Vitamin C is a powerful antioxidant that supports lung function. The public interest about this all-around supplement is on the rise during the ongoing COVID-19 pandemic. So, can vitamin C help with the new coronavirus? Let’s see what the available evidence suggests.
This article is for informational purposes only. The current coronavirus outbreak is an ongoing event, and details may change as new information comes to light. No effective or FDA-approved products are yet available to treat or prevent COVID-19 infection.
In chicken, supplementation of the feed with vitamin C increased resistance to the coronavirus that causes infectious bronchitis [1].
In an old study on chick embryo lung cultures, exposure to vitamin C increased the resistance to avian coronavirus infection [2].
The above studies haven’t tested the effects on the specific COVID-19 virus, which may have distinct features. Also, their results haven’t been confirmed in humans and are thus of low relevance.
The new coronavirus or COVID-19 can compromise the immune system and lung function. This fact has sparked the public interest in drugs and supplements that support the respiratory system and fight-off viral infections.
Vitamin C or ascorbic acid is one of the essential antioxidants that protect our body from oxidative stress and free radicals. Its role in the lungs is particularly important, where it reaches up to 30 times higher level than in the blood [3].
Once ingested, vitamin C instantly reaches the lining of our airways, acting as the first life of defense against harmful oxidation caused by microbes, smoking, and other stressors [4, 5].
Viral infections activate our immune cells and cause oxidative stress, depleting vitamin C levels. Increased intake under such conditions can ensure antioxidant protection, support the immune response, and suppress viral replication [6, 7, 8, 9].
Like COVID-19, the influenza A virus infection or flu can compromise lung function and lead to pneumonia. Vitamin C is essential for the antiviral response in the early stage of flu infection, and a deficiency may worsen lung damage [10, 11].
It’s believed that older people are more susceptible to die from COVID-19 because lowered immunity, especially B- and T- cell numbers.
Because vitamin C can increase B- and T-cells, it may help fight off infections in general [9].
However, there is currently no evidence that vitamin C can treat or prevent COVID-19 infection.
Vitamin C Supplementation for Respiratory Conditions
Respiratory Infections
A study on over 1,500 women associated high vitamin C intake with a reduced incidence of upper respiratory tract infections [12].
In over 19,000 men, high blood vitamin C levels correlated with a reduced incidence of different respiratory conditions, including chronic respiratory disease, pneumonia, and lung cancer [13].
Vitamin C supplementation decreased the duration and severity of respiratory infections in male swimmers but not in women. It wasn’t able to prevent infections in either group [14].
A 2019 meta-analysis including 3,135 children found that vitamin C didn’t prevent upper respiratory tract infections but reduced their duration [15].
A meta-analysis of three small studies found that vitamin C reduced airway narrowing in response to exercise [16].
Common Cold
The common cold is a viral infection of the upper respiratory tract (sinuses, nose, and throat). It’s usually caused by rhinoviruses, but the potential threats include influenza and coronaviruses, too [17].
Vitamin C may function as a weak antihistamine agent to provide relief from flu‐like symptoms such as sneezing, a running or stuffy nose, and swollen sinuses [18].
In a clinical trial of 715 students, megadoses of vitamin C (3g/day prevention, 6g/day treatment) reduced cold and flu symptoms by 85% [19].
A comprehensive meta-analysis gathered the data from 44 trials on vitamin C for the common cold and came to the following conclusions for preventive supplementation [20]:
- It doesn’t lower the risk in adults
- It cuts the risk in half in people exposed to intense exercise
- It reduces the cold duration by 8% in adults and 14-18% in children
- It decreases the severity of colds in all populations
Therapeutic supplementation (once the symptoms begin) didn’t significantly impact the cold duration or severity [20].
Pneumonia
Pneumonia stands for lung inflammation leading to persistent cough and shortness of breath. Although typically caused by bacterial infections, pneumonia is a potential complication of the COVID-19 infection, too [21, 22].
A meta-analysis investigated the effects of vitamin C supplementation on pneumonia prevention (2,335 patients) and treatment (197 patients).
According to their results, preventive supplementation may reduce the incidence of pneumonia by 80%. When it comes to treatment, vitamin C may reduce the duration, severity, and mortality of pneumonia. That said, the authors emphasized the poor quality of most included studies [23].
In a clinical trial of 30 severe pneumonia patients, vitamin C supplementation reduced [24]:
Lung Failure
The worst thing about the new coronavirus is that susceptible patients can develop severe pneumonia that progresses into the severe acute respiratory syndrome (SARS) or lung failure [25].
Infused vitamin C failed to reduce lung inflammation and failure in a clinical trial on 167 people with sepsis (blood poisoning) and acute lung failure (ARDS), but it did reduce the death rate [26].
The same therapy was effective in two young women with ARDS caused by viral and bacterial infections [27, 28].
A meta-analysis of 5 studies found that intravenous vitamin C may reduce the need for mechanical ventilation in the critically ill [29].
Based on the above findings, a recent study published in The Lancet journal listed vitamin C infusion as potential rescue therapy for critical cases of a COVID-19 infection [30].
Keep in mind that intravenous vitamin C application requires strict medical care, and its effects don’t translate to supplementation with high oral doses!
Cytokine Storm
It’s believed that many people die from COVID-19 as a result of a cytokine storm [31].
Patients with COVID-19 who were admitted to the ICU had higher levels of TNF-alpha and other inflammatory cytokines [32].
In a clinical trial on 30 people with pneumonia, supplementation with vitamin C reduced cytokines such as TNF-α & IL-6 [24].
Summary
Vitamin C supplementation may reduce the duration and severity of different respiratory infections, while its role in prevention is less conclusive and requires further research.
The beneficial effects on pneumonia, a common complication of the COVID-19 infection, are particularly encouraging. However, none of the above studies examined the effects of vitamin C supplementation on this particular virus.
Scientists have announced multiple clinical trials investigating vitamin C supplementation in COVID-19 patients. We will have to wait for their results before jumping to conclusions [33, 34].
Vitamin C Dosage and Daily Needs
Recommended Daily Intake
The current recommended daily intake for Vitamin C is 75 mg/day for women and 90 mg/day for men. Amounts up to 125 mg/day are recommended for pregnant or lactating women, and an additional 35 mg per day for smokers [35].
The RDA for a given nutrient is calculated based on avoiding deficiency. Several sources now suggest that RDA should be as much as double the currently advised intakes depending on age, gender, pregnancy, and smoking habits [35].
At the intakes above 60 mg/d, vitamin C begins to appear in the urine. However, the intakes of 250-400 mg/d and higher are required to saturate vitamin C concentrations in the blood and white blood cells [8, 35].
Respiratory Infections
The most common daily doses were 200-300 mg for the prevention of respiratory infections and 1,000-3,000 mg for the treatment [20, 23].
The ‘tolerable upper intake level’ is 2 g/day for adults. People receive much higher doses in clinical settings without suffering from apparent side effects, but you should avoid taking megadoses without medical supervision [36].
Takeaway
Vitamin C is a crucial antioxidant that protects the respiratory system from viral infections, cigarette smoke, and other stressors. Supplementation may reduce the severity and duration of different respiratory conditions, while the effects on prevention are less conclusive.
Vitamin C may aid in the prevention and treatment of pneumonia, a common complication of the COVID-19 (2019-nCoV) infection. However, no studies examined the effects on this particular virus, so it’s too early to draw any conclusions.
There is not enough evidence to suggest vitamin C supplementation for the prevention or treatment of the COVID-19 infection. While researchers work to identify potential treatments, the best protective measures you can take are social distancing, hand washing, and avoiding touching your face.
