9 Supplements to Support a Stronger Immune System

While no single supplement can prevent specific diseases, there are many vitamins, minerals, herbs, and antioxidants that can help to support your immune system to function more efficiently.

During periods of viral outbreaks, in particular, keeping your immunity healthy by providing it with beneficial amounts of nutrients can give you the extra ability to fight off potential pathogens that you encounter. To keep your immunity army fighting as strong as possible, consider these nine supplements to support your body from the inside out.

1. Vitamin C

You've likely heard that vitamin C helps the immune system, and with good reason! This water-soluble nutrient also acts as an antioxidant, which is beneficial for fighting inflammatory oxidative damage and free radicals.

Vitamin C is antimicrobial and enhances the actions of various immune cells, resulting in the body being better able to fight and clear infections. Although the Recommended Dietary Allowance (RDA) for vitamin C is just 75 mg or 90 mg for adult females and males, respectively, research has found that 100-200 mg daily best promotes healthy immune function by fully saturating our tissues.

Supplemental vitamin C may both prevent and shorten illnesses, like the common cold. In a July 2018 meta-analysis published in BioMed Research International, a therapeutic dose of vitamin C of 3 to 4 grams at the onset of an upper respiratory infection was able to reduce the duration and relieve symptoms, including chest pain, fever, and chills.

The daily dose of preventive vitamin C varies individually, but due to its water-soluble nature, it's likely not harmful to take more; the most notable adverse effect is gastrointestinal symptoms.

2. Zinc

The essential mineral zinc supports the immune system by regulating inflammation, minimizing oxidative stress, and reducing susceptibility to infections.

Zinc lozenges that dissolve in the mouth may be more effective than supplements in terms of immune system benefits. A systematic review of 13 trials found that high doses of zinc lozenges, at 75 mg per day or more, reduced the duration of the common cold by 42%, while doses of less than 75 mg did not have a significant benefit. Zinc may deplete copper reserves in the body, so you might need to talk with your doctor about adding in a small dose of copper or taking a break from zinc from time to time.

3. Glutathione

Glutathione is our master antioxidant; it's used by every cell in the body. Glutathione also supports the functioning of immune system cells and the regeneration of other antioxidants, like vitamins C and E. However, glutathione has limited bioavailability when ingested orally; a sublingual (under the tongue) and liposomal (a lipid bilayer) form may be better absorbed and utilized.

In a January 2018 study published in the European Journal of Clinical Nutrition, doses of both 500 and 1000 mg of oral liposomal glutathione per day led to reductions in oxidative stress, biomarkers, and enhanced immune cell markers. Natural killer cell functioning was elevated by 400% after two weeks of supplementation.

4. N-acetylcysteine (NAC)

NAC is a supplemental form of the amino acid cysteine, which is necessary to form and replenish glutathione stores. In addition to increasing stores of our master antioxidant, NAC also works as an antioxidant on its own by scavenging for free radicals.

NAC can be helpful in preventing or reducing symptoms of various respiratory conditions, like chronic obstructive pulmonary disease (COPD) and bronchitis, due to its anti-inflammatory and antioxidant effects in the lungs. NAC has also been shown to inhibit seasonal influenza viruses.

5. Vitamin D

Vitamin D has many roles in the body, one of which is supporting immune function and modulating inflammation. Vitamin D stimulates the production of antimicrobial peptides, which are pathogen-fighting components of various immune cells, like neutrophils and natural killer cells, as well as in the cells that line the respiratory tract. Antimicrobial peptides are an important line of defense in fighting foreign bacteria and viruses.

In a February 2017 study published in BMJ, vitamin D supplementation protected against acute respiratory tract infections in a meta-analysis of 25 randomized controlled trials, with the greatest benefit seen in those who were vitamin D deficient and those receiving daily or weekly doses, rather than one large bolus dose.

6. Magnesium

In addition to its involvement in over 300 biochemical processes in the body, magnesium is also an important factor in supporting immune function. Magnesium deficiency in animal studies has been linked to the overexpression of pro-inflammatory cytokines.

In the elderly, magnesium levels in the body may be reduced due to changes in the metabolism of the mineral as we age or insufficient dietary intake. Magnesium deficiency is linked to an increased susceptibility to inflammation and infection.

7. B-Vitamin Complex

B-complex supplements typically put all eight B-vitamins into one pill (B1, B2, B3, B5, B6, B7, B9, and B12). The B vitamin family is a water-soluble group that plays a major role in energy and nutrient metabolism, with additional functions in modulating the immune system.

As reviewed in an April 2019 article published in Frontiers in Nutrition, vitamins B1 and B2 contribute to immunomodulation, while vitamin B3 (niacin), a precursor to nicotinamide adenine dinucleotide (NAD), inhibits overexpression of pro-inflammatory cytokines.

In an animal study, mice with a deficiency in vitamin B6 had alterations in their immune cells that promoted inflammatory immune cells and reduced anti-inflammatory compounds. Vitamin B12 has been studied for its antioxidant properties, by directly scavenging free radicals, as well as preserving glutathione stores.

8. Ashwagandha

Ashwagandha is an ancient Indian herb that functions as an adaptogen, meaning it can modulate the stress response, depending on the needs of the individual. Supplementing with ashwagandha has been shown to significantly reduce levels of cortisol, which is a measure of the stress response; individuals who are stressed are more susceptible to getting sick.

9. Astragalus

Astragalus is a Chinese herb that has been used for centuries in herbal medicinal remedies due to its immunomodulating effects, especially with increasing the body's production of white blood cells.

Also known as Huang Qi in Traditional Chinese Medicine (TCM), astragalus is able to promote autophagy, which reduces inflammation and increases the clearance of pathogens from the body. In an animal study, astragalus has been shown to reduce the replication of the H9N2 influenza virus and promote a quicker immune response.

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