Table 2.

Registered clinical trials of food supplements (Source: ClinicalTrials.gov).

Serial number	Food supplements	Registered clinical trials for COVID-19
1	Zinc (Zn)	1. Evaluation of the Relationship Between Zinc Vitamin D and b12 Levels in the COVID-19 positive Pregnant Women (Pinar Yalcin Bahat Istanbul, Istanbul, Turkey). 2. Zinc with Chloroquine/Hydroxychloroquine in Treatment of COVID-19 (Tanta University hospital Tanta, Egypt). 3. A Study of Hydroxychloroquine, Vitamin C, Vitamin D, and Zinc for the Prevention of COVID-19 Infection (Progena Biome Ventura, California, United States).
2	Vitamin D (VD)	1. COVID-19 and Vitamin D in Nursing- home (Angers University Hospital Angers, France). 2. Vitamin D Supplementation in Patients with COVID-19 (Clinical Hospital of the School of Medicine, University of São Paulo São Paulo Brazil). 3. Vitamin D Testing and Treatment for COVID 19 (Arizona State University Tempe, Arizona, United States).
3	Vitamin C (VC)	1. Administration of Intravenous Vitamin C in the Novel Coronavirus Infection (COVID-19) and Decreased Oxygenation (Hunter Holmes Mcguire veteran Affairs Medical Center Richmond, Virginia, United States). 2. A Study of Hydroxychloroquine, Vitamin C, Vitamin D, and Zinc for the Prevention of COVID-19 Infection (ProgenaBiome Ventura, California, United States). 3. The Study of Quadruple Therapy Zinc, Quercetin, Bromelain and Vitamin C on the Clinical Outcomes of Patients Infected With COVID-19 (Ministry of Health. First health cluster, Riyadh, Riyadh, Saudi Arabia).
4	Curcumin	1. A phase II, Controlled Clinical Study Designed to Evaluate the Effect of ArtemiC in Patients Diagnosed With COVID-19 (Hillel Yaffe Medica Center Hedera, Haifa, Israel Nazareth Hospital EMMS Nazareth, North, Israel Rambam Health Care Campus Haifa, Israel).
5	Probiotics	1. Effect of Lactobacillus on the Microbiome of Household Contacts Exposed to COVID-19 (Duke University Durham, North Carolina, United States). 2. Oxygen-Ozone as Adjuvant Treatment in Early Control of COVID-19 Progression and Modulation of the gut Microbial Flora (Francesco Pugliese Rome, RM Italy). 3. Evaluation of the Probiotic Lactobacillus Coryniformis K8 on COVID-19 Prevention in Healthcare Workers (Raquel Rodrigues Blanque Granada, Spain). 4. Study to Evaluate the Effect of a Probiotic in COVID-19 (Hospital Universitario de Vinalopo Elache, Alicante, Spain, Hospital Universitario de Torrevieja Torreviveja, Alicante, Spain).
6	Quercetin	1. Effect of Quercetin on Prophylaxis and Treatment of COVID-19 (Kanuni Sultan Suleyman Training and Research Hospital Istanbul, Turkey). 2. The Study of Quadruple Therapy Zinc, Quercetin Bromelain and Vitamin C on the Clinical Outcomes of Patients Infected With COVID-19 (Ministry of Health. First Health cluster, Riyadh. Riyadh, Saudi Arabia). 3. Estrogen Patch for COVID-19 Symptoms (Stony Brook University Hospital, Stony Brook, New York. USA).