Finding ways to boost your immune system naturally with supplements is all the rage these days. From vitamin D to elderberry capsules to zinc and vitamin C, in this article we’ll take a deeper dive into some of the best immune defense supplements out there.
We’ll share the latest and greatest research about the benefits, risks, and optimal dosing for several of the best natural immune booster supplements, according to science.
What Is Vitamin D?
Vitamin D is a fat-soluble vitamin found in a small amount of foods and a hormone our bodies make.
Since few foods naturally contain vitamin D, for most people the best way to get enough vitamin D is by spending time in the sunshine (which is good for getting vitamin D but not-so-good for your skin) or by taking supplements.
Vitamin D Benefits
- Helps the body absorb more calcium and phosphorus, both of which are critical for building bone.
- Supplementation with 800 IU of vitamin D per day reduced hip and nonspinal fractures by about 20%.
- A randomized clinical trial in Japanese school children tested whether taking daily vitamin D supplements would prevent seasonal flu. The trial followed nearly 340 children for four months during the height of the winter flu season. Half of the study participants received pills that contained 1,200 IU of vitamin D; the other half received placebo pills. Researchers found that type A influenza rates in the vitamin D group were about 40% lower than in the placebo group.
- A large meta-analysis of individual participant data indicated that daily or weekly vitamin D supplementation lowers risk of acute respiratory infections.
- One study of people with autoimmune conditions found “the beneficial effects of supplementing vitamin D deficient individuals with autoimmune disease may extend beyond effects on bone and calcium homeostasis.”
- In the Health Professionals Follow-up Study, nearly 50,000 healthy men were followed for 10 years. Those who had the lowest levels of vitamin D were twice as likely to have a heart attack as men who had the highest levels.
Vitamin D Adverse Effects / Risks
According to the Mayo Clinic, vitamin D is generally considered safe when used in appropriate doses.
However, taking too much vitamin D supplements can be harmful. Children age 9 years and older, adults, and pregnant and breastfeeding women who take more than 4,000 IU a day of vitamin D might experience:
- Nausea and vomiting
- Poor appetite and weight loss
- Confusion and disorientation
- Heart rhythm problems
- Kidney stones and kidney damage
Possible drug interactions include:
- Atorvastatin (Lipitor)
- Calcipotriene (Dovonex, Sorilux)
- Cholestyramine (Prevalite)
- Cytochrome P-450 3A4 (CYP3A4) substrates
- Digoxin (Lanoxin)
- Diltiazem (Cardizem, Tiazac, others)
- Orlistat (Xenical, Alli)
- Thiazide diuretics
- Stimulant laxatives
- Verapamil (Verelan, Calan SR)
Talk to your doctor about vitamin D supplementation if you’re taking any of these.
Vitamin D Dosing
According to the Harvard School of Public Health, many people may not be getting enough vitamin D.
Recommended Dietary Allowance for vitamin D (the daily amount needed to maintain healthy bones and normal calcium metabolism in healthy people, assuming minimal sun exposure), is:
600 IU daily for men and women 19 years and older, and 800 IU daily for adults >70 years.
The Tolerable Upper Intake Level (UL)–the maximum daily intake unlikely to cause harmful effects on health–is 4,000 IU of vitamin D for adults and children ages 9+.
What Is Vitamin C?
Vitamin C is an essential nutrient involved in the repair of tissue, the formation of collagen, and the enzymatic production of certain neurotransmitters.
Vitamin C Immune Defense Benefits
Vitamin C is one of the most powerful antioxidants for immunity. It has been shown in clinical studies to:
- Lower the severity and duration of colds.
- Contribute to immune defense by supporting various cellular functions of both the innate and adaptive immune system.
- Reduce the risk, severity, and duration of infectious diseases (when combined with zinc).
- Reduce chronic inflammation.
- Speed up the healing process.
Since the human body can’t create or store its own vitamin C, it needs to be constantly replenished and that’s where supplements can help.
Vitamin C Adverse Effects / Risks
According to a 2020 research review, potential adverse effects of Vitamin C supplementation include headaches, flushing, nausea or vomiting, and dizziness. There have been reports of migraine headaches with a daily dose of 6 grams.
Significant amounts of vitamin C can increase the risk of kidney stones and elevate uric acid and oxalate because it acidifies the urine.
Vitamin C supplementation is contraindicated in blood disorders like thalassemia, G6PD deficiency, sickle cell disease, and hemochromatosis. Avoid taking supplements immediately before or following angioplasty. Diabetic patients should take vitamin C supplements with care as it raises blood sugar levels.
Vitamin C Dosing
The average protective adult dose of vitamin C is 70 to 150 mg daily.
What Is Zinc?
Zinc is a trace mineral that’s found at high levels in oysters, beef and crab, and in lower amounts in legumes, tofu, pumpkin seeds, cashews and other nuts and seeds.
The World Health Organization (WHO) reports that between 17% and 30% of the world population has a zinc deficiency.
Zinc Immunity Benefits
Zinc is known as the “gatekeeper” of immune function and its immune-boosting benefits include:
- Shorten the duration of colds when used in supplement form.
- Reducing risk of disease and inflammation.
- Protecting the body against an overreactive immune system causing autoimmune diseases, chronic inflammation or allergies.
Zinc Adverse Effects / Risks
Acute adverse effects of high zinc intake include nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches.
Taking 150–450 mg of zinc per day have been associated with chronic effects such as low copper status, altered iron function, reduced immune function, and reduced levels of high-density lipoproteins.
Zinc supplements can interact with several types of medications, including:
Talk to your doctor about using a zinc supplement if you’re on any of these medications.
Zinc has been studied in clinical trials in doses ranging from 45 mg to 300 mg. Research has shown that use of total daily zinc lozenge doses of over 75 mg reduced the duration of the common cold, whereas lower doses did not.
However, the U.S. Food and Nutrition Board (FNB) has established a daily Upper Limit (UL) for zinc because long-term intakes above the UL increase the risk of adverse health effects.
|0–6 months||4 mg||4 mg|
|7–12 months||5 mg||5 mg|
|1–3 years||7 mg||7 mg|
|4–8 years||12 mg||12 mg|
|9–13 years||23 mg||23 mg|
|14–18 years||34 mg||34 mg||34 mg||34 mg|
|19+ years||40 mg||40 mg||40 mg||40 mg|
We recommend starting with adding 15 to 30 milligrams of zinc to your daily supplement regimen daily, especially during the fall and winter months and at the first signs of cold or flu. If you get sick, talk to your healthcare professional about upping the dose of zinc for the duration of your symptoms for increased immune defense.
What Is Turmeric?
Turmeric is a spice that comes from the root of curcuma longa, a plant in the ginger family. Its main active ingredient is a compound called curcumin, which gives turmeric its yellow color.
Turmeric Immune Health Benefits
Turmeric is known for its antioxidant profile and anti-inflammatory properties.
- One study showed turmeric/curcumin may help protect your body from free radicals.
- A 2020 research review found that turmeric’s antioxidant effects may also stimulate the action of other antioxidants in your body.
- A 2017 research review found that turmeric “aids in the management of oxidative and inflammatory conditions, metabolic syndrome, arthritis, anxiety, and hyperlipidemia”.
- In one study of patients with ulcerative colitis, a common autoimmune disease, patients who took 2 grams of curcumin / day along with prescription medication were more likely to stay in remission than those who took the medication alone.
- Turmeric may reduce joint swelling and stiffness from rheumatoid arthritis.
- A 2018 study found that “turmeric shows pivotal role in the modulation of immune system”.
Turmeric Adverse Effects / Risks
When taken orally in supplement form, turmeric is usually well tolerated.
In human studies, doses of up to 8000 mg / day of turmeric / curcumin have been used for eight months without toxic effects.
The most common side effects were GI-related, including:
- abdominal distension
- gastroesophageal reflux
- yellow stool
- stomach ache
Turmeric extracts can trigger biliary colic (abdominal pain) in people with gallstones. About 7% of the adverse reactions reported to the MHRA for curcuma were for hepatobiliary disorders or abnormal liver function test results.
Turmeric or curcumin-containing preparations may cause heart rate or rhythm disorders.
Curcumin may also have antiplatelet (blood thinning) effects.
Talk to your doctor before supplementing with turmeric / curcumin.
Research shows that 500 milligrams of a turmeric / curcumin supplement twice daily with food appears to be a safe and efficacious dose for most people.
The dose that’s right for you depends on your overall health and pre-existing conditions you may have. More isn’t necessarily better, and in some cases can be worse, so talk to your doctor first.
Another important caveat: on its own, curcumin is poorly absorbed. So look for a curcumin / turmeric capsule with piperine (a black pepper extract) or combine it with some healthy fats (olive oil, avocado, nuts, etc.) to increase absorption.
It’s usually best to take turmeric with or immediately before a meal to avoid any side effects.
What Is Elderberry?
Elderberries come from a tree variety known as Sambucus. The berries and flowers of these trees are edible, but must be cooked before they’re consumed (because they’re toxic and can cause diarrhea, vomiting and nausea if consumed uncooked).
Elderberry Immune Boosting Benefits
A 2016 randomized, double-blind placebo-controlled clinical trial of 312 economy class passengers traveling overseas from Australia sought to investigate whether elderberry extract has beneficial effects on physical, especially respiratory, and mental health.
Researchers found that the group that didn’t take the elderberry supplement had a significantly longer duration of cold episode days and the average symptom score over these days was also significantly higher. These data suggest a significant reduction of cold duration and severity in air travelers.
Elderberry also may be an effective option for:
- Treating viral illness, according to a 2021 research review,
- Relieving symptoms and duration of the flu.
- Helping treat upper respiratory infections.
It should be noted that elderberry’s ability to fight the flu has been a point of contention, with one study showing “no evidence that elderberry benefits the duration or severity of influenza”.
Elderberry Adverse Effects / Risks
- Raw unripe elderberries and other parts of the elder tree, such as the leaves and stem, contain toxic substances that can cause nausea, vomiting, and diarrhea; cooking eliminates this toxin. Large quantities of the toxin may cause serious illness.
- Little is known about whether it’s safe to use elderberry during pregnancy or while breastfeeding.
- Don’t rely on elderberry or other dietary supplements for prevention or treatment of COVID-19. They have not been shown to be effective.
Elderberry is available in many different types of products, including syrups, mouth rinses, and capsules. But there are currently no dosing standards for elderberry supplements. It has been studied in doses ranging from 500 mg to 1200 mg daily.
Long story short, elderberry is a promising but understudied supplement: it may reduce the symptoms of colds and the flu, but the evidence is still preliminary.
Larger controlled clinical studies are needed to better understand the safety, efficacy, and dosing.
What Are Probiotics?
Probiotics are gut microbes that may exert some health benefits.
Which Probiotics Support Immunity?
Here are the strain-specific probiotics that may work for boosting your immune system:
|Probiotic Strain||Immune System Benefit|
|Bifidobacterium bifidum||Reduces cold and flu incidence.|
|Lactobacillus brevis||Reduces the incidence of flu.|
|Lactobacillus GG||Decreased risk of upper respiratory infections for children in daycare.|
|Lactobacillus acidophilus and Bifidobacterium bifidum||Reduces the risk of colds in school-aged children.|
|Lactobacillus rhamnosus||Reduces the incidence of pneumonia in people in the intensive care unit.|
|B. longum||Helps prevent the flu in elderly patients.|
|Lactobacillus plantarum and Lactobacillus paracasei||Reduces the number of days with symptoms and severity of colds.|
Also, a 2016 review and meta-analysis of 23 randomized controlled trials found that probiotics appear to decrease the incidence of respiratory tract infections in children.
See our article Which Probiotics Are Best for Immunity? for further reading on this topic.
Probiotics Adverse Effects / Risks
According to the Cleveland Clinic:
Because microbes used as probiotics already exist naturally in your body, probiotic foods and supplements are generally considered safe. They may trigger allergic reactions, and may also cause mild stomach upset, diarrhea, or flatulence (passing gas) and bloating for the first few days after starting to take them.
There are certain people who need to use caution when using probiotic supplements, including those who:
- Have a weakened immune system (those going through chemotherapy for example).
- Have a critical illness.
- Recently had surgery.
Caution should also be used when giving probiotics to very sick infants.
Always talk to your healthcare provider before starting a probiotic supplement.
Probiotics are measured in colony forming units (CFUs), which indicate the number of viable cells.
Many probiotic supplements contain 1 to 10 billion CFU per dose, but some products contain up to 50 billion CFU or more.
However, higher CFU counts do not necessarily improve the product’s health effects.
And unfortunately, at this point there are too many strains and not enough clear evidence about the optimal dose for each strain, so probiotic supplementation can often take some trial and error. Be sure to stick with supplements that use strains that have been studied for safety and efficacy in clinical trials (like the ones mentioned above).
How to Find the Best Natural Immune Booster Supplements
There are a few things to look for to find the best immune boosting supplements for you.
- Stick with supplements that are supported by research and have some efficacy and safety data to support them: vitamin D, vitamin C, zinc, elderberry, and probiotics.
- Choose a product with optimal doses for efficacy and safety (if optimal doses have been established).
- Look for supplements made in the USA in a GMP-compliant, FDA-approved facility that have been third party lab tested for purity and safety.
We recommend trying an elderberry with Vitamin C and zinc supplement, along with vitamin D and probiotics to support immune health.
If you’re interesting in exploring Pure Food supplements for a strong immune system, read more here:
Pure Food Immunity Bundle: 4 Proven Immune Defense Supplements