Factors influencing micronutrient bioavailability in biofortified crops : Biofortified crops: micronutrient bioavailability

Vitamin A deficiency (VAD) persists in Uganda and the consumption of β-carotene-rich orange sweet potato (OSP) may help to alleviate it. Two large-scale, 2-y intervention programs were implemented among Ugandan farmer households to promote the production and consumption of OSP. The programs differed in their inputs during year 2, with one being more intensive (IP) and the other being reduced (RP). A randomized, controlled effectiveness study compared the impact of the IP and RP with a control on OSP and vitamin A intakes among children aged 6-35 mo (n = 265) and 3-5 y (n = 578), and women (n = 573), and IP compared with control on vitamin A status of 3- to 5-y-old children (n = 891) and women (n = 939) with serum retinol 30 percentage points) and women (>25 percentage points) (P < 0.01), with no differences between the IP and RP groups of children (P = 0.75) or women (P = 0.17). There was a 9.5 percentage point reduction in prevalence of serum retinol <1.05 μmol/L for children with complete data on confounding factors (n = 396; P < 0.05). At follow-up, vitamin A intake from OSP was positively associated with vitamin A status (P < 0.05). Introduction of OSP to Ugandan farming households increased vitamin A intakes among children and women and was associated with improved vitamin A status among children.

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).