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Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals.
Eur J Clin Nutr. 2008 Mar; 62(3):336-41.EJ

Abstract

OBJECTIVE

To evaluate the influence of oxalic acid (OA) on nonhaem iron absorption in humans.

DESIGN

Two randomized crossover stable iron isotope absorption studies.

SETTING

Zurich, Switzerland.

SUBJECTS

Sixteen apparently healthy women (18-45 years, <60 kg body weight), recruited by poster advertizing from the staff and student populations of the ETH, University and University Hospital of Zurich, Switzerland. Thirteen subjects completed both studies.

METHODS

Iron absorption was measured based on erythrocyte incorporation of (57)Fe or (58)Fe 14 days after the administration of labelled meals. In study I, test meals consisted of two wheat bread rolls (100 g) and either 150 g spinach with a native OA content of 1.27 g (reference meal) or 150 g kale with a native OA content of 0.01 g. In study II, 150 g kale given with a potassium oxalate drink to obtain a total OA content of 1.27 g was compared to the spinach meal.

RESULTS

After normalization for the spinach reference meal absorption, geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P=0.86). Spinach was significantly higher in calcium and polyphenols than kale and absorption from the spinach meal was 24% lower compared to the kale meal without added OA, but the difference did not reach statistical significance (P>0.16).

CONCLUSION

Potassium oxalate did not influence iron absorption in humans from a kale meal and our findings strongly suggest that OA in fruits and vegetables is of minor relevance in iron nutrition.

Authors+Show Affiliations

Institute of Food Science and Nutrition, ETH Zurich, Zurich, Switzerland. stefan.storcksdieck@ilw.agrl.ethz.chNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Randomized Controlled Trial

Language

eng

PubMed ID

17440529

Citation

genannt Bonsmann, S Storcksdieck, et al. "Oxalic Acid Does Not Influence Nonhaem Iron Absorption in Humans: a Comparison of Kale and Spinach Meals." European Journal of Clinical Nutrition, vol. 62, no. 3, 2008, pp. 336-41.
genannt Bonsmann SS, Walczyk T, Renggli S, et al. Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals. Eur J Clin Nutr. 2008;62(3):336-41.
genannt Bonsmann, S. S., Walczyk, T., Renggli, S., & Hurrell, R. F. (2008). Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals. European Journal of Clinical Nutrition, 62(3), 336-41.
genannt Bonsmann SS, et al. Oxalic Acid Does Not Influence Nonhaem Iron Absorption in Humans: a Comparison of Kale and Spinach Meals. Eur J Clin Nutr. 2008;62(3):336-41. PubMed PMID: 17440529.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals. AU - genannt Bonsmann,S Storcksdieck, AU - Walczyk,T, AU - Renggli,S, AU - Hurrell,R F, Y1 - 2007/04/18/ PY - 2007/4/19/pubmed PY - 2008/7/2/medline PY - 2007/4/19/entrez SP - 336 EP - 41 JF - European journal of clinical nutrition JO - Eur J Clin Nutr VL - 62 IS - 3 N2 - OBJECTIVE: To evaluate the influence of oxalic acid (OA) on nonhaem iron absorption in humans. DESIGN: Two randomized crossover stable iron isotope absorption studies. SETTING: Zurich, Switzerland. SUBJECTS: Sixteen apparently healthy women (18-45 years, <60 kg body weight), recruited by poster advertizing from the staff and student populations of the ETH, University and University Hospital of Zurich, Switzerland. Thirteen subjects completed both studies. METHODS: Iron absorption was measured based on erythrocyte incorporation of (57)Fe or (58)Fe 14 days after the administration of labelled meals. In study I, test meals consisted of two wheat bread rolls (100 g) and either 150 g spinach with a native OA content of 1.27 g (reference meal) or 150 g kale with a native OA content of 0.01 g. In study II, 150 g kale given with a potassium oxalate drink to obtain a total OA content of 1.27 g was compared to the spinach meal. RESULTS: After normalization for the spinach reference meal absorption, geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P=0.86). Spinach was significantly higher in calcium and polyphenols than kale and absorption from the spinach meal was 24% lower compared to the kale meal without added OA, but the difference did not reach statistical significance (P>0.16). CONCLUSION: Potassium oxalate did not influence iron absorption in humans from a kale meal and our findings strongly suggest that OA in fruits and vegetables is of minor relevance in iron nutrition. SN - 0954-3007 UR - https://www.unboundmedicine.com/medline/citation/17440529/Oxalic_acid_does_not_influence_nonhaem_iron_absorption_in_humans:_a_comparison_of_kale_and_spinach_meals_ L2 - https://doi.org/10.1038/sj.ejcn.1602721 DB - PRIME DP - Unbound Medicine ER -