Review: The potential of the common bean (Phaseolus vulgaris) as a vehicle for iron biofortification

Abstract

Common beans are a staple food and the major source of iron for populations in Eastern Africa and Latin America. Bean iron concentration is high and can be further increased by biofortification. A major constraint to bean iron biofortification is low iron absorption, attributed to inhibitory compounds such as phytic acid (PA) and polyphenol(s) (PP). We have evaluated the usefulness of the common bean as a vehicle for iron biofortification. High iron concentrations and wide genetic variability have enabled plant breeders to develop high iron bean varieties (up to 10 mg/100 g). PA concentrations in beans are high and tend to increase with iron biofortification. Short-term human isotope studies indicate that iron absorption from beans is low, PA is the major inhibitor, and bean PP play a minor role. Multiple composite meal studies indicate that decreasing the PA level in the biofortified varieties substantially increases iron absorption. Fractional iron absorption from composite meals was 4%-7% in iron deficient women; thus the consumption of 100 g biofortified beans/day would provide about 30%-50% of their daily iron requirement. Beans are a good vehicle for iron biofortification, and regular high consumption would be expected to help combat iron deficiency (ID).

Figure 1

Scatterplot (including regression lines) showing the correlation between total iron content of 21 common bean genotypes versus their ferritin-bound iron (◊) and non-ferritin-bound iron (□) fractions [53].

Figure 2

The predominant PP units in beans that occur mostly in various polymeric forms.

Figure 3

3. Correlation between non-ferritin-bound iron in ppm and PA in g/100 g bean [53].

Figure 4

Fractional iron absorption and total amount of iron absorbed from a biofortified and a control bean with natural PA level, after partial and almost total dephytinization [38].