From the COVID-19 pandemic, we continue to learn about the critical importance of maintaining adequate levels of essential nutrients. When the body is under stress from an illness such as an infection, merely eating an excellent diet may not provide sufficient nutrients to support the immune system. To stave off a fast-moving infection may require higher levels of essential vitamins and minerals. Vitamin C has an essential role in empowering the immune system. Its oxidized form can be recycled by red blood cells (erythrocytes), but a fast-moving illness can overpower this system, causing vitamin C levels to precipitously drop.

A recent study in Spain measured plasma vitamin C levels in 67 critically ill hospitalized adult COVID-19 patients meeting the Berlin criteria for acute respiratory distress syndrome (ARDS).¹ The results fell into three categories: undetectable (<0.1 mg/dL), low (0.1 – 0.4 mg/dL), and “normal” (0.4 – 2 mg/dL). 12 (18%) patients had undetectable plasma vitamin C, 43 (64%) patients had low levels of plasma vitamin C (mean for this group was 0.14 mg/dL with a standard deviation of 0.05), and 12 (18%) patients had vitamin C levels within the normal range (mean for this group was 0.59 mg/dL with a standard deviation of 0.18). In summary, 82% of patients had low or undetectable plasma vitamin C levels, and 18% had values within the reference range, mostly on the low side of the reference range. (Riordon Clinic Bio-Center Laboratory has an established reference range of 0.6 – 2.0 mg/dL for plasma vitamin C). A smaller study of 18 adult COVID-19 patients with ARDS found similar results: 17 (94%) patients had undetectable plasma vitamin C, and 1 (6%) patient had a plasma vitamin C level of 0.24 mg/dL.² The assay used in this study had a lower limit of detection of 0.15 mg/dL, above the mean of the low-level group in the first study.