Iron and Zinc bioavailabilities to pigs from red and white beans (Phaseolus vulgaris L.) are similar

Common beans contain relatively high concentrations of iron (Fe) and zinc (Zn) but are also high in polyphenols and phytates, factors that may inhibit Fe and Zn availability and absorption. In vitro (Caco-2 cells) and in vivo (pigs) models were used to compare Fe and Zn bioavailability between red and white beans, which differ in polyphenol content. Bean/maize diets containing 37% of either white or red cooked beans were formulated. Fe uptake by Caco-2 cells was 14-fold higher from the white bean diet compared to the red bean diet. The diets were fed to anaemic piglets (n = 10) for 35 days. On experiment days 7 and 21, pigs were given meals containing beans intrinsically labelled with stable isotopes of Fe and Zn (58 Fe, 70 Zn), followed by intravenous injections of 54Fe and 67Zn, to assess Fe and Zn absorption. Isotope ratios determined by inductively coupled plasma mass spectrometry in whole blood and plasma samples were used to calculate iron and zinc absorption, respectively. On day 35, animals were killed and duodenal sections were collected for divalent metal transporter 1DMT1 gene expression analysis.

Fe absorption was 14 and 16% from the first labelled meal and 9 and 10.5% from the second labelled meal for the white and red beans, respectively (P > 0.05). Zn absorption was 28 and 23% from the first meal (P > 0.05) and 31 and 29% from the second meal (P > 0.05) for the white and red beans, respectively. DMT1 gene expression did not differ between treatments.
It was concluded that bean colour does not affect Fe or Zn bioavailability in vivo and that beans are a good source of bioavailable Fe and Zn.