Diet and heterogeneity of COVID-19 death rates between and within countries
Large differences exist when assessing death rates between and within countries. Most countries with a very low COVID-19 death rate (Asia, Africa, Central European countries, the Balkans or the Middle East) are well-known to have a diet containing fermented vegetables.
To test the potential role of fermented foods in the COVID-19 mortality in Europe, an ecological study, the European Food Safety Authority (EFSA) Comprehensive European Food Consumption Database, was used to study country consumption of fermented vegetables, pickled/marinated vegetables, fermented milk, yoghurt and fermented sour milk.7 Of all the variables considered, including confounders, only fermented vegetables reached statistical significance with the COVID-19 death rate per country. For each g/day increase in consumption of fermented vegetables of the country, the mortality risk for COVID-19 was found to decrease by 35.4%.
Another diet component potentially relevant in the COVID-19 mortality may be the food supply chain and traditional groceries that may be inferred from death rates in Italian regions (Figure 1B).8 The impact of the long supply chain of food on health is measurable by an increase in metabolic syndrome and insulin resistance 9. Therefore, areas that are more prone to short supply food and traditional groceries may have been able to better tolerate COVID-19 with a lower death toll.
In Switzerland, the French- and Italian-speaking cantons had a far higher death rate than the German-speaking ones (Figure 3) (Office fédéral de la santé publique, Switzerland,https://www.bag.admin.ch/bag/fr/home.html). It may be proposed that the high-death rate cantons were contaminated by French and Italian people. However, the Mulhouse airport serves the region of Basel (Switzerland), the Haut-Rhin department (France) and the region of Freiburg (Germany). There was a COVID-19 outbreak in the Haut-Rhin department, in particular in Mulhouse and Colmar. The death rate for COVID-19 (May 20, 2020) was 935 per million inhabitants in France but only 10 to 25 in Switzerland and 7 in Germany (Figure 2).