Effects of an Iron or Iron and Vitamin D–Fortified Flavored Skim Milk on Iron Metabolism: A Randomized Controlled Double-Blind Trial in Iron-Deficient Women

Abstract

Objectives: Iron deficiency anemia and vitamin D deficiency are considered global pandemics. The aim of this study was to determine whether the consumption of a dairy product fortified with iron and vitamin D, compared to the equivalent with only added iron, exerts an additional effect on iron metabolism in iron-deficient menstruating women.

Methods: The design was a randomized, placebo-controlled, double-blind, parallel-group trial of 16 weeks’ duration. Subjects were randomized into 2 groups that consumed, as part of their usual diet, 500 mL/day of an iron (n = 54) or iron- and vitamin D–fortified (n = 55) flavored skim milk. At baseline and monthly, dietary intake, body weight, and hematological and iron metabolism biomarkers were determined. Serum 25-hydroxyvitamin D was analyzed at baseline and weeks 8 and 16. Data were analyzed by analysis of variance (ANOVA) of repeated measures for time and Time×Group interaction effects.

Results: A total of 109 volunteers completed the study. Calcium and iron intakes increased during the intervention (p < 0.001 for both groups). Serum 25-hydroxyvitamin D significantly increased in Fe + D group during the assay (p < 0.001) and at week 16 it was higher compared to the Fe group (p < 0.05). Serum ferritin, serum transferrin, mean corpuscular volume, mean corpuscular hemoglobin, and red blood cell distribution width showed significant time effects but no Time×Group interaction. Higher values of erythrocytes (p = 0.01), hematocrit (p = 0.05), and hemoglobin (p = 0.03) at week 8 were observed in the Fe + D group compared to the Fe group.

Conclusion: Iron-fortified flavored skim milk does not improve iron status in iron-deficient menstruating women. However, vitamin D fortification slightly enhances erythropoiesis and iron status.

Key words:

• vitamin D
• ferric pyrophosphate
• fortification
• skim milk
• iron deficiency
• women

ACKNOWLEDGMENTS

This study was financed by Project AGL2009-11437. L.T. and R.B.R. were supported by a JAE-predoc grant from the Spanish National Research Council (CSIC) and European Social Fund. The authors are grateful to Sara Lorigados and Jorge Parra for the lab assistance, Leticia Calera for helping with dietary calculation, and the volunteers who participated in the study. CAPSA, Spain, is acknowledged for providing the dairy products.

ClinicalTrial.gov: NCT01739907.

The authors declare no conflict of interest.

Abbreviations: Hb = hemoglobin, MCH = mean corpuscular hemoglobin, MCV = mean corpuscular volume, RDW = red blood cell distribution width, sTfR = serum transferrin receptor, TIBC = total iron binding capacity.