To investigate the postprandial impact of kefir consumption on the digestive tract metabolites and microbiome and glycaemic and gut hormone response in metabolic syndrome participants: a double-blind, inpatient, crossed-over randomized controlled clinical trial
Metabolic syndrome
Participants will attend two 4-day inpatient stays at the NIHR Imperial Clinical Research Facility (CRF), separated by at least one week. This is a double-blind, randomized crossover trial. Eligible participants will be randomly assigned to the order of the dietary intervention using a web-based sealed envelope randomization service provided by Sealed Envelope (https://www.sealedenvelope.com). Arm 1 (Kefir): Participants consume either 200 ml or 600 ml of milk kefir daily at breakfast. Arm 2 (Placebo): Participants consume a matched volume of a pasteurized, acidified, and flavored milk placebo. Methodology: Day 1: Nasoenteric tube installation and dietary standardization. Day 2: Ileal sample collection will start with two baseline samples taken before kefir/placebo intake and 60, 120, 180, 240, 300, 360, 420 and 480 minutes post-intake. Day 3: Intravenous cannulation for postprandial blood samples at baseline, 10, 20, 30, 45, 60, 90, 120, 180, 240 and 300 minutes post intake of a 600 ml dose to measure hormones and metabolites. Gastric and duodenal tubes are installed later that day. Day 4: Gastric samples will be collected on Day 4 of both study visits via the enteric tubes with the use of a syringe. Samples will be taken at 15, 30, 45, 60, 90 and 120 minutes post intake. Duodenal fluid will be collected on Day 4 of both study visits via the enteric tubes with the use of a syringe. Samples will be taken at 30, 60, 90, 120, 150, 180 and 240 minutes post intake.
1. 18-65 years old 2. Subjects diagnosed with metabolic syndrome according to the International Diabetes Federation (IDF) criteria (file://icnas1.cc.ic.ac.uk/igarciap/downloads/IDF_Meta_def_final.pdf) 3. Low consumption (max intake 3 servings/week) of kefir or supplements/foods labelled as having probiotic effect during the prior 3 months 4. Consumption of fruits and vegetables ≤3 servings per day 5. Willing to take one daily portion of kefir or placebo and to follow the procedures as well as a 2-3 h metabolic exploration day every month of follow-up 6. Written informed consent
1. Existence of lactose intolerance 2. Existence of type 1 diabetes 3. Existence of abnormal thyroid hormone levels 4. Existence of chronic gastrointestinal system disease 5. Existence of cancer 6. Existence of severe liver disease 7. Existence of kidney insufficiency 8. Existence of immunodeficiency 9. Presence of a pacemaker or other implanted electromedical device 10. Taking medication to regulate blood glucose (except metformin) or lipid levels for less than 3 months 11. Taking antibiotics prior to one month of the study 12. Taking supplement which may affect the metabolic outcomes such as prebiotic or omega-3 13. Dieting for weight loss or for another disease 14. Adherence to a vegetarian or vegan diet 15. Pregnant, parturient, or breastfeeding woman; for women of childbearing age: positive urine pregnancy test 16. Alcohol consumption exceeding 30 g of alcohol/day (1 alcoholic beverage dose = 10 g of alcohol) or proven abuse or dependence on another drug. Consumption of more than 3 alcoholic beverages per day is considered abusive. An alcoholic beverage corresponds, for example, to 30 ml of spirits, 120 ml of wine or 330 ml of beer 17. Contemporary participation in other studies 18. Blood donors in the last 2 months 19. Pathology detectable on clinical examination and medical questioning that may interfere with the study's evaluation criteria 20. Adult subject to a legal protection measure (guardianship, curatorship) 21. Person deprived of liberty by judicial or administrative decision