Potential COVID-19 adjuvant: Vitamin C, D supplementation could support COVID-19 treatment – Review

By Nurul Ain Razali

- Last updated on GMT

Vitamin C and D supplements, besides a healthy diet, could be promoted as a co-adjuvant therapy for COVID-19, according to new research. ©Getty Images
Vitamin C and D supplements, besides a healthy diet, could be promoted as a co-adjuvant therapy for COVID-19, according to new research. ©Getty Images

Related tags COVID-19 Supplements Probiotics Vitamin c

The consumption of vitamin C and D supplements, in addition to a healthy diet, could be promoted as a co-adjuvant therapy for COVID-19, according to a team of international researchers.

In a review titled “The Role of Diet and Supplements in the Prevention and Progression of COVID-19: Current Knowledge and Open Issues”​ published in the journal Preventive Nutrition and Food Science, researchers said the most robust results from human studies involve vitamin C, which could decrease inflammatory markers and suppress cytokine storm.

Meanwhile, for vitamin D, there is evidence that it could significantly reduce the need for intensive care if hospitalised for COVID-19.

“Natural compounds have been shown to exert antiviral, antifibrotic, antioxidant, anti-inflammatory and immunomodulatory actions, which might synergise as prophylactic or supportive agents to reduce some typical COVID-19 symptoms.

“Furthermore, a healthy nutritional status has been reported to support immune function and prevent the onset of severe infection. This suggests the potential role of a healthy diet together with dietary supplements as co-adjuvants in treating COVID-19 and possibly even in the prevention of severe forms of the disease,” ​said the researchers.

Therefore, the team aimed to critically review the current evidence on the impact of diet and different dietary components on the prevention and progression of COVID-19. The analysis was categorised according to nutrients, like vitamins, minerals and phytochemicals, and probiotics.

Different nutrients, different impact

Vitamin C supplementation has been known to improve the immune system, reduce the risk, severity and duration of different infectious diseases, and exert antiviral effects on illnesses like the common cold and pneumonia. These effects were demonstrated through studies done by Marik et al​. (2017), Kim et al.​ (2018) and Ran et al.​ (2018). However, the actual clinical relevance and optimal efficacy of its dosage in preventing and treating infections remain unknown.

Alamdari et al.​’s work in 2020 showed that oral or intravenous administration of vitamin C with other substances improved survival rates, whereas Hiedra et al.​’s (2020) study showed the nutrient was linked to decreased inflammatory markers.

Despite various promising clinical studies, further clinical trials are needed to fully delineate the effects of vitamin C on COVID-19 infection and recommend its supplementation.

The possible association between vitamin D deficiency and COVID-19 has also been investigated in several studies.

According to a meta-analysis by Pal et al.​ (2022), vitamin D supplementation might be associated with improved clinical outcomes, especially when administered after the diagnosis of COVID-19. However, Hastie et al.​ (2020) and Darling et al. ​(2021) showed it was unclear whether there is an association between low vitamin D levels and mortality. Martineau et al.​ (2017) suggested that vitamin D supplementation could effectively prevent acute respiratory tract infections.

The other nutrients explored include vitamin E, minerals like zinc, selenium and iron, and substances like phytochemicals and probiotics. Very little is known today about the association between COVID-19 and the gut, but the incidences of diarrhoea, nausea and vomiting that comes with COVID-19 suggest a possible interaction between the two. Hence, probiotics were also touted as a promising, supplementary treatment against viral infections.

In conclusion, the team said that widely-available supplements with no relevant side effects might help with the battle against COVID-19 in light of the limited therapeutic options. However, it is unknown whether similar findings would apply to patients with an earlier stage of the disease and whether basic vitamin D levels would modify the results.

“Limited clinical trial evidence exists, with even less evidence for vitamin E. Foodstuffs, such as green tea and curcumin, can be easily included in the diet as supplements with no significant toxicities. Probiotics stimulating the gut immune system also have interesting properties needing further evaluation.

“The mechanisms underlying the potential benefits of these supplements are mainly linked to their ability to regulate the immune system, modulating the cytokine cascade, which is primarily responsible for the development of acute respiratory distress syndrome and organ failure leading to death in the most severe cases of COVID-19,”​ said the researchers.

Source:​ Preventive Nutrition and Food Science

“The Role of Diet and Supplements in the Prevention and Progression of COVID-19: Current Knowledge and Open Issues”


Authors: ​Roberta Elisa Rossi et al.

Probiotics, healthy ageing and protein are major focus areas of our upcoming Growth Asia Summit in Singapore from 11 to 13 October. Check out big-name brands, international experts and pioneering start-ups slated to present here.

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