Analysis of zinc sufficiency showing a positive correlation between sufficiency and COVID-19 within European countries.
Unmeasured confounders are likely to be significant, for example the higher sufficiency countries also have significantly higher tourism and international travel on average. This confounder is not mentioned and could more than account for the observation.
Sufficiency levels were relatively high in all countries. Zinc sufficiency estimates were from 2005.
Higher sufficiency countries: Iceland France Ireland Finland UK Switzerland Netherlands Spain Italy Sweden Norway Denmark
Lower sufficiency countries: Portugal Belgium Lithuania Hungary Germany Poland Estonia Czechia Ukraine Bulgaria Slovakia
Singh et al., 17 Sep 2021, peer-reviewed, 4 authors.