Iron bioavailability from common beans is negatively influenced by phytic acid (PA) and polyphenols (PPs). Newly developed low-PA (lpa) beans with 90% less PA and variable PPs might improve iron bioavailability. The aim of this study was to evaluate the influence of lpa beans on iron bioavailability in women (n = 20). We compared iron absorption from 4 different beans using a paired, double meal, crossover design. Iron absorption was measured as erythrocyte incorporation of stable iron isotopes (Fe(57), Fe(58)) from 2 lpa bean lines, one high in PPs (means ± SDs; PA = 124 ± 10 mg/100 g; PPs = 462 ± 25 mg/100 g) and one low in PPs (PA = 70 ± 10 mg/100 g; PPs = 54 ± 2 mg/100 g). The other 2 beans used were their parents with a normal PA concentration, one high in PPs (PA = 1030 ± 30 mg/100 g; PPs = 676 ± 19 mg/100 g) and one low in PPs (PA = 1360 ± 10 mg/100 g; PPs = 58 ± 1 mg/100 g). Fractional iron absorption from the lpa bean high in PPs was 6.1% (95% CI: 2.6, 14.7), which was 60 and 130% higher compared with the parent high in PPs (P < 0.001) and low in PPs (P < 0.001), respectively. The total amount of iron absorbed per test meal from the lpa bean high in PPs (372 μg; 95% CI: 160, 890) was 60 and 163% higher compared with the parent high in PPs (P < 0.001) and low in PPs (P < 0.001), respectively. Fractional iron absorption from the lpa line low in PPs (4%; 95% CI: 1.8, 8.7) was 50% higher and the total amount of iron absorbed per test meal (261 μg; 95% CI: 120, 570) was 85% higher than iron from the parent low in PPs (P < 0.001). There was no difference between the lpa beans high or low in PPs or between the parents high or low in PPs. A 90% reduction in PA leads to an increase in bioavailable iron from beans, independent of the PP concentration. The lpa mutation could be a key tool for improving iron bioavailability from beans.
Trial registration: ClinicalTrials.gov NCT01472484.