The role that vitamin C might play in recovery from coronavirus has come to light recently as doctors from the United States and around the world are reportedly prescribing high doses of vitamin C to patients in intensive care.
As COVID-19 is a novel illness, there’s very limited research into the role that vitamin C might play in either prevention or recovery. Understandably, there’s a lot of public interest in potential treatments as the pandemic unfolds for those who become critically unwell with the coronavirus infection.
This guide will take a look at the role of vitamin C in immunity, the current evidence for vitamin C supplementation, and whether or not we should be taking vitamin C supplements regularly to prevent infections.
What is vitamin C good for?
Many of us are familiar with vitamin C from the era of the sailors, when a lack of fresh fruit and vegetables onboard ships resulted in severe vitamin C deficiencies and the development of scurvy.
Vitamin C (also known as ascorbic acid) is a water-soluble vitamin, which means the body can’t store it. If we have too much, our body will get rid of the extra amounts through our urine. Interestingly, most animals have the ability to make vitamin C in their body. However, humans no longer have the necessary enzymes to do this, which scientists believe may be an evolutionary adaptation.
Because we can’t store or make vitamin C, we need to be getting it regularly through our diet.
Vitamin C is an important antioxidant, meaning it protects the body from oxidative stress and prevents damage to our cells and other tissues.
It also helps the body to form collagen, which is the main protein in our connective tissue (i.e. our skin, tendons, ligaments, and bones). This means it plays a vital role in wound healing.
Finally, and most relevant due to the current coronavirus pandemic, vitamin C helps to regulate our immune system. This is because our immune cells, such as white blood cells, contain high levels of vitamin C. When we become unwell with an infection, the vitamin C levels within our immune cells become depleted, which can impact how our body responds to these infections.
- Vitamin C is water soluble, which means the body is unable to store it
- Because our body can’t store or make its own vitamin C, we need to be getting it regularly through our diet
- Vitamin C is an important antioxidant. It also plays a role in regulating wound healing and our immune system.
Does vitamin C prevent the common cold?
Despite the high amount of public interest in vitamin C supplements to prevent or aid recovery from the common cold, the results from research studies have been inconsistent.
Conclusions from a review published in the Cochrane Database of Systematic Reviews found that if you’re already unwell, taking vitamin C supplements won’t have much of an impact on your recovery. Similarly, taking preventative vitamin C supplements has been found to have no impact on the risk of developing a cold, or the frequency of colds in the general population.
However, it was found that vitamin C supplements may shorten the duration of the common cold and reduce the severity of symptoms, but these benefits were only seen if the supplements were taken before the onset of cold and flu symptoms.
The Cochrane review concluded that no firm recommendations can be made about supplementing regularly with vitamin C, but given the safety and low cost of vitamin C, a supplement can’t hurt.
- Having extra vitamin C when you’re already ill doesn’t have much of an impact
- Some evidence suggests that regular supplementation might reduce the length of time and severity of illness
- We don’t have enough evidence to draw firm conclusions on the role of vitamin C supplements in preventing or overcoming a common cold
Vitamin C supplements and coronavirus
Given that coronavirus is a very new illness, experts have limited knowledge of any treatments that may enhance recovery or improve outcomes.
It’s important to note that coronavirus comes from a different family of viruses to the common cold and flu, so we can’t draw direct comparisons between the studies conducted on vitamin C and the common cold or flu.
Studies have begun which are looking at the impacts of high-dose vitamin C supplementation and coronavirus, but it’s still very early days. One study, currently being conducted at Wuhan University in China, has taken a sample of 140 coronavirus patients and given them high doses of vitamin C intravenously (injected through the veins) to see whether this improves their outcomes. However, we won’t have the results from this study until at least September.
The hypothesis put forward by researchers is that vitamin C can prevent damage to the lungs. This damage occurs when our inflammation pathways are activated as a result of a viral infection. This can prevent the destruction of alveolar capillaries, which play a vital role in transporting oxygen to the lungs.
Currently, there’s no evidence that vitamin C supplements can prevent the likelihood of getting coronavirus in the first place. However, this doesn’t mean we can conclude that vitamin C does nothing for prevention, it just means we don’t have any validated research on this yet.
- Coronavirus is a very new illness, so experts have limited knowledge into preventative or curative treatments
- Coronavirus is different from a common cold or flu, so we can’t draw conclusions from previous research done on these
- Studies have begun on the role of high doses of vitamin C in treating coronavirus in critically ill patients, but these results won’t be available for a few months
- We don’t have any research to help us understand the role of vitamin C supplements in preventing coronavirus, so we can’t make conclusions about this yet.
Where can I get vitamin C from?
The best sources of vitamin C are fresh fruits and vegetables, in particular:
- Kiwi fruit
- Brussels sprouts
Vitamin C is easily damaged compared to other vitamins because it’s very sensitive to light, heat, and oxygen. As a result, it can be destroyed through cooking, drying, or storage of foods.
Tips to preventing vitamin C damage in foods:
- Store fruits and vegetables high in vitamin C whole and uncut in the refrigerator until you need them
- Only prepare these foods right before serving and cut them into larger pieces to lower their contact with the air or exposure to light
- Vitamin C dissolves in cooking water, so try cooking vitamin C rich vegetables in as little water as possible, or steam/stir fry the vegetables instead. Alternatively, you can preserve the cooking water to use in soups, stocks, or gravy.
- Freezing foods for longer than two months can destroy vitamin C, so try to eat foods within this timeframe
- The best sources of vitamin C are fresh fruits and vegetables
- Vitamin C is easily destroyed by light, heat, and oxygen
- There are ways of food preparation and storage which can prevent the loss of vitamin C from our food sources.
How much vitamin C do I need?
In the UK, it’s recommended that adults need 40mg of vitamin C a day to maintain general health. For context, one orange contains 51mg of vitamin C, and five large strawberries contain 53mg. It’s always best to eat the whole piece of fruit, rather than having fruit juice.
Do I need a vitamin C tablet or supplement?
Research conducted into the benefits of vitamin C supplementation has typically used larger doses, between 200-1000mg or more each day.
However, we should be able to obtain all the vitamin C our body needs by eating a range of fresh fruits and vegetables each day. Eating foods that are high in vitamin C, and following the tips above to prevent the vitamin C from getting destroyed in the cooking or preparation process, should be sufficient.
If you think you’re not getting enough vitamin C from your diet alone, supplements are generally considered relatively safe and cheap.
Can I take too much?
Because vitamin C is water soluble, most people can tolerate high doses without any significant side effects. It seems that exceeding 2000mg per day may cause gastrointestinal discomfort, diarrhoea, and abdominal cramps in some people. These impacts are likely due the effects of the unabsorbed vitamin C drawing more water into the gastrointestinal tract.
- We can easily get the recommended amount of vitamin C each day by eating the equivalent of one orange
- Research studies conducted on the benefits of vitamin C supplements have used significantly higher doses than the daily recommended intake
- Vitamin C is a water-soluble vitamin, meaning the body will remove any excess amounts. This makes the risk of overdose or toxicity low.
- We should be able to get adequate amounts of vitamin C from our diet alone, but vitamin C supplements are generally considered relatively safe
Other ways to boost immunity
Whilst there’s uncertainty about the impact of vitamin C in preventing or overcoming coronavirus, there are other well-established measures that have been proven to boost our immune system.
Getting enough high quality sleep is one of our best weapons against illness. When we sleep, our autonomic nervous system, which comprises both a ‘fight’ or ‘break’ mode, is shifted into ‘break’ mode by deep sleep. In ‘break’ mode our heart rate decreases, cortisol (the stress hormone) decreases, and our body goes into immune stimulation mode. During this process, our immune army restocks, and we can fight infection better.
A fascinating study demonstrated that just one night of sleep deprivation in healthy individuals results in a 70% drop in natural killer cells. Natural killer cells are like immune assassins that attack cancer cells, which naturally appear in your body every day, and fight infection.
Eating a balanced diet
Secondly, it’s important that we’re limiting our intake of ultra-processed foods and those high in added sugar. Research suggests that a typical Western diet (i.e. high in processed foods, sugar, and refined carbohydrates) can have a negative impact on our gut microbiome, which then compromises our immune function.
Rather than focusing on one individual nutrient, it’s better to eat a variety of whole foods from each of the food groups. This will ensure you’re getting all the necessary vitamins and minerals to help your body fight infection.
Aim to build your meals around proteins (e.g. meat and pulses), healthy fats (e.g. olive oil and avocado), and non-starchy vegetables (e.g. peppers and courgette) rather than refined carbohydrates (e.g. white pasta). There are also certain foods, like garlic, which have been proven to be effective at boosting our immune system, so adding this into your meals could be beneficial!
- There are other well-researched ways of boosting our immune function, including getting adequate amounts of sleep and eating a balanced diet
- By limiting our intake of ultra-processed foods, and increasing whole, unprocessed foods, we can ensure we’re getting a wide range of vitamins to boost our immunity.
Take home message
- Vitamin C is an important antioxidant that helps to regulate our immune function and the process of wound healing in the body
- We need to eat foods containing vitamin C every day to ensure we have adequate levels, because the body is unable to make or store vitamin C
- Research on the role of vitamin C in preventing and treating the common cold is inconsistent
- Some evidence suggests that regular supplementation might reduce the length of time and severity of illness, but having extra vitamin C when you’re already ill doesn’t have much of an impact
- The role of vitamin C in preventing or treating Coronavirus is unknown, as this is a novel illness
- We should be able to get adequate amounts of vitamin C from our diet by eating a range of fresh fruits and vegetables
- However, vitamin C supplements are generally considered relatively affordable and safe to take
- When looking to enhance our immune system, it’s important we also optimise other areas of our lifestyle, including getting enough sleep and limiting ultra-processed foods.