SARS-CoV-2, the virus that causes COVID-19, has caused global devastation since emerging from Wuhan, China, in December 2019. There have been many treatment and prevention methods investigated for COVID-19 including dietary supplements, which have gained much attention. Below, we examine the effects of vitamin D, vitamin C, zinc, and N-acetylcysteine on treating COVID-19.
Vitamin D is a fat-soluble vitamin that is critical for bone and musculoskeletal health. Vitamin D deficiency is common with some studies showing approximately 40 percent of the United States population being affected especially during the winter months1. Prior to COVID-19, observational data associated low vitamin D levels with acute respiratory tract infections. Vitamin D may enhance the immune response by contributing to the maintenance cell physical barrier integrity and enhanced activity of our innate and adaptive immunity2. Recent epidemiologic or observational studies have suggested associations between low vitamin D concentrations and higher rates of COVID-19 but these were likely related to ethnicity, age, and general health rather than a causal relationship. A joint statement released by the American Society for Bone and Mineral Research (ASBMR), American Association of Clinical Endocrinologists (AACE), Endocrine Society, European Calcified Tissue Society (ECTS), National Osteoporosis Foundation (NOF), and International Osteoporosis Foundation (IOF) stated that current data does not provide any evidence regarding vitamin D supplementation to help prevent or treat COVID-19. The joint statement further states the best sources of vitamin D is through 15 to 30 minutes of direct sunlight daily (while avoiding a sunburn), food, and/or vitamin D supplementation. Furthermore, vitamin D supplementation is safe when taken at acceptable dosages 3. However, individuals should still follow recommendations for daily vitamin D consumption with guidance from their healthcare provider.
Vitamin C (ascorbic acid) has always been an attractive option to treat and prevent viral infections. Vitamin C is thought to attack free radicals, decrease gene expression of pro-inflammatory cytokines, and enhance microbial killing in certain cell types. However, evidence does not support the routine use of vitamin C for viral infections including the “common cold”. Meta-analyses do suggest a shortening in common cold duration by a modest 8 percent with regular vitamin C intake. Even though the common cold is caused by a coronavirus, SARS-CoV-2 has a different genome sequence and therefore cannot be assumed to have the same outcome. Interestingly, physicians from China have stated on various media outlets that more than 50 patients with moderate to severe COVID-19 were successfully treated with large doses of IV vitamin C leading to shorter hospital length of stay and no incidences of death. However, these findings have not been published yet at the time of this writing. Furthermore, it is important to note that high doses of vitamin C have significant side effects including formation of kidney stones, nausea, vomiting, heartburn, and abdominal cramps. There are currently randomised controlled trials of vitamin C currently registered on the National Institutes of Health Clinical Trials website2.
Zinc is a trace mineral that has been hypothesized to inhibit viral replication and attachment to the nasopharyngeal mucous2. Deficiency of zinc can cause an increase in pro-inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) along with decreasing antibody production3. In vitro studies have suggested that zinc modifies effects of several pathogens including SARS-COV, the virus that caused severe acute respiratory distress (SARS). Many clinical trails evaluating zinc supplements have had conflicting results. One systemic review found moderate quality evidence that zinc supplementation reduced the common cold by only 1.65 days. Adverse effects include nausea, vomiting, and changes in taste. Furthermore, the nasal preparation should not be used due to reports of a permanent loss of smell2.
N-acetylcysteine (NAC) is rapidly converted to cysteine, which is a precursor to glutathione. Glutathione is an endogenous antioxidant that is frequently depleted in patients with oxidative stress or systemic inflammation, including those with chronic obstructive pulmonary disease (COPD). Furthermore, NAC leads to antioxidant effects and anti-inflammatory effects such as a decrease in IL-6 and TNF-α concentrations. NAC has mucolytic activity due to the ability to disrupt disulfide cross-bridges of respiratory mucus. Unfortunately, these effects have not been consistent in clinical outcomes in patients with hyperinflammatory diseases. However, patients with COVID-19 can progress into acute respiratory distress syndrome (ARDS) and may have respiratory mucus buildup limiting adequate airflow making NAC possibly beneficial in this specific setting1.
These vitamins and supplements have biological favourability for the prevention and treatment of COVID-19. However, more robust clinical trails evaluating their efficacy are still needed. At the time of this writing, clinical evidence does not support their routine use1.