Vitamin C is an essential nutrient known for its role in immune function and as an antioxidant. During the COVID-19 pandemic, public interest grew regarding its potential to prevent or treat the virus. This article explores the scientific evidence behind Vitamin C’s use in the context of COVID-19.
Research on Vitamin C for COVID-19
Studies investigating Vitamin C’s impact on COVID-19 outcomes have yielded mixed results. Some research indicates that patients with severe respiratory infections, including COVID-19, often have depleted Vitamin C levels, leading to a hypothesis that supplementation might be beneficial for critically ill individuals.
Clinical trials have explored high-dose intravenous Vitamin C for severe COVID-19. While some pilot studies suggested benefits, larger meta-analyses and robust randomized controlled trials have generally not found a significant reduction in in-hospital mortality or length of ICU stay with Vitamin C supplementation.
Recommended Vitamin C Intake
The general recommended daily allowance (RDA) for Vitamin C for most adult men is 90 milligrams per day, and for adult women, it is 75 milligrams per day. Pregnant individuals need about 85 mg/day, and breastfeeding individuals require around 120 mg/day.
In the context of COVID-19, dosages much higher than the RDA have been explored in clinical trials, some reaching several grams per day, particularly for intravenous administration. For instance, some studies have used doses of 6 to 24 grams daily intravenously for critically ill patients. Oral doses of 8 grams per day have also been investigated for recovery from symptomatic infection. Major health organizations do not currently recommend specific high dosages of Vitamin C for COVID-19 treatment or prevention beyond general healthy eating.
Obtaining Vitamin C from food sources is generally preferred, as fruits and vegetables provide additional beneficial nutrients. Foods such as citrus fruits, red and green peppers, kiwi, broccoli, and strawberries are rich in Vitamin C. While synthetic Vitamin C in supplements is chemically identical to that found in food, whole foods offer a broader spectrum of compounds. The body’s absorption of Vitamin C decreases at higher doses, with less than 50% absorbed when intake exceeds 1 gram per day.
Potential Side Effects and Safety
Vitamin C is water-soluble, with excess amounts typically excreted in the urine, making it generally safe even at higher intakes. However, taking large amounts, particularly above the Tolerable Upper Intake Level (UL) of 2,000 milligrams (2 grams) per day for adults, can lead to side effects.
Common mild side effects include gastrointestinal distress such as stomach pain, diarrhea, and nausea. These digestive issues are more likely with doses exceeding 2 grams per day. A more serious, though rare, concern is the increased risk of kidney stones. This risk is higher in susceptible individuals and has been observed with supplemental Vitamin C intake, especially at doses of 1,000 mg/day or more.
Official Health Recommendations
Major health organizations maintain consistent guidance regarding Vitamin C and COVID-19. They do not endorse Vitamin C supplementation as a specific treatment or preventative measure for COVID-19. Their recommendations emphasize a balanced diet that provides adequate Vitamin C for overall immune health.
While Vitamin C plays a role in general immune function, there is currently insufficient robust evidence to support high-dose supplementation as a targeted intervention for COVID-19. Individuals should always consult with a healthcare professional before starting any new supplement regimen, especially if they have existing medical conditions or are taking other medications.