To the Editor, The fermentation process, born as a preservation method in the Neolithic age, enabled humans to eat not-so-fresh food and to survive.1 Fermented foods are “foods or beverages made via controlled microbial growth (including lactic acid bacteria (LAB)) and enzymatic conversions of food components.” 2 Not all fermented foods contain live cultures, as some undergo further processing after fermentation: pasteurization, smoking, baking, or filtration. These processes kill or remove the live microorganisms in foods such as soy sauces, bread, most beers and wines as well as chocolate. Live cultures can be found in fermented vegetables and fermented milk (fermented sour milk, yoghurt, probiotics, …). The westernized diet is lacking many traditional fermented foods.3The gut microbiota has an inter-individual variability due to genetic predisposition and diet 3. Some foods like cabbage can be fermented by the gut microbiota. 4 The westernized diet has been associated with changes in the gut microbiome.5In this Rostrum, we consider loss of food fermentation either as a reduction of fermented food consumption in the diet or as a change in the microbiome leading to a reduction of fermentation of foods in the gut. This paper is based on the hypothesis that diet may partly explain differences in COVID-19 death rates within and between countries.6