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Vitamin C supplementation against COVID-19: Is it necessary?

Maggie Nathania and Diyah Eka Andayani


Jakarta  /  Fri, May 8, 2020  /  05:43 pm
Vitamin C supplementation against COVID-19: Is it necessary?

Vitamin C is found naturally in various fruits, nuts and vegetables. (Shutterstock/Evan Lorne)

Since the COVID-19 pandemic began in December 2019, the disease has continued to spread, highlighting the urgent need for immunization and a cure. While waiting for that day to come, taking preventive action or following precautions is considered the best approach. The severity of the disease ranges from asymptomatic to severe respiratory tract infections leading to death. This variability indicates the existence of factors that influence the severity of the disease, one of which is our immune system. As researchers have pointed out, nutrition plays a pivotal role in maintaining the immune system balance. Deficiencies in micronutrients negatively affect immune homeostasis and increase individual susceptibility to infections. Currently, there is no shortage of advertisements and endorsement for supplements said to boost immunity. This creates a lot of public confusion about the type of supplementation recommended, the ideal dosage and actual indications.

Vitamin C, also known as ascorbic acid, is one of the long-known supernutrients, and it is relatively easy to get. Humans cannot synthesize vitamin C, because we don't have the specific enzyme needed. Hence, we need to get it from an exogenous source, aka food. Vitamin C play a role in maintaining the immune system comprehensively through its antioxidant ability, collagen synthesis or directly strengthening immune cells in the fight against infection.

Although the role of vitamin C in the immune system has been well established, its effectiveness in reducing the risk of respiratory tract infections is still debated. The two most extensive studies that combine the results of existing research (Cochrane) show that vitamin C supplementation significantly reduced the incidence of community-acquired pneumonia and the common cold. Still, these studies cannot be extrapolated to the general population, as the study was carried out in populations with special conditions (soldiers, those with high physical stress and children from low-income families). However, the study indicated that 200 mg or more of vitamin C supplementation daily was effective in improving the duration and severity of the common cold. The reduced duration of respiratory tract infections was also observed in children aged three months to 18 years old.

To date, the recommended dose for disease prevention, also known as “prophylactic”, is controversial. Some reviews pointed out that 100-200 mg of vitamin C proved to be adequate to optimize cell and tissue levels for the reduction of chronic disease risks. This exceeds the recommended daily allowance in Indonesia (Angka Kecukupan Gizi 2019), which is 90 mg/day for adult men and 75 mg/day for women.

One hundred to 200 mg of vitamin C can be easily achieved by eating a variety of food, especially fruits and vegetables. For example, one large red guava contains around 120 mg of vitamin C, one medium-sized orange contains 70-80 mg of vitamin C and one cup (approximately 100 grams) of broccoli contains 90 mg of vitamin C. One study showed that supplementation with kiwifruit of roughly 250 mg/day of vitamin C resulted in an enhanced immune function in participants who had low vitamin C status. People who smoke may need an upper dose of antioxidant vitamins, because they have higher oxidative stress than nonsmokers.

In contrast, the treatment of established infections requires significantly higher dosages of the vitamin to compensate for the increased metabolic and inflammatory demand. In the management of COVID-19, for instance, the Association of Indonesian Clinical Nutrition Specialists (PDGKI) recommends administering 1 gram of vitamin C orally daily (mild case) or a high dose of 4 grams intravenously, followed by 1 gram every 8 hours (critical or severe case).

This sometimes misleads the public, as they follow therapy guidelines, not prophylaxis. Vitamin C supplementation products sold on the market generally have high doses, with an average dose of 1000 mg, along with endorsements along the lines of "the higher, the better". As a water-soluble vitamin, excess vitamin C will be excreted in the urine. Excretion rates will increase with increasing doses of vitamin C, which suggests that high doses of supplementation do not indicate more absorption.

Not only it can be a waste of money from a cost-benefit perspective, the more important issue here is whether there are any side effects of using high doses of vitamin C supplementation without indication. As previously described, we know that most of it predictably will be excreted in the urine. This requires extra work of the kidney in charge of filtering remnants of the body's metabolites and fluid in the formation of urine. Vitamin C intake has been proposed as a risk factor for kidney stone formation, as the vitamin increases urinary oxalate excretion, a component of kidney stones. Thus, it should be noted that there is a risk of kidney stones in vitamin C supplementation, especially with consumption of 1000 mg or more per day. Even though there is still uncertainty about the risk and safety dose, those with a history of calcium-oxalate kidney stones, liver or kidney disorders and gout (high uric acid level) should not consume excessive doses of vitamin C. Another fact is this caution applies only to vitamin C supplements and not to vitamin C naturally found in foods. Administration above the upper level (2000 mg for adults and 400 mg for children 1-3 years old) may also cause gastrointestinal discomforts such as diarrhea, nausea, gastritis, fatigue, heartburn or insomnia.

Therefore, it is recommended to meet the nutrient requirement from natural food sources during this time. If this cannot be done and supplementation is required, it is preferable to consume a combined supplementation of vitamins and other minerals, called multiple micronutrient supplementations (MMN). This is because MMN generally has a lower dose. It is also necessary to fulfill a balanced nutrition both from the needs of calories, carbohydrates, proteins, fats and various vitamins and minerals. Along with that, doing regular moderate-intensity exercise, refraining from smoking, having a healthy mind, sunbathing, practicing hygiene and sleeping adequately also contribute to our immune balance. People with specific health conditions are advised to consult with medical personnel before taking any supplementation. (wng)


Maggie Nathania is a post-graduate student at the Department of Nutrition at the University of Indonesia’s School of Medicine/Cipto Mangunkusumo Hospital. Maggie was a general practitioner in Siloam Hospital Kebon Jeruk, a research assistant at Dharmais Cancer Hospital and a freelance medical writer. Reach out to Maggie on Instagram @nathmaggie.     

Diyah Eka Andayani is a nutrition physician, a lecturer at the Department of Nutrition at the University of Indonesia’s School of Medicine/Cipto Mangunkusumo Hospital.

Disclaimer: The opinions expressed in this article are those of the author and do not reflect the official stance of The Jakarta Post.