Heat maps for clinical nutrition in patients during pre-, acute, and chronic/post- stages of COVID-19. (A) To the right of the vertical line are studies with original evidence (increasing strength left to right) exposing research gaps, and to the left are studies with nonoriginal evidence, referred to as mentions, exposing knowledge gaps; above the horizontal line are nutrition topics (that can be mapped to specific PICO-T questions for relevance) pertinent for the acute stage of COVID-19, and below are nutrition topics pertinent for the pre- and chronic/post-stages of COVID-19. (B) Setting by population to address research gaps. (C) Setting by population to address knowledge gaps. COVID-19, coronavirus disease 2019. ICU, intensive care unit. PICO-T, Population, Intervention, Comparator, Outcome, and Time.