Is there a role for vitamin C in Covid?


While vitamin C won’t prevent you from getting infected with Covid-19, the potential benefits it offers to help you fight infection make it worth prioritizing, argues associate professor Anitra Carr

Commentary: Vitamin C has known immune support functions, and as a result, worldwide sales of vitamin C supplements and vitamin C rich foods, such as citrus and kiwifruit, have skyrocketed since the new coronavirus pandemic. A similar phenomenon occurred during the 1918 flu pandemic, when demand for citrus exceeded supply.

Anecdotally, a patient with Covid-19 recently shared: “I was exposed to Covid-19 in late December and became seriously ill. Everyone has a different experience with the virus, but what struck me was my constant craving for orange juice, I drank liters of it, which I normally don’t drink. The illness passed and I stopped longing for it.”

Humans cannot make vitamin C because of genetic mutations that have eliminated our ability to make the vitamin in our livers, as most other animals do. As a result, we need to get the vitamin through our diet, primarily from fresh fruits and vegetables, to survive.

Because vitamin C is water-soluble, it is not stored by the body, so if we don’t get enough vitamin C through our diet, it results in a potentially fatal deficiency.

Vitamin C has many important functions. Besides being one of the most powerful antioxidants in the body, it also has anti-inflammatory properties and supports several functions of the white blood cells. Note that people with chronic vitamin C deficiency are very prone to developing serious respiratory infections such as pneumonia.

Studies conducted by researchers at the University of Otago in patients with pneumonia and sepsis have shown severely reduced levels of vitamin C in their blood, with the lowest levels seen in people with sepsis. Sepsis is a potentially life-threatening condition consisting of the body’s uncontrolled inflammatory response to a serious infection.

Both pneumonia and sepsis are common complications of severe Covid-19 and often require the patient to be admitted to the ICU for respiratory support. International studies have shown that these people have the lowest vitamin C levels of all.

Although selected vitamin deficiencies are associated with many infectious diseases, the efficacy of supplementation is less proven. The gold standard test for the effectiveness of an intervention is the randomized controlled trial (or RCT).

However, this type of research is intended to test new pharmaceutical drugs, for example, and does not work as well in the case of vitamins, where everyone in the control group (non-treated) is already getting variable amounts of the vitamin through their daily diet.

In many cases, they may already be consuming enough, so extra vitamin is unlikely to have a significant effect. In other words, you can’t make a wet sponge wetter.

However, in severe infections such as pneumonia, sepsis and Covid-19, it is known that people’s vitamin C levels will already be very low, so supplementation is expected to have more effect.

In support of this, a handful of studies in adults and children with pneumonia have shown shorter hospital stays and reduced symptom severity in the most severely ill patients receiving vitamin C.

As the severity of the disease increases, so does the demand for vitamin C. This is why intravenous vitamin C is usually used in critically ill ICU patients, as oral doses are unable to get enough vitamin C into the body when you are very sick.

After some initially encouraging studies in the United States, interest in the use of intravenous vitamin C in critically ill patients with sepsis has increased in recent years.

The largest study to date was conducted in septic patients with acute lung injury and was published in 2019 in the prestigious US journal JAMA. This study showed a 36 percent reduction in mortality and shorter hospital stays in intensive care and hospital settings in patients receiving intravenous vitamin C.

In 2020, the World Health Organization highlighted vitamin C as a potential adjunctive therapy with biological plausibility for patients with critical Covid-19, based on the previous vitamin C intervention studies in patients with sepsis.

To date, there have been a handful of small RCTs examining both oral and intravenous vitamin C for coronavirus infection and Covid-19. The first study to be published was from Wuhan, China, and showed an improvement in lung oxygenation and a decrease in mortality in the most critically ill patients receiving vitamin C infusions.

Analysis of another study conducted in the United States showed a 70 percent faster recovery in patients with coronavirus infection who received oral vitamin C.

The recently published studies on vitamin C and Covid-19 are small and of lower quality, therefore larger multi-centre studies are currently underway, and will hopefully provide more definitive results.

What can you do in the meantime?

Vitamin C supplementation won’t prevent you from getting a coronavirus infection, just as it won’t necessarily prevent you from getting a cold (which can also be caused by coronaviruses).

However, numerous clinical studies have shown that regular vitamin C supplementation can reduce the severity and duration of the common cold and also reduce the risk of developing pneumonia.

If you do get a respiratory infection, whether coronavirus or not, increasing your vitamin C intake, along with other immune-supporting micronutrients, can support your immune system enough so that the infection doesn’t progress to the more serious complications of pneumonia, sepsis or Covid-19 that hospitalization is required.

*The author declares no conflicts of interest

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