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The fermented ingredients are usually simple or complex sugars and protein, while the products produced during fermentation are alcohol and carbon dioxide (produced by yeast), acetic acid (Acetobacter bacteria), lactic acid (lactic acid bacteria belonging to the genera Leuconostoc, Lactobacillus and Streprococcus), propionic acid (Propionibacterium freudenreichii) and ammonia and fatty acids (Bacillus, molds).
What’s up?
Various foods are fermented all over the world, including vegetables, fruits and grains, as well as meat, fish and dairy products. Moreover, due to the wide variety of microorganisms, there are countless fermented products derived from the same raw materials (e.g. soybeans can be fermented with different microorganisms, thus giving different end products). Unfortunately, with the increase in industrialization, many fermented products are disappearing, especially in Western countries.
On the other hand, the subject of gastrointestinal microbiota is gaining popularity and more and more people are realizing that the composition of bacteria in our gut affects our health. Therefore, many people pay attention to eating well not only themselves but also their bacteria. We then try to supply the ingredients desired by beneficial bacteria (e.g. prebiotics), but we also supply these bacteria with fermented foods.
Many people are starting to experiment with fermenting various products at home. In addition, in the so-called In health food stores or at markets, in addition to pickled cucumbers and cabbage, you can buy products such as: pickled beets, garlic, peppers, lemon, turnips or kimchi, and a whole range of juices: pickled beetroot, carrot, celery or tomato.
Do fermented products have any nutritional value?
Is silage a temporary fashion or is it really worth including this type of product in your daily menu? Why should we even believe that the fermented product will have any additional nutritional value beyond that of the raw material used for fermentation itself? It turns out that fermented products have a changed composition because: • during fermentation, compounds present in fermented products are decomposed and new compounds are formed, eg lactose is broken down into simple sugars: glucose and galactose, the so-called conjugated linoleic acid (CLA), bioactive proteins, flavonoids are transformed into biologically active metabolites and phytic acid, which hinders the absorption of minerals, is broken down, • substances produced by bacteria, such as lactase, an enzyme that breaks down milk sugar, can pass into the product. This enzyme, produced by yoghurt bacteria, is able to survive the acidic conditions in the stomach and then help digest lactose in the small intestine. • they contain large amounts of beneficial bacteria, most of which are able to survive the conditions prevailing in the digestive tract and reach the intestine, thus supplying the ranks of naturally occurring microorganisms in our intestines.
How could the consumption of fermented foods affect your health?
Eating fermented milk products has been shown to be beneficial maintaining a healthy body weight. In addition, frequent consumption of yoghurt is associated with reducing the risk of cardiovascular disease and type 2 diabetes. Consuming fermented milk products improves glucose metabolism as well as muscle soreness caused by endurance exercise. But beware, we are talking primarily about non-sweetened products! It has also been shown that kimchi can have an anti-diabetic effect, improve the lipid profile and help maintain a healthy body weight by reducing fat accumulation.
It should be mentioned, however, that there is some concern about the health effects of eating fermented foods because of the high salt content in these foods, as there is a known link between high salt intake and hypertension. However, studies have not shown an effect of consuming fermented salted foods on the risk of hypertension.
It is also worth noting that in some fermented foods like e.g. in salted fish, N-nitro compounds are present, which show carcinogenic properties and a higher risk of developing certain types of cancer has been reported in people consuming this type of product. On the other hand, however anti-cancer properties have been demonstrated for many products such as kefir, sauerkraut and kimchi.
Are there any official recommendations?
Some scientists are in favor of introducing recommendations for the consumption of fermented foods. So far, only Indian recommendations can be found in guidelines for the consumption of fermented products, especially by pregnant women. In addition, few countries specify yoghurts and kefirs among dairy products as recommended for consumption (eg the United States, Canada).
On what basis could such recommendations be made?
Why is it that such recommendations are missing? This may be due to the small number of studies that clearly demonstrate the need for such recommendations. In addition, if we wanted to conduct observational studies, we would need to find people with a high consumption of a product whose effect we would like to test, so the studies that can usually be found relate to the consumption of yoghurt or kimchi.
There is no information on the impact of consumption of cabbage or pickled cucumbers, and even less popular products, on health. Moreover, in order to assess the impact of consumption of silage on health, the diet of the respondents who eat and do not eat silage would have to be similar to eliminate the effect of consumption of another product. Thus, to assess the impact of consumption of fermented products, experimental studies are used, i.e. those in which volunteers gathered as part of the study first eat the fermented product, then unfermented, for a specified period of time, and the effects are monitored during the study.
So is it worth introducing fermented foods into your diet?
Although there aren’t many official recommendations, many studies show that yoghurts and fermented vegetables should be an indispensable part of our diet. In addition, thanks to this, we can diversify this diet. Therefore, if you have not tried kimchi, tempeh, miso or other pickled vegetables except cucumbers or cabbage – we encourage you to try them. Or maybe you will cook something yourself?
Anna Malinowska, the author of this article, is a PhD at the University Przyrodniczy in Poznań and conducts a research project Microflora-Diet-Metabolism in which he studies the effects of diet on the intestinal microbiota and, inter alia, on the potential of the gut microbiota to metabolizing dietary fiber or cholesterol.
References 1. Marco ML, Heeney D, Binda S, Cifelli CJ, Cotter PD, Foligné B, Gänzle M, Kort R, Pasin G, Pihlanto A, Smid EJ, Hutkins R. Health benefits of fermented foods: microbiota and beyond. Curr Opin Biotechnol. 2017;44:94-102 2. Patra JK, Das G, Paramithiotis S, Shin HS. Kimchi and Other Widely Consumed Traditional Fermented Foods of Korea: A Review. Front Microbiol. 2016;7:1493 3. Song HJ, Park SJ, Jang DJ, Kwon DY, Lee HJ. High consumption of salt-fermented vegetables and hypertension risk in adults: a 12-year follow-up study. Asia Pac J Clin Nutr. 2017;26(4):698-707 4. Tamang JP, Shin DH, Jung SJ, Chae SW.Functional Properties of Microorganisms in Fermented Foods. Front Microbiol. 2016;7:578
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