Influence of a low- and a high-oxalate vegetarian diet on intestinal oxalate absorption and urinary excretion

Eur J Clin Nutr. 2008 Sep;62(9):1090-7. doi: 10.1038/sj.ejcn.1602832. Epub 2007 Jul 4.


Objective: To compare quantitatively the effect of a low- and a high-oxalate vegetarian diet on intestinal oxalate absorption and urinary excretion.

Subjects and methods: Eight healthy volunteers (three men and five women, mean age 28.6+/-6.3) were studied. Each volunteer performed the [(13)C(2)]oxalate absorption test thrice on a low-oxalate mixed diet, thrice on a low-oxalate vegetarian diet and thrice on a high-oxalate vegetarian diet. For each test, the volunteers had to adhere to an identical diet and collect their 24-h urines. In the morning of the second day, a capsule containing [(13)C(2)]oxalate was ingested.

Results: On the low-oxalate vegetarian diet, mean intestinal oxalate absorption and urinary oxalate excretion increased significantly to 15.8+/-2.9% (P=0.012) and 0.414+/-0.126 mmol/day (P=0.012), compared to the mixed diet. On the high-oxalate vegetarian diet, oxalate absorption (12.5+/-4.6%, P=0.161) and urinary excretion (0.340+/-0.077 mmol/day, P=0.093) did not change significantly, compared to the mixed diet.

Conclusions: A vegetarian diet can only be recommended for calcium oxalate stone patients, if the diet (1) contains the recommended amounts of divalent cations such as calcium and its timing of ingestion to a meal rich in oxalate is considered and (2) excludes foodstuffs with a high content of nutritional factors, such as phytic acid, which are able to chelate calcium.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Calcium Oxalate / administration & dosage
  • Calcium Oxalate / metabolism
  • Carbon Radioisotopes
  • Diet, Vegetarian*
  • Female
  • Humans
  • Intestinal Absorption / drug effects*
  • Male
  • Middle Aged
  • Oxalates / metabolism
  • Oxalates / pharmacology*
  • Oxalates / urine
  • Young Adult


  • Carbon Radioisotopes
  • Oxalates
  • Calcium Oxalate