Folic acid enrichment of bread does not appear to affect zinc absorption in young women.
BACKGROUND
In several countries cereals are now enriched with folic acid to reduce the risk of neural tube defects. Human studies suggest that folic acid interferes with zinc absorption. This raises concerns about the zinc status of high-risk groups such as infants, pregnant women, and older persons.


OBJECTIVE
We sought to determine the effect of added folic acid on zinc absorption from white bread with high and low zinc contents.


METHODS
Zinc absorption was measured in 15 healthy women (22-33 y), each of whom consumed 4 single meals spaced 2 wk apart in a randomized crossover design. The servings of bread (100 g) differed in zinc and folic acid contents as follows: A, 1.2 mg Zn and 17 microg folic acid; B, 1.2 mg Zn and 144 microg folic acid; C, 3.0 mg Zn and 17 microg folic acid; and D, 2.9 mg Zn and 144 microg folic acid. Meals were extrinsically labeled with 65Zn and absorption was estimated from whole-body retention measurements. Folate status was assessed by measuring plasma and erythrocyte folate and plasma homocysteine concentrations.


RESULTS
Mean (+/-SD) zinc absorption did not differ significantly in relation to the folate content of the breads at either the low zinc content (38.8 +/- 13.5% and 40.6 +/- 16.5% for A and B, respectively; P = 0.74) or the high zinc content (26.7 +/- 9.3% and 22.7 +/- 6.6% for C and D, respectively; P = 0.16). There was no significant correlation between folate status and zinc absorption (r < 0.3, P > 0.1).


CONCLUSIONS
Fortification of white bread with a commonly used amount of folic acid did not appear to influence zinc absorption at either a high or a low zinc content.
Hansen
M
M
Research Department of Human Nutrition, LMC Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark. mha@kvl.dk
Samman
S
S
Madsen
L T
LT
Jensen
M
M
Sørensen
S S
SS
Sandström
B
B
D000328:Adult; D001939:Bread; D018592:Cross-Over Studies; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D005527:Food, Fortified; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D009436:Neural Tube Defects / Q000517:prevention & control; D015032:Zinc / Q000378:metabolism / Q000493:pharmacokinetics*; D015033:Zinc Isotopes
D015033:Zinc Isotopes; D006710:Homocysteine; D005492:Folic Acid; D015032:Zinc