genannt Bonsmann SS Walczyk T Renggli S Hurrell RF 2008 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. application/pdf https://sonar.ch/global/documents/222341 eng info:eu-repo/semantics/altIdentifier/doi/10.1038/sj.ejcn.1602721 info:eu-repo/semantics/altIdentifier/pmid/17440529 info:eu-repo/semantics/openAccess European journal of clinical nutrition. - 2008 Adult Biological Availability Brassica Cross-Over Studies Dose-Response Relationship, Drug Erythrocytes Female Humans Intestinal Absorption Iron Isotopes Iron, Dietary Oxalic Acid Spinacia oleracea Oxalic acid does not influence nonhaem iron absorption in humans: a comparison of kale and spinach meals. http://purl.org/coar/resource_type/c_6501