Vitamin C, also known as L-ascorbic acid, is a nutrient humans must obtain through their diet, as the body cannot produce it. During the COVID-19 pandemic, there was public interest in whether vitamin C could play a role in preventing infection or treating the illness. This interest stemmed from its reputation for supporting overall health and its involvement in various bodily functions.
Vitamin C’s General Immune Support
Vitamin C supports the immune system. It functions as an antioxidant, neutralizing reactive oxygen species (ROS) and free radicals that can damage cells, including immune cells. This helps maintain their proper function.
It also contributes to the function and production of white blood cells, central to the immune response. It enhances the activity of phagocytes, like neutrophils, which engulf and destroy pathogens. It supports the differentiation and proliferation of lymphocytes, including B-cells and T-cells, involved in adaptive immunity by producing antibodies and directly attacking infected cells. Vitamin C also helps maintain the integrity of epithelial barriers, such as the skin, which act as a first line of defense.
Research on Vitamin C and COVID-19
Studies explored vitamin C’s potential role in COVID-19 prevention and treatment. Researchers theorized its antioxidant and immune-supporting functions might benefit against the inflammatory cascade in COVID-19. However, data supporting its use for prevention or treatment of respiratory viral illnesses, including COVID-19, has been limited.
Clinical trials investigated high-dose intravenous vitamin C for severe cases. One trial in Wuhan, China, assessed intravenous vitamin C in patients with severe COVID-19 pneumonia, evaluating outcomes like mechanical ventilation, organ failure, and mortality. Despite some promising observations in smaller studies, larger randomized controlled trials, including those with COVID-19 patients, generally did not show significant improvements in outcomes like organ dysfunction or inflammatory markers.
For non-critically ill patients, studies have also largely found no significant benefit from vitamin C supplementation. While some research suggested low oral doses might be used as prophylaxis or high-dose intravenous vitamin C could reduce respiratory symptoms in moderate to severe cases, overall clinical investigations have been mixed or inconclusive regarding substantial benefits for preventing or treating COVID-19. Further research is ongoing to understand any potential role vitamin C might play, particularly in the early stages of hospitalization for COVID-19.
Official Health Guidance and Recommendations
Health organizations have provided guidance on vitamin C’s role in COVID-19. These organizations do not recommend high-dose vitamin C supplements for COVID-19 prevention or treatment. This stance is based on current scientific evidence, which has not conclusively demonstrated significant benefits for these applications.
Organizations like the National Institutes of Health (NIH) state there is insufficient data to recommend for or against vitamin C for COVID-19 treatment in critically ill or non-critically ill patients. While a balanced diet rich in vitamin C and other nutrients is encouraged for general health and immune support, it is not a substitute for established medical treatments or vaccines for COVID-19. Official recommendations emphasize evidence-based interventions for managing the virus, such as vaccination and prescribed medications.
Safety and Dosage
Vitamin C is generally safe when consumed at appropriate doses, primarily through food sources. The Recommended Dietary Allowance (RDA) for vitamin C varies by age and gender: 90 milligrams per day for adult males, 75 milligrams for adult females, 85 milligrams for pregnant individuals, and 120 milligrams for those breastfeeding.
Taking very large amounts of vitamin C, especially through supplements exceeding 2,000 milligrams daily, can lead to side effects. These may include mild digestive disturbances like diarrhea, nausea, stomach cramping, bloating, and abdominal discomfort. High doses might also increase the risk of kidney stone formation in some individuals, especially those with a history of kidney stones. Megadoses are generally not recommended without medical supervision. Individuals with underlying health conditions or those taking other medications should consult a healthcare professional before considering high-dose vitamin C supplements.