Vitamin D3 for reducing mortality from cancer and other outcomes before, during and beyond the COVID‐19 pandemic: A plea for harvesting low‐hanging fruit

Abstract

Abbreviations COVID-19 Coronavirus Disease 2019 25(OH)D 25-hydroxyvitamin D RCT randomized controlled trial UVB ultraviolet B INTRODUCTION Vitamin D3, also known as cholecalciferol, is a fat-soluble secosteroid whose key role in calcium and phosphate homeostasis and bone health has been recognized for long. A recent meta-analysis of randomized controlled trials (RCTs) has estimated a 13% reduction in cancer mortality by vitamin D3 supplementation in daily doses between 400 and 2000 International Units among older adults from the general population [ 7]. Furthermore, several RCTs included in the meta-analyses employed supplementation by single or intermittent non-physiological high doses (“bolus”), such as doses of 100,000 or 200,000 International Units, which seems to be far less effective [ 17], possibly due to the triggering of countervailing factors such as 24-hydroxylase (CYP24A1), that results in the downregulation of the active vitamin D metabolite 1,25-dihydroxyvitamin D. VITAMIN D IN TIMES OF THE COVID-19 PANDEMIC Most recently, a large number of studies have addressed the potential use of vitamin D3 supplementation for preventing COVID-19 infections and/or adverse outcomes in those who were infected [ 18]. PUBLIC HEALTH AND CLINICAL IMPLICATIONS Notwithstanding many remaining open questions regarding the benefits of vitamin D3 supplementation or food fortification, their established benefits for a number of health outcomes, such as bone health and respiratory infections, along with emerging evidence of beneficial effects on reducing cancer mortality, their low cost and proven safety (unless extremely overdosed), call for their more widespread use.