A deficiency of certain vitamins, including vitamin C, zinc and others, can weaken the immune system. Taking supplements with these vitamins can support immune system function.
Your immune system is a complex collection of cells, processes and chemicals that constantly defend your body against invading pathogens, including viruses, toxins and bacteria.
A year-round healthy immune system is the key to avoiding infection and disease.
A healthy lifestyle with a nutritious diet, sufficient sleep and physical activity are the most important measures to strengthen the immune system.
In addition, research has shown that taking supplements containing certain vitamins, minerals, herbs and other substances can improve immune defense and potentially protect against disease.
Be aware, however, that some supplements may interact with prescription or over-the-counter medications you are taking. Some may not be suitable for people with certain health conditions. Be sure to talk to your doctor before you start taking supplements.
Here are supplements known for their immune-boosting potential:
Vitamin D
Vitamin D is a fat-soluble nutrient that is essential for the health and functioning of the immune system.
Vitamin D enhances the pathogen-fighting effects of monocytes and macrophages - white blood cells that are important components of the immune defense - and reduces inflammation, which boosts the immune response.
Many people suffer from a deficiency of this important vitamin, which can have a negative impact on immune function. In fact, low vitamin D levels have been linked to an increased risk of upper respiratory tract infections, including influenza and allergic asthma.
Some studies show that taking vitamin D can improve immune response. Recent research even suggests that taking this vitamin may protect against respiratory infections.
A 2019 review of randomized control trials involving 11,321 people found that taking vitamin D significantly reduced the risk of respiratory tract infections in people with vitamin D deficiency and lowered the risk of infection in people with adequate vitamin D levels.
This suggests a general protective effect.
Other studies suggest that vitamin D supplements may improve the response to antiviral treatments in people with certain infections, including hepatitis C and HIV.
Depending on blood levels, 1,000 to 4,000 IU of supplemental vitamin D per day is sufficient for most people, with people with more severe deficiencies often requiring much higher doses.
Vitamin D has been extensively researched in the context of COVID-19 because of its effect on the immune system. Studies have shown that vitamin D can accelerate healing and inhibit inflammation in the respiratory system.
A recent study concluded that further research is needed to recommend vitamin D supplementation for the prevention and treatment of COVID-19.
However, many health and scientific professionals believe that vitamin D supplementation is generally safe and may help protect against the virus.
Vitamin D is important for immune function. Healthy vitamin levels can help reduce the risk of respiratory infections.
Supplements 101: Vitamin D
Zinc
Zinc is a mineral that is often added to supplements and other health products, such as lozenges, that are designed to boost your immune system. The reason for this is that zinc is essential for the functioning of the immune system.
Zinc is needed for the development and communication of immune cells and plays an important role in inflammatory responses. Zinc also protects the body's tissue barriers and helps prevent the invasion of foreign pathogens.
A deficiency of this nutrient impairs the immune system's ability to function properly and leads to an increased risk of infection and disease, including pneumonia.
Research has shown that 16% of all serious respiratory infections worldwide are due to zinc deficiency.
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 to be deficient in this nutrient.
In North America and industrialized countries, zinc deficiency is relatively rare.
Nevertheless, many people in the United States have marginal zinc deficiency related to intake or absorption. Older people are generally at increased risk.
Numerous studies show that zinc supplements can protect against respiratory infections such as the common cold.
In addition, zinc supplementation can be beneficial for people who are already ill.
In a 2019 study of 64 children hospitalised with acute lower respiratory tract infections, taking 30 mg of zinc per day reduced the total duration of infection and length of hospital stay by an average of 2 days compared to a placebo group (21 Trusted Source).
The additional intake of zinc can also help to shorten the duration of a cold (22 Trusted Source). In addition, zinc has an antiviral effect (23, 24 Trusted Source).
The long-term intake of zinc is generally safe for healthy adults as long as the daily dose is below the specified upper limit of 40 mg of elemental zinc (13Trusted Source)Trusted Source.
Excessive doses can impair copper absorption, which can increase the risk of infection.
Supplemental zinc intake may help protect against respiratory infections and shorten the duration of these infections.
Vitamin C
Vitamin C is perhaps the most popular supplement taken to protect against infection, as it plays an important role in the health of the immune system.
This vitamin supports the function of various immune cells and improves their ability to protect against infection. It is also necessary for cell death, which helps to keep the immune system healthy by breaking down old cells and replacing them with new ones.
Vitamin C also acts as a powerful antioxidant and protects against damage caused by oxidative stress, which is caused by the accumulation of reactive molecules called free radicals.
Oxidative stress can have a negative impact on the health of the immune system and has been linked to numerous diseases.
Vitamin C supplementation has been shown to reduce the duration and severity of upper respiratory tract infections, including the common cold.
A large review of 29 studies involving 11,306 people showed that regular supplementation with vitamin C at an average dose of 1 to 2 grams per day reduced the duration of colds by 8% in adults and 14% in children.
Interestingly, the research also showed that regular use of vitamin C supplements reduced the incidence of colds by up to 50% in people with high levels of physical exertion, including marathon runners and soldiers.
In addition, 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) due to viral infections.
However, other studies indicate that the role of vitamin C in this context is still under investigation.
All in all, these results confirm that vitamin C supplements can have a significant impact on immune health, especially in people who do not get enough vitamin C in their diet.
The upper limit for vitamin C is 2,000 mg. The daily dose for supplements is usually between 250 and 1,000 mg.
Vitamin C is important for the health of the immune system. Supplementing with this nutrient can help reduce the duration and severity of upper respiratory infections, including the common cold.
Elderberry
Long used to treat infections, black elderberry (Sambuca's nigra) is currently being studied for its effects on immune health.
In test tube studies, elderberry extract has shown strong antibacterial and antiviral potential against bacterial pathogens responsible for upper respiratory tract infections and against strains of the influenza virus.
It has also been shown to improve the immune system's response and may help shorten the duration and severity of colds and alleviate symptoms associated with viral infections.
A review of 4 randomised control trials involving 180 people found that elderberry supplements significantly reduced upper respiratory symptoms caused by viral infections.
An older, five-day study from 2004 showed that flu sufferers who took 1 tablespoon (15 ml) of elderberry syrup four times a day experienced relief of their symptoms four days earlier than those who did not take the syrup and were less dependent on medication.
However, this study is outdated and was sponsored by the manufacturer of elderberry syrup, which may have biased the results.
While it has been claimed that elderberry can relieve the symptoms of certain infections and the flu virus, it is important to be aware of the risks. Some report that elderberries can lead to the production of excess cytokines, which can potentially damage healthy cells.
For this reason, some researchers recommend taking elderberries only in the early stages of COVID-19.
It should be noted that no published research studies have investigated the use of elderberries in COVID-19.
A systematic review of elderberry came to this conclusion:
In animal and human studies, elderberry had antiviral effects and inhibited several strains of influenza A and B.
- Raw elderberries must be cooked to avoid the risk of nausea, vomiting or cyanide toxicity.
- Elderberry should only be used under the guidance of a qualified physician.
- Elderberry supplements are usually sold in liquid or capsule form.
Taking elderberry supplements can help relieve upper respiratory symptoms caused by viral infections and improve flu symptoms. However, elderberry also carries risks. Further research is needed.
Medicinal mushrooms
Medicinal mushrooms have been used since ancient times to prevent and treat infections and diseases. Many types of medicinal mushrooms have been studied for their immune-boosting potential.
Over 270 recognized medicinal mushroom species are known to have immune-boosting properties.
Cordyceps, lion's mane, maitake, shitake, reishi and turkey tail are all species that have been shown to promote immune health.
Some research shows that ingesting certain types of medicinal mushrooms can improve immune health in various ways and alleviate the symptoms of certain conditions, such as asthma and lung infections.
For example, a study of mice suffering from tuberculosis, a serious bacterial disease, found that treatment with cordyceps significantly reduced the bacterial load in the lungs, boosted the immune response and reduced inflammation, compared with a placebo group.
In a randomized, 8-week study of 79 adults, taking 1.7 grams of an extract from the culture of Cordyceps mycelium led to a significant 38% increase in the activity of natural killer (NK) cells, a type of white blood cell that protects against infection.
Turkey tail is another medicinal mushroom that has powerful effects on the health of the immune system. Human studies suggest that turkey tail can improve immune response, especially in people with certain types of cancer.
Many other medicinal mushrooms have also been studied for their positive effects on immune health. Medicinal mushroom products are available in the form of tinctures, teas and dietary supplements.
Many types of medicinal mushrooms, including cordyceps and turkey tail, may have immune-boosting and antibacterial effects.
6-15 Other dietary supplements with immune-boosting potential
In addition to the supplements mentioned above, there are many others that can improve immune defense:
- Astragalus. Astragalus is a herb commonly used in traditional Chinese medicine (TCM). Animal studies suggest that its extract can significantly improve immune responses (54Trusted Source).
- Selenium. Selenium is a mineral that is essential for the health of the immune system. Animal studies show that selenium supplements can improve antiviral defences against flu strains, including H1N1.
- Garlic. Garlic has strong anti-inflammatory and antiviral properties. It has been shown to improve the health of the immune system by stimulating protective white blood cells such as NK cells and macrophages. However, human research is limited.
- Andrographis. This herb contains andrographolide, a terpenoid compound that has antiviral effects against viruses that cause respiratory diseases, including enterovirus D68 and influenza A.
- Liquorice. Liquorice contains many substances, including glycyrrhizin, which can help protect against viral infections. According to test tube studies, glycyrrhizin shows an antiviral effect against severe acute respiratory syndrome coronavirus (SARS-CoV),
- Pelargonium sidoides. Some human studies support the use of the extract of this plant to relieve the symptoms of acute respiratory viral infections, including the common cold and bronchitis. However, results are inconsistent and further research is needed (64Reliable source).
- B-complex vitamins. B vitamins, including B12 and B6, are important for healthy immune defences. However, many adults are deficient in these vitamins, which can have a negative impact on immune health.
- Curcumin. Curcumin is the main active ingredient in turmeric. It has strong anti-inflammatory properties and animal studies suggest that it may help improve immune function.
- Echinacea. Echinacea is a genus of plants in the Asteraceae family. Certain species have been shown to improve immune health and may have antiviral effects against various respiratory viruses, including respiratory syncytial virus and rhinoviruses.
- Propolis. Propolis is a resin-like material that honey bees produce as a sealant in their hives. Although it has impressive immune-boosting effects and may also have antiviral properties, further research on humans is needed.
According to the results of scientific research, the supplements listed above may have immune-boosting properties.
However, it should be noted that many of these potential effects of these supplements on immune health have not yet been thoroughly tested in humans, emphasizing the need for future studies.
Astragalus, garlic, curcumin and echinacea are just some of the supplements that may have immune-boosting properties. However, they have not yet been thoroughly tested in humans. Further research is needed.
The bottom line
Many of the supplements on the market can improve the health of the immune system.
Zinc, elderberry and vitamins C and D are just some of the substances that have been studied for their immune-boosting potential.
While these supplements may provide some small benefit to immune health, they should not and cannot be used as a substitute for a healthy lifestyle.
Eating a nutritious, balanced diet, getting enough sleep, exercising regularly and quitting smoking (or considering quitting smoking) are among the most important things you can do to keep your immune system healthy and reduce the risk of infection and disease.