Zinc absorption from low-phytate hybrids of maize and their wild-type isohybrids.
BACKGROUND
Identification of allelic variants in a single gene that determine the phytate content of maize kernels and the subsequent breeding of low-phytate maize have facilitated studies designed to determine quantitatively the effects of maize phytate on the bioavailability of minerals in maize.


OBJECTIVE
The objective was to determine the relation between the fractional absorption of zinc (FAZ) and the phytate content and phytate:zinc molar ratios of maize tortillas prepared from hybrids with different phytate contents.


METHODS
Six healthy adults were fed, as the only food for 2 d, maize tortillas prepared from 1 of 2 low-phytate mutants: lpa1-1 (lpa1-1-LP) or Nutridense Low Phytate (ND-LP), which have phytate reductions of approximately 60% and approximately 80%, respectively, compared with their respective wild-type isohybrids. Four additional subjects were fed tortillas prepared from the corresponding wild-type isohybrids (lpa1-1-WT and ND-WT) according to the same study design. Meals were extrinsically labeled with zinc stable isotopes, and FAZ was determined with a dual-isotope-tracer ratio technique. Overall FAZ values were examined in relation to dietary phytate and phytate:zinc molar ratios by using a mixed nonlinear regression model.


RESULTS
The mean (+/-SD) FAZ values from tortillas prepared from ND-LP, lpa1-1-LP, lpa1-1-WT, and ND-WT were 0.38 +/- 0.07, 0.28 +/- 0.04, 0.15 +/- 0.07, and 0.13 +/- 0.05, respectively. A negative relation (P < 0.001) was found between FAZ and both dietary phytate and the phytate:zinc molar ratio. The effect of dietary zinc (8-14 mg Zn/d) under these experimental conditions was not significant.


CONCLUSIONS
FAZ from maize tortillas is positively related to the extent of phytate reduction achieved with low-phytate hybrids.
Hambidge
K Michael
KM
University of Colorado Health Sciences Center, Department of Pediatrics, Section of Nutrition, Denver 80262, USA. michael.hambidge@uchsc.edu
Huffer
John W
JW
Raboy
Victor
V
Grunwald
Gary K
GK
Westcott
Jamie L
JL
Sian
Lei
L
Miller
Leland V
LV
Dorsch
John A
JA
Krebs
Nancy F
NF
D000328:Adult; D001682:Biological Availability; D004032:Diet; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D010833:Phytic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D003313:Zea mays / Q000235:genetics*; D015032:Zinc / Q000008:administration & dosage / Q000493:pharmacokinetics*; D015033:Zinc Isotopes / Q000493:pharmacokinetics
D015033:Zinc Isotopes; D010833:Phytic Acid; D015032:Zinc