TABLE 3.
Knowledge gap and Research recommendations1
| What we know | What we do not know |
|---|---|
| The preventive and therapeutic effects of a high dosage of vitamin D, C, and zinc on patients with COVID-19 were identified. | What is the optimal dosage of nutrients for treatment? |
| How does the practice of regular supplement therapy with these nutrients among the population affect COVID-19? | |
| Studies about the role of supplement therapy with vitamins D and C, and zinc on COVID-19 patients have already been carried out. | What is the effect of other nutrients such as selenium, omega-3, which are suggested to be effective in some studies? |
| A healthy dietary pattern with adequate nutrients plays a key role to improve the immune system against bacterial and viral infection. | How does dietary pattern affect COVID-19 patients either at a preventive or therapeutic level? |
| No side effect has been reported by high dosage of these nutrients. | Is there any long-term adverse effect of high-dose nutrient therapy in COVID-19 patients? |
| The role of vitamin D deficiency in the severity of COVID-19 has been suggested. | What other nutrient deficiencies affect COVID-19 patients? |
| What is the adequate serum concentration of immunomodulatory nutrients to be protective against COVID-19? | |
| The combinations of several nutrients showed a positive effect on complications of COVID-19. | What is the impact of other potential combinations of nutrients? |
| What is the role of combined therapy with nutrients and other compounds such as melatonin? | |
| Only a few randomized clinical controlled trials with a short intervention period and low sample size reported the effectiveness of these nutrients on COVID-19. | How can a more powerful study design with larger sample size and longer intervention help to better understand these effects? |
1COVID-19, coronavirus disease 2019.