An In Vivo (Gallus gallus) Feeding Trial Demonstrating the Enhanced Iron Bioavailability Properties of the Fast Cooking Manteca Yellow Bean (Phaseolus vulgaris L.)

Abstract

The common dry bean (Phaseolus vulgaris L.) is a globally produced pulse crop and an important source of micronutrients for millions of people across Latin America and Africa. Many of the preferred black and red seed types in these regions have seed coat polyphenols that inhibit the absorption of iron. Yellow beans are distinct from other market classes because they accumulate the antioxidant kaempferol 3-glucoside in their seed coats. Due to their fast cooking tendencies, yellow beans are often marketed at premium prices in the same geographical regions where dietary iron deficiency is a major health concern. Hence, this study compared the iron bioavailability of three faster cooking yellow beans with contrasting seed coat colors from Africa (Manteca, Amarillo, and Njano) to slower cooking white and red kidney commercial varieties. Iron status and iron bioavailability was assessed by the capacity of a bean based diet to generate and maintain total body hemoglobin iron (Hb-Fe) during a 6 week in vivo (Gallus gallus) feeding trial. Over the course of the experiment, animals fed yellow bean diets had significantly (p ≤ 0.05) higher Hb-Fe than animals fed the white or red kidney bean diet. This study shows that the Manteca yellow bean possess a rare combination of biochemical traits that result in faster cooking times and improved iron bioavailability. The Manteca yellow bean is worthy of germplasm enhancement to address iron deficiency in regions where beans are consumed as a dietary staple.

Keywords: Caco-2 cell bioassay; Gallus gallus; Phaseolus vulgaris L.; cooking time; iron; iron bioavailability; kaempferol 3-glucoside; phytate; polyphenols; yellow bean.

Figure 1

Photographs depicting the five genotypes used to evaluate the iron bioavailability of the African yellow bean. To compare differences in seed sizes, all photographs were taking to scale under standardized lighting conditions.

Figure 2

Cumulative feed intake (A), Fe intake (B), body weight (C), total body hemoglobin Fe (D), hemoglobin concentration (E) and hemoglobin maintenance efficiency (HME); (F) during the 6 weeks of consuming bean based diets. Values are means ± SEM (n = 10–13 animals per treatment group). * Significantly (p ≤ 0.05) lower values measured in the group receiving the Red Hawk diet. ** Significantly (p ≤ 0.05) higher cumulative Fe intakes and higher body weights measured in the groups receiving the Ervilha and PI527538 diets. *** Significantly (p ≤ 0.05) higher hemoglobin measured at day 42 in the group receiving the Uyole 98 diet versus the group receiving the PI527538 diet. Ψ Significantly (p ≤ 0.05) higher total body hemoglobin Fe and HME values measured in the group receiving the Ervilha diet versus the other four treatment groups.

Figure 3

Gene expression of iron proteins in the duodenum after 6 weeks of consuming bean based diets. Values are means ± SEM (n = 5 per treatment group). Means sharing the same letter in each column are not significantly different at p ≤ 0.05. DMT-1, Divalent Metal Transporter-1; DcytB, Duodenal cytochrome b.

Figure 4

Genera and species-level bacterial populations (AU) from cecal contents after 6 weeks of consuming bean based diets. Values are means ± SEM (n = 6 per treatment group). Means sharing the same letter in each column are not significantly different at p ≤ 0.05.