10 Best Immune Support Supplements in 2023, according to Evidence

What are the best immune support supplements?

Here is a list of evidence-based supplements that are known for their immune-boosting potential, supported by overwhelming research. 

Since we are in still in the pandemic or endemic phase, we have compiled research and studies specifically related to immune boosting supplements.

Methodology: The selection or short-listing of the list below is based on the available scientific evidence retrieved from scientific database such as PubMed and scientific search engine such as Google Scholar.

This list will be updated from time to time based on updated scientific evidence.

1. Vitamin D

At this point, there is simply no question that vitamin D optimization is a crucial component of COVID-19 prevention and treatment. In addition to the many studies published during 2020 and 2021, since December 2021, four large systematic meta-analyses (R, R, R, R) have been published, looking at either vitamin D levels, supplementation or both.

In a peer-reviewed study published in Nature (Nov 2022), treatment with Vitamin D can actually reduce the risk of severe COVID-19 infection.

In all cases, the data consistently show that low vitamin D levels raises your risk of COVID while higher baseline levels and/or supplementation lowers all risks by 1.5 to three times.

Vitamin D, as an immuno-modulator, is a perfect candidate for countering the immune dysregulation common with COVID-19. Vitamin D deficiency affects the body’s susceptibility to infection and has been associated with influenza, hepatitis C, human immunodeficiency virus (HIV) and other viral diseases [Source]. Surveys indicate that most people in the United States consume less than recommended amounts of vitamin D. Sun exposure, which increases serum 25(OH)D levels, is one of the reasons serum 25(OH)D levels are usually higher than would be predicted on the basis of dietary vitamin D intakes alone. Vitamin D deficiency is also known to enhance a process known as the “cytokine storm” (Marik 2020).

According to a July 2022 paper:

“Each 10 ng/mL increase in vitamin D levels was associated with a 45 % and 26 % lower risk of 45-day mortality (HR: 0.55, 95 % CI: 0.40–0.74) and ICU mortality due to COVID-19 (HR: 0.74, 95 % CI: 0.60–0.92), respectively.”

Since the outbreak of the pandemic, many vitamin D sufficiency studies have been conducted. Almost all of them show that an adequate vitamin D level reduces the chance of (a) getting ill, (b) ending up in the hospital, and (c) dying.

Almost all studies consider a vitamin D blood serum level of >30 ng/mL ‘adequate/good’. Several studies have shown that people with a blood serum level of >50 ng/mL hardly get sick at all. Results of a systematic review and meta-analysis (Nutrients 2021) suggested that COVID-19 mortality risk correlates inversely with vitamin D3 status, and a mortality rate close to zero could theoretically be achieved at 50 ng/ml 25(OH)D3.

In a June 2022 review paper titled “The Role of Diet and Supplements in the Prevention and Progression of COVID-19: Current Knowledge and Open Issues”​ published in the journal Preventive Nutrition and Food Science, researchers said:

"The consumption of vitamin C and D supplements, in addition to a healthy diet, could be promoted as a co-adjuvant therapy for COVID-19..."

For more evidence, check out the evidence tracker on vitamin D and COVID-19 from c19vitamind.com (constantly updated), with more than 100 published treatment studies and more than 130 sufficiency studies by more than 1,000 scientists.

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Vitamin D is higher than ivermectin and hydroxychloroquine in this COVID-19 drug league table for 'early treatment study results':

Vitamin D has also been shown to have an anticoagulant effect. A decrease in 25-hydroxyvitamin D [25(OH)D] concentration has also been associated with an increased risk of venous thromboembolism (PubMed).

Safety: Daily intakes of up to 25–100 mcg (1,000 IU–4,000 IU) vitamin D in foods and dietary supplements are safe for children (depending on their age) and up to 100 mcg (4,000 IU) are safe for adults. These values, however, do not apply to individuals receiving vitamin D treatment under the care of a physician. Higher intakes (usually from supplements) can lead to nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, excessive urination and thirst, and kidney stones. In extreme cases, vitamin D toxicity causes renal failure, calcification of soft tissues throughout the body (including in coronary vessels and heart valves), cardiac arrhythmias, and even death.

Vitamin D and Omicron

Will Vitamin D Work Against Omicron BA4 and BA 5? Vitamin D is not variant specific because it's primary mode of action is to support the body’s immune system which reacts in a variety of ways against viral attack, not just in a specific antibody reaction to a specific spike protein. 

Related: Best Vitamin D3 Supplement

2. Quercetin - Anti-inflammatory, anti-coagulant, zinc ionophore and anti-viral

As of September 2022, there have been 9 published studies of quercetin and COVID-19 (c19quercetin.com). 

Quercetin is also no. 1 in this prevention studies league table:

Quercetin is a pigment that is found in plants, vegetables, and fruits, and serves as an immune nutrient offering many health benefits. Elderberry, red onions, white onions and cranberries are the richest sources of quercetin. It is a flavonoid and antioxidant that may help to reduce inflammatory cytokines, infections, allergies and anti-blood clot property. Research has found that quercetin may be particularly beneficial for viral respiratory infections.

Quercetin as a Zinc Ionophore

Quercetin is a zinc ionophore (J Agric Food Chem. 2014). A 2015 study found that that Quercetin shows inhibitory activity in the early stages of a wide range of influenza viruses, including H1N1 and H5N1 (Viruses 2016). Although influenza is not in the same family of viruses as the coronavirus, it’s plausible that a similar mechanism could apply here. There is actually some evidence that Quercetin has already proven effective at treating Ebola and Zika viruses.

Quercetin and Vitamin C

Incidentally, ascorbic acid (vitamin C) and the bioflavonoid quercetin (originally labeled vitamin P) were both discovered by the same scientist — Nobel prize winner Albert Szent-Györgyi. Quercetin and vitamin C also act as an antiviral drug, effectively inactivating viruses. 

Quercetin Dosage

The FLCCC I-MASK+ protocol recommends 250 mg daily for prevention and 250 mg twice daily for early treatment.

Quercetin works best when taken with vitamin C and Bromelain, as vitamin C helps activate it and bromelain helps with the absorption.

Precaution: Quercetin should be used with caution in patients with hypothyroidism (low thyroid hormone) and relevant thyroid hormone levels should be monitored.

Quercetin and ivermectin interactions? According to Drugs.com: "No interactions were found between ivermectin and Quercetin. This does not necessarily mean no interactions exist. Always consult your healthcare provider."

Quercetin and COVID-19

For an updated list of studies, check out c19quercetin.com. 

A word about quercetin: Some physicians are recommending this supplement to reduce viral illnesses because quercetin acts as a zinc ionophore to improve zinc uptake into cells. It is much less potent than HCQ (hydroxychloroquine) as a zinc transporter, and it does not reach high concentrations in lung cells that HCQ does. Quercetin may help reduce risk of viral illness if you are basically healthy. But it is not potent enough to replace HCQ for treatment of COVID once you have symptoms, and it does not adequately get into lung tissue unless you take massive doses (3-5 grams a day), which cause significant GI (gastrointestinal) side effects such as diarrhea.

Related: Best Quercetin Zinc Supplement

3. Zinc - Anti-viral 

Zinc is another powerful immune nutrient known for its benefits for providing immune health support and inflammation reduction as well as for improving cold and respiratory symptoms, wound healing, acne reduction, and lowering the risk of age-related diseases. This trace element is essential to to cell function and involved in over 100 enzymes. Research on atherosclerosis and diabetes mellitus suggests that zinc deficiency may contribute to low-grade systemic inflammation.

Aging is associated with compromised immunity, that just means that your immune response to pathogens and infections starts to slow and is less robust, including a reduced vaccine immune response/efficacy. ⁣
⁣
Improving zinc intake/zinc status improves/modulates/enhances immune function. The flip side is, while some aspects of immunity slow, others increase. Uncontrolled immune responses drive excess inflammation. Zinc helps to balance all of this. ⁣

The National Institutes of Health (NIH) states:

“Zinc is involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of approximately 100 enzymes and it plays a role in immune function, protein synthesis, wound healing, DNA synthesis, and cell division. Zinc also supports normal growth and development during pregnancy, childhood, and adolescence and is required for proper sense of taste and smell.”

Zinc and COVID-19

The use of zinc for SARS-CoV-2 was a topic routinely flagged by COVID fact checkers as “misinformation,” so word didn’t really get out about its potential as an anti-COVID agent. However, research once again shows zinc’s promise for keeping people healthy if they get COVID.

A team of researchers with Fattouma Bourguiba University Hospital in Tunisia set out to determine zinc’s efficacy in treating adults with COVID-19. “Like in many other diseases, regulation of white blood cell production using immuno-nutrition is a novel concept that could be applied to COVID-19,” they noted. “Some molecules and nutrients such as zinc play central roles in keeping the function and integrity of the immune system.” (R)

They conducted a randomized, double-blind, placebo-controlled trial, during which patients who tested positive for COVID-19 — including 190 outpatients and 280 hospitalized patients (R) — received either oral zinc or a placebo twice daily for 15 days. Those taking zinc had a nearly 40% lower rate of death and admission to the intensive care unit (ICU). They also had shorter hospital stays and cut the number of days needed for their symptoms to resolve. (R)

Specifically, mortality after 30 days was 6.5% in the zinc group compared to 9.2% in the placebo group. ICU admission rate was 5.2% in the zinc group and 11.3% in the placebo group. Further, those in the zinc group had, on average, a 3.5-day shorter hospital stay while their symptoms resolved 1.9 days sooner than those who received a placebo. (R)

The beneficial effects of zinc were seen even in subgroups of patients, including those under 65, people with comorbidities and those who needed oxygen therapy at the start of the study. No severe adverse effects were seen. In fact, more minor adverse events occurred in the placebo group (7.1%) than in those taking zinc (3.9%). (R) The researchers concluded: (R)

“To our knowledge, this study is the first well powered, placebo-controlled clinical trial to report results of zinc for the treatment of patients with COVID-19.

When administered orally to patients hospitalized with COVID-19 without end-organ failure, zinc demonstrated its efficacy to prevent ICU admission and to reduce hospital length of stay; for outpatients, zinc reduced symptom duration. Zinc should be considered for the treatment of patients with COVID-19.”

For more evidence, check out the evidence tracker on zinc and COVID-19 from c19zinc.com (constantly updated). 

Foods that are high in zinc include oysters, crab, lobster, mussels, red meat, and poultry. Cereals are often fortified with zinc. Most multivitamin and nutritional supplements contain zinc.

Safety: 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 (PubMed). Be aware that typical daily doses of zinc provided by zinc lozenges generally exceed tolerable upper limits for zinc, and for this reason, they should not be used for longer than about a week. 

Excessive doses may interfere with copper absorption, which could negatively affect your immune system as it can cause copper deficiencies, blood disorders and potentially permanent nerve damage. Zinc can also impair the absorption of antibiotics, and use of zinc nasal gels or swabs has been linked to temporary or permanent loss of smell.

Zinc Form and Dosage

There are several types of zinc supplements. Supplements contain several forms of zinc, including zinc gluconate, zinc citrate and zinc picolinate. The percentage of elemental zinc varies by form. To find out the percentage of elemental zinc in each form, check out elemental zinc percentage.

Chelated zinc is a general form of supplementary zinc in which the zinc is chelated — or bound — to a compound to make it easier for the body to absorb. Zinc picolinate or zinc gluconate are formed when zinc is chelated to picolinic acid or gluconic acid, so the main difference between zinc gluconate and picolinate is what compound it is bound to.

To find out which zinc supplement to consider, check out best zinc supplement.

Most people do not lack an intake of zinc, but in disease state, there might be an increase in demand by the body. The FLCCC I-MASK+ protocol recommends 30 mg a day for prevention and 100 mg a day for early treatment of COVID-19. This should not be taken long term without evaluation of your zinc/copper ratios.

The ideal dose for prevention while the COVID-19 risk is high is 40-100 mg/d, a portion of which comes from zinc lozenges to spread the zinc through the tissues of the nose, mouth and throat. It should be accompanied by at least 1 mg copper from food and supplements for every 15 mg zinc.

Do take note that you should keep the dosage back to within 40 mg/d once the exposure risk is back to normal.

4. Nigella Sativa (Black Seed Oil) and Cytokine Storm - Anti-inflammatory

Nigella sativa (N. sativa) is a small flowering plant that grows in Southwest Asia, the Middle East, and Southern Europe (Source). This shrub produces fruit with tiny black seeds. Commonly referred to as black seed, N. sativa seeds go by many other names, such as black cumin, black caraway, nigella, fennel flower, and Roman coriander (Source).

Black seed oil is extracted from N. sativa seeds and has been used in traditional medicine for over 2,000 years due to its many therapeutic benefits.

Thymoquinone which is the active ingredient in N. sativa seeds has demonstrated effects in significantly reducing the cytokine storm chances and consequent mortalities (Source).

Summary results of 7 published clinical studies are available on this dedicated webpage: c19ns.com. The 4 RCTs (Randomized Controlled Trials) provide promising evidence that Nigella Sativa was associated with an average improvement of 69% in decreasing the likelihood of death and hospitalization if given as early treatment.

5. Melatonin- Anti-inflammatory and anti-viral

Melatonin is a hormone produced by the pineal gland in the brain, mainly during the night, that helps regulate circadian rhythms [Source]. Its levels decrease with aging. Most melatonin supplementation studies have evaluated its ability to control sleep and wake cycles, promote sleep, and reduce jet lag.

The potential utility of melatonin in treating COVID patients has not gone unnoticed, with a PubMed search combining melatonin and COVID producing more than 50 citations.

Check out the evidence tracker on melatonin and COVID-19 from c19melatonin.com (constantly updated).

As of September 2022, there are more than 15 published clinical studies of melatonin for treatment and prevention in COVID-19 and the results are promising even when it's given as a late treatment.

The 2 early treatment studies provide promising evidence that melatonin was associated with an average improvement of 78% (below).

Melatonin is a hormone synthesized in your pineal gland and many other organs. While it is most well-known as a natural sleep regulator, it also has many other important functions. For example, melatonin is a potent antioxidant (Antioxidants, 2020) with the rare ability to enter your mitochondria, where it helps “prevent mitochondrial impairment, energy failure and apoptosis of mitochondria damaged by oxidation.” It also helps recharge glutathione and glutathione deficiency has been linked to COVID-19 severity.

Production of melatonin diminishes with age, contributing to immune dysfunction and increasing oxidative stress, inflammation, and infection susceptibility (Ref). In addition, infectious viruses can suppress melatonin production, disrupting circadian controls and impairing immune function (Ref).

According to a review (Cardinali et al. 2020), melatonin might counteract the consequences of COVID-19 via salutary effects on the sleep/wake cycle and more generally on chronobiology, as well as through its antioxidant and anti-inflammatory effects.

Based on melatonin’s therapeutic potential and well-established safety profile, it has been suggested those at higher risk for severe illness and complications from viral respiratory infection, including the elderly and those with chronic medical conditions, may benefit most from regular use of 3–10 mg melatonin at bedtime (Ref). 

Fluvoxamine (Selective Serotonin Reuptake Inhibitor) might also exert beneficial effects in COVID patients through its well-characterized ability to substantially increase (~ 2–3-fold) night-time plasma levels of melatonin. This increase appears to result from fluvoxamine’s inhibition of the melatonin-metabolizing liver enzymes (von Bahr et al. 2000).

An Iranian randomised controlled trial (Arch Med Res 2021), studied 74 mild to moderate hospitalized patients. The study showed that adjuvant use of melatonin has a potential to improve clinical symptoms of COVID-19 patients and contribute to a faster return of patients to baseline health.

Some researchers have suggested high doses of melatonin, ranging from 50 to 200 mg twice daily, might help treat patients hospitalized for severe acute respiratory illness (Ref).

In a small Philippine case series study of 10 hospitalised COVID-19 patients, high dose melatonin (hdM) was given in addition (adjuvant) to standard therapy. According to the authors:

"High dose melatonin may have a beneficial role in patients treated for COVID19 pneumonia, in terms of shorter time to clinical improvement, less need for MV, shorter hospital stay, and possibly lower mortality."

Safety: If you take a melatonin supplement, be careful: Too much can cause daytime sleepiness. There is no federal RDA nor any formal advice on supplement dose ranges. Based on an on-going Spanish study, a 2 mg daily dose protocol is being investigated for prevention of COVID-19. Do take note that the dosage for 'prevention' and 'treatment' is different, For prevention or maintenance, a lower dosage is normally recommended whereas a 'treatment' or 'therapeutic' dosage is normally higher.

Typical doses of 1–10 mg/day melatonin appear to be safe for short-term use (Source). Reported side effects, which are usually minor, include dizziness, headache, nausea, upset stomach, rash, and sleepiness. However, some reports have linked high blood levels of melatonin with delayed puberty and hypogonadism.

Studies have not evaluated melatonin supplementation during pregnancy and breastfeeding, but some research suggests that these supplements might inhibit ovarian function (Source). Therefore, some experts recommend that women who are pregnant or breastfeeding avoid taking melatonin.

6. Vitamin A

Summary results of 10 vitamin A and COVID-19 studies are available on this dedicated webpage: c19early.com/va. 

Based on this early treatment mortality studies drug league table below, vitamin A might even out-perform vitamin D, ivermectin and hydroxychloroquine:

That said, most clinicians will use the multi-drug or combination approach to get the best outcome.

Scientists are also investigating if taking vitamin A could aid patients who have lost their sense of smell due to COVID-19. The 12-week 'Apollo study' would use nasal drops containing the vitamin to treat individuals who have lost or changed their sense of smell.

7. Curcumin and Turmeric - Anti-inflammatory and anti-viral

Curcumin, a yellow carotenoid from turmeric, is a nutritional therapeutic recommended as part of the FLCCC I-CARE early treatment protocol, and has antiviral, anti-inflammatory, antioxidant and immune modulating properties.

There are more than 20 completed studies of curcumin in COVID-19 that suggest that it improves clinical outcome of patients.

Curcumin also acts as natural zinc ionophores and can promote the cellular uptake of zinc and can be used with zinc to increase the effectiveness of these compounds in the inhibition of the virus (Ref).

Curcumin has been demonstrated (Ref) to suppress several inflammatory cytokines and mediators of their release such as tumor necrosis factor-alpha (TNF-alpha), IL-1, IL-8 and nitric oxide synthase.

8. Vitamin C - Anti-inflammatory

Vitamin C, which most of us reach for with any cold or flu, was used in high doses to great effect by COVID-19 early treatment doctors.

Vitamin C may be one of the most well-known immune nutrients that protect against immune deficiencies and which supports the prevention and recovery from the common cold and upper-respiratory issues, and also protects your cardiovascular system, eyes, skin, and other parts of your body. Research has found that vitamin C may help to optimize the immune system.

Do take note that the vitamin C dosages given in the hospitals intravenously are different from those over the counter vitamin C supplements. Therefore, when you come across studies on vitamin C, you need to differentiate those that are given intravenously vs oral vitamin C.

Vitamin C and COVID-19

 

Check out the evidence tracker on vitamin C and COVID-19 from c19vitaminc.com (constantly updated).

Safety: The U.S. Recommended Dietary Allowance (RDA) for vitamin C is 75 to 120 milligrams per day. Taking large doses of vitamin C (ascorbic acid) on a regular basis lowers your level of copper, so if you are already deficient in copper and take high doses of vitamin C, you can compromise your immune system.

While generally considered safe even in high doses, way too much vitamin C — anything above 2,000 milligrams daily—can cause headaches, insomnia, diarrhea, heartburn, and other issues.

Temporarily taking megadoses of vitamin C supplements to combat a case of the cold or flu is likely not going to cause a problem. 

Many vitamin C supplements that are above the US RDA are sold in the market. It’s important to seek a physician’s advice if you intend to take high dose vitamin C on a long term basis. To be on the safe side, you may also request for your kidney functions to be monitored.

For long-term, daily use, your best bet is to eat a diet that is full of high quality organic vegetables and fruits that are minimally processed. Not only will you get vitamin C, but you will get all the other accessory nutrients and micronutrients that are needed to optimize it. 

Vitamin C, Omicron and Deltacron

Will Vitamin C Work Against Omicron or Deltracron? Vitamin C is not variant specific because it's primary mode of action is to support the body’s immune system which reacts in a variety of ways against viral attack, not just in a specific antibody reaction to a specific spike protein. 

Related: Best Vitamin C Supplement

9. NAC, Glutathione and COVID-19 - Anti-inflammatory and anti-coagulant

N-acetylcysteine (NAC) is a precursor to glutathione. It is an antioxidant and increases glutathione levels in the body (Source). NAC has mucolytic activity, so it helps reduce respiratory mucus levels. Laboratory research suggests that NAC might boost immune system function and suppress viral replication. NAC also decreases levels of interleukin-6 and has other anti-inflammatory effects.

Much of the research on NAC has used an inhaled, liquid form of this compound. This form—which is classified as a drug, not a dietary supplement—is approved by the U.S. Food and Drug Administration (FDA) as a mucolytic agent and for decreasing respiratory secretion viscosity (Source). Products containing NAC are also sold as dietary supplements.

NAC and COVID-19

Considering many COVID-19 cases involve blood clots in addition to excessive oxidative stress, and NAC effectively addresses both, NAC should be seriously included in standard of care for COVID-19.

 

For a compilation of more than 10 studies of NAC and COVID-19, check out the list of studies here (constantly updated).

However, in terms of early treatment, the improvement rate is not as impressive as the other natural alternatives i.e. quercetin, black seed oil and vitamin A.

That said, NAC is a natural alternative for aspirin and an over-the-counter supplement that both prevents blood clots and breaks up existing ones i.e. anticoagulant effects. 

Studies have shown that NAC may protect against coagulation problems associated with COVID-19, as it has both anticoagulant (source) and thrombolytic effects (source), meaning it may both prevent clots and break up clots that have already formed.

A 2017 paper found NAC has potent thrombolytic effects, meaning it breaks down blood clots once they've formed.

Many COVID-19 patients experience serious blood clots, and NAC counteracts hypercoagulation, as it has both anticoagulant and platelet-inhibiting properties.

Consider taking around 500 milligrams/day of NAC, as it helps prevent blood clots and is a precursor for your body to produce the important antioxidant glutathione.

Why are some retailers and Amazon no longer selling NAC? The US FDA made it clear in 2020 that it considers NAC to be a drug and not a dietary supplement, so, for legal reasons, some companies have stopped selling it in United States.

Foods that have a positive impact on glutathione production include cruciferous vegetables such as broccoli, green tea, curcumin, rosemary and milk thistle. Getting quality sleep may also help.

Different types of exercise can influence your levels as well. In one study, researchers enrolled 80 healthy but sedentary volunteers to measure the type of exercise that may have the greatest effect. They found that aerobic training in combination with circuit weight training showed the greatest benefit.

What Is the Primary Cause of Severe COVID-19 Illness: Glutathione or Vitamin D Deficiency?

The hypothesis that vitamin D (VD) deficiency is responsible for severe manifestations and death in COVID-19 patients has been proposed and is actively being discussed by the scientific community. 

Several studies reported that glutathione levels positively correlate with active vitamin D. (PubMed, PubMed) 

Interestingly, a recent experimental study (PubMed) showed that Glutathione deficiency and the associated increased oxidative stress epigenetically alters vitamin D regulatory genes and, as a result, the suppressed gene expression decreases Vitamin D production, ultimately leading to a secondary deficiency of vitamin D. This study provides important information that glutathione is essential for the control of endogenous vitamin D production and demonstrates potential benefits of Glutathione treatment in reducing the deficiency of vitamin D. Taken together, these findings suggest that glutathione deficiency rather than vitamin D deficiency is a primary cause underlying biochemical abnormalities, including the decreased biosynthesis of vitamin D, and is responsible for serious manifestations and death in COVID-19 patients.

NAC (N-Acetyl Cysteine) vs Glutathione

N-acetyl L-cysteine (NAC), as a precursor of glutathione, helps to replenish intracellular glutathione, a vital cellular antioxidant. NAC has a low molecular weight and is well absorbed via oral administration as compared to glutathione.

NAC may also protect against coagulation problems associated with COVID-19, as it counteracts hypercoagulation and breaks down blood clots.

Glutathione and Zinc

To improve your glutathione, you need zinc, and zinc in combination with hydroxychloroquine (a zinc ionophore or zinc transporter) has been shown effective in the treatment of COVID-19.

Glutathione and Molecular Hydrogen 

One of the best ways to increase glutathione, though, is molecular hydrogen. Molecular hydrogen does so selectively and will not increase glutathione unnecessarily if you don’t need it. You can view Tyler LeBaron’s lecture on the details of how it does this in “How Molecular Hydrogen Can Help Your Immune System.”

Glutathione and Selenium

Selenium is also important, as some of the enzymes involved in glutathione production are selenium-dependent.

Safety: As an FDA-approved drug, the safety profile of NAC has been evaluated (Source). Reported side effects of oral NAC include nausea, vomiting, abdominal pain, diarrhea, indigestion, and epigastric discomfort. No safety concerns have been reported for products labeled as dietary supplements that contain NAC. (Source)

For NAC contra-indications, check out here.

Update: NAC supplements are now available on Amazon US. 

10. B Vitamins and COVID-19 - Anti-inflammatory

'B vitamins' as a topic is a complicated subject and that's probably why they are called 'B Complex'. 

B vitamins may constitute a long list, but each one is important for different reasons. B vitamins are especially effective in boosting your immunity when you combine the foods containing them so they can all work together for maximum effect. These include vitamin B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B7 (biotin), B9 and B12.

B vitamins can be found in a variety of foods including red meat, beans, milk, cheese, broccoli, spinach, avocados and brown rice. Despite the availability of vitamin B-rich foods, many Americans may be deficient in this nutrient — and not even know it. According to a blog post from Harvard University, using the National Health and Nutrition Examination Survey, “3.2 percent of adults over age 50 have a seriously low B12 level” and “up to 20 percent may have a borderline vitamin B12 deficiency.”

Dr. Uma Naidoo, a nutrition expert at Harvard Medical School, explains that:

"In a poorly regulated immune system, the body's cytokine storm induced by COVID cause lots of inflammation in the body, just as if little grenades were being tossed around. This is what causes the worst outcomes and death in COVID.

It follows that anything that improves immune system function and decreases the chances that an infected person will have a catastrophic cytokine storm may improve the outcome of COVID-19 cases and decrease the overall death rate. Therefore, it’s quite feasible that B-vitamin supplementation could contribute to preventing the worst COVID outcomes.”

Thiamine (vitamin B1), a water-soluble B-complex vitamin, is rapidly depleted during times of metabolic stress, including severe illness. Thiamine deficiency is common in hospitalized patients, especially those with critical illness (Ref). Thiamine is needed for cellular energy production and helps regulate reduction-oxidation balance, immune function, nervous system function, and vascular function (Ref).

Thiamine, at 200 mg twice daily, reduced mortality in patients with septic shock and thiamine deficiency, and laboratory research suggests it may inhibit the hyper-inflammatory immune response that accompanies cytokine storm (Ref). It is a key therapeutic in the MATH+ protocol (methylprednisolone, ascorbic acid [vitamin C], thiamine, and heparin, plus other supportive nutrients and medications), a treatment strategy proposed for managing advanced stages of severe acute viral respiratory illness (Ref). Although high-quality clinical evidence is lacking, two US hospitals implementing the MATH+ protocol in patients with a severe acute viral respiratory illness reported mortality rates that were approximately one-quarter of those reported from other US hospitals using standard care (Ref).

In a study in Saudi Arabia (Al Sulaiman et al. Crit Care 2021), 738 critically ill COVID-19 patients from two centers were included in the study. The in-hospital death rate and 30-day death rate were significantly lower in the group that received thiamine as an adjunctive treatment (a therapy given in addition to standard therapy). In addition, the thiamine group also were less likely to have blood clot during ICU stay.

Another study of COVID-19 patients with severe symptoms found 26.3% among diabetics with COVID-19 were vitamin B1 deficient.

Niacin or vitamin B3 is a precursor to nicotinamide adenine dinucleotide (NAD+). There are three main forms of niacin, which are dietary precursors to nicotinamide adenine dinucleotide (NAD). These are nicotinamide riboside (NR), nicotinic acid and nicotinamide mono nucleotide (NMN).

Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor in all living cells that is involved in fundamental biological processes. 

Structurally, the closest molecule to NAD+ is NMN, requiring only one enzymatic step to be converted to NAD+. NR, which is two enzymatic steps away from NAD+, is also being studied clinically (David Sinclair. Trends Immunol. 2022).

Vitamin B9 and folic acid help repair tissues and aid in cell metabolism and immune support. They’re found in dark leafy greens, wild-caught, cold water fish like herring, mackerel, sardines, anchovies and wild-caught Alaskan salmon, and pastured, organic chicken.

B12, also known as cobalamin, is a powerful cold- and flu-fighting nutrient in your system, as is vitamin B6, another important, germ-combating vitamin that naturally benefits and strengthens your immune system and even protects against the damaging effects of air pollution.

Adequate amounts of folate, vitamin B6 and vitamin B12 are also needed for your body to make the amino acid cysteine. N-acetyl cysteine (NAC) is a supplement form of cysteine. Consuming adequate cysteine and NAC is important for a variety of health reasons — including replenishing the most powerful antioxidant in your body, glutathione. 

Related: Niacin and COVID-19 - Is Niacin a Missing Piece of the COVID Puzzle?

Conclusion

Do take note that the most important thing you can do to avoid infection with the latest coronavirus is to prevent exposure by following the latest recommendations of the CDC and World Health Organization and take steps to stay healthy, including getting adequate sleep and exercise and eating a healthful diet that includes adequate (but not excessive) intakes of essential nutrients. Also take steps to control hypertension and blood sugar fluctuations with diabetes, as these conditions are associated with more severe disease if infected.

Another point to note is that the dosages for micronutrients or vitamins are higher for treatment as opposed to maintenance or preventive. This is probably due to higher demand of the body or the deficiency of the micronutrients are worse during a complicated viral infection. However, for prevention or maintenance, the dosages for most of the micronutrients are much lower.

The risk for hospitalizations, ventilation, and death from COVID-19 are all elevated in people with pre-existing conditions, especially high blood pressure and diabetes. Viral infections like the COVID-19 also put added stress on your body, which can affect your blood pressure, heart rate, and overall heart function. That can raise your probability of having a heart attack or stroke. Therefore, make sure your blood pressure is well controlled during this pandemic.

Aside from supplements, there are other ways that may help improve immune response and to prevent you from catching the coronavirus.

• Wear protective face mask. This is to protect not only yourself but others.
• Abundant evidence suggests that eating whole in fruits, vegetables and whole grains—all rich in networks of naturally occurring antioxidants and their helper molecules—provides protection against free radicals.
• Getting Enough Sleep
• Avoid Sugar, red meat and processed foods.
• Don't smoke.
• Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly.
• Try to minimize stress.
• Drink enough water to keep your body hydrated.
• Avoid excess alcohol.
• Avoid crowded areas.
• Regular physical activity (outdoor activities may not be allowed in countries with 'lock-down').
• Vaccination
• Consult your nearest local healthcare provider if you have any doubt.