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Obesity-Related Hypoferremia Is Not Explained by Differences in Reported Intake of Heme and Nonheme Iron or Intake of Dietary Factors that Can Affect Iron Absorption

https://doi.org/10.1016/j.jada.2007.10.034Get rights and content

Abstract

Hypoferremia is more prevalent in obese than nonobese adults, but the reason for this phenomenon is unknown. To elucidate the role dietary factors play in obesity-related hypoferremia, the intake of heme and nonheme iron and the intake of other dietary factors known to affect iron absorption were compared cross-sectionally from April 2002 to December 2003 in a convenience sample of 207 obese and 177 nonobese adults. Subjects completed 7-day food records, underwent phlebotomy for serum iron measurement, and had body composition assessed by dual-energy x-ray absorptiometry, during a 21-month period. Data were analyzed by analysis of covariance and multiple linear regression. Serum iron (mean±standard deviation) was significantly lower in obese than nonobese individuals (72.0±61.7 vs 85.3±58.1 μg/dL [12.888±11.0443 vs 15.2687±10.3999 μmol/L]; P<0.001). The obese cohort reported consuming more animal protein (63.6±34.5 vs 55.7±32.5 g/day; P<0.001) and more heme iron (3.6±2.8 vs 2.7±2.6 mg/day; P<0.001). Groups did not differ, however, in total daily iron consumption, including supplements. Obese subjects reported consuming less vitamin C (77.2±94.9 vs 91.8±89.5 mg/day; P=0.01), which may increase absorption of nonheme iron, and less calcium (766.2±665.0 vs 849.0±627.2 mg/day; P=0.038), which may decrease nonheme iron absorption, than nonobese subjects. Groups did not significantly differ in intake of other dietary factors that can impact absorption of iron, including phytic acid, oxalic acid, eggs, coffee, tea, zinc, vegetable protein, or copper. After accounting for demographic covariates and dietary factors expected to affect iron absorption, fat mass (P=0.007) remained a statistically significant negative predictor of serum iron. This cross-sectional, exploratory study suggests that obesity-related hypoferremia is not associated with differences in reported intake of heme and nonheme iron or intake of dietary factors that can affect iron absorption.

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Study Design

This cross-sectional study was conducted using baseline data from a randomized clinical trial examining the effects of calcium supplementation on body weight, body composition, and comorbid conditions (9). From April 2002 to December 2003, healthy overweight adults, defined as having body mass index (BMI; calculated as kg/m2) ≥25.0, and healthy normal weight adults (BMI of 18.0 to 24.9) were recruited. Eligibility criteria for subjects included age older than 18 years, being in good general

Results and Discussion

Two-hundred and seven obese and 178 nonobese adults were enrolled (Table). Data from 10 subjects were excluded for reporting implausible energy intake of <600 calories or >3,500 calories per day for women and <800 calories or >4,200 calories per day for men (12), or for incomplete dietary records. Obese and nonobese subjects did not differ substantially in their demographic characteristics, other than BMI.

Hypoferremia was significantly more prevalent in obese compared to nonobese adults (25.1%

Conclusion

Etiology of the hypoferremia of obesity remains uncertain. The current cross-sectional, exploratory study suggests that differences in intake of heme and nonheme iron, or of dietary factors known to affect iron absorption, are not associated with lower serum iron concentrations found in obese adults. Additional studies investigating other factors that may be associated with the hypoferremia of obesity are warranted.

C. M. Menzie is a research associate, L. B Yanoff is a fellow in endocrinology, and J. A. Yanovski is head, Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institute of Child Health and Human Development; B. I. Denkinger and N. G. Sebring are clinical research dietitians, T. McHugh is a clinical research nurse; K. A. Calis is pharmacist and director of Drug Information Service, Clinical Center Pharmacy Department, all at the National Institutes of Health, Bethesda, MD.

References (23)

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    C. M. Menzie is a research associate, L. B Yanoff is a fellow in endocrinology, and J. A. Yanovski is head, Unit on Growth and Obesity, Developmental Endocrinology Branch, National Institute of Child Health and Human Development; B. I. Denkinger and N. G. Sebring are clinical research dietitians, T. McHugh is a clinical research nurse; K. A. Calis is pharmacist and director of Drug Information Service, Clinical Center Pharmacy Department, all at the National Institutes of Health, Bethesda, MD.

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