Folate plays a role in the prevention of certain birth defects and possibly also in prevention of neurocognitive diseases, cancer and cardiovascular disease. The proportion of dietary folate that is absorbed and becomes available for metabolic processes in the body has been estimated between 30 and 98%, but an accurate figure is lacking. Since subjects generally differ a lot in their folate or homocysteine response upon a change in dietary folate intake, the between-person variability in these responses is high. Therefore, bioavailability estimates derived from these responses have large confidence intervals. With this trial the researchers want to determine folate bioavailability with a higher precision than previous trials. A good estimate of folate bioavailability from the general diet is necessary to construct reliable dietary reference intakes for folate.