Can nutrients from foods, supplements or herbs help protect you from the coronavirus?
The fact is, no one can say for sure. With COVID-19 being so new, there has simply been too little time for any trials to take place. That said, here are five nutrients you can get from foods or supplements that have a promising research base suggesting they might be beneficial. At the very least, they are unlikely to do any harm.
In each case we dug into the literature to find evidence of potential protective effects against SARs-like viruses or the associated conditions linked to COVID-19 such as pneumonia, respiratory distress and septic shock.
Evidence to date shows that COVID-19 is particularly problematic for people with underlying lung conditions. Among hospitalised patients the main complication involves lung inflammation, secondary lung infection and acute respiratory distress. Several of the nutrients below support lung health, improve immune status, or have anti-viral properties.
Zinc is an important mineral in the human body, involved in huge variety of biological processes. Importantly, it has anti-viral actions and is able to reduce viral replication. Zinc supplementation has shown beneficial effects in a range of viral conditions, as well as in associated lung infections, tuberculosis, pneumonia, acute lower respiratory tract infection and the common cold. It even helps in hepatitis C. Zinc supplementation has also been effective in decreasing incidences of infections in the elderly, [Prassad, 2009]
Zinc inhibited RNA polymerase activity of a number of viruses including coronavirus, arterivirus, rhinovirus, and hepatitis C virusKar et al, 2019
A 1 year study of elderly patients found that those with plasma concentrations of zinc greater than 70 μg/dL had a significantly lower risk of pneumonia with influenza than did participants with plasma zinc levels of less than 70 μg/dL. [Sandstead & Prassard: Zinc intake and resistance to H1N1 influenza, 2010]
The people at the highest risk of zinc deficiency are older adults as well as infants who are breastfeeding. Pregnant women need more zinc than usual because the zinc in their body is needed to help the developing baby. Alcohol appears to reduce zinc absorption. [ref] Vegetarian, and especially vegan diets tend to be low in zinc. [ref]
Zinc lozenges, providing a dose of zinc between 80 and 95 mg/day have been shown to reduce the duration of the common cold by 30 to 45%. These lozenges were typically taken six times per day with 13mg per lozenge. Unfortunately, many commercial zinc lozenges have loo low a dose of zinc or include substances like citric acid that binds zinc.
Interest in zinc lozenges for the treatment of the common cold arose when the common cold symptoms of a 3-year-old girl with leukaemia disappeared within a few hours after she had slowly dissolved a therapeutic zinc tablet in her mouth instead of immediately swallowing it as instructed. The benefit seemed to be obtained from the slow dissolution of the tablet in her mouth, which implied that zinc has local effects in the pharyngeal region.Hemilä, 2017
Foods highest in zinc
Oysters, red meat, baked beans, pumpkin and sesame seeds [full list]
Foods that reduce zinc absorption
Phytic acid, present in many foods, drastically reduces the amount of zinc we can obtain even from high zinc foods. Whole grain cereal products, legumes/beans and nuts/seeds contain high levels of phytate [ref] so should be eaten at separate meals from high zinc foods or zinc supplements.
Zinc gluconate or zinc citrate are readily absorbed. Zinc pincolinate is even better. [ref]
Normal daily adult requirements are 15–30 mg of elemental zinc. For acute conditions or to treat deficiency, higher doses are used, for example:
“As the zinc lozenges formulation has been widely studied and there is a significant reduction in the duration of cold at a dose of ≥ 75 mg/day, for those considering using zinc it would be best to use it at this dose throughout the cold.” Cochrane Collaboration, 2015
However, to avoid excess, a maximum daily dose of 40 mg should be observed for supplementation unless under medical direction.
Overdose of zinc:
There have been no reported cases of zinc poisoning from foods, only from excess supplementation. Signs and symptoms of zinc overdose here.
2 Vitamin C
25th March 2020: New York hospitals are treating coronavirus patients with high dosages of VITAMIN C after promising results from China, reports the Daily Mail. Doctors have been injecting 1.5 g of vitamin C three or four times per day. These quantities are far higher than can be achieved through oral supplementation, but are being used for critically ill patients.
‘The patients who received vitamin C did significantly better than those who did not get vitamin C,’ Dr Andrew Weber, a Long Island based pulmonologist and critical-care specialist said. ‘It helps a tremendous amount, but it is not highlighted because it’s not a sexy drug.’
Intravenous vitamin C might be a life-saver for critically ill patients heading into sepsis but can oral supplementation help reduce the risk of catching the virus in the first place? or at least reduce the risk of ending up in critical care if you do get it? It seems quite likely so…
Vitamin C is an essential antioxidant, enzyme cofactor and immune potentiator. It is found in white blood cells at ten times the levels as blood plasma, indicating its importance to the immune system. Vitamin C deficiency increases the incidence and severity of infections [ref].
It is well known that vitamin C can protect against influenza. In a recent mouse study, the increased susceptibility to the H1N1 influenza virus and associated pneumonia caused by stress was reversed by vitamin C supplementation while also reducing the associated lung damage.
As a health supplement, vitamin C is thought to work in a synergic way that interacts with the virus and the body to keep the body in a fine balance[Cai et al, 2015]
In controlled trials, vitamin C has demonstrated improved endothelial function, reducing blood pressure, increased left ventricular ejection fraction, decreased the incidence of atrial fibrillation, protected against contrast-induced acute kidney injury, decreased glucose levels in patients with type 2 diabetes, decreased bronchoconstriction, shortened the duration of colds, decreased the incidence of colds in physically stressed people, and it has prevented pain. There is also evidence that vitamin C may have a beneficial effect on pneumonia. All of these are relevant to reported Coronavirus complications.
Critical illness is frequently accompanied by severe vitamin C deficiency. “Supplementing vitamin C 1g twice daily to critically ill patients has a solid pathophysiological rationale and a good safety profile. ” [Honore et al, 2020]
In trials, vitamin C supplementation at 2g per day (mean), has reduced the time patients spend in intensive care units by 8%. And In three trials in which patients needed mechanical ventilation for over 24 hours, vitamin C supplementation shortened the duration of mechanical ventilation by 18.2% [Hemilä & Chalker, 2019]
Groups at high risk for Corona virus — smokers, the elderly and type 2 diabetics — typically are found to have low vitamin C levels. According to Carr and Maggini  “Patients with acute respiratory infections, such as pulmonary tuberculosis and pneumonia, have decreased plasma vitamin C concentrations relative to control subjects. Administration of vitamin C to patients with acute respiratory infections returns their plasma vitamin C levels to normal and ameliorates the severity of the respiratory symptoms. Cases of acute lung infections have shown rapid clearance of chest X-rays following administration of intravenous vitamin C.”
All of this suggests that supplementing with high dose (1 to 3 g per day) of vitamin C — especially among high risk groups — is likely to be beneficial, and at least not harmful.
Foods highest in vitamin C
Rose hips, yellow peppers, blackcurrants, broccoli, Brussels sprouts, lemons, oranges [more] Note: cooking and storing reduces vitamin C levels.
Supplemental vitamin C
Bulk ascorbic acid powder (e.g. Holland and Barrette or Bulk Powders) is economic. This form is very acidic — hence sharp tasting. Some people may find sodium ascorbate more digestible as it is non-acidic.
At my clinic I use liposomal vitamin C which permits a higher dose to be taken, and absorbed, than oral supplements.
Dosing at 1 to 3 grams per day is generally well tolerated.
Excess vitamin C:
Vitamin C is a water soluble vitamin which cannot be stored in the body. Excess is therefore excreted in the urine. Only so much can be absorbed orally, and an excessive single dose can cause stomach upset or loose stools. Prolonged supplementation may contribute to kidney stones, although this depends on other factors. Vitamin C increases non-heam iron absorption (from plant-based foods) which could contribute to iron overload. More details here.
3 Zinc ionophores: Quinine and Quercetin
Certain compounds increase the concentration of zinc inside cells. These are known as zinc ionophores. The title of this 2010 paper makes the point:
In other words, there is evidence that zinc on its own inhibits coronavirus, but in the presence of zinc ionophores replication is also blocked.
It turns out that bark from the Peruvian tree, Cinchona calisaya was discovered to be an excellent treatment for the fevers of malaria and it came to fame when successfully used in the treatment of the Countess of Chinchon, in 1663.
In 1820 the alkaloid quinine was isolated from the bark and in 1944 synthesised in the lab, having become a valuable medicine in the treatment of malaria across the world. It was incorporated into tonic water and used extensively in India, by the British, often with gin, with a view to reducing the vulnerability to malaria there.
Natural quinine and the synthetic forms, chloroquine and hydroxychloraquine are zinc ionophores, i.e. cause cells to take up zinc. They are currently receiving a lot of attention as possible treatments for coronavirus. Unfortunately, these pharmaceuticals along with quinine and herbal Cinchona tincture have the potential for side effects so must be administered cautiously as they can cause serious neurological problems.
(Note: tonic water contains quinine at safe levels, and although it is unlikely that knocking back lots of g&t will fully protect you from coronavirus, it might make lockdown a little more tolerable!)
Fortunately there are a number of much safer zinc ionophores that are available for self-medication, chief among these being quercetin. Quercetin is a natural plant colouring (flavonoid) found in onions, broccoli, apples, pears, berry crops, wine, and tea, which has a wide range of anti-inflammatory, antioxidant and anti-tumour effects. [Fernández-Palanca et al, 2019]
Quercertin’s anti-inflammatory properties have been found to reduce allergic responses such as asthma. Consumption of fruits high in quercetin (and particularly apples and pears) is associated with better lung health. [Mlcek et al, 2016] With covid-19 appearing to attack the lungs and being especially problematic for people with underlying lung conditions, the daily consumption of apples or pears (or a quercetin supplement) may be beneficial and at least is unlikely to do any harm.
Quercetin is readily available as a supplement, so if you prefer to keep dietary sugars low, and are therefore avoiding eating excess fruit, you can fortify yourself with up to 1g per day in tablet form, as well as by increasing your intake of the non-fruit high-quercetin foods.
Foods highest in Quercetin
Capers, watercress, radicchio, asparagus, onion, red lettuce
elderberry, cranberry, blueberry, apple, blackberries, figs and tea (black and green varieties)
There is no established dose to maximise the zinc ionophore effect. Quercetin is typically supplemented at 500 to 1000mg per day.
Excess and Contraindications:
There is no established excess dose, and quercetin is considered safe when supplemented for short periods. Taken orally, it has been reported to cause headache and tingling of the arms and legs in some people. Very high doses might cause kidney damage. Quercetin should not be taken if you have kidney problems. (more detail here)
Quercetin can interfere with a range of antibiotics and other drugs. Find more detail here. Quercetin also slightly slows down the function of a gene (COMT) which some people have in a form that functions more slowly anyway. They might find that quercetin doesn’t suit them well, if it leads to feeling somewhat anxious or unable to calm down readily after an episode of excitability or anxiety. They should not take quercetin supplements regularly but the amount in foods is unlikely to bring about these effects.
Glycine is an amino acid which is insufficiently available in the human diet. Supplementing glycine at 10g per day has multiple health benefits which we have written extensively about here.
In relation to the coronavirus the most important benefit of glycine may well be its role in protecting the lungs.
In one rat study, 4 weeks of supplementing with glycine protected lung from inflammation. [Wheeler et al, 2000]
In a human trial, cystic fibrosis patients supplemented with glycine for 8 weeks showed multiple improvements in lung function, while those receiving placebo continued to deteriorate [Vargas et al, 2017]
In a recent mouse study, it was shown that glycine significantly reduced the lung injury caused by bacterial toxins by maintaining the mucin layer, down-regulating inflammatory markers, and enhancing the antioxidant system (NRF2) [Zhang et al, 2020]
Of patients hospitalized with COVID-19, 26% were sick enough to be treated in an intensive care unit (ICU) – of these, approximately 60% developed respiratory failure and 31% developed septic shock. [Global Sepsis Alliance]
Amazingly, glycine has been shown to reduce the damage caused by septic shock and reduce the mortality rate in animal experiments:
Glycine improves function of liver, cures liver injury, and prevents mortality in experimental sepsis … From the scientific literature it is clear that glycine is very potent in protecting septic, endotoxin, and hemorrhagic shockRazak et al, 2017
Foods highest in Glycine
Meat, gelatine, collagen, bone broth
Glycine is cheap and easily available. It is a sweet, white crystalline powder that can be easily added to foods and drinks.
Humans need approximately 10g supplemental glycine per day to meet physiological demands. In the cystic fibrosis study patients were given 0.5 g/kg/day glycine for 8 weeks. This equates to 25g per day for a 50kg adult.
Excess and Contraindications:
Oral glycine is generally considered safe and is used as a food additive in Europe. As a supplement it has been found to be “very well tolerated” with few side effects in daily doses as high as 50g or more. Some reports of digestive discomfort have been reported.
For more details about dosing ways of utilising glycine please see our main article here.
5 Vitamin D
Vitamin D has many effects throughout the body where it plays many anti-inflammatory and immune signalling roles. Vitamin D deficiency is associated with increased risk of infection
Although a small amount of Vitamin D comes from the diet, most is produced in the skin when exposed to the UV rays in sunlight. At the latitudes of the US and Europe, this can only take place in the summer months; consequently, vitamin D levels begin falling in the autumn and reach their lowest levels in late spring, at which point many people are borderline deficient. It has been hypothesised that this contributes to ‘flu being most infectious in winter months. [Epidemic influenza and vitamin D, Cannell et al, 2006]
Whether vitamin D supplements can prevent influenza (or more specifically reduce the risk of COVID-19 infection) remains unclear, but it seems prudent to ensure that one’s vitamin-D status is kept up though the winter, or at very least that deficiency is avoided. The following short paper is interesting and worth a read: Vitamin D for influenza, Schwalfenberg, 2015
Foods highest in vitamin D
Meat, dairy, fish, eggs, mushrooms and fish roe (caviar being by far the best dietary source).
Supplementing with 3000 IUs of vitamin D3 per day should maintain summer levels or having weekly or fortnightly skin exposure under a D-Light (phototherapy)
Excess and Contraindications
Single doses of 50,000 IU Vit-D have been shown to be non-toxic.
If using sunlight or UVB narrowband lamps (with light of 311 nm wavelength) avoid getting burnt. Skin tone/colour has a big influence on how many minutes exposure is safe. Fairer skins need less time.
In the UK vitamin D can be produced on bare skin exposed to mid-day (1pm) sunshine from April 15th. (See this article for details)