BIOFORTIFIED COWPEA (Vigna unguiculata L. Walph) INCREASES IRON BIOACCESSIBILITY IN CACO-2 CELLS AND LOWERS THE GLYCEMIC INDEX

Vol 2, 2022 - 153696
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Abstract

Cowpea (Vigna unguiculata L. Walph) is a common food consumed mainly in the North and Northeast regions of Brazil. Cowpea is a source of protein, carbohydrate, bioactive compounds, and dietary fibers, which can modulate blood glucose. In addition, iron biofortified cowpeas may be an alternative strategy to reduce iron deficiency anemia. The present study aimed to determine the iron bioaccessibility in Caco-2 cells and the glycemic index of biofortified and conventional cowpeas. The biofortified cowpeas BRS Aracê, BRS Tumucumaque and BRS Xiquexique and the conventional Pajeu were cooked in pressure pan with water (1:2, w:v), freeze-dried, and ground to produce flours. Then, the Caco-2 cells, on the 13th day, after complete differentiation, were kept in iron-free medium for 24h, and received, for another 24h, solutions of the test cowpeas (1mg/ml). The cells were harvested and the ratio of ferritin/total protein was used as indicative of iron bioaccessibility. Assays were performed in three replicates. To determine the glycemic index, eleven healthy volunteers consumed each cowpea and three doses of the control glucose solution, in amounts to provide 25 g of available carbohydrates, on different non-consecutive days. Post-prandial glucose response was obtained over 120 minutes, from capillary glycemia. The data were analyzed by ANOVA and post-hoc of Tukey (p<0.05). The study was approved by Research Ethics Committee of UFES (# 5.181.338). It was observed that the beans presented high amounts of fiber (between 22.7 ± 1.3 g/100g and 36.1 ± 1.1 g/100g), with insoluble fibers being predominant. The phytate content was similar (p>0.05) between BRS Pajeu (0.97 ± 0.02 g/100g) and BRS Xiquexique (0.97 ± 0.02 g/100g) that had higher values (p<0.05) than BRS Tumucumaque (0.89 ± 0.01 g/100g) and BRS Aracê (0.66 ± 0.02 g/100g). The iron content was higher in the BRS Xiquexique cultivar (60.8 ppm), however, BRS Aracê and BRS Tumucumaque were the varieties with the best iron bioaccessibility in Caco-2 cells (p<0.05), which may be associated with the lower phytate/iron ratio observed in these varieties. As for the glycemic index, every cowpeas had lower incremental area under the glycemic curve (iAUC) then glucose. The conventional BRS Pajeu (1520 ± 331.6 mg/dl x min) had similar iAUC value then BRS Xiquexique (1215 ± 382.9 mg/dl x min), however was greater than BRS Tumucumaque (1090 ± 333.9 mg/dl x min) and BRS Aracê (612.7 ± 318.1 mg/dl x min). Then, the glycemic index of BRS Aracê (25.89) was the lowest value between the cowpeas, followed by BRS Tumucumaque (46.05), BRS Xiquexique (51.33), and the conventional cowpea BRS Pajeu (64.22). The high fiber of beans may explain these results, since dietary fibers delay the absorption of sugars, improving glycemic control. Furthermore, the best results of biofortified cowpeas demonstrates the ability of iron to control de insulin release. In addition, this study demonstrates the nutritional richness of cowpea, which presents itself as a low glycemic index food with health-promoting properties. In this way, biofortified beans are presented as alternatives to control the glycemic index and improve the bioaccessibility of iron.

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Institutions
  • 1 Federal University of Viçosa
  • 2 Universidade Federal do Espírito Santo, Brazil
Track
  • Food and health (AS)
Keywords
Glycemia
biofortification
Iron
in vitro