Use of soaking to enhance the bioavailability of iron and zinc from rice‐based complementary foods used in the Philippines

Abstract

Complementary foods used in the Philippines are predominantly rice-based, although enrichment with mung beans and sesame seeds is recommended despite their high content of phytic acid, a potent inhibitor of iron and zinc absorption. We have investigated the effect of soaking on the inositol penta-(IP5) and hexaphosphate (IP6) (analysed by HPLC), zinc, iron and calcium (via AAS) content of rice-based complementary foods with and without the addition of mung beans and sesame seeds. Soaking rice¯our for 1, 6 and 12 h at 30°C reduced the content of IP5 IP6 by 60, 65 and 98% respectively, with only slight changes in zinc, iron and calcium. Levels of IP5 IP6 were reduced by 10 and 47% by soaking mung bean¯our, but not whole beans, for 1 and 6 h respectively. In conclusion, soaking can be used to reduce the IP5 and IP6 content of complementary foods based on mung bean our and/or rice¯our and thus enhance the bioavailability of iron and zinc. INTRODUCTIONRice (Oryza sativa L) is the staple food of the Philippines and is consumed by all age groups. 1 Even complementary foods in the Philippines are predominantly rice-based, 2,3 although enriching them with mung beans and sesame seeds is recommended to enhance their energy and protein density. 4 Rice, mung beans and sesame seeds are known to contain phytic acid (myo-inositol hexaphosphate; IP6) and small amounts of inositol pentaphosphate (IP5). These higher inositol phosphates form insoluble complexes with zinc, iron and calcium at the physiologic pH of the gastrointestinal tract, thus reducing their bioavailability. 5±7 As well, for iron, even the lower inositol phosphates (eg IP4 and IP3) inhibit non-haem iron absorption to some degree. 8,9 The inhibitory effect of phytates on non-haem iron absorption is dose-dependent, 10 whereas for zinc it occurs when the phytate/zinc ([Phy]/[Zn]) molar ratio is 15 or above. 11 High levels of calcium potentiate the inhibitory effect of phytate on zinc absorption by forming a zinc± calcium±phytate complex that is even less soluble than the zinc±phytate complexes alone, further reducing the bioavailability of zinc. 12 Several methods have been advocated to reduce the IP5 and IP6 content of cereal-based complementary foods, thereby increasing the bioavailability of calcium, iron and zinc. These include milling, soaking, fermentation and germination of cereal grains. 13 Some

The concentrations of iron, calcium, zinc and phytate in cereals and legumes habitually consumed by infants living in East Lombok, Indonesia

“…to o10) after boiling white rice are noteworthy because of the beneficial effects on mineral absorption. They are consistent with the findings of others (Hurrell et al, 2002(Hurrell et al, , 2003Perlas and Gibson, 2002). In contrast, as noted earlier (Perlas and Gibson, 2002), the inclusion of mung bean flour in the infant porridges dramatically increased the phytate: mineral molar ratios.…”

“…They are consistent with the findings of others (Hurrell et al, 2002(Hurrell et al, , 2003Perlas and Gibson, 2002). In contrast, as noted earlier (Perlas and Gibson, 2002), the inclusion of mung bean flour in the infant porridges dramatically increased the phytate: mineral molar ratios. Hence, when making foodbased recommendations, the nutritional benefits of using mung bean flour in this way would need to be weighed against the potential detrimental effects of the high dietary phytate levels.…”

Iron Dialyzability from Hospital Duplicate Meals: Daily Intake

“…Despite this, several researchers have reported the negative influence of the phytic acid content of food and meals on iron dialyzability (1,(7)(8)12,18,20,23,29,(30)(31)(32).…”

Reduction of phytic acid and enhancement of bioavailable micronutrients in food grains

“…Together soaking and cooking has shown much more effective to reduce phytic acid than only soaking for a short duration (Vidal-Valverde et al 1994). In case of grains and beans soaking to be quite effective for reduction of phytic acid as well as consequent increase in mineral bioavailability (Perlas and Gibson 2002;Coulibaly et al 2011). This method involves the complete submergence of grains in water for certain amount of time period which results in the activation of endogenous phytases.…”