Procedure during test days.
BLOOD
Participants came for a baseline visit and were then randomly assigned to an order of three test days. During each of the test days, participants received one of the three preloads 20 minutes before the mixed–meal tolerance test. Blood was drawn at t = –20, 0, 15, 30, 60, 120 and 240 minutes after the mixed–meal tolerance test.Participants visited the Research Centre in Hoorn four times: once for a baseline visit, and three times for the study visits, with at least one week separating each visit to allow enough time for wash-out. Participants were asked to collect fecal samples at home prior to each visit, to determine the microbiome composition. Participants had to remain fasted from 22:00 the night before the test, with some water allowed, and were asked to avoid physical exercise and eating spicy foods during the 24 hours preceding the test. This study was conducted according to the principles of the Declaration of Helsinki. The study protocol was approved by the Medical Ethical Committee from VUmc, registration number NL63702.029.17 (