Phytic acid added to white-wheat bread inhibits fractional apparent magnesium absorption in humans.
BACKGROUND
Phytic acid has been reported to impair the absorption of minerals and trace elements such as calcium, zinc, and iron in humans. However, limited information is available on the effect of phytic acid on magnesium absorption.


OBJECTIVE
The objective was to evaluate the effect of phytic acid on fractional apparent magnesium absorption in humans.


METHODS
Two stable-isotope studies were performed with 8-9 healthy adults per study. Test meals were based on 200 g phytic acid-free wheat bread; test meals with and without added phytic acid were served on days 1 and 3 according to a crossover design. Phytic acid was added in amounts similar to those naturally present in whole-meal (1.49 mmol) and in brown bread (0.75 mmol). Each test meal was labeled with 0.7 mmol (25)Mg or 1.1 mmol (26)Mg. The total magnesium content was standardized to 3.6 mmol in all test meals. Apparent magnesium absorption was based on fecal monitoring.


RESULTS
The addition of phytic acid lowered fractional apparent magnesium absorption from 32.5 +/- 6.9% (no added phytic acid) to 13.0 +/- 6.9% (1.49 mmol added phytic acid; P < 0.0005) and from 32.2 +/- 12.0% (no added phytic acid) to 24.0 +/- 12.9% (0.75 mmol added phytic acid; P < 0.01). The inhibiting effect of phytic acid was dose dependent (P < 0.005).


CONCLUSIONS
The results show that fractional magnesium absorption from white-wheat bread is significantly impaired by the addition of phytic acid, in a dose-dependent manner, at amounts similar to those naturally present in whole-meal and brown bread.
Bohn
Torsten
T
Laboratory for Human Nutrition, Institute of Food Science and Nutrition, Swiss Federal Institute of Technology, Zurich.
Davidsson
Lena
L
Walczyk
Thomas
T
Hurrell
Richard F
RF
D000328:Adult; D001682:Biological Availability; D001939:Bread; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D007554:Isotopes; D016014:Linear Models; D008274:Magnesium / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D010833:Phytic Acid / Q000494:pharmacology*; D014908:Triticum
D007554:Isotopes; D010833:Phytic Acid; D008274:Magnesium