Fractional magnesium absorption is significantly lower in human subjects from a meal served with an oxalate-rich vegetable, spinach, as compared with a meal served with kale, vegetable with a low oxalate content

Torsten Bohn, Lena Davidsson, Thomas Walczyk, Richards F. Hurrell

Research output: Contribution to journalArticle

33 Citations (Scopus)


The aim of the present study was to evaluate Mg absorption from a test meal served with an oxalate-rich vegetable, spinach, as compared with a test meal served with a vegetable with a low oxalate content, kale. Mg absorption was measured by a stable-isotope technique based on extrinsic labelling of the test meals and faecal monitoring of the excreted isotope labels. Nine healthy adults participated in the study. The test meals were based on 100 g phytate-free white bread, served with 300 g spinach (6.6 mmol oxalate; 0.7 mmol 25Mg label added, 5.0 mmol total Mg) or 300 g kale (0.1 mmol oxalate; 1.2 mmol 26Mg label added, 4.8 mmol total Mg). The test meals were served on days 1 and 3, at breakfast and lunch, using a cross-over design. The results from the present study demonstrated that apparent Mg absorption was significantly lower from the meal served with spinach (26.7 (SD 10.4) %) than the meal served with kale (36.5 (SD 11.8) %) (P=0.01). However, the lower fractional apparent Mg absorption from the test meal served with spinach can be assumed to be, at least partly, counterbalanced by the higher native Mg content of spinach as compared with kale. Although based on indirect evidence, i.e. not based on an evaluation of added (or removed) oxalic acid, the difference in Mg absorption observed in the present study is attributed to the difference in oxalic acid content between the two vegetables.

Original languageEnglish
Pages (from-to)601-606
Number of pages6
JournalBritish Journal of Nutrition
Issue number4
Publication statusPublished - 1 Apr 2004



  • Faecal monitoring
  • Magnesium absorption
  • Oxalate
  • Spinach
  • Stable isotopes

Cite this