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Effect of Consuming Zinc-fortified Bread on Serum Zinc and Iron Status of Zinc-deficient Women: A Double Blind, Randomized Clinical Trial

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This Iranian randomized trial gave zinc-deficient women one loaf a day of non-fortified bread or bread made from flour fortified with 50 or 100 mg zinc per kg as zinc sulfate, for one month. Serum zinc and iron rose in both fortified groups but not in controls. Fortification also lowered the phytate to zinc molar ratio of the bread.

Key numbers

  • Bread zinc (mean ± SD, mg/100 g): control 1.35 ± 0.02; high-zinc 10.10 ± 0.08; low-zinc 5.72 ± 0.05. Phytate to zinc molar ratio 10.83, 1.41 and 2.52 respectively (Table 1, p. S126).
  • Serum zinc (µg/dL) before and after: control 65.53 ± 3.38 to 67.73 ± 2.17 (not significant); group 2, 65.06 ± 3.6 to 86.8 ± 10.78; group 3, 66.53 ± 3.5 to 78.73 ± 8.1 (P < 0.001 for both fortified groups) (Table 4, p. S127).
  • Estimated dietary zinc intake 4.96 to 6.02 mg/day across groups, described as 60 to 70% of the 8 mg/day recommended allowance for adult women (Table 3 and Results, p. S126 to S127).
  • 75 of 80 women completed (25 per group); inclusion required serum zinc of 70 µg/dL or less (Methods and Results, pp. S125 to S126).

Methods (brief)

Taftoon bread was baked from 90% extraction wheat flour with zinc sulfate heptahydrate dissolved into the dough. Participants ate one loaf daily for one month. Serum zinc was measured by flame atomic absorption spectrophotometry; bread zinc and phytate by AACC methods.

Evidence fitness

The trial supports the use of zinc-fortified flour to raise serum zinc in deficient women over a month and gives measured zinc and phytate ratios for plain and fortified flatbread. It does not establish long-term safety, effects on copper status, or population outcomes.

Limitations

Group labels are inconsistent: the methods assign 50 and 100 mg/kg to groups 2 and 3, while the abstract and results describe group 2 as the high-zinc bread. The trial lasted one month in 75 women. The journal’s suggested citation box prints the title of a different article.

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