Can Vitamin C Protect You during this Coronavirus Pandemic?

Vitamin C has been a subject of controversy for many years. It may appear to be as simple as ABC, but is not. What's so confusing about Vitamin C? Let's dive into some facts and evidence.

Vitamin C - The Basics

Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. Humans, unlike most animals, are unable to synthesise vitamin C endogenously, so it is an essential dietary component.

The recommended daily intake for vitamin C is 75 mg for women and 90 mg for men.

While it’s commonly advised to get your vitamin C intake from foods, many people turn to supplements to meet their needs.

Can Vitamin C Protect You against COVID-19?

As of July, 2020, there were 27 studies ( in progress on the use of vitamin C in COVID-19 and some are in combination with Vitamin D and/or Zinc and/or Hydroxychloroquine.

However, Vitamin C is not a face mask or a sanitiser; and cannot be compared with more effective methods recommended by health authorities like social distancing, proper hand hygiene practices, face masks and personal protective equipments (PPEs). Vitamin C does not prevent a virus from entering the body as compared to physical measures mentioned above. It may sound like an obvious common sense answer but I do read comments from people thinking that there is no need to practice those measures mentioned above just because they are on Vitamin C supplement!

There is also a common confusion with the terms 'primary prevention' and 'secondary prevention' on the internet. Primary prevention includes those measures that prevent the onset of illness or to prevent the virus from entering into your body in the first place. Secondary prevention includes those measures that lead to early diagnosis and prompt treatment of a disease. This is what normally doctors would refer to when it comes to hospital treatment. The secondary prevention here is to prevent the patient from becoming more serious or to prevent death.

An article published in the Chinese Journal of Infection Diseases, the Shanghai Medical Association endorsed the use of high dose vitamin C as a treatment for hospitalized people with COVID-19 (

Doses that are magnitudes higher than the DV (daily value) are recommended to be given through IV to improve lung function, which may help keep a patient off of mechanical ventilation or life support (, PubMed, PubMed).

Additionally, a 2019 review found that both oral and IV high dose vitamin C treatment may aid people admitted to intensive care units (ICUs) for critical illnesses by reducing ICU stay length by 8% and shortening the duration of mechanical ventilation by 18.2% (PubMed).

Though high dose IV vitamin C is currently being tested to see if it can improve lung function in people with COVID-19, no evidence suggests that high doses of oral vitamin C supplements can help with the disease. In fact, they can cause complications like diarrhea (

That said, the New York Post, March 24, 2020 reported:

"Seriously sick coronavirus patients in New York state's largest hospital system are being given massive doses of vitamin C … Dr. Andrew G. Weber, a pulmonologist and critical-care specialist affiliated with two Northwell Health facilities on Long Island, said his intensive-care patients with the coronavirus immediately receive 1,500 milligrams of intravenous vitamin C.

Identical amounts of the powerful antioxidant are then re-administered three or four times a day, he said … The regimen is based on experimental treatments administered to people with the coronavirus in Shanghai, China …

'The patients who received vitamin C did significantly better than those who did not get vitamin C,' he said. 'It helps a tremendous amount, but it is not highlighted because it's not a sexy drug' …

Weber … said vitamin C levels in coronavirus patients drop dramatically when they suffer sepsis, an inflammatory response that occurs when their bodies overreact to the infection. 'It makes all the sense in the world to try and maintain this level of vitamin C,' he said."

Can oral Vitamin C supplement prevent COVID-19?

Currently, no definitive evidence supports the use of oral vitamin C supplements to prevent COVID-19.

Vitamin C may help shorten the duration and severity of colds caused by other viruses, but this is no guarantee that it will have the same effect on the coronavirus that causes COVID-19.

Additionally, vitamin C is a water-soluble vitamin. It dissolves in water, meaning that excess amounts aren’t stored in your body but instead eliminated through your urine. Taking more vitamin C does not mean that your body is absorbing more (nih).

High dose vitamin C supplements may even cause diarrhea, as they can signal your body to pull water out of the cells and into your digestive tract (NIH).

Moreover, although high dose vitamin C appears promising for COVID-19 treatment, these doses were exceptionally high and given via IV — not taken orally. Additionally, it was only given in cases severe enough to require hospitalization.

Your best bet is to eat a diet that’s full of a variety of fruits and vegetables, which naturally provide all the vitamin C a healthy person needs — along with many other nutrients and antioxidants.

Vitamin C Clinical Trials 2019 / 2020 (Updated)

As of July 2020, there were 27 studies in progress on the use of vitamin C in COVID-19 and some are in combination with Vitamin D and/or Zinc and/or Hydroxychloroquine.

A commentary article published in The Lancet Respiratory Medicine (March 20, 2020) has recommended rescue therapy with high-dose vitamin C to be considered.

The CITRIS-ALI randomised trial published in Oct 2019 in JAMA showed a 30% absolute mortality reduction. However,  there was no statistical difference in primary outcomes (based on the clinical trial design) among patients with sepsis treated with vitamin C versus placebo. The difference was in a secondary outcome - overall mortality.

Dr Perry Wilson reviewed the above study and provided a commentary on Medscape:

But basically, this is a pretty low-risk intervention. It's easy for me to sit here and say, "Unless the patient has scurvy, wait for more data." But if a loved one was in the ICU with sepsis, would you ask for vitamin C? After reviewing the literature to prepare for this commentary, I'd be hard-pressed to dismiss it out of hand.

Another major trial to watch is VICTAS. VICTAS is a clinical trial to test the combination of Vitamin C, thiamine and hydrocortisone for the treatment of sepsis. It will be conducted across 30 to 40 major academic medical centers in the United States and will enroll at least 500 patients. All patients in the clinical trial will receive the regular best intensive care available for sepsis, and half of the patients will additionally receive vitamin C, thiamine and hydrocortisone. By testing a large number of patients, the doctors can then see if the group of patients that got the combination of medications did better than the group that did not.

Sources of Vitamin C - Food

Fruits and vegetables are the best sources of vitamin C. Citrus fruits, tomatoes and tomato juice, and potatoes are major contributors of vitamin C to the American diet. Other good food sources include red and green peppers, kiwifruit, broccoli, strawberries, Brussels sprouts, and cantaloupe. Although vitamin C is not naturally present in grains, it is added to some fortified breakfast cereals. The vitamin C content of food may be reduced by prolonged storage and by cooking because ascorbic acid is water soluble and is destroyed by heat. Steaming or microwaving may lessen cooking losses. Fortunately, many of the best food sources of vitamin C, such as fruits and vegetables, are usually consumed raw. Consuming five varied servings of fruits and vegetables a day can provide more than 200 mg of vitamin C.

Sources of Vitamin C - Dietary supplements and Different Forms of Vitamin C

Supplements typically contain vitamin C in the form of ascorbic acid, which has equivalent bioavailability to that of naturally occurring ascorbic acid in foods, such as orange juice and broccoli. Other forms of vitamin C supplements include sodium ascorbate; calcium ascorbate; other mineral ascorbates; ascorbic acid with bioflavonoids; and combination products, such as Ester-C®, which contains calcium ascorbate, dehydroascorbate, calcium threonate, xylonate and lyxonate.

A few studies in humans have examined whether bioavailability differs among the various forms of vitamin C. In one study, Ester-C® and ascorbic acid produced the same vitamin C plasma concentrations, but Ester-C® produced significantly higher vitamin C concentrations in leukocytes 24 hours after ingestion. Another study found no differences in plasma vitamin C levels or urinary excretion of vitamin C among three different vitamin C sources: ascorbic acid, Ester-C®, and ascorbic acid with bioflavonoids.

Liposomal Vitamin C

Liposomal vitamins don’t use capsules or tablets or powders to deliver nutrients. Instead, the vitamins are encapsulated in pockets of fat cells called liposomes (hence the name). Apparently this is the most effective way of ensuring the vitamins in the supplement actually get absorbed into your body.

You can purchase liposomal Vitamin C as a dietary supplement online and from local health stores.

Vitamin C To Boost Your Immune System

One of the main reasons people take vitamin C supplements is to boost their immunity, as vitamin C is involved in many parts of the immune system. 

First, vitamin C helps encourage the production of white blood cells known as lymphocytes and phagocytes, which help protect the body against infection (PubMed).

Second, vitamin C helps these white blood cells function more effectively while protecting them from damage by potentially harmful molecules, such as free radicals.

Third, vitamin C is an essential part of the skin’s defense system. It’s actively transported to the skin, where it can act as an antioxidant and help strengthen the skin’s barriers (ScienceDirect).

Studies have also shown that taking vitamin C may shorten wound healing time (PubMedPubMed).

What’s more, low vitamin C levels have been linked to poor health outcomes.

Other Benefits

People who have pneumonia tend to have lower vitamin C levels, and vitamin C supplements have been shown to shorten the recovery time (PubMedPubMed).

A large review of 29 studies in 11,306 people demonstrated that regularly supplementing with vitamin C at an average dose of 1–2 grams per day reduced the duration of colds by 8% in adults and 14% in children (PubMed).

Interestingly, the review also demonstrated that regularly taking vitamin C supplements reduced common cold occurrence in individuals under high physical stress, including marathon runners and soldiers, by up to 50% (PubMedPubMed).

Additionally, 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) resulting from viral infections (PubMedPubMed).

Side Effects of too much Vitamin C

Since vitamin C is water-soluble and your body excretes excess amounts of it within a few hours after you consume it, it’s quite difficult to consume too much.

In fact, it is nearly impossible for you to get too much vitamin C from your diet alone. In healthy people, any extra vitamin C consumed above the recommended daily amount simply gets flushed out of the body (PubMed).

To put it in perspective, you would need to consume 29 oranges or 13 bell peppers before your intake reached the tolerable upper limit (USDAUSDA).

However, the risks of vitamin C overdose are higher when people take supplements, and it is possible to consume too much of the vitamin in some circumstances.

For example, those with conditions that increase the risk of iron overload or are prone to kidney stones should be cautious with their vitamin C intake (PubMedPubMed).

For those with beta-thalassemia major and sickle cell anemia who suffer from iron overload due to regular blood transfusions or excessive destruction of red blood cells need specialized medical treatment with iron chelators and should also control their intake of iron (PubMed).

All the adverse effects of vitamin C, including digestive distress and kidney stones, appear to occur when people take it in mega doses greater than 2,000 mg (PubMed).

In summary, individuals with existing renal disease, Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD), kidney stones, or Hemochromatosis should avoid high dose Vitamin C.

Choosing a Vitamin C supplement

If you do choose to take a vitamin C supplement, it’s important to choose one that’s high quality and to take the correct dose.

Related: Best Vitamin C in Malaysia 2020

While supplements are regulated by the Food and Drug Administration (FDA), they aren’t held to the same safety standards as pharmaceuticals. Thus, it’s important to purchase supplements from reputable companies.

Some third-party organizations, such as NSF International, ConsumerLab, and United States Pharmacopeia (USP), test supplements for purity and label accuracy. You may want to choose a vitamin C supplement that has been tested by one of these companies.

Additionally, the Upper Limit (UL) for supplemental vitamin C — the amount most people can consume daily without negative effects — is 2,000 mg (

Most vitamin C supplements provide a daily dose of anywhere from 250–1,000 mg, so it can be easy to exceed the UL if you’re not careful. Be sure to read the packaging and take only the recommended dose to avoid complications.

Vitamin C may also interfere with chemotherapy, radiation treatments, or cholesterol lowering drugs (

That said, when used in clinical settings treating critically ill patients, very high dose vitamin C treatments are safe and not associated with significant side effects (Critical Care).

If you have any concerns about vitamin C supplements, you should consult your healthcare provider before adding it to your routine.



Editor's Note: The subject on Vitamin C supplement has been controversial. Although we have tried to summarise and tried to provide important essential information on this topic, it's also likely that we have missed out some important information as well; or it's still confusing.

Allow us to provide a few practical tips:

Let's begin with the non-controversial part. Yes, we need Vitamin C and we should ideally get it from whole fruits and vegetables.

The controversial part is on Vitamin C 'supplement'. Should we supplement our diet with Vitamin C supplement? My answer is Yes, as most people do not take 5 servings of fruits and vegetables. Further, Vitamin C is easily destroyed by heat during cooking and our human bodies are not capable of producing and storing Vitamin C. That being said, I would not recommend taking high dose of Vitamin C as maintenance. Up to 500 mg/day should be reasonable.

As for high dose Vitamin C supplement, I would suggest that you discuss with your doctor. This is a more complicated subject as the indications for high dose Vitamin C are considered prescription dosage and is meant for 'treatment' and not 'maintenance'.

So should you just focus on Vitamin C alone or should you consider other supplements? Vitamin C alone might not be enough as an optimal strategy. A combination and a synergistic mix of supplements would be better. To read more, check out Vitamin Supplements and Ways to Boost Your Immunity.

What if you have seen multiple doctors and they are giving you mixed recommendations? Our recommendation is to stick to a data driven principle and discuss the evidence out there with doctors who are open to be updated with data-driven science and evidence based medicine.

Let's not lose to this virus. Let's battle this virus together!


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