The COVID-19 pandemic has served as a wake-up call for people to look deep into their lives and realize just how important it is to have a robust immune system. As researchers and scientists around the world struggle to understand the novel coronavirus more and find an antidote to this fatal virus, the only resort for humans for surviving this pandemic is to develop a strong resistance against infections and such viral attacks. This can only be done by naturally boosting one’s immunity by making the immune system stronger. It is important to realize that no amount of supplements and medical substitutes can promote your overall health. Therefore, it is essential to try natural ways of improving your immunity.
Vitamin C has been of interest to researchers in this fight against the COVID-19. There is a lot of ongoing research to determine just how helpful vitamin C can prove in battling against the novel coronavirus.1,2,3 In fact, researchers in the US are planning to try using a combination of vitamin C, vitamin D, hydroxychloroquine, and zinc for the prevention of COVID-19 in healthy adults.4
Vitamin C has many roles to play in your body. This essential nutrient is a powerful antioxidant. This means that it can neutralize the unstable compounds in the body known as free radicals. Vitamin C also helps prevent or even reverse cellular damage caused by free radicals.5
The body also needs vitamin C for various biochemical processes, many of which are closely linked to your immune health.
While the Daily Value (DV) for vitamin C should be around 90 milligrams per day, for breastfeeding women, it should be increased by 30 mg per day. People who are smokers need to take an additional 35 mg of vitamin C per day.6
A healthy adult can easily meet their daily requirement of vitamin C through a nutritious diet, as long as they consume a wide variety of fruits and vegetables. For example, having one medium orange itself will provide you with 77 percent of the DV of vitamin C. Additionally, one cup (approximately 160 grams) of cooked broccoli can deliver a whopping 112 percent of the DV of vitamin C.7,8
Vitamin C and the Immune System
We have all heard about how vital vitamin C is for our immune system and how we can boost our immune health by taking vitamin C. Vitamin C has a profound impact on our immune health in many ways. The antioxidant activity of vitamin C can reduce inflammation in the body, which helps improve the overall immune function.9
Vitamin C helps keep the skin healthy as it increases the body’s collagen production. At the same time, it helps the skin function as a barrier to keep harmful irritants or compounds from entering the body. Vitamin C present in the skin also promotes faster wound healing. The vitamin also enhances the activity of phagocytes in the body. Phagocytes are a type of immune cell that ‘swallow’ harmful bacteria and other disease causing microorganisms. Additionally, vitamin C also boosts the growth and spread of a different kind of immune cell known as lymphocytes. Lymphocytes increase the level of circulating antibodies in the bloodstream. Circulating antibodies are proteins that attack harmful or foreign ‘invaders’ or substances in the bloodstream.5
Several studies have been carried out to show the effectiveness of vitamin C against viruses that are responsible for the common cold, and results found that though vitamin C does not make it any less likely for a person to catch a cold, but it does help a person tide over a cold faster. Regular intake of vitamin C also makes you experience less severe symptoms when you have a cold.10,11,12
Evidence from various animal studies and case studies on humans indicate that a high dose of vitamin C or IV vitamin C can decrease lung inflammation in cases of severe respiratory illnesses that are caused by H1N1 (such as the swine flu) or other viruses.13,14,15 However, the doses administered in these studies were far above the daily value. There is a lack of research to support the use of such high doses of vitamin C for treating lung inflammation in such cases. Furthermore, it is necessary to be aware that you should not be taking very high doses of vitamin C supplements, even if taken orally, because they can cause severe side effects, such as persistent diarrhea.
Benefits of Vitamin C in Fighting Covid-19
The Shanghai Medical Association, in an article published in the Chinese Journal of Infection Diseases, supported the use of high doses of vitamin C for the treatment of hospitalized people with COVID-19.16
Doses that are significantly higher than the daily recommended intake of vitamin C are typically recommended to be administered through IV for improving lung function. This is expected to keep a patient with COVID-10 off a ventilator or life support.17,18
A 2019 review discovered that both IV and orally administered high doses of vitamin C could help people admitted to the intensive care units for critical illnesses by decreasing the length of ICU stay by eight percent. It also shortens the duration of mechanical ventilation by 18.2 percent.19
A clinical trial has also been registered by a team of Chinese researchers to further examine the effectiveness of high dose IV vitamin C in people hospitalized with COVID-19.20
However, currently, vitamin C in any form is not a standard part of the treatment regimen for COVID-19, as there is still a lack of substantial evidence to show it can help.21 Nevertheless, high dose IV vitamin C is being actively tested to determine if it can help improve lung function in people with COVID-19. No evidence has been found yet to show that high doses of orally administered vitamin C supplements can help fight against COVID-19. In fact, high doses of oral vitamin C can further complicate the condition of a COVID-19 patient by causing side effects like severe diarrhea.
Can Vitamin C Supplements Prevent COVID-19?
While research is still ongoing, but currently, there is no evidence to support the use of vitamin C supplements for preventing COVID-19. However, vitamin C has been shown to reduce the duration and severity of the common cold caused by viruses, but this does not mean that is going to have the same impact on the novel coronavirus that causes COVID-19. Furthermore, vitamin C is a water-soluble vitamin, meaning excess amounts of the vitamin are not stored in the body. They are eliminated through urine. Therefore, taking excess amounts of vitamin C in hopes of preventing COVID-19 will not help. Your body will not absorb the extra vitamin C and simply flush it out through your urine.22
Even though high doses of vitamin C seems to be a promising treatment for COVID-19, these doses would have to be exceptionally high and administered through IV, not taken orally. Furthermore, such high doses of vitamin C were given only in cases where the person’s condition was severe enough to warrant hospitalization.
This is why it is best to consume a diet that consists of a wide variety of fruits and vegetables, thus naturally getting all the vitamin C the body needs. At the same time, you will also be giving the body other nutrients and antioxidants to boost your immune system and ward off infections.
Foods Rich in Vitamin C
Here are some of the best foods to include in your diet if you want to boost your vitamin C levels.
- Chili Peppers: Chili peppers are not only rich in vitamin C, but also in the compound capsaicin, which is what lends them the hot taste and helps reduce pain and inflammation.23 One green chili pepper has 109 mg of vitamin C, which is 121 percent of your DV. On the other hand, one red chili pepper contains 65 mg of vitamin C, or 72 percent of your DV.24,25 Studies have shown that just one tablespoon or around 10 grams of red chili powder may enhance fat burning in the body.26
- Acerola Cherries (also known as West Indian Cherry): One-half cup of red acerola cherries (around 49 grams) contains 822 mg of vitamin C, which is an astounding 913 percent of your DV.27 Studies done on animals have found that acerola cherry extract may have potent cancer-fighting properties, decrease damage caused to the DNA by a poor diet, and also prevent skin damage caused by ultraviolet B light. However, there are no human studies to corroborate these findings.28,29,30
- Kakadu Plums: Many people might not have heard of Kakadu plums. That’s because this is a superfood native to Australia. It is the richest known source of vitamin C, and just one small plum can deliver roughly 530 percent of your DV of vitamin C. Per 100 grams of Kakadu plums contain over 5,300 mg of vitamin C. One plum provides 481 mg of vitamin C. This superfood is also rich in vitamin E, potassium, and the antioxidant lutein, which is known to have health benefits, especially for the eyes.31,32,33
- Oranges: Oranges are high in nutrients and low in calories. The popular fruit is an excellent source of vitamin C. One medium-sized orange can easily provide around 70 mg of vitamin C, around 78 percent of your DV. If eaten regularly, oranges can make up a substantial portion of a person’s dietary vitamin C intake.34
- Strawberries: Strawberries are rich in vitamin C and also contain many other essential minerals and nutrients like flavonoids, manganese, folate, and antioxidants. Studies have shown that strawberries can help prevent diabetes, dementia, vascular disease, and even cancer due to the fruit’s high antioxidant content.35 Around 152 grams of strawberries (one cup of strawberry halves) contains 89 mg of vitamin C, around 99 percent of the DV.36
- Brussels Sprouts: Apart from vitamin C, Brussels sprouts are high in fiber, vitamin K, manganese, vitamin A, and potassium. Just one-half cup of this cooked vegetable provides around 49 mg of vitamin C, roughly 54 percent of your DV.37 Apart from boosting your immunity, vitamin C is also associated with an improvement in bone strength and function. A 2018 review found that people who had a high dietary intake of vitamin C had a 26 percent lesser risk of hip fractures and a 33 percent reduced risk of developing osteoporosis.38
- Lemons: One whole lemon (raw), with its peel, contains 83 mg of vitamin C, which is 92 percent of the DV for the vitamin.39 Vitamin C present in lemon juice also functions as an antioxidant.
- Kiwis: Kiwis, also known as the Chinese gooseberry or kiwifruit, is a nutrient-rich fruit with many health benefits. It also has a high vitamin C content – one medium kiwi provides 71 mg of vitamin C or 79 percent of the daily requirement.40 Studies have found that kiwis help decrease oxidative stress in the body, improve immunity, and also reduce cholesterol. A 2004 study found that eating two to three kiwis every day for 28 days decreased the stickiness of blood platelets by 18 percent, and also lowered triglyceride levels by 15 percent. This helped lower the risk of developing blood clots and having a stroke or heart attack.41 Another study done on men with vitamin C deficiency found that having just two kiwis each day for four weeks increased their white blood cell activity by over 20 percent, thus significantly boosting their immunity. The blood levels of vitamin C in the deficient participants also normalized in just one week, increasing by 304 percent.42
- Guavas: One single guava provides 126 mg of vitamin C, around 140 percent of the DV.43 Guavas can also help in lowering blood pressure and total cholesterol levels.
Potatoes: People don’t usually associate potatoes with vitamin C. However, this high-carb vegetable contains many vitamins and minerals, especially vitamin C and potassium. Potatoes are also rich in fiber, folate, manganese, vitamin B6, niacin, phosphorus, and pantothenic acid. This root vegetable also contains healthy antioxidants that are primarily concentrated in its skin. One medium baked potato provides 20 mg of vitamin C.44
Vitamin C is one of the most important nutrients that your body needs for the upkeep of the immune system. It is believed that high doses of vitamin C administered through IV can help improve lung function in people hospitalized with COVID-19. However, there is no evidence to show that that oral intake of vitamin C supplements helps treat or even prevent COVID-19. This is why it is best to focus on increasing your intake of dietary vitamin C by increasing the variety of fruits and vegetables you eat. Even though there is presently no cure for COVID-19, following preventive measures such as proper hygiene and physical distancing can keep you protected from catching the disease.
- Hemilä, H. and Chalker, E., 2020. Vitamin C as a Possible Therapy for COVID-19. Infection & chemotherapy.
- Liu, F., Zhu, Y., Zhang, J., Li, Y. and Peng, Z., 2020. Intravenous high-dose vitamin C for the treatment of severe COVID-19: study protocol for a multicentre randomised controlled trial. BMJ open, 10(7), p.e039519.
- Carr, A.C., 2020. A new clinical trial to test high-dose vitamin C in patients with COVID-19. Critical Care, 24(1), pp.1-2.
- Clinicaltrials.gov. 2020. A Study Of Hydroxychloroquine, Vitamin C, Vitamin D, And Zinc For The Prevention Of COVID-19 Infection – Full Text View – Clinicaltrials.Gov. [online] Available at: <https://clinicaltrials.gov/ct2/show/NCT04335084> [Accessed 7 October 2020].
- Carr, A.C. and Maggini, S., 2017. Vitamin C and immune function. Nutrients, 9(11), p.1211.
- Ods.od.nih.gov. 2020. Office Of Dietary Supplements – Vitamin C. [online] Available at: <https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/> [Accessed 7 October 2020].
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- Stanislavovich Rogovskii, V., 2017. The linkage between inflammation and immune tolerance: interfering with inflammation in cancer. Current cancer drug targets, 17(4), pp.325-332.
- Hemilä, H. and Chalker, E., 2013. Vitamin C for preventing and treating the common cold. Cochrane database of systematic reviews, (1).
- Hemilä, H. and Chalker, E., 2013. Vitamin C for preventing and treating the common cold. Cochrane database of systematic reviews, (1).
- Sasazuki, S., Sasaki, S., Tsubono, Y., Okubo, S., Hayashi, M. and Tsugane, S., 2006. Effect of vitamin C on common cold: randomized controlled trial. European journal of clinical nutrition, 60(1), pp.9-17.
- Kim, H., Jang, M., Kim, Y., Choi, J., Jeon, J., Kim, J., Hwang, Y.I., Kang, J.S. and Lee, W.J., 2016. Red ginseng and vitamin C increase immune cell activity and decrease lung inflammation induced by influenza A virus/H1N1 infection. Journal of Pharmacy and Pharmacology, 68(3), pp.406-420.
- Cai, Y., Li, Y.F., Tang, L.P., Tsoi, B., Chen, M., Chen, H., Chen, X.M., Tan, R.R., Kurihara, H. and He, R.R., 2015. A new mechanism of vitamin C effects on A/FM/1/47 (H1N1) virus-induced pneumonia in restraint-stressed mice. BioMed research international, 2015.
- Fowler III, A.A., Kim, C., Lepler, L., Malhotra, R., Debesa, O., Natarajan, R., Fisher, B.J., Syed, A., DeWilde, C., Priday, A. and Kasirajan, V., 2017. Intravenous vitamin C as adjunctive therapy for enterovirus/rhinovirus induced acute respiratory distress syndrome. World Journal of Critical Care Medicine, 6(1), p.85.
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Hammond, B.G., Garcia-Filion, P., Kang, P., Rao, M.Y., Willis, B.C. and Dalton, H.J., 2017. Identifying an oxygenation index threshold for increased mortality in acute respiratory failure. Respiratory Care, 62(10), pp.1249-1254.
- Alshahrani, M.S., Sindi, A., Alshamsi, F., Al-Omari, A., El Tahan, M., Alahmadi, B., Zein, A., Khatani, N., Al-Hameed, F., Alamri, S. and Abdelzaher, M., 2018. Extracorporeal membrane oxygenation for severe Middle East respiratory syndrome coronavirus. Annals of intensive care, 8(1), p.3.
- Hemilä, H. and Chalker, E., 2019. Vitamin C can shorten the length of stay in the ICU: a meta-analysis. Nutrients, 11(4), p.708.
- Clinicaltrials.gov. 2020. Vitamin C Infusion For The Treatment Of Severe 2019-Ncov Infected Pneumonia – Full Text View – Clinicaltrials.Gov. [online] Available at: <https://clinicaltrials.gov/ct2/show/NCT04264533> [Accessed 7 October 2020].
- Arabi, Y.M., Fowler, R. and Hayden, F.G., 2020. Critical care management of adults with community-acquired severe respiratory viral infection. Intensive care medicine, 46(2), pp.315-328.
- Shibata, K., Hirose, J. and Fukuwatari, T., 2014. Relationship between urinary concentrations of nine water-soluble vitamins and their vitamin intakes in Japanese adult males. Nutrition and metabolic insights, 7, pp.NMI-S17245.
- Yoshioka, M., St-Pierre, S., Suzuki, M. and Tremblay, A., 1998. Effects of red pepper added to high-fat and high-carbohydrate meals on energy metabolism and substrate utilization in Japanese women. British Journal of Nutrition, 80(6), pp.503-510.
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- Tirosh, A., 2013. Red Hot Chili Peppers Rock Obesity Research. Science Translational Medicine, 5(195), pp.195ec123-195ec123.
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- Nagamine, I., Akiyama, T., Kainuma, M., Kumagai, H., Satoh, H., Yamada, K., Yano, T. and Sakurai, H., 2002. Effect of acerola cherry extract on cell proliferation and activation of Ras signal pathway at the promotion stage of lung tumorigenesis in mice. Journal of nutritional science and vitaminology, 48(1), pp.69-72.
- Hanamura, T., Uchida, E. and Aoki, H., 2008. Skin-lightening effect of a polyphenol extract from Acerola (Malpighia emarginata DC.) fruit on UV-induced pigmentation. Bioscience, biotechnology, and biochemistry, 72(12), pp.3211-3218.
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- Corrective effects of acerola (Malpighia emarginata DC.) juice intake on biochemical and genotoxical parameters in mice fed on a high-fat diet. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 770, pp.144-152.
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