4.3.1. Blood Plasma, Serum, Fecal, and Urine Collection and Measurements
At W0, W4 and W8, blood samples were collected in two ethylenediaminetetraacetic acids (EDTA)-coated tubes, one serum tube, and one lithium heparin plasma tube. One plasma tube was used for blood count analysis (Sindelfingen laboratory GbR, Sindelfingen, Germany). The other one was centrifuged at 500× The stool samples were collected before the W0 and W8 visit (max. two days before) in two tubes and stored at −20 °C in the participant’s home until delivery to the laboratory or, alternatively, when convenient the samples were transported directly to the laboratory by the study participant. Once at the laboratory, the two tubes were stored at −80 °C until the analysis commenced. One of the tubes was used to measure the gut barrier marker zonulin and the other was used for SCFA analysis. Urine for intestinal permeability measurements was collected at baseline (W0) and at the end of the intervention (W8) at home during 24-h, as described later. These samples were frozen at −80 °C and stored until further transport to Orebro University.