IRON (FE) BIOAVAILABILITY AND THE DISTRIBUTION OF ANTI-FE NUTRITION BIOCHEMICALS IN THE UNPOLISHED, POLISHED GRAIN AND BRAN FRACTION OF FIVE RICE GENOTYPES

Authors: PROM-U-THAI, CHANAKAN - UNIV. OF QUEENSLAND; Glahn, Raymond; Welch, Ross; HUANG, LONGBIN - UNIV. OF QUEENSLAND; RERKASEM, BENJAVAN - CHIANG MAI UNIV.

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2006
Publication Date: 8/1/2006
Citation: Prom-U-Thai, C., Glahn, R.P., Welch, R.M., Huang, L., Rerkasem, B. 2006. Iron (fe) bioavailability and the distribution of anti-fe nutrition biochemicals in the unpolished, polished grain and bran fraction of five rice genotypes. Journal of the Science of Food and Agriculture. 86(8):1209-1215.

Interpretive Summary: Iron (Fe) bioavailability in white and brown rice from five different varieties with high and low-Fe content was measured by a simulated digestion/cell culture model. Significant differences in iron bioavailability were observed among the white and brown varieties. Milling and polishing the grain to produce polished white rice, the form preferred for most of people who consume rice as the staple food increased Fe bioavailability in all genotypes. Iron bioavailability in polished rice was high in the UBON2 and Nishiki, low in CMU122, and moderate in both IR68144 and KDML105 varieties. All genotypes had low bioavailability of Fe in bran fraction (i.e. the part removed by polishing) compared to bioavailability in unpolished and polished grain, except in CMU122. The unpolished dark purple colored grain of CMU122 contained the lowest amount of bioavailable Fe in unpolished, polished grain including bran. Bioavailable Fe was not significantly correlated with grain-Fe concentration or grain-phytate levels. Bioavailability of Fe in unpolished, polished grain and bran fraction of rice was found to be inhibited by total extractable phenol (r=0.72**) as well as tannin content. The results suggest that there are variations of bioavailability of Fe in unpolished, polished grain and bran fraction of all genotypes and Fe in polished rice is more available for absorption, because most inhibitors of iron absorption are removed during the polishing process.

Technical Abstract: Iron (Fe) bioavailability in unpolished, polished grain and bran fraction of rice from five different genotypes with high and low-Fe content was measured by in vitro digestion and cultured Caco-2 cells of cooked grain. There was a significant difference in Fe bioavailability among the unpolished and polished grain as well as bran fraction of the five rice genotypes. Unpolished grain of CMU122 contained about one-third the bioavailable Fe of the other four genotypes. Milling and polishing the grain to produce polished rice, the form preferred for most of people who consume rice as the staple food increased Fe bioavailability in all genotypes. Iron bioavailability in polished rice was high in the UBON2 and Nishiki, low in CMU122, and moderate in both IR68144 and KDML105. All genotypes had low bioavailability of Fe in bran fraction compared to bioavailability in unpolished and polished grain, except in CMU122. The unpolished dark purple colored grain of CMU122 contained the lowest amount of bioavailable Fe in unpolished, polished grain including bran. Bioavailable Fe was not significantly correlated with grain-Fe concentration (r=0.58ns) or grain-phytate levels (r=0.42ns). Bioavailability of Fe in unpolished, polished grain and bran fraction of rice was found to be inhibited by total extractable phenol (r=0.72**) as well as tannin content. The results suggest that there are variations of bioavailability of Fe in unpolished, polished grain and bran fraction of all genotypes and Fe in polished rice is more available for absorption, because most inhibitors are removed during the polishing process.