Kefir microbial composition is a deciding factor in the physiological impact of kefir in a mouse model of obesity

Kefir as a therapeutic agent in clinical research: a scoping review

Increasing research has been conducted on the role of probiotics in disease treatment. Kefir, a safe, low-cost probiotic fermented milk drink, has been investigated in many in vitro and animal studies, although parameters for human therapeutic dose or treatment time have not yet been determined. Here we perform a scoping review of clinical studies that have used kefir as a therapeutic agent, compiling the results for perspectives to support and direct further research. This review was based on Joanna Briggs Institute guidelines, including studies on the effects of kefir-fermented milk in humans. Using the term KEFIR, the main international databases were searched for studies published in English, Spanish or Portuguese until 9 March 2022. A total of 5835 articles were identified in the four databases, with forty-four eligible for analysis. The research areas were classified as metabolic syndrome and type 2 diabetes, gastrointestinal health/disorders, maternal/child health and paediatrics, dentistry, oncology, women's and geriatric health, and dermatology. The many study limitations hampered generalisation of the results. The small sample sizes, methodological variation and differences in kefir types, dosage and treatment duration prevented clear conclusions about its benefits for specific diseases. We suggest using a standard therapeutic dose of traditionally prepared kefir in millilitres according to body weight, making routine consumption more feasible. The studies showed that kefir is safe for people without serious illnesses.

Fermented foods and gastrointestinal health: underlying mechanisms

Although fermentation probably originally developed as a means of preserving food substrates, many fermented foods (FFs), and components therein, are thought to have a beneficial effect on various aspects of human health, and gastrointestinal health in particular. It is important that any such perceived benefits are underpinned by rigorous scientific research to understand the associated mechanisms of action. Here, we review in vitro, ex vivo and in vivo studies that have provided insights into the ways in which the specific food components, including FF microorganisms and a variety of bioactives, can contribute to health-promoting activities. More specifically, we draw on representative examples of FFs to discuss the mechanisms through which functional components are produced or enriched during fermentation (such as bioactive peptides and exopolysaccharides), potentially toxic or harmful compounds (such as phytic acid, mycotoxins and lactose) are removed from the food substrate, and how the introduction of fermentation-associated live or dead microorganisms, or components thereof, to the gut can convey health benefits. These studies, combined with a deeper understanding of the microbial composition of a wider variety of modern and traditional FFs, can facilitate the future optimization of FFs, and associated microorganisms, to retain and maximize beneficial effects in the gut.

Liver Biopsy Handling of Metabolic-Associated Fatty Liver Disease (MAFLD): the Children's Hospital of Eastern Ontario grossing protocol

Metabolic-(non-alcoholic) associated fatty liver disease (MAFLD/NAFLD) has increasingly become a worldwide epidemic. It has been suggested that renaming NAFLD to MAFLD is critical in identifying patients with advanced fibrosis and poor cardiovascular outcomes. There are concerns that the progression to non-alcoholic steatohepatitis (NASH) may become a constant drive in the future healthcare of children and adolescents. There is a necessity to tackle the emerging risk factors for NASH-associated hepatocellular carcinoma (HCC). In this narrative review, we present the current protocol of liver biopsy separated between pre-analytical, analytical, and post-analytical handling. Genetic association investigations have identified single nucleotide polymorphisms implicated in the progression of MAFLD-HCC, many of which seem to belong to the lipid metabolism pathways. PNPLA3 rs738409 variant, TM6SF2 rs58542926 variant, MBOAT7 rs641738 variant, and GCKR variants seem to be significantly associated with NAFLD disease susceptibility. In disclosing the current comprehensive protocol performed at the Children's Hospital of Eastern Ontario, Ottawa, ON, Canada, we support the most recent Kulkarni-Sarin's pledge to rename NAFLD to MAFLD. Grossing of the liver biopsy is key to identifying histologic, immunophenotypical, and ultrastructure data and properly preserving tissue for molecular genomics data.

Use of reconstituted kefir consortia to determine the impact of microbial composition on kefir metabolite profiles

Kefir is fermented traditionally with kefir grains, but commercial kefir production often relies on fermentation with planktonic cultures. Kefir has been associated with many health benefits, however, the utilization of kefir grains to facilitate large industrial production of kefir is challenging and makes to difficult to ensure consistent product quality and consistency. Notably, the microbial composition of kefir fermentations has been shown to impact kefir associated health benefits. This study aimed to compare volatile compounds, organic acids, and sugar composition of kefir produced through a traditional grain fermentation and through a reconstituted kefir consortium fermentation. Additionally, the impact of two key microbial communities on metabolite production in kefir was assessed using two modified versions of the consortium, with either yeasts or lactobacilli removed. We hypothesized that the complete kefir consortium would closely resemble traditional kefir, while the consortia without yeasts or lactobacilli would differ significantly from both traditional kefir and the complete consortium fermentation. Kefir fermentations were examined after 12 and 18 h using two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOFMS) to identify volatile compounds and high performance liquid chromatography (HPLC) to identify organic acid and sugar composition. The traditional kefir differed significantly from the kefir consortium fermentation with the traditional kefir having 15-20 log2(fold change) higher levels of esters and the consortium fermented kefir having between 1 and 3 log2(fold change) higher organic acids including lactate and acetate. The use of a version of kefir consortium that lacked lactobacilli resulted in between 2 and 20 log2(fold change) lower levels of organic acids, ethanol, and butanoic acid ethyl ester, while the absence of yeast from the consortium resulted in minimal change. In summary, the kefir consortium fermentation is significantly different from traditional grain fermented kefir with respect to the profile of metabolites present, and seems to be driven by lactobacilli, as evidenced by the significant decrease in multiple metabolites when the lactobacilli were removed from the fermentation and minimal differences observed upon the removal of yeast.

Analysis of the milk kefir pan-metagenome reveals four community types, core species, and associated metabolic pathways

A comprehensive metagenomics-based investigation of the microorganisms present within milk kefir communities from across the globe was carried out with a view to defining the milk kefir pan-metagenome, including details relating to core and non-core components. Milk kefir samples, generated by inoculating full fat, pasteurized cow's milk with 64 kefir grains sourced from 25 different countries, were analyzed. We identified core features, including a consistent pattern of domination by representatives from the species Lactobacillus helveticus or the sub-species Lactobacillus kefiranofaciens subsp. kefiranofaciens, Lactococcus lactis subsp. lactis or Lla. cremoris subsp. cremoris in each kefir. Notably, even in kefirs where the lactococci did not dominate, they and 51 associated metabolic pathways were identified across all metagenomes. These insights can contribute to future efforts to create tailored kefir-based microbial communities for different applications and assist regulators and producers to ensure that kefir products have a microbial composition that reflects the artisanal beverage.

Dairy products and constituents: a review of their effects on obesity and related metabolic diseases

Obesity has become a global public health problem that seriously affects the quality of life. As an important part of human diet, dairy products contain a large number of nutrients that are essential for maintaining human health, such as proteins, peptides, lipids, vitamins, and minerals. A growing number of epidemiological investigations provide strong evidence on dairy interventions for weight loss in overweight/obese populations. Therefore, this paper outlines the relationship between the consumption of different dairy products and obesity and related metabolic diseases. In addition, we dive into the mechanisms related to the regulation of glucose and lipid metabolism by functional components in dairy products and the interaction with gut microbes. Lastly, the role of dairy products on obesity of children and adolescents is revisited. We conclude that whole dairy products exert more beneficial effect than single milk constituent on alleviating obesity and that dairy matrix has important implications for metabolic health.

Consumption of kefir made with traditional microorganisms resulted in greater improvements in LDL cholesterol and plasma markers of inflammation in males when compared to a commercial kefir: a randomized pilot study

Kefir has long been associated with health benefits; however, recent evidence suggests that these benefits are dependent on the specific microbial composition of the kefir consumed. This study aimed to compare how consumption of a commercial kefir without traditional kefir organisms and a pitched kefir containing traditional organisms affected plasma lipid levels, glucose homeostasis, and markers of endothelial function and inflammation in males with elevated LDL cholesterol. We utilized a crossover design in n = 21 participants consisting of two treatments of 4 weeks each in random order separated by a 4-week washout. Participants received either commercial kefir or pitched kefir containing traditional kefir organisms for each treatment period. Participants consumed 2 servings of kefir (350 g) per day. Plasma lipid profile, glucose, insulin, markers of endothelial function, and inflammation were measured in the fasting state before and after each treatment period. Differences within each treatment period and comparison of treatment delta values were performed using paired t tests and Wilcoxon signed-rank test, respectively. When compared to baseline, pitched kefir consumption reduced LDL-C, ICAM-1, and VCAM-1, while commercial kefir consumption increased TNF-α. Pitched kefir consumption resulted in greater reductions in IL-8, CRP, VCAM-1, and TNF-α when compared to commercial kefir consumption. These findings provide strong evidence that microbial composition is an important factor in the metabolic health benefits associated with kefir consumption. They also provide support for larger studies examining these to assess whether traditional kefir organisms are necessary to confer health benefits to individuals at risk of developing cardiovascular disease.

Fermented foods: a perspective on their role in delivering biotics

Fermented foods are often erroneously equated with probiotics. Although they might act as delivery vehicles for probiotics, or other 'biotic' substances, including prebiotics, synbiotics, and postbiotics, stringent criteria must be met for a fermented food to be considered a 'biotic'. Those criteria include documented health benefit, sufficient product characterization (for probiotics to the strain level) and testing. Similar to other functional ingredients, the health benefits must go beyond that of the product's nutritional components and food matrix. Therefore, the 'fermented food' and 'probiotic' terms may not be used interchangeably. This concept would apply to the other biotics as well. In this context, the capacity of fermented foods to deliver one, several, or all biotics defined so far will depend on the microbiological and chemical level of characterization, the reproducibility of the technological process used to produce the fermented foods, the evidence for health benefits conferred by the biotics, as well as the type and amount of testing carried out to show the probiotic, prebiotic, synbiotic, and postbiotic capacity of that fermented food.

Consumption of the cell-free or heat-treated fractions of a pitched kefir confers some but not all positive impacts of the corresponding whole kefir

Introduction

Kefir consumption can have many metabolic health benefits, including, in the case of specific kefirs, improvements in plasma and liver lipid profiles. Our group has previously shown that these health benefits are dependent on the microbial composition of the kefir fermentation, and that a pitched kefir (PK1) containing specific traditional microbes can recapitulate the health benefits of a traditional kefir. In this study we investigated how different preparations of kefir impact cholesterol and lipid metabolism and circulating markers of cardiovascular disease risk and determine if freeze-drying impacts health benefits relative to past studies.

Materials and methods

Eight-week-old male and female C57Bl/6 mice were fed a high fat diet (40% kcal from fat) supplemented with one of 3 freeze-dried kefir preparations (whole kefir, cell-free kefir, or heat-treated kefir) for 8 weeks prior to analysis of plasma and liver lipid profiles, circulating cardiovascular disease (CVD) biomarkers, cecal microbiome composition, and cecal short-chain fatty acid levels. These groups of mice were compared to others that were fed a control low-fat diet, control high fat diet or high fat diet supplemented with milk, respectively.

Results

All kefir preparations lowered plasma cholesterol in both male and female mice, while only whole kefir lowered liver cholesterol and triglycerides. Plasma vascular cell adhesion molecule 1 (VCAM-1) was lowered by both whole kefir and heat-treated kefir in male mice but not females, while c-reactive protein (CRP) was unchanged across all high fat diet fed groups in males and females.

Conclusion

These results indicate that some of the metabolic benefits of consumption of this kefir do not require whole kefir while also indicating that there are multiple compounds or components responsible for the different benefits observed.

Biological Role of Nutrients, Food and Dietary Patterns in the Prevention and Clinical Management of Major Depressive Disorder

Major Depressive Disorder (MDD) is a growing disabling condition affecting around 280 million people worldwide. This complex entity is the result of the interplay between biological, psychological, and sociocultural factors, and compelling evidence suggests that MDD can be considered a disease that occurs as a consequence of an evolutionary mismatch and unhealthy lifestyle habits. In this context, diet is one of the core pillars of health, influencing multiple biological processes in the brain and the entire body. It seems that there is a bidirectional relationship between MDD and malnutrition, and depressed individuals often lack certain critical nutrients along with an aberrant dietary pattern. Thus, dietary interventions are one of the most promising tools to explore in the field of MDD, as there are a specific group of nutrients (i.e., omega 3, vitamins, polyphenols, and caffeine), foods (fish, nuts, seeds fruits, vegetables, coffee/tea, and fermented products) or dietary supplements (such as S-adenosylmethionine, acetyl carnitine, creatine, amino acids, etc.), which are being currently studied. Likewise, the entire nutritional context and the dietary pattern seem to be another potential area of study, and some strategies such as the Mediterranean diet have demonstrated some relevant benefits in patients with MDD; although, further efforts are still needed. In the present work, we will explore the state-of-the-art diet in the prevention and clinical support of MDD, focusing on the biological properties of its main nutrients, foods, and dietary patterns and their possible implications for these patients.

Traditional Grain-Based vs. Commercial Milk Kefirs, How Different Are They?

Traditional kefir, which is claimed for health-promoting properties, is made from natural grain-based kefir, while commercial kefirs are made of defined mixtures of microorganisms. Here, approaches are described how to discriminate commercial and traditional kefirs. These two groups of kefirs were characterized by in-depth analysis on the taxonomic and functional level. Cultivation-independent targeted qPCR as well as next-generation sequencing (NGS) proved a completely different microbial composition in traditional and commercial kefirs. While in the traditional kefirs, Lactobacillus kefiranofaciens was the dominant bacterial species, commercial kefirs were dominated by Lactococcus lactis. Volatile organic compounds (VOCs) analysis using headspace-gas chromatography-ion mobility spectrometry also revealed drastic differences between commercial and traditional kefirs; the former built a separate cluster together with yogurt samples. Lactose and galactose concentrations in commercial kefirs were considerably higher than in traditional kefirs, which is important regarding their health properties for people who have specific intolerances. In summary, the analyzed commercial kefirs do not resemble the microbial community and metabolite characteristics of traditional grain-based kefir. Thus, they may deliver different functional effects to the consumers, which remain to be examined in future studies.

Exploitation of Yeasts with Probiotic Traits for Kefir Production: Effectiveness of the Microbial Consortium

Kefir is a fermented milk made by beneficial lactic acid bacteria and yeasts inoculated as grains or free cultures. In this work, five yeast strains with probiotic aptitudes belonging to Candida zeylanoides, Yarrowia lipolytica, Kluyveromyces lactis, and Debaryomyces hansenii species were assessed in a defined consortium, in co-culture with a commercial strain of Lactobacillus casei, in order to evaluate the yeasts’ fermentation performance during kefir production, using different milks. The concentration of each yeast was modulated to obtain a stable consortium that was not negatively affected by the bacteria. Furthermore, all yeasts remained viable for five weeks at 4 °C, reaching about 8.00 Log CFU in 150 mL of kefir, a volume corresponding to a pot of a commercial product. The yeasts consortium showed a suitable fermentation performance in all milks, conferring peculiar and distinctive analytical and aromatic properties to the kefirs, confirmed by a pleasant taste. Overall, the panel test revealed that the cow’s and sheep’s kefir were more appreciated than the others; this evaluation was supported by a distinctive fermentation by-products’ content that positively influences the final aroma, conferring to the kefir exalted taste and complexity. These results allow us to propose the yeasts consortium as a versatile and promising multistarter candidate able to affect industrial kefir with both recognizable organoleptic properties and probiotic aptitudes.

Kefir ameliorates specific microbiota-gut-brain axis impairments in a mouse model relevant to autism spectrum disorder

Autism spectrum disorder (ASD) is one of the most severe developmental disorders, affecting on average 1 in 150 children worldwide. There is a great need for more effective strategies to improve quality of life in ASD subjects. The gut microbiome has emerged as a potential therapeutic target in ASD. A novel modulator of the gut microbiome, the traditionally fermented milk drink kefir, has recently been shown to modulate the microbiota and decrease repetitive behaviour, one of the hallmarks of ASD, in mice. As such, we hypothesized that kefir could ameliorate behavioural deficits in a mouse model relevant to ASD; the BTBR T⁺ Itpr3^tf/J mouse strain. To this end, adult mice were administered either kefir (UK4) or a milk control for three weeks as treatment lead-in, after which they were assessed for their behavioural phenotype using a battery of tests. In addition, we assessed systemic immunity by flow cytometry and the gut microbiome using shotgun metagenomic sequencing. We found that indeed kefir decreased repetitive behaviour in this mouse model. Furthermore, kefir prolonged stress-induced increases in corticosterone 60 min post-stress, which was accompanied by an ameliorated innate immune response as measured by LY6C^hi monocyte levels. In addition, kefir increased the levels of anti-inflammatory Treg cells in mesenteric lymph nodes (MLNs). Kefir also increased the relative abundance of Lachnospiraceae bacterium A2, which correlated with reduced repetitive behaviour and increased Treg cells in MLNs. Functionally, kefir modulated various predicted gut microbial pathways, including the gut-brain module S-Adenosylmethionine (SAM) synthesis, as well as L-valine biosynthesis and pyruvate fermentation to isobutanol, which all correlated with repetitive behaviour. Taken together our data show that kefir modulates peripheral immunoregulation, can ameliorate specific ASD behavioural dysfunctions and modulates selective aspects of the composition and function of the gut microbiome, indicating that kefir supplementation might prove a viable strategy in improving quality of life in ASD subjects.

Enhancement of the Antibacterial Properties of Kefir by Adding Lactobacillus fermentum grx08

ABSTRACT

Kefir is an acidic-alcoholic fermented milk that can provide probiotic benefits, such as intestinal microecological balance regulation, antibacterial activity, and anti-inflammatory activity. In this study, Lactobacillus fermentum grx08 isolated from longevous people was used to further improve the health properties of kefir. L. fermentum grx08 and kefir grains obtained from Xinjiang, People's Republic of China, were mixed at ratios of 1:1, 5:1, and 25:1 as starters. The six gram-positive and gram-negative foodborne pathogens were able to grow in the supernatant of kefir but not in the supernatant of kefir with L. fermentum grx08. With increasing amounts of inoculated L. fermentum grx08, the antibacterial activity of the mixed fermented kefir gradually increased. The contents of lactic acid, fumaric acid, and malic acid in the mixed fermented milk were significantly increased by adding L. fermentum grx08 (P < 0.05), while the content of acetic acid decreased with the increase of L. fermentum grx08 and the content of citric acid was unaffected. This study suggests that the addition of L. fermentum grx08 shortened the fermentation time, improved the acidity, and retained the quality of fermented milk. Moreover, the antibacterial properties of kefir is enhanced by increasing the production of certain acids.

HIGHLIGHTS

AB-Kefir Reduced Body Weight and Ameliorated Inflammation in Adipose Tissue of Obese Mice Fed a High-Fat Diet, but Not a High-Sucrose Diet

Consumption of different types of high-calorie foods leads to the development of various metabolic disorders. However, the effects of multi-strain probiotics on different types of diet-induced obesity and intestinal dysbiosis remain unclear. In this study, mice were fed a control diet, high-fat diet (HFD; 60% kcal fat and 20% kcal carbohydrate), or western diet (WD; 40% kcal fat and 43% kcal carbohydrate) and administered with multi-strain AB-Kefir containing six strains of lactic acid bacteria and a Bifidobacterium strain, at 10⁹ CFU per mouse for 10 weeks. Results demonstrated that AB-Kefir reduced body weight gain, glucose intolerance, and hepatic steatosis with a minor influence on gut microbiota composition in HFD-fed mice, but not in WD-fed mice. In addition, AB-Kefir significantly reduced the weight and size of adipose tissues by regulating the expression of CD36, Igf1, and Pgc1 in HFD-fed mice. Although AB-Kefir did not reduce the volume of white adipose tissue, it markedly regulated CD36, Dgat1 and Mogat1 mRNA expression. Moreover, the abundance of Eubacterium_coprostanoligenes_group and Ruminiclostridium significantly correlated with changes in body weight, liver weight, and fasting glucose in test mice. Overall, this study provides important evidence to understand the interactions between probiotics, gut microbiota, and diet in obesity treatment.

Commercial kefir products assessed for label accuracy of microbial composition and density

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Using 16S rRNA gene sequencing combined with traditional plating techniques offers greater label accuracy testing of commercial fermented foods than plating alone.

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The Loop sequencing method allows for high-throughput identification of species-level bacterial taxa present in fermented foods.

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Although a moderate level of label accuracy was observed, some bacterial species, including Streptococcus salivarius and Lactobacillus paracasei, were detected in 4 of 5 products yet not claimed on labels.

Kefirs are fermented beverages containing yeast and bacteria produced by the fermentation of water or milk with kefir grains. Because microorganism density may influence a product's health benefits, label accuracy regarding viable bacterial density and taxonomy of fermented foods is important. In this study, the microbiota of 5 commercial kefir products were measured quantitatively using standard plating techniques and characterized using high-resolution, long-read 16S rRNA gene amplicon sequencing. To enumerate viable lactic acid bacteria, 2 lots of each product were plated on de Man, Rogosa and Sharpe agar upon opening and following 14 d and incubated under anaerobic and aerobic conditions. Results revealed that 66% of products with a guaranteed count of colony-forming units per gram overstated microorganism density by at least 1 log, with only product E exceeding 1 × 10⁹ cfu/g. Sequencing results demonstrated moderate product label accuracy in regard to taxonomy, yet several products contained bacterial species above the minimum detectable threshold (0.001% relative abundance) that were not included on the labels (e.g., Streptococcus salivarius, Lactobacillus paracasei). Our results demonstrate a moderate level of labeling accuracy for commercial kefir products intended for human consumption. Regulatory agencies and consumers must continue to scrutinize these products and demand a higher level of accuracy and quality.