Bioavailability of iron and zinc as affected by phytic acid content in rice grain

Abstract

Phytic acid (PA) is considered as an anti‐nutritional factor (ANF) present in cereals and legumes and bind to cationic minerals including iron (Fe) and zinc (Zn), thus reducing their bioavailability in both ruminants and nonruminants. The present study was aimed at finding the impact of PA on bioavailability of Fe and Zn. Six rice cultivars with contrasting PA were evaluated for total phosphorus (P), PA, Fe, and Zn in brown and processed rice. A significant correlation of PA of brown rice with PA of milled rice (r = .69) was observed. PA and Zn content were negatively correlated (r = −.55) in brown rice while no significant correlation was found between PA and Zn in milled rice. The rice cultivar Bindli, with lowest PA (0.82 g/100 g) was found to exhibit high Zn bioavailability, while PB267, with highest PA (2.62 g/100 g) showed low Zn and Fe bioavailability. Practical applications Rice is staple food for millions of people, especially the Asians. Fe and Zn are essential micronutrients required for human growth and development, but the rice grain is deficient in Fe and has only moderate amounts of Zn. The bioavailability of these minerals are impaired by PA which chelates and bind cationic minerals in both ruminants and nonruminants. Screening of rice genotypes with low PA and high minerals bioavailability may be suitable for people suffering from micronutrient malnutrition.

Phytic acid content may affect starch digestibility and glycemic index value of rice (Oryza sativa L.)

“…However, the pattern of gene expression was varied in these cultivars. IPK1 expression was reported to be higher in the mid‐stage (7 DAA) of grain development in three rice cultivars with contrasting PA content …”

“…Further, the PA–mineral complexes are not easily digested by monogastrics (including humans) due to the absence of endogenous phytase enzymes which reduces their bioavailability . In colored rice, phenolics and tannins are present in high amounts compared to white rice which may also play an important role in chelating a high proportion of Fe and Zn in the grain …”

“…Fe and Zn bioavailability was estimated using the in vitro method reported by Kumar et al . Rice samples (5 g) were suspended in a beaker with 30 mL of DW and placed in a water bath shaker for 16 h. Next day, 2 mL of α ‐amylase (6.25 g L −1 ) was added to the sample and incubated for 30 min at room temperature.…”

Retention of Zn, Fe and phytic acid in parboiled biofortified and non-biofortified rice

“…Rice also contains phytic acid (PA) which is a chelator of divalent minerals such as Zn and Fe and limit their absorption ( Kumar et al, 2017 ). Given the impact of PA on Zn and Fe absorption, the ratio between PA and Zn and Fe is commonly used to better understand how well the mineral could be absorbed in the body ( Hambidge et al, 2008 , Al Hasan et al, 2016 ).…”

Seed targeted RNAi-mediated silencing of GmMIPS1 limits phytate accumulation and improves mineral bioavailability in soybean

“…ZIPS, IRT, YSL, etc., and the mineral content of harvested seeds impact food and feed quality. Most of these divalent cations are chelated by PA, which reduces the mineral bioavailability in non-ruminants 44,45 , probably due to lack of phytase enzyme in them 26 . In view of these assumptions, we analyzed the bioavailability of Fe/Ca/Zn using an in vivo mimicking model 33 and observed a significant increase in the minerals bioavailability in MS14-28-12-29-3-5 and MI51-32-22-1-13-6 lines compared with NT control.…”