Background: Folate has come into focus due to its protective role against child birth defects such as neural tube defects (NTD). Swedish authorities recommend all fertile women to increase their folate intake to 400 microg/day by eating folate-rich foods. Because not all women follow these recommendations, there is a discussion today about whether Sweden should introduce folic acid fortification in wheat flour and sifted rye flour. This decision needs knowledge about the bioavailability of folic acid from fortified foods.
Aim of the study: To investigate effects of two folic acid fortification levels on folate status in healthy female volunteers and to study the folic acid stability during the baking procedure and storage of the fortified breakfast rolls.
Method: Twenty-nine healthy women were recruited. Folic acid-fortified wheat breakfast rolls were baked with the purpose to contain 200 microg folic acid/roll (roll L) and 400 microg folic acid/roll (roll H). Fourteen women were given one roll/day of roll L (group L) and 15 one roll/day of roll H (group H) during 12 weeks of intervention. Fasting venous blood samples were collected on days 0, 30, 60 and 90. Serum homocysteine concentrations were determined using an immunoassay. Serum and erythrocyte folate concentrations were analysed using a protein-binding assay with fluorescent quantification. The folic acid concentration in the breakfast rolls was analysed by HPLC on days 0, 30, 60 and 90. Total folate concentration was measured with microbiological assay on day 45.
Results: Group L Group L had initially an average erythrocyte folate concentration of 577 +/- 93 nmol/L. After 90 days of intervention, an increase of 20 % (p < 0.05) was observed. At day 0, mean serum folate concentrations were 16.9 +/- 4.3 nmol/L. The mean serum folate concentrations increased by 30 % (p < 0.001) after 90 days. At day 0, mean serum homocysteine concentrations were 9.1 +/- 2.0 micromol/L, which decreased by 20 % (p < 0.01) after 30 days. Group H Group H had an initial erythrocyte folate concentration of 784 +/- 238 nmol/L. After 90 days, an increase of 26 % (p < 0.05) was observed. Serum folate increased at least 22 % after 30 days, from a level of 18.7 +/- 4.8 nmol/L at day 0. Thereafter, all women of group H had serum concentrations at or above the upper limit of quantification (23 nmol/L). At day 0, mean serum homocysteine concentrations were 8.4 +/- 1.7 micromol/L, which decreased by 16 % (p < 0.05) after 30 days. The baking procedure resulted in 20-25 % loss of fortified folic acid in the rolls used in the present study. The size of the rolls affected the retention of folic acid during baking. No significant loss was seen in folic acid concentration in the rolls during the intervention period.
Conclusion: The present study showed that in healthy women, subjected to a 12-week intervention with breakfast rolls fortified with either 166 microg or 355 microg folic acid, serum homocysteine concentration decreased (p < 0.05) and erythrocyte folate increased (p < 0.05). The lower level of fortification seems to be sufficient to improve the folate status. Together with the average daily intake of natural folates, these women reach the recommended intake of 400 microg/day. Folic acid is stable in fortified bread for 90 days storage at -20 degrees C.