A Randomized Pilot Trial to Evaluate the Bioavailability of Natural versus Synthetic Vitamin B Complexes in Healthy Humans and Their Effects on Homocysteine, Oxidative Stress, and Antioxidant Levels

Figure 2

Study design. Time schedule for blood sampling (T1-T11) and supplementation with vitamin B complex (natural vs. synthetic) applicable to both study groups. The study was initiated with a three-week run-in phase before the first study day. After study onset, blood samples for information on the diurnal cycle were taken at baseline (T1), 1.5 hours after the first ingestion of the vitamin B complex (T2), 4 hours after the first ingestion (T3), and 7 hours after the first ingestion (T4). Supplementation was terminated after a period of 6 weeks (T5) followed by a 2-week washout period (T6), to complete the first phase of this crossover study. This timepoint was simultaneously the baseline for the second study phase. The vitamin B complex was crossed over in the two groups (natural vs. synhtetic and vice versa), and blood samples were taken after 1.5 hours after ingestion of the first substituted vitamin B complex (T7), then after 4 hours (T8) and 7 hours (T9). Supplementation in the second study phase was terminated after a period of 6 weeks (T10), followed by a washout period of another 6 weeks (T11) at the end point of the study. Due to carryover effects in the majority of biomarkers, crossover comparisons were generally dispensed with, resulting in a restriction to group comparisons in phase 1, as emphasized by dark arrows.