Heaney R P, Weaver C M, Recker R R
Department of Medicine, Creighton University, Omaha, NE 68178.
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.
在一项随机交叉设计中，对13名健康成年人进行了研究，比较了菠菜中钙的吸收能力与牛奶中钙的吸收能力。在该设计中，牛奶或菠菜的测试餐均含有200毫克用45Ca标记的钙。采用标准双同位素方法测量吸收情况，其中测试食物和可混溶钙池均用不同的钙示踪剂进行标记。对我们测试的菠菜中的钙和草酸盐进行测量后发现，草酸盐在化学计量上略有过量；因此，菠菜中的所有钙很可能都被有效结合了。在每种情况下，牛奶中钙的吸收都更高，牛奶中钙的平均吸收率为27.6%，菠菜中为5.1%。牛奶和菠菜中钙吸收的受试者内平均差异为22.5 +/- 9.5%（P小于0.0001）。这些结果确凿地表明，菠菜中的钙比牛奶中的钙更难被吸收利用。
