The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods

Until now, no definition of fermented foods was agreed upon by the scientific community. But see here for the recently published scientific consensus definition of fermented foods created by 13 global experts, in Nature Reviews Gastroenterology & Hepatology. The proposed definition is: “foods made through desired microbial growth and enzymatic conversions of food components”. The authors of the paper also clarified the difference between probiotics and fermented foods -- see this infographic for an explanation.

Fermented-Food Metagenomics Reveals Substrate-Associated Differences in Taxonomy and Health-Associated and Antibiotic Resistance Determinants

A research group in Ireland greatly expanded what we know about the diversity of microbes in fermented foods by undertaking a shotgun metagenomics survey of 58 artisanal plant and dairy fermented foods from around the world. They found the substrate (what was being fermented) was the main determinant of microbial diversity in the foods, no matter what their country of origin. Dairy fermented foods had the lowest microbial diversity -- meaning that a limited collection of microbes tended to thrive in them. The genetic 'equipment' to promote host health was more likely to be present in fermented foods compared to their non-fermented counterparts, and the authors noted that water kefirs, sauerkrauts, and kvasses contained the highest numbers of potentially health-associated gene clusters. See this summary of the study by first author John Leech.

Diversity and composition of microbiota during fermentation of traditional Nuodeng ham

Fermented meats or fish were not included in the above analysis of fermented foods, but they're of cultural importance to many groups around the world that have eaten them for thousands of years. While it's worthwhile to study these types of foods, scientists must be cautious to avoid making food safety judgments about properly prepared traditional foods. This article on fermented ham is a nice example of a fermented meat study that honors the safe traditional way of making this product.

Effects of a Fermented Dairy Drink Containing Lacticaseibacillus paracasei subsp. paracasei CNCM I-1518 (Lactobacillus casei CNCM I-1518) and the Standard Yogurt Cultures on the Incidence, Duration, and Severity of Common Infectious Diseases: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Can daily consumption of probiotics be a means of preventing infections? This is a tricky question, because it depends on which probiotics you're talking about. Here's a systematic review and meta-analysis of one particular well-studied probiotic strain (Lacticaseibacillus paracasei subsp. paracasei CNCM I-1518) delivered in a dairy product. The analysis looks at the evidence for whether the probiotic strain can mitigate common infectious diseases in healthy people. Authors found that those who consumed the product regularly had a reduced risk of infectious diseases and a reduced number of illnesses per person, but there was no difference in how long they were sick for, or in the severity of their illnesses. While no data were collected on COVID-19 specifically, this analysis provides evidence that the probiotic strain helps protect against common infections. See this chart for information on where to find this strain in products available in Canada.

Local immune response to food antigens drives meal-induced abdominal pain

Abdominal pain following meals is commonly reported by individuals with irritable bowel syndrome (IBS). Visceral hypersensitivity is thought to be triggered by the release of mast cells and its mediators, but it is largely unknown what activates these events. This particular mechanistic study used a rodent model of infectious colitis (C. rodentium) to examine if a breakdown in oral tolerance to food antigens may be responsible for increased visceral hypersensitivity. Curiously, the researchers found that a bacterial infection caused by C. rodentium led to an increase in IgE antibodies in the intestine, which subsequently triggered the release of mast cells and increased pain in these mice. The researchers then took dietary antigens (wheat, soy, gluten, and milk) and injected them into the rectosigmoid colon of individuals with IBS and healthy volunteers. All of the individuals with IBS showed mucosal reactions to the antigens, yet were not deemed allergic to these foods prior to the testing. The patients with IBS had more IgE positive mast cells closer to nerve fibres, which correlated with severity of the abdominal pain. In summary, the researchers concluded that gut bacterial infection can cause a breakdown in oral tolerance to foods -- with pain resulting from mast cell activation through a mucosal driven IgE mediated response.

E-cigarettes compromise the gut barrier and trigger inflammation

Most of us have never been more aware of what we breathe in than during this pandemic, trying to avoid a disease that's spread via aerosols. A new study shows histologic and transcriptome analyses in mouse models and other models to show that the chemicals found in e-cigarettes -- not nicotine, but the e-liquid -- disrupt the gut barrier and trigger inflammation in the body, potentially leading to a variety of health concerns. With chronic vaping, say the authors, the intestinal barrier may become permeable, increasing susceptibility to bacterial infections.

The Role of Nutritional Factors and Intestinal Microbiota in Rheumatoid Arthritis Development

This concise review recently published in Nutrients discusses whether nutritional factors and the intestinal microbiota are contributors (along with genetics) to the development of rheumatoid arthritis (RA). The researchers review how dietary patterns and individual food items/beverages protect or confer risk associated with the preclinical and established phases of RA. Inflammation-promoting microbes, such as Prevotella species -- in particular Prevotella copri and Collinsella aerofaciens -- are discussed in the context of how they influence intestinal inflammation and intestinal permeability. Although more research is needed in this area, this review certinaly provides “food for thought” on the role of diet and preventative nutrition in RA.