Calcium absorbability from spinach

Am J Clin Nutr. 1988 Apr;47(4):707-9. doi: 10.1093/ajcn/47.4.707.


The absorbability of calcium from spinach was compared with the absorbability of Ca from milk in 13 healthy adults in a randomized cross-over design in which the test meal of either milk or spinach had 200 mg of Ca labeled with 45Ca. Absorption was measured by the standard double-isotope method in which both the test food and the miscible Ca pool are labeled with different Ca tracers. Measurement of both Ca and oxalate in our test spinach revealed a very slight stoichiometric excess of oxalate; hence it is likely that all of the spinach Ca was effectively bound. Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%. The mean within-subject difference between Ca absorption from milk and from spinach was 22.5 +/- 9.5% (P less than 0.0001). These results conclusively establish that spinach Ca is much less readily available than milk Ca.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Animals
  • Biological Availability
  • Calcium / metabolism*
  • Cattle
  • Female
  • Humans
  • Intestinal Absorption*
  • Male
  • Milk / analysis
  • Random Allocation
  • Reference Values
  • Vegetables*


  • Calcium