Calcium absorbability from spinach.
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.
Heaney
R P
RP
Department of Medicine, Creighton University, Omaha, NE 68178.
Weaver
C M
CM
Recker
R R
RR
D000328:Adult; D000818:Animals; D001682:Biological Availability; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D005260:Female; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008892:Milk / Q000032:analysis; D011897:Random Allocation; D012016:Reference Values; D014675:Vegetables
D002118:Calcium