Heterogeneity of COVID-19 death rates in countries and relation to diet
When comparing death rates, large differences exist between and within countries (Figure 1). Although many factors are involved in COVID-19 mortality,5-11 a recent hypothesis has proposed that differences between countries may partly be explained by diet: the diet of low-death rate countries often includes certain vegetables that are potent anti-oxidants.12 Two studies have examined the association between the COVID-19 mortality rate in EU countries and diet. Fermented vegetables, head cabbage and cucumber have been associated with lower death rates.13,14 Even though these are ecological studies, they support the association between diet and fatality. A healthy diet, rich in antioxidants, has been proposed as a therapeutic strategy to mitigate the cytokine storm that developed in COVID-19.15 In Asia and the Middle East, a diet high in fermented cruciferous vegetables is common, and these countries have a lower COVID-19 mortality rate. Fermentation food processing is known to increase the antioxidant activity of foods.16Certain compounds found in the diet can interact with Nrf2 (nuclear factor erythroid 2 p45-related factor 2), a transcription factor involved in the protection against oxidative stress.17