Functionality of endogenous folates from rye and orange juice using human in vivo model

Summary.

Background: Cereals contribute about a quarter of the daily folate intake from a typical diet in several European countries. However, studies on bioavailability of endogenous folates, in particular of cereal sources, are scarce. Aim of the study: We aimed to study how well natural folates from rye (different rye breads and muesli made of malted rye) and orange juice function in improving folate status of human volunteers compared to a diet containing folic acid fortified wheat bread. Methods: Healthy human volunteers aged 20–66 y took part in a four-week intervention trial in which bread, breakfast cereal and juice were provided. The study had a parallel design with two groups, 1) rye and orange juice group (33 volunteers) and 2) fortified wheat bread and apple juice group (31 volunteers). The test foods provided on average 184 μg and 188 μg folate per day in rye and wheat groups, respectively. Test foods were consumed as part of the subjects' normal diet. Results: In both groups statistically significant increases in serum and red cell folates were observed after the intervention period. The serum folate increased 26 % and 31 %, and red cell folate levels increased 17 % and 15 % in rye and orange juice and wheat and apple juice groups, respectively. The effects did not differ between the rye and wheat groups. Increases in serum and red cell folate were more profound among subjects with low starting folate levels. Decrease in the plasma homocysteine concentrations was observed only in the highest tertile of both groups but not in the group means. Conclusions: Endogenous folates incorporated into a healthy diet, even in moderate amounts, is an efficient way to improve folate status among healthy adults. Folates from different rye products and orange juice showed good bioavailability that was similar to folic acid from fortified white bread.