Cabbage and fermented vegetables: From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19

Abstract

Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT₁ R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT₁ R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.

Keywords: COVID-19; Lactobacillus; angiotensin-converting enzyme 2; cabbage; diet; fermented vegetable; kimchi; sulforaphane.

FIGURE 1

COVID‐19 deaths per million inhabitants (from Johns Hopkins Coronavirus Center)

FIGURE 2

Regional differences of death rates in Italy (from Worldometer)

FIGURE 3

Regional differences of death rates (May 20) (from Office fédéral de la santé publique, Switzerland, Gouvernement français, Lander Bade Wurtenberg)

FIGURE 4

Consumption of head cabbage and COVID‐19 death rate at a country level (from Fonseca et al ¹² )

FIGURE 5

Putative mechanisms of fermented or Brassica vegetables against COVID‐19. (A) Oxidative stress induced by SARS‐CoV‐2 after its binding to ACE2. (B) Preventive effects of cabbage and fermented vegetables through Nrf2

FIGURE 6

Putative role of diet in COVID‐19