Bioavailability of folic acid from fortified pasteurised and UHT-treated milk in humans.
OBJECTIVE
The aim of this study was to investigate whether milk fortified with folic acid enhances the folate status of humans and whether the presence of folate-binding proteins (FBP) in pasteurised milk affects the bioavailability of folic acid from fortified milk. In untreated and pasteurised milk, folate occurs bound to FBP, while FBP is (partly) denatured in ultra-high-temperature (UHT)-treated milk. The effect of FBP on folate bioavailability is still unclear.


METHODS
Healthy, free-living subjects (n=69) aged 18-49 y participated in a 4-week double-blind, placebo-controlled dietary intervention study.


METHODS
In addition to a fully controlled diet, the subjects consumed each day 500 ml of pasteurised or UHT milk, either fortified or not with 200 mug folic acid.


RESULTS
Consumption of fortified milk increased folate concentrations in serum and in red blood cells (RBC) by 6.6-7.0 nmol/l (P<0.001) and 32-36 nmol/l (P<0.01), respectively. Similarly, plasma homocysteine concentrations were lowered 0.88-0.89 micromol/l (P=0.001) in subjects who consumed fortified milk. The bioavailability of folic acid from pasteurised milk relative to that of folic acid from UHT milk was 74-94% (NS), depending on the parameter used.


CONCLUSIONS
Milk fortified to supply an additional 200 microg of folic acid/s substantially increased folate status, and decreased plasma total homocysteine concentrations in young, healthy subjects. Milk is therefore a suitable matrix for fortification to enhance the folate status in humans. No significant effect of endogenous FBP was found on the bioavailability of folic acid from milk.
de Jong
R J
RJ
TNO-WU Centre for Micronutrient Research, Zeist and Wageningen, The Netherlands.
Verwei
M
M
West
C E
CE
van Vliet
T
T
Siebelink
E
E
van den Berg
H
H
Castenmiller
J J M
JJ
D000293:Adolescent; D000328:Adult; D000818:Animals; D001682:Biological Availability; D002352:Carrier Proteins / Q000378:metabolism*; D004311:Double-Blind Method; D004912:Erythrocytes / Q000737:chemistry; D005260:Female; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000378:metabolism / Q000493:pharmacokinetics*; D005511:Food Handling / Q000379:methods*; D005527:Food, Fortified / Q000032:analysis; D006710:Homocysteine / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D008892:Milk / Q000737:chemistry*; D009436:Neural Tube Defects / Q000517:prevention & control; D011956:Receptors, Cell Surface / Q000378:metabolism*
D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D011956:Receptors, Cell Surface; D006710:Homocysteine; D005492:Folic Acid