Fermented foods and health: an overview of current knowledge

Humans have been fermenting foods for millennia, initially with the purpose of ensuring food safety and preventing spoilage. This practice has resulted in the development of a wide array of fermented foods, many of which are still consumed today. In fact, interest in fermented foods has recently boomed due to their attribution to certain health benefits. To this effect, a review article explores the broader impacts of fermented foods on health, summarizing both current evidence and underscoring gaps in the knowledge.

In this review, the authors state that microbial fermentation is an efficient way to increase the nutritional quality of foods, by producing health promoting compounds and by degrading deleterious ones (such as certain allergens, anti-nutritional factors, and lactose for those who are intolerant). An overview of potential mechanisms underlying the health impacts of fermented foods is provided. To this effect, four main mechanisms are proposed: 

• Introducing microbes that modify the composition of the consumer’s microbiota;
• Delivering microorganisms that have probiotic effects through various pathways, such as the production of short-chain fatty acids or enzymes;
• Exerting anti-inflammatory or antioxidative effects, strengthening the gut barriers, and other neuroregulatory effects;
• Contributing non-viable forms of microbes that may still contribute residual bioactive compounds.

However, there are significant challenges associated with assessing the health benefits of fermented foods, considering their often unique compositions. The ingredients used, the fermentation process, and the bacterial/yeast strains generate a complex and dynamic food ecosystem, the effects of which may further be modulated by the human microbiota during digestion. While in vitro and animal studies provide controlled environments for conducting clinical research, human studies have generally provided less consistent results. For many lesser studied fermented foods, such as kimchi, tempeh, or kombucha, it has been difficult to disentangle the effects of the raw ingredients from those of the fermentation.

The authors note that fermented dairy foods are the most robustly researched, with evidence linking fermented dairy foods to lower risks of type 2 diabetes and colon cancer. There also seem to be slight beneficial effects on risk of stroke. The authors note that these positive effects may be attributable to other factors, such as the dairy matrix. The mild benefits that dairy seems to exert on gastrointestinal transit regulation (constipation or diarrhea) are, however, believed to be a result of the fermentation process. Overall, scientific data have not linked fermented dairy foods to mortality risk, cardiovascular disease, and many types of cancer.

Overall, while there is general agreement regarding the benefits of certain components associated with the fermentation process, the relationship between the intakes of fermented foods and chronic health conditions remains unclear. More robust research with adequate adjustment for confounding factors is needed.