Extrinsic Labeling of Staple Food Crops with Isotopic Iron Does Not Consistently Result in Full Equilibration: Revisiting the Methodology
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- 作者：Raymond P. Glahn ; Zhiqiang Cheng ; Shree Giri
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2015
- 出版时间：November 4, 2015
- 年：2015
- 卷：63
- 期：43
- 页码：9621-9628
- 全文大小：395K
- ISSN：1520-5118
文摘
Extrinsic isotopic labeling of food Fe has been used for over 50 years to measure Fe absorption. This method assumes that complete equilibration occurs between the extrinsic and the intrinsic Fe prior to intestinal absorption. The present study tested this assumption via in vitro digestion of varieties of maize, white beans, black beans, red beans, and lentils. Prior to digestion, foods were extrinsically labeled with 58Fe at concentrations of 1, 10, 50, and 100% of the intrinsic 56Fe. Following an established in vitro digestion protocol, the digest was centrifuged and the Fe solubilities of the extrinsic 58Fe and the intrinsic 56Fe were compared as a measure of extrinsic/intrinsic equilibration. In the beans, significantly more of the extrinsic Fe (up to 2鈥? times, p < 0.001) partitioned into the supernatant. The effect varied depending upon the seed coat color, the harvest, and the concentration of the extrinsic Fe. For lentils and maize the extrinsic Fe tended to partition into the insoluble fraction and also varied depending on variety and harvest. There was no crop that consistently demonstrated full equilibration of the extrinsic Fe with the intrinsic Fe. These observations challenge the accuracy of Fe absorption studies in which isotopic extrinsic Fe was used to evaluate Fe absorption and bioavailability.