Absorbability of calcium from common beans
1993
Weaver, C.M. | Heaney, R.P. | Proulx, W.R. | Hinders, S.M. | Packard, P.T.
Absorption of calcium from white, red, and pinto beans, labeled with 45Ca, was measured in 24 women in a three-way randomized design using a calcium load of 72 mg and milk as the referent. Fractional absorption for the three beans averaged 0.219 +/- 0.047 and did not differ by type. Milk calcium absorption at the same load was more than two times higher, 0.451 +/- 0.088 (P < 0.001). Oxalate content averaged 0.34%, and phytate averaged 1.7%, a stoichiometric excess relative to calcium. To evaluate the relation of phytate to reduced absorbability, labeled pinto beans were pre-treated with phytase and fed to 10 subjects. Fractional absorption rose, averaging 0.318 +/- 0.071, (P < 0.01 vs. untreated beans), but was significantly below that of milk. The difference was partly accounted for by phytate, with the remainder probably due to relatively high oxalate.
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