The main objectives of this project are:

1. to determine the relative bioavailability of dietary folate from a total diet, compared with synthetic folic acid and
2. to determine the bioavailability with a higher precision than previous methods.

The hypothesis is that the bioavailability of dietary folate within a confidence interval of +/-20% can be estimated.

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.

Inclusion Criteria:

• Serum B12 >118pmol/L;
• Serum creatinine <125micromol/L;
• Plasma total homocysteine <26micromol/L.

Exclusion Criteria:

• Cardiovascular disease, cancer, rheumatoid arthritis, epilepsy, gastro-intestinal disorders;
• Use of drugs interfering with folate metabolism;
• Use of B vitamins within the period three months prior to the study.
• Body Mass Index (BMI) > 30