The idea of allowing bacteria to proliferate among our foods may seem incongruous. And yet, fermentation is an ancestral method of preservation. This process allows the proliferation of "good" bacteria beneficial to our body.
Yoghurt, sourdough bread, sauerkraut or even pickles:all these homemade fermented dishes have aroused renewed interest in recent months. Fermentation is a process that has been used for a long time (especially before the appearance of refrigerators and freezers), because it serves above all to extend the life of products. Under the action of a ferment naturally present or added by man (rennet, sourdough, kefir, etc.), the food acidifies, which prevents rotting or the development of "bad" bacteria or fungi. This transformation changes its taste, but also its nutritional profile.
Fermentation has the effect of changing the composition of the food (see box 1 ). In particular, it will degrade what are called antinutritional factors. These substances prevent the release of certain nutrients, such as calcium, zinc or iron. Thanks to the action of the ferment, they become available and assimilated by the body. Another benefit:the concentration of vitamins increases. This is particularly the case of vitamin B12 (or cobalamin), essential for the production of red blood cells and the proper functioning of the nervous system. Fermentation also affects the speed at which food is digested and, therefore, how the body absorbs different nutrients. It is therefore better to favor sourdough bread than that made with yeast, because the compound difficult to digest (the physical acid) is degraded there. Likewise, people who are lactose intolerant can eat yoghurts and cheeses, which are better tolerated than milk.
Fermented foods are rich in microorganisms. But can these come to enrich our microbiota, that is to say all the bacteria, yeasts, viruses and fungi that populate our intestine and participate in our immune system? To answer this question, researchers at Stanford University (United States) studied the impact of a diet rich in fermented foods on 18 people for 10 weeks. Their findings, published in the journal Cell in July 2021, show an increase in microbial diversity in the microbiota and a reduction in levels of inflammation. This positive finding does not, however, confirm that such a diet has a protective effect, or that it has the ability to prevent pathologies such as diabetes. The researchers are therefore continuing their investigations on the subject.
The different types of fermentation
Lactic fermentation, or lacto-fermentation, transforms sugars into lactic acids. Beware, although the word "lactic" may suggest lactose, it has nothing to do with milk. This technique is used to preserve dairy products (yogurts and cheeses), cold cuts (sausages), mushrooms or vegetables (cabbage, beets, carrots, etc.). Alcoholic fermentation transforms sugars into ethanol. This is how bread, beer and wine are made. Acetic fermentation transforms ethanol into ethanoic acid, which notably makes it possible to obtain vinegar.
Beware of false claims
"Strengthens immunity", "Helps the body to defend itself", "Activates health", "Balances the intestinal flora"... None of these health claims concerning fermented foods are accepted to date. The European Food Safety Authority only recognizes the benefits of two types of ferments contained in yogurts, which relieve lactose intolerance.
