Impacts of Fermented Oat-based Product on Gut Microbiota and Health

Plant-based protein sources, such as those derived from oats, are experiencing high demand due to their role in reducing reliance on animal products and promoting a more sustainable food system. Despite this, there is limited information available regarding the impact of components like fibre in plant-based foods on protein and other nutrients' metabolism.

Food fermentation emerges as a potential solution to enhance the absorption of plant-based protein and various nutrients in the small intestine. This is achieved by reducing antinutrients and facilitating the absorption process. Additionally, food fermentation has implications for the composition and metabolic activity of the gut microbiota, influencing metabolism, immune responses, intestinal function, and overall health. The metabolism of tryptophan in the gut, modulated by the gut microbiota and the production of various metabolites, may serve as a key link in these observed effects.

The fermentation of plant-based foods potentially enhances the beneficial health effects of these foods, and investigating this contributes to an increased understanding of the gut-mediated health effects of foods and the mechanisms behind them. This study will be part of a European research project HealthFerm.

Detailed objectives are to:

• compare fermented and unfermented plant-based food products to blood lipid and glucose metabolism and gastrointestinal comfort as well as perceived and observed overall well-being.
• study the effects of fermented and unfermented plant-based food consumption on the markers for gut permeability and inflammation.
• study the difference in microbiota composition and diversity after consuming fermented and unfermented plant-based foods and its contribution to cardiometabolic outcomes.
• study the difference in microbiota-related metabolites, especially tryptophan metabolites between fermented and unfermented plant-based foods.

A total of 100 participants will be enrolled in this randomized, controlled, cross-over trial, during which they will eat both fermented and unfermented oat-based products as part of their habitual diet. The study follows this sequence:

Weeks 1-3: Habitual diet Weeks 4-6: Dietary Intervention 1 Weeks 7-9: Habitual diet (wash-out) Weeks 10-12: Dietary Intervention 2

Blood, urinary and faecal samples, as well as food diaries and questionnaires, are collected at the end of each study period to assess participants' perceived health, inflammatory markers, glucose and lipid metabolism, tryptophan metabolites, gastrointestinal symptoms, and gut microbiota. In addition, participants' values and attitudes towards fermented foods are assessed. At the end of the study, participants will receive their laboratory results and dietary guidance for their habitual diet from a registered dietitian.

Inclusion criteria

• Waist circumference >90 cm (women) or >100 cm (men) OR BMI 26-38 kg/m2
• One of the following:

• raised blood pressure (systolic ≥ 130 mmHg and/or diastolic 85 mmHg)
• raised fasting plasma glucose (≥ 5.6 mmol/l)
• raised triglycerides (≥ 1.7 mmol/l)
• raised total cholesterol (≥ 5 mmol/l)
• raised LDL (≥ 3 mmol/l)
• reduced HDL (women < 1.3 mmol/l, men 1.0 mmol/l)
• Use of cereal products and dairy products or their plant-based alternatives as a part of habitual diet
• Willingness to follow intervention diets for the whole study

Exclusion criteria

• Diagnosed chronic diseases and conditions which could hamper the adherence to the dietary intervention protocol, e.g., chronic liver, thyroid, kidney, or gastrointestinal diseases
• Pregnancy and lactation
• Gluten-free or vegan diet
• Recent use of antibiotics (within 3 months)
• Gastrointestinal surgery (within 6 months)
• Alcohol abuse (AUDIT ≥ 15 p and measures of liver function)
• regular smoking or use of snus