Nutritional and metabolic biomarkers
In the MedLey trial, venous blood samples were taken at baseline, 3 and 6 months post randomisation after 8 h of fasting, centrifuged and stored at −80°C. High-performance liquid chromatography (HPLC) with photo-diode array detection was used to assay carotenoids [In EPIC-InterAct, venous blood samples were collected at baseline. Plasma samples were stored in liquid nitrogen (up to −196°C). HPLC with ultraviolet light detection was used to measure carotenoids [Five carotenoid variables were measured in both the MedLey trial and EPIC-InterAct: α-carotene, β-carotene, β-cryptoxanthin, lutein, and sum of lutein and zeaxanthin. For fatty acids measured in the MedLey trial, units were converted from weight% to mol% to harmonise the data with assays of fatty acids in the EPIC-InterAct. After exclusion of fatty acids with mean concentrations <0.05 mol% of total fatty acids measured, 24 fatty acids overlapped between the MedLey trial and EPIC-InterAct.