Iron and Zinc Absorption from Two Bean (Phaseolus vulgaris L.) Genotypes in Young Women

Abstract

Extrinsic and intrinsic iron and zinc labels were used to test iron and zinc absorption from two bean (Phaseolus vulgaris) genotypes, containing normal (common beans, CB) or higher (HFeZnB) iron and zinc concentrations, fed in single meals to young women with low iron reserves. The women were divided into two groups, with one receiving a CB test meal (n = 12) and the other, an HFeZnB test meal (n = 11). The beans were intrinsically labeled hydroponically with (55)Fe (CB and HFeZnB) and with (70)Zn (HFeZnB). Concentrations of zinc and iron were 98 and 65% higher, respectively, in HFeZnB as compared to CB, but phytic acid contents were similar. Extrinsic labels were (59)Fe (CB and HFeZnB), (67)Zn (CB), and (68)Zn (HFeZnB). Iron and zinc percent absorption levels were calculated from radio-iron activity in red blood cells and from urinary excretion of zinc isotopes. Intrinsic and extrinsic iron absorption measures were highly correlated (R (2) = 0.986) (average extrinsic/intrinsic ratio was 1.00). Iron absorption was low (geometric mean < 2%) in both bean types, and total iron absorbed was not different between types. Intrinsic zinc absorption from the HFeZn beans was higher than extrinsic absorption (15.2% vs 13.4%, p < 0.05) (average extrinsic/intrinsic was 0.90). The correlation between intrinsic and extrinsic zinc measures was not as high as that for iron (R (2) = 0.719). Percent zinc absorption levels were similar in both bean types, but total extrinsic zinc absorbed was 90% higher (p < 0.05) from the HFeZnB meal. Thus, the less expensive and time-consuming extrinsic labeling may be used to screen various varieties of beans for iron bioavailability in humans, but it underestimates zinc absorption by approximately 10%. Selective breeding for high-zinc bean genotypes may improve zinc status. However, high-iron genotypes appear to have little effect on iron status when fed alone in single meals to women with low iron reserves.

Comparison of color, anti-nutritional factors, minerals, phenolic profile and protein digestibility between hard-to-cook and easy-to-cook grains from different kidney bean (Phaseolus vulgaris) accessions

“…Among HTC grains, TPC was negatively correlated to Zn. Earlier, it has been reported that Fe and Zn bio-availability was negatively affected by the presence of PCs in Phaseolus v. (Donangelo et al 2003). Bean grains were considered to be the best inexpensive source of minerals but their bioavailability was reported to constrain by the presence of anti-nutritional constituents like phytic acid and PCs (Nyombaire et al 2007).…”

Biofortified Crops Can Alleviate Micronutrient Deficiencies: Review of Evidence from Randomized Feeding Trials

“…In the studies on iron biofortified crops the biochemical tests that were done to test improvement in the iron status were: Inflammation (measured by C-reactive protein and α-1-acid glycoprotein concentrations) [14,15], total body iron [13][14][15][16][17][18]21,22], haemoglobin concentration [16], serum ferritin concentration [13][14][15][16][17], acute phase proteins [18] and serum transferrin receptor concentration [19]. The baseline cut-offs for each of the parameter differed among the studies (Table 2).…”

“…The biofortified crops that were used in the studies were; Vitamin A (Orange) maize [25,26,29], vitamin A (yellow) cassava [24], Vitamin A (Orange) sweet potatoes [23,27,28], high iron beans [13,15,16,19,22], iron pearl millet [14,18,21], Zinc wheat [32], High iron rice [17], high zinc maize [31], High zinc millet [21] and high zinc beans [22].…”

“…Furthermore study [20] showed that the amount of iron absorbed from the diet of the children aged 2 years is more than adequate to meet the physiological requirements of these children for iron needs. Study [22] reported that the total iron absorbed from the test meal of high iron/ high zinc beam varieties (HFEZnB) was very low (0.03-0.04 mg).…”

“…Studies [21,22,31,32] showed that intake of staple food biofortified with zinc increases the amount of zinc absorbed in the diets of the subjects, which could translate to improved zinc status in the zinc deficient populations.…”