evidence: In May 2020, Glenn Grothman, a Republican congressman from Wisconsin, said that research illustrated a correlation between vitamin D deficiencies and higher COVID-19 mortality rates. We rated that True, as early studies supported the claim. [...] - Instagram post, November 3, 2021 - Lorenz Borsche, independent researcher, co-author of "COVID-19 Mortality Risk Correlates Inversely with Vitamin D3 Status, and a Mortality Rate Close to Zero Could Theoretically Be Achieved at 50 ng/mL 25(OH)D3: Results of a Systematic Review and Meta-Analysis," October 14, email exchange with PolitiFact on Nov. 9-10, 2021 - Margherita T. Cantorna, Ph.D., Professor of Molecular Immunology, Pennsylvania State University, email exchange with PolitiFact on Nov. 9-10, 2021 - Metabolism Clinical and Experimental, "The link between COVID-19 and VItamin D (VIVID): A systematic review and meta-analysis," March 16, 2021 - Michael F. Holick, MD, PhD, Director of Vitamin D, Skin and Bone Research Laboratory at Boston University, Professor of Medicine, Physiology and Biophysics at Boston University School of Medicine, email exchange with PolitiFact on Nov. 9, 2021 - National Institutes of Health, COVID-19 Treatment Guidelines: Vitamin D, April 21, 2021 - Nutritional Journal, "Low vitamin D levels do not aggravate COVID-19 risk or death, and vitamin D supplementation does not improve outcomes in hospitalized patients with COVID-19: a meta-analysis and GRADE assessment of cohort studies and RCTs," October 31, 2021 - PolitiFact, "Glenn Grothman on target about tie between vitamin D and COVID-19, but