pneumonia, and Immune Senescence.

2 How to Test Your Immune System

Several lab tests can shed light on various aspects of immune system function and response to infection. For instance, white blood cell (WBC) levels are often elevated in acute infections.44,45 And, paradoxically, lower levels of total WBCs or lymphocytes, the primary immune responder in viral infections, might be seen in severe infections.46,47

Assessing the numbers of different types of WBCs in a patient’s blood can help determine the type of pathogen (e.g., a virus or bacteria) that is causing the infection. This can be helpful in avoiding the overuse of unnecessary antibiotics since antibiotics do not work against viruses (which are the most common cause of acute respiratory infections).

High levels (or relative proportion) of neutrophils, another type of white blood cell, may be suggestive of a bacterial cause of a respiratory infection. Lower levels of WBCs may be seen in non-infectious diseases that affect the immune system, such as autoimmune disease or cancer, as well as with chronic use of glucocorticoid medications, which can hamper the body’s response in acute illness.48-50

Lab tests to assess other immune cell types can be insightful as well. For example, CD8+ killer T cells target and destroy cancer cells and cells infected with viruses, while macrophages (also called “big eaters”) engulf and destroy harmful bacteria.51-53 On the other hand, regulatory T cells help ensure the immune system does not over-react and drive chronic inflammation or autoimmune diseases.54

In certain settings of acute infection, specific tests such as reverse transcription polymerase chain reaction (RT-PCR) or antigen testing may be employed to determine if a patient’s symptoms are being caused by specific pathogens.55 Typically, a clinician will obtain a sample from the nose and/or throat to perform these types of tests.56 Antibody testing of levels of IgG, IgA, and/or IgM antibodies for specific pathogens may be useful to determine past or current infection and immunity status. Latent or chronic infections can contribute to immune dysregulation and a poor response to acute infection.

Table 1 below summarizes these and several other key laboratory tests that may help assess the immune system’s response to infectious agents, as well as tests to assess levels of nutrients that may influence immune function.

Table 1: Laboratory Assessment of Immune Parameters
Optimal Levels
Nutrients Related to Immune Function
Vitamin D (25-hydroxy vitamin D)
Many studies have found associations between low vitamin D levels and impaired immune function
50 – 80 ng/mL
Vitamin C, plasma
Plays a role in many aspects of immune cell function and metabolism
>1.2 mg/dL
Zinc, plasma or serum
Involved in several aspects of immune cell function, including regulating intracellular signaling pathways in innate and adaptive immune cells
>85 μg/dL
Acute Infection and Immune Function Tests
White blood cell (WBC) count
  • Neutrophils
  • Eosinophils
  • Basophils
  • Lymphocytes
  • Monocytes
Typically, a part of a complete blood count (CBC); abnormal levels may be sign of infection, blood cancer, or immune system disorder
Reverse transcription polymerase chain reaction (RT-PCR)
RT-PCR testing amplifies genetic material to determine the cause of infection and is more sensitive than antigen testing
Antigen tests
Rapid antigen tests help determine the cause of infection but are less accurate than RT-PCR
IgG, IgA, IgM antibodies to specific pathogens
Useful to assess for past or current infection and immunity status
C-reactive protein (hs-CRP)
Highly sensitive marker of inflammation that indicates immune activation, possibly due to conditions such as cancer, infection, injury, or autoimmune disease; correlates with cardiovascular risk
Men <0.55 mg/L
Women <1.0 mg/L
Cytokines, eg, TNF-α and interleukins IL-1beta, IL-6, IL-8
Proteins that are critical mediators of the inflammatory response
Natural Killer (NK) cell Function
Assesses functional (ie, cell-killing) capacity of NK cells
Natural Killer (NK) cell surface antigen (CD3-CD56+ Marker Analysis)
Determines levels of NK cells in circulation
Immunoglobulins IgA, IgG, IgM
Elevated in some autoimmune diseases, multiple myeloma, and acute and chronic infections; decreased in immune deficiencies
T-Lymphocyte helper/suppressor profile
May be helpful in assessing immunodeficiency states
Cortisol and dehydroepiandrosterone sulfate (DHEA-S)
Cortisol is immunosuppressive, while DHEA stimulates immune function; an imbalance between these hormones may contribute to immune dysregulation


  • Apr: Initial publication

Disclaimer and Safety Information

This information (and any accompanying material) is not intended to replace the attention or advice of a physician or other qualified health care professional. Anyone who wishes to embark on any dietary, drug, exercise, or other lifestyle change intended to prevent or treat a specific disease or condition should first consult with and seek clearance from a physician or other qualified health care professional. Pregnant women in particular should seek the advice of a physician before using any protocol listed on this website. The protocols described on this website are for adults only, unless otherwise specified. Product labels may contain important safety information and the most recent product information provided by the product manufacturers should be carefully reviewed prior to use to verify the dose, administration, and contraindications. National, state, and local laws may vary regarding the use and application of many of the therapies discussed. The reader assumes the risk of any injuries. The authors and publishers, their affiliates and assigns are not liable for any injury and/or damage to persons arising from this protocol and expressly disclaim responsibility for any adverse effects resulting from the use of the information contained herein.

The protocols raise many issues that are subject to change as new data emerge. None of our suggested protocol regimens can guarantee health benefits. Life Extension has not performed independent verification of the data contained in the referenced materials, and expressly disclaims responsibility for any error in the literature.

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