The efficacy of a local ascorbic acid-rich food in improving iron absorption from Mexican diets: a field study using stable isotopes

BACKGROUND: One potentially sustainable approach to improving iron status at the community level is to encourage the consumption of local ascorbic acid-rich foods, in conjunction with meals high in nonheme iron. OBJECTIVE: The study, conducted in rural Mexico, measured stable isotopes of iron to evaluate the effect on iron absorption of the addition of 25 mg ascorbic acid as agua de limón (limeade) to 2 typical meals per day for 2 wk. DESIGN: Fifteen nonpregnant, nonlactating, iron-deficient (ferritin < 12 microg/L) women (x +/- SD age: 28.3 +/- 7.7 y) fasted overnight and were brought to a community clinic. After an initial blood sample, subjects consumed 0.25 mg (57)Fe with both breakfast and lunch for 14 d. On day 29, another blood sample was taken, and a reference dose of 2.7 mg (58)Fe with 25 mg ascorbic acid was given. For the following 15 d, participants consumed 0.25 mg (57)Fe added to both breakfast and lunch with 25 mg ascorbic acid added to each meal as limeade. A final blood sample was taken on day 59. RESULTS: Iron absorption was calculated from recovery of isotopes in blood obtained 14 d after administration of each isotope. When 25 mg ascorbic acid as limeade was added to test meals twice a day for 2 wk, iron absorption increased significantly (P < 0.001) in every subject: the mean absorption rose from 6.6 +/- 3.0% to 22.9 +/- 12.6%. CONCLUSIONS: The consumption of 25 mg ascorbic acid as limeade twice daily with meals substantially improved iron absorption and may improve the iron status of nonpregnant, nonlactating, iron-deficient women.