Your immune system consists of a complex collection of cells, processes, and chemicals that constantly defends your body against invading pathogens, including viruses, toxins, and bacteria (1Trusted Source, 2Trusted Source).

Keeping your immune system healthy year-round is key to preventing infection and disease.

Making healthy lifestyle choices by consuming nutritious foods and getting enough sleep and exercise are the most important ways to bolster your immune system.

In addition, research has shown that supplementing with certain vitamins, minerals, herbs, and other substances can help improve immune response and potentially protect against illness.

However, note that some supplements can interact with prescription or over-the-counter medications you’re taking. Some may not be appropriate for people with certain health conditions. Be sure to talk with a healthcare professional before starting any supplements.

Here are 15 supplements that are known for their immune-boosting potential.Yaroslav Danylchenko/Stocksy United

1. Vitamin D

Vitamin D is a fat-soluble nutrient essential to the health and functioning of your immune system.

Vitamin D enhances the pathogen-fighting effects of monocytes and macrophages — white blood cells that are important parts of your immune defense — and decreases inflammation, which helps promote immune response (3Trusted Source).

Many people are deficient in this important vitamin, which may negatively affect immune function. In fact, low vitamin D levels are associated with an increased risk of upper respiratory tract infections, including influenza and allergic asthma (4Trusted Source).

Some studies show that supplementing with vitamin D may improve immune response. In fact, recent research suggests that taking this vitamin may protect against respiratory tract infections.

In a 2019 review of randomized control studies in 11,321 people, supplementing with vitamin D significantly decreased the risk of respiratory infections in people deficient in this vitamin and lowered infection risk in those with adequate vitamin D levels (5Trusted Source).

This suggests an overall protective effect.

Other studies note that vitamin D supplements may improve response to antiviral treatments in people with certain infections, including hepatitis C and HIV (6Trusted Source, 7Trusted Source, 8Trusted Source).

Depending on blood levels, anywhere from 1,000 to 4,000 IU of supplemental vitamin D per day is sufficient for most people, though those with more serious deficiencies often require much higher doses (4Trusted Source).

Vitamin D has been highly researched in connection with COVID-19 because of its effect on the immune system. Studies have shown that Vitamin D can expedite healing and stall inflammation in the respiratory system (9Trusted Source).

In a recent rapid review study, it was concluded that more research is needed to recommend Vitamin D supplementation for the prevention and treatment of COVID-19 (10).

However, many professionals within the health and science community argue that supplementing with Vitamin D is generally safe and could possibly help protect individuals from the virus (11Trusted Source).

Summary

Vitamin D is essential for immune function. Healthy levels of this vitamin may help lower your risk for respiratory infections.

Supplements 101: Vitamin D

2. Zinc 

Zinc is a mineral that’s commonly added to supplements and other healthcare products like lozenges that are meant to boost your immune system. This is because zinc is essential for immune system function.

Zinc is needed for immune cell development and communication and plays an important role in inflammatory response. Zinc also specifically protects tissue barriers in the body and help prevent foreign pathogens from entering (12Trusted Source).

A deficiency in this nutrient significantly affects your immune system’s ability to function properly, resulting in an increased risk of infection and disease, including pneumonia (13Trusted Source, 14Trusted Source).

According to research, 16% of all deep respiratory infections worldwide have been found to be due to zinc deficiency (15Trusted Source).

Zinc deficiency affects around 2 billion people worldwide and is very common in older adults. In fact, up to 30% of older adults are considered deficient in this nutrient (16Trusted Source).

Zinc deficiency is relatively rare in North America and in developed countries (17Trusted Source, 18Trusted Source).

Nevertheless, many individuals in the United States have marginal zinc deficiency related to intake or absorption. Older individuals are generally at an increased risk (18Trusted Source).

Numerous studies reveal that zinc supplements may protect against respiratory tract infections like the common cold (19Trusted Source, 20Trusted Source).

What’s more, supplementing with zinc may be beneficial for those who are already sick.

In a 2019 study in 64 hospitalized children with acute lower respiratory tract infections (ALRIs), taking 30 mg of zinc per day decreased the total duration of infection and the duration of the hospital stay by an average of 2 days, compared with a placebo group (21Trusted Source).

Supplemental zinc may also help reduce the duration of the common cold (22Trusted Source). Additionally, zinc demonstrates antiviral activity (23, 24Trusted Source).

Taking zinc long term is typically safe for healthy adults, as long as the daily dose is under the set upper limit of 40 mg of elemental zinc (13Trusted Source)Trusted Source.

Excessive doses may interfere with copper absorption, which could increase your infection risk.

Summary

Supplementing with zinc may help protect against respiratory tract infections and reduce the duration of these infections.

3. Vitamin C 

Vitamin C is perhaps the most popular supplement taken to protect against infection due to its important role in immune health.

This vitamin supports the function of various immune cells and enhances their ability to protect against infection. It’s also necessary for cellular death, which helps keep your immune system healthy by clearing out old cells and replacing them with new ones (25Trusted Source, 26Trusted Source).

Vitamin C also functions as a powerful antioxidant, protecting against damage induced by oxidative stress, which occurs with the accumulation of reactive molecules known as free radicals.

Oxidative stress can negatively affect immune health and is linked to numerous diseases (27Trusted Source).

Supplementing with vitamin C has been shown to reduce the duration and severity of upper respiratory tract infections, including the common cold (28Trusted Source).

A large review of 29 studies in 11,306 people demonstrated that regularly supplementing with vitamin C at an average dose of 1–2 grams per day reduced the duration of colds by 8% in adults and 14% in children (29Trusted Source).

Interestingly, the review also demonstrated that regularly taking vitamin C supplements reduced common cold occurrence in individuals under high physical stress, including marathon runners and soldiers, by up to 50% (29Trusted Source, 30Trusted Source).

Additionally, high-dose intravenous vitamin C treatment has been shown to significantly improve symptoms in people with severe infections, including sepsis and acute respiratory distress syndrome (ARDS) resulting from viral infections (31Trusted Source).

Still, other studies have suggested that the role of vitamin C in this setting is still under investigation (32, 33Trusted Source).

All in all, these results confirm that vitamin C supplements may significantly affect immune health, especially in those who don’t get enough of the vitamin through their diet.

The upper limit for vitamin C is 2,000 mg. Supplemental daily doses are typically between 250 and 1,000 mg (34Trusted Source).

Summary

Vitamin C is vital for immune health. Supplementing with this nutrient may help reduce the duration and severity of upper respiratory tract infections, including the common cold.

4. Elderberry 

Black elderberry (Sambucus nigra), which has long been used to treat infections, is being researched for its effects on immune health.

In test-tube studies, elderberry extract demonstrates potent antibacterial and antiviral potential against bacterial pathogens responsible for upper respiratory tract infections and strains of the influenza virus (35Trusted Source, 36).

What’s more, it has been shown to enhance immune system response and may help shorten the duration and severity of colds as well as reduce symptoms related to viral infections (37Trusted Source, 38Trusted Source).

A review of 4 randomized control studies in 180 people found that elderberry supplements significantly reduced upper respiratory symptoms caused by viral infections (39Trusted Source).

An older, 5-day study from 2004 demonstrated that people with the flu who supplemented with 1 tablespoon (15 mL) of elderberry syrup 4 times a day experienced symptom relief 4 days earlier than those who didn’t take the syrup and were less reliant on medication (40).

However, this study is outdated and was sponsored by the elderberry syrup manufacturer, which may have skewed results (40).

Though it has been suggested that elderberry can help relieve symptoms of certain infections and the influenza virus, we also must be aware of the risks. Some report that elderberries can lead to the production of excess cytokines, which could potentially damage healthy cells (41Trusted Source).

For that reason, some researchers recommend elderberry supplements only be used in the early course of COVID-19 (41Trusted Source).

It should be noted no published research studies have evaluated the use of elderberry for COVID-19 (42Trusted Source). These recommendations are based on previous research done on elderberries.

A systemic review of elderberry (43) concluded:

• In laboratory animal and human research, elderberry had antiviral effects, inhibiting several strains of influenza A and B.
• Raw elderberries must be cooked to avoid risk of nausea, vomiting, or cyanide toxicity.
• Elderberry should be used under the direction of a qualified healthcare professional.

Elderberry supplements are most often sold in liquid or capsule form.

Summary

Taking elderberry supplements may help reduce upper respiratory symptoms caused by viral infections and help alleviate flu symptoms. However, elderberry also has risks. More research is needed.

5. Medicinal mushrooms 

Medicinal mushrooms have been used since ancient times to prevent and treat infection and disease. Many types of medicinal mushrooms have been studied for their immune-boosting potential.

Over 270 recognized species of medicinal mushrooms are known to have immune-enhancing properties (44Trusted Source).

Cordyceps, lion’s mane, maitake, shitake, reishi, and turkey tail are all types that have been shown to benefit immune health (45Trusted Source).

Some research demonstrates that supplementing with specific types of medicinal mushrooms may enhance immune health in several ways as well as reduce symptoms of certain conditions, including asthma and lung infections.

For example, a study in mice with tuberculosis, a serious bacterial disease, found that treatment with cordyceps significantly reduced bacterial load in the lungs, enhanced immune response, and reduced inflammation, compared with a placebo group (46Trusted Source).

In a randomized, 8-week study in 79 adults, supplementing with 1.7 grams of cordyceps mycelium culture extract led to a significant 38% increase in the activity of natural killer (NK) cells, a type of white blood cell that protects against infection (47Trusted Source).

Turkey tail is another medicinal mushroom that has powerful effects on immune health. Research in humans indicates that turkey tail may enhance immune response, especially in people with certain types of cancer (48Trusted Source, 49Trusted Source).

Many other medicinal mushrooms have been studied for their beneficial effects on immune health as well. Medicinal mushroom products can be found in the form of tinctures, teas, and supplements (50Trusted Source, 51Trusted Source, 52Trusted Source, 53Trusted Source).

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Source: healthline