Vegetable relishes,high in β-carotene,increase the iron,zinc and β-carotene nutritive values from cereal porridges

Iron, zinc and vitamin A deficiencies are serious public health problems in sub-Saharan Africa, which can be alleviated by dietary diversification. The effects of adding cowpea leaf (CL) and orange-fleshed sweet potato (OFSP) relishes to sorghum and maize porridges on iron, zinc and β-carotene contents and bioaccessibilities were determined. Despite the high iron content of the CL relish (14.59?mg/100?g), the vegetable relishes had little effect on the iron bioaccessibility from the cereal porridges. Importantly, the addition of the CL relish increased the percentage and amount of bioaccessible zinc 2- and 3-fold, respectively. Addition of CL and OFSP relishes resulted in β-carotene contents of 10–13?mg/100?g. The β-carotene from the OFSP relish meals was double as bioaccessible than that from the CL relish meals. Addition of the vegetable relishes has real potential to improve especially the vitamin A and zinc nutritive value of cereal diets.     

Dimensions of Sandawe diet

Rural African children consuming plant‐based diets low in animal products are at risk for sub‐optimal zinc nutriture. Consequently, we investigated indigenous dietary strategies for inproving the zinc nutriture of rural southern Malawian and Ghanaian children.

Seasonal dietary intakes, and the portion sizes of foods consumed by 4–6 year old Malawian and Ghanaian girls (n = 112) were determined from 3‐day weighed food records. The optimal combination of food items for enhancing zinc bioavailability was determined by comparing the zinc content, and the phytate‐to‐zinc molar ratio (PZ) of isocaloric meals and snacks consumed by these girls. The energy content and portion sizes of the recommended meals and snacks were based on actual average intakes.

Results showed that in Malawi the amount of available zinc could be enhanced by using refined corn flour nsima or a non‐traditional fermented corn dough nsima with relishes prepared from small fish, and snacks with moderate to low PZ. In Ghana, fermented corn dough banku, or cocoyam, for root‐based meals, together with a soup/stew of small fish, and zinc‐dense snacks were recommended.     

Chemical and Toxicological Evaluation of Extracts of Fermented Red Acalypha (A Calypha Wilkes/A Na) : A Suggested Tea Adjunct

This study aimed to develop and assess the feasibility of a home-based method to reduce the phytate content of maize and improve zinc bioavailability from maizebased complementary diets in rural Malawi. A method of extracting phytate through the soaking of pounded maize was developed, and found to reduce phytate content to 49% of unrefined maize. An educational program was used to teach the processing method to mothers of children receiving complementary foods in rural Malawian communities. Samples of maize flour prepared by this process by participants were collected and analysed for phytate and zinc content. Of these, 70% of samples were found to be adequately prepared; mean phytate content of these samples was 48% of unprocessed, unrefined maize flour controls. Most participants found the cooked product to have an acceptable taste (99%) and texture (68%), and felt the processing method took little or no extra time (86%) and was culturally acceptable (96%). The phytate and zinc content of the processed maize flour samples analysed from community prepared samples was substituted into the dietary analysis of complementary foods for 9- to 11-month-old children (n = 31). The bioavailability of zinc from the complementary diet would predict an increase from low (24%) to moderate (33%) levels.     

A home-based method to reduce phytate content and increase zinc bioavailability in maize-based complementary diets

This study aimed to develop and assess the feasibility of a home-based method to reduce the phytate content of maize and improve zinc bioavailability from maize-based complementary diets in rural Malawi. A method of extracting phytate through the soaking of pounded maize was developed, and found to reduce phytate content to 49% of unrefined maize. An educational program was used to teach the processing method to mothers of children receiving complementary foods in rural Malawian communities. Samples of maize flour prepared by this process by participants were collected and analysed for phytate and zinc content. Of these, 70% of samples were found to be adequately prepared; mean phytate content of these samples was 48% of unprocessed, unrefined maize flour controls. Most participants found the cooked product to have an acceptable taste (99%) and texture (68%), and felt the processing method took little or no extra time (86%) and was culturally acceptable (96%). The phytate and zinc content of the processed maize flour samples analysed from community prepared samples was substituted into the dietary analysis of complementary foods for 9- to 11-month-old children (n = 31). The bioavailability of zinc from the complementary diet would predict an increase from low (24%) to moderate (33%) levels.     

Content of zinc, iron, calcium and their absorption inhibitors in foods commonly consumed in Ethiopia

The zinc, iron, calcium, phosphorus, phytate, tannin and moisture content of 36 foods consumed in rural Ethiopia were analysed. The foods analysed included those based on cereals, starchy tubers and roots, and legumes and vegetables as well as some fruits. Although many foods were relatively rich in zinc and iron, many also contained high levels of phytic acid and tannins, which impair bioavailability of zinc and iron. The phytate:zinc molar ratios were >20 for non-fermented cereal foods, >15 for legumes, and <12 for fermented cereals, starchy tubers and roots. Ratios >15 are associated with low bioavailability of zinc. Given the high iron content and the relatively favourable phytate:iron molar ratio, tef enjera was the best source of bioavailable iron of all foods analysed. Foods prepared from tef, enset and kale are rich sources of calcium. The consumption of diets based on cereals and legumes but poor in animal products can lead to deficiencies of zinc and iron. However, since fermentation can decrease the phytate content by a factor of 3–4, traditional household practices such as fermentation need to be encouraged to address the problem of zinc deficiency, which is particularly prevalent in Ethiopia.     

Phytate, zinc, and calcium contents of 30 East African foods and their calculated phytate:Zn, Ca:phytate, and [Ca][phytate]/[Zn] molar ratios

Representative samples of 30 staple Malawian foods, raw and prepared “as eaten,” were analyzed for phytate using an anion-exchange method, and for calcium and zinc by flame atomic absorption spectrophotometry. Phytic acid contents expressed on a fresh weight (FW) basis ranged from 211–1089 mg/100 g for cereals and 166–1297 mg/100 g for legumes, to 4–97 mg/100 g for leaves, 10–59 mg/100 g for roots, and 11–25 mg/100 g for fruits. In general, leaves had the highest calcium content (81–514 mg/100 g FW), followed by kidney beans (90 mg/100 g FW), and dry pigeon peas (112 mg/100 g FW). The calcium content of other foods analyzed was relatively low. The zinc content of wild blight, cassava leaves, and okra leaves was comparable to that for the less refined cereals and legumes (i.e., > 1.0 mg/100 g FW), but higher than that of highly refined cereals, pumpkin leaves, chinese cabbage, and other foods analysed (i.e., < 1.0 mg/100 g FW). Cooking had no effect on the phytate content of cereals, but milling and fermentation reduced both the phytate and zinc contents of maize flour. The phytate:Zn molar ratios calculated for all cereals and most legumes analyzed were greater than 20:1. Corresponding Ca:phytate molar ratios were low. Fruits, except for mangoes, vegetables, and roots, had low phytate: Zn molar ratios, but their Ca:phytate and [Ca][phytate]/[Zn] molar ratios were high. Mangoes had high phytate:Zn, Ca:phytate, and [Ca][phytate]/[Zn] molar ratios. These analytical results suggest that the bioavailability of zinc in the Malawian diet is probably low, due to the high phytic acid content of the staple foods.     

Iron bioavailability and utilization in rats are lower from lime-treated corn flour than from wheat flour when they are fortified with different sources of iron

Although iron bioavailability from wheat flour fortified with iron has been widely studied, the bioavailability of lime-treated corn flour has not been evaluated sufficiently. We compared iron bioavailability and utilization of lime-treated corn flour and wheat flour supplemented with various iron sources. Bioavailability and utilization were determined in Sprague-Dawley rats using the iron balance and hemoglobin depletion-repletion methods. Rats were iron depleted by feeding them a low iron, casein diet for 10 d. During the repletion period, the rats were fed diets based on lime-treated corn flour or wheat flour, both supplemented with ferrous fumarate, ferrous sulfate, ferric citrate and reduced iron for 14 d. Hemoglobin was determined at the end of depletion and repletion periods. The phytate concentration was lower in wheat flour (114 mg/100g) than in lime-treated corn flour (501 mg/100g). Iron bioavailability and utilization by rats were higher from fortified and unfortified wheat flour than from the lime-treated corn flour counterparts. Iron utilization was greater in rats fed wheat flour supplemented with ferrous sulfate, followed by fumarate and citrate than in rats fed reduced iron. In lime-treated corn flour, iron utilization by rats fed unfortified flour and flour fortified with reduced iron did not differ, but utilization was higher in rats fed corn flour fortified with iron sulfate, fumarate and citrate than with reduced iron. We conclude that fortification of lime-treated corn flour with reduced iron has no effect on iron bioavailability or utilization, probably due to the high phytate content. Other iron compounds must be selected to fortify lime-treated corn flour when intended for public nutrition programs.     

Improving the bioavailability of nutrients in plant foods at the household level

Plant foods are the major staples of diets in developing countries, in which the consumption of animal-source foods is often low because of economic and/or religious concerns. However, such plant-based diets are often associated with micronutrient deficits, exacerbated in part by poor micronutrient bioavailability. Diet-related factors in plant foods that affect bioavailability include: the chemical form of the nutrient in food and/or nature of the food matrix; interactions between nutrients and other organic components (e.g. phytate, polyphenols, dietary fibre, oxalic acid, protein, fat, ascorbic acid); pretreatment of food as a result of processing and/or preparation practices. Consequently, household strategies that reduce the content or counteract the inhibiting effects of these factors on micronutrient bioavailability are urgently needed in developing-country settings. Examples of such strategies include: germination, microbial fermentation or soaking to reduce the phytate and polyphenol content of unrefined cereal porridges used for young child feeding; addition of ascorbic acid-containing fruits to enhance non-haem-Fe absorption; heating to destroy heat-labile anti-nutritional factors (e.g. goitrogens, thiaminases) or disrupt carotenoid-protein complexes. Such strategies have been employed in both experimental isotope-absorption and community-based studies. Increases in Fe, Zn and Ca absorption have been reported in adults fed dephytinized cereals compared with cereals containing their native phytate. In community-based studies in rural Malawi improvements in dietary quality and arm-muscle area and reductions in the incidence of anaemia and common infections in young children have been observed.     

Fermentation of soybean flour with Aspergillus usamii improves availabilities of zinc and iron in rats

Soybean flour was fermented with Aspergillus usamii to improve the availabilities of dietary zinc and iron through the degradation of phytate. Three kinds of experimental diets that differed in protein sources were prepared: one consisting of 40% fermented soybean flour (RS diet), one consisting of 40% fermented soybean flour (FS diet), and one consisting of 20% regular soybean flour and 20% fermented soybean flour (RF diet). Zinc solubilities in the upper and the lower segments of the small intestine were higher in rats fed the FS diet than in rats fed the RS diet. The FS group showed higher solubility of iron in the lower small intestine than the RS group did. Zinc concentrations in the femur and plasma and iron concentrations in the liver and plasma were higher in the FS group than in the RS group. These results suggested that the fermentation of soybean flour improved the availabilities of dietary zinc and iron, which may be induced by increasing the solubilities of these minerals in the small intestine through the reduction of phytate content. Femoral and plasma zinc concentrations in the RF group were higher than in the RS group, but lower than in the FS group. No difference was noted in liver and plasma iron concentrations between the RF group and the FS group. Although phytase activity in FS degrades phytate in the RF diet, higher activity may be needed to degrade phytate completely.     

Determination of phytate, iron, zinc, calcium contents and their molar ratios in commonly consumed raw and prepared food in malaysia

The inhibitory effect of phytate on the bioavailability of iron, zinc and calcium was determined by measuring their molar ratios. A total of 29 food samples consisting of 12 rice and rice products, 5 wheat and wheat products, 5 grains and cereal based products and 7 different popular varieties of cooked rice and rice products were selected. The phytate content was analysed using anion-exchange chromatography whereas mineral contents were analysed using atomic absorption spectrophotometry(AAS). One-way ANOVA test was used to statistically analyse the mean difference between the phytate and mineral contents between the food group samples. In general, results show that cooked products have lower content of phytate and minerals as compared to raw products. This could be due to the influence of the cooking method on phytate and mineral content in the food. Based on one-way ANOVA test, there were no significant difference in phytate and zinc content between four food groups (p >0.05). Significant differences were found only in iron and calcium content (p <0.05). Of the 29 food samples, 25 food samples had a phytate/iron molar ratio > 1, 5 food samples had a phytate/zinc molar ratio > 15 and 23 food samples had a phytate/calcium molar ratio of 0.24. These results show that although many of the food samples analysed had high mineral content, the high phytate content may impair the bioavailability of the mineral in the body.     

Availability to rats of zinc in green and mature soybeans

A slope ratio assay was conducted with young albino rats to investigate the effect of maturity of soybean seeds on the bioavailability of their intrinsic zinc. Seeds (Williams) were harvested when well-developed but green (25% dry matter) and when mature (86% dry matter). The blanched seeds were wet-milled, freeze-dried and incorporated into 20% egg white protein diets at the expense of egg white to provide 20% protein diets containing equal calories and calcium but varying in zinc and phytate content. Zinc in the mature bean flour diets was 58% as available for weight gain and 57% as available for tibia zinc accumulation as was zinc in the green bean flour diets. The difference between zinc availabilities can be ascribed to the higher phytate content of the mature beans.     

Phytate intake and molar ratios of phytate to zinc, iron and calcium in the diets of people in China

OBJECTIVE: To assess the phytate intake and molar ratios of phytate to calcium, iron and zinc in the diets of people in China. DESIGN: 2002 China Nationwide Nutrition and Health Survey is a cross-sectional nationwide representative survey on nutrition and health. The information on dietary intakes was collected using consecutive 3 days 24 h recall by trained interviewers. SUBJECTS: The data of 68 962 residents aged 2-101 years old from 132 counties were analyzed. RESULTS: The median daily dietary intake of phytate, calcium, iron and zinc were 1186, 338.1, 21.2 and 10.6 mg, respectively. Urban residents consumed less phytate (781 vs 1342 mg/day), more calcium (374.5 vs 324.1 mg/day) and comparable amounts of iron (21.1 vs 21.2 mg/day) and zinc (10.6 vs 10.6 mg/day) than their rural counterparts. A wide variation in phytate intake among residents from six areas was found, ranging from 648 to 1433 mg/day. The median molar ratios of phytate to calcium, iron, zinc and phytate x calcium/zinc were 0.22, 4.88, 11.1 and 89.0, respectively, with a large variation between urban and rural areas. The phytate:zinc molar ratios ranged from 6.2 to 14.2, whereas the phytate x calcium/zinc molar ratios were from 63.7 to 107.2. The proportion of subjects with ratios above the critical values of phytate to iron, phytate to calcium, phytate to zinc and phytate x calcium/zinc were 95.4, 43.7, 23.1 and 8.7%, respectively. All the phytate/mineral ratios of rural residents were higher than that of their urban counterparts. CONCLUSIONS: The dietary phytate intake of people in China was higher than those in Western developed countries and lower than those in developing countries. Phytate may impair the bioavailability of iron, calcium and zinc in the diets of people in China.     

In vitro accessibility of carotenes from green leafy vegetables cooked with sunflower oil or red palm oil

Although vegetables and fruits are readily available and consumed in most areas of Tanzania, vitamin A deficiency is still prevalent. The objective of the present study was to measure the in vitro accessibility (available for absorption) of alpha-carotene and beta-carotene in vegetable relishes prepared with or without oil. Derived results were used to calculate the contribution of vegetable relish to recommended daily intake of retinol. Five sundried green leafy vegetables from Tanzania were cooked without oil, with sunflower oil or with red palm oil. The total amount and in vitro accessibility of alpha-carotene and beta-carotene from a portion (100 g) of vegetable relish was determined. The in vitro method used simulated the digestion process in the gastrointestinal tract. Carotenoids released after digestion were quantified using high-performance liquid chromatography. The total amount of beta-carotene varied between 1211 and 3659 microg/100 g among the five vegetable sources studied. From green leaves cooked without oil, 8-29% of the beta-carotene content became accessible after in vitro digestion and 39-94% from leaves cooked with sunflower oil or red palm oil. Adding red palm oil instead of sunflower oil resulted in about twice as much accessible beta-carotene, due to the high accessibility of its beta-carotene content. The red palm oil contributed also a considerable amount of alpha-carotene. The results showed that by eating vegetable relishes with added oil daily, it should be possible to provide the recommended intake level of vitamin A.     

Bioavailability to rats of iron and zinc in wheat bran: response to low-phytate bran and effect of the phytate/zinc molar ratio

Low-phytate wheat bran was produced by enzymatic hydrolysis and extraction. Rat bioassay methods were utilized to determine bioavailability of iron and zinc in the low-phytate brans and to study the effect of dietary phytate/zinc molar ratio on zinc bioavailability when the phytate source was bran. Endogenous phytase activity hydrolyzed 80-100% of the phytate when wheat bran was incubated in water overnight. The relative biological values of the iron in raw bran and phytate-free bran were 98 and 113, respectively, compared to 100 for ferrous ammonium sulfate in a hemoglobin repletion assay. Low-phytate brans with phytate/zinc molar ratios of 8 or less were equivalent to zinc sulfate as dietary sources of zinc for growth of rats. Rats fed diets that contained wheat bran with zinc sulfate added to reduce the dietary phytate/zinc molar ratio from 40 or 50 to 20 grew at the same rate as rats fed a phytate-free diet, but femur zinc values were lower than those in the reference group. Gel filtration chromatography of extracts of raw and low-phytate brans suggested that zinc might be associated with phytate in wheat bran.     

Iron absorption from bread in humans: inhibiting effects of cereal fiber, phytate and inositol phosphates with different numbers of phosphate groups.

Iron absorption was measured from five kinds of bread made from various types of flour and fermented in different ways in order to obtain a wide variation in the content of fiber, phytate (inositol hexaphosphate) and its degradation products, inorganic phosphate and inositol phosphates with fewer numbers of phosphate groups (inositol pentaphosphate through monophosphate). Each experiment had 9-10 subjects and, in each subject, iron absorption was measured from control rolls made from low extraction wheat flour and one kind of test roll using two different radioiron tracers: 55Fe and 59Fe. The inhibition of iron absorption was closely related to the content of phytate-phosphorous as determined using the AOAC method, and to the sum of the tri- through hexaphosphate groups as determined using the HPLC method. As an example, prolonged fermentation of whole-rye bread reduced total inositol phosphates to the same amount as in the control rolls and increased fractional iron absorption to the same high level, in spite of a fiber content five times as great. The results strongly suggest that the inhibitory effect of bran on iron absorption is due to its content of phytate and other inositol phosphates present after fermentation, rather than to its content of fiber or other constituents. Thus, effective fermentation will increase the bioavailability of iron in whole-meal bread.     

The supply of bioavailable iron and zinc may be affected by phytate in Beninese children

Food composition data are important for estimating energy and nutrient intakes. The objectives of this study were, first, to evaluate the proximate and inorganic composition of foods eaten in northern Benin and second, to estimate the potentially inhibiting effect of phytate on iron and zinc bioavailability. Chemical analyses were performed in 23 samples of most frequently consumed foodstuffs collected from retailers in local markets. Proximate composition was analysed by routine methods. Inorganic constituents and phytate were analysed using ICP-AES and HPLC. Protein contents were in agreement with those in FAO food composition database. Fat and fibre were in general higher whereas carbohydrate and energy were lower. Differences were mainly due to analytical or calculation methods. The most important sources of iron and zinc in children's diets were maize, sorghum and millet. In these cereals, iron and zinc ranged from 2.6 to 8.4 and 2.2 to 3.4 mg/100 g, respectively. Phytate ranged from 104 to 503 mg/100 g. Phytate/iron and phytate/zinc molar ratios ranged from 1 to 11 and 3 to 22, respectively. They suggest poor iron and zinc bioavailability. Reducing phytate and polyphenol contents in order to improve iron and zinc bioavailability from the most frequently consumed cereal food needs to be studied.     

Low zinc,iron, and calcium intakes of Northeast Thai school children consuming glutinous rice-based diets are not exacerbated by high phytate

Phytate, a salt of phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate), is found in certain plant-based foods. It strongly chelates minerals, forming insoluble complexes in the small intestine that cannot be digested or absorbed. Information on the phytate content of rice-based diets of children in Northeast Thailand is limited. In this study 1-day weighed duplicate diet composites were collected from 40 Northeast Thai children (age 6–13 years) randomly selected from participants (n=567) of an efficacy trial in Ubon Ratchathani province. Diet composites were analyzed for zinc, iron, and calcium by atomic absorption spectrophotometry, and for phytate (as inositol penta-phosphate and hexa-phosphate) by high-performance liquid chromatography; the accuracy and precision were established using a certified reference material for the minerals and an inter-laboratory comparison for phytate. The median (1st, 3rd quartiles) zinc, iron, and calcium contents of the diet composites were 4.3 (3.7, 6.1), 4.3 (3.2, 6.5) and 130 (82, 216) mg/day, respectively. The inositol penta-phosphate and hexa-phosphate levels were so low they were below the detection limit, attributed in part to leaching of water-soluble potassium and magnesium phytate from glutinous rice after soaking overnight before cooking. Clearly, phytate will not compromise mineral absorption from these diets. Instead, low zinc intakes are probably primarily responsible for the low zinc status of these children. In contrast, although intakes of dietary iron appear low, the prevalence of biochemical iron deficiency was also low, suggesting that iron absorption may have been higher than previously assumed. Whether the low calcium intakes compromise optimal bone health in these growing Northeast Thai school children is unknown.     

Bioavailability to rats of iron and zinc in calcium-iron-phytate and calcium-zinc-phytate complexes

The bioavailability of iron in Fephytate and Ca₃Fephytate and of zinc in Zn₂phytate and Ca₄Zn₂phytate was assayed in rats. Hemoglobin response was the same to the iron of Fephytate as the reference iron compound, Fe(NH₄)₂(SO₄)₂.6H₂) but the response to iron of Ca₃Fephytate was significantly less than to both Fephytate and the reference. The zinc of Zn₂phytate and Ca₄Zn₂phytate promoted growth as effectively as did ZnSO₄. The femur bone zinc response to Ca₃Zn₂phytate and Zn₂phytate did not differ significantly but the femur zinc responses to both complexes were significantly less than to ZnSO₄. In contrast to iron, calcium in a preformed calcium-zinc-phytate complex appears to have no significant effect on the bioavailability to rats of the zinc in the complex.     

Phytic acid and inositol phosphates in raw flours and infant cereals: The effect of processing

Inositol phosphate modification in infant cereals was examined during industrial processing which included roasting and alpha-amylase treatment. A considerable (p<0.05) decrease in phytate content was observed after both treatments in all the samples analysed. However, the industrial processing observed was not sufficient to cause degradation of the phytate to achieve phytate mineral ratios optimal for mineral absorption in infant cereals. All samples analysed had a phytate/iron molar ratio >1.3, and of the 6 samples, 5 had a phytate/zinc molar ratio >14. The bioavailability of minerals is particularly important during weaning when minerals stores in infants are naturally low. Further studies are needed to evaluate the efficacy and effectiveness of phytase treatment to increase mineral bioavailability in infant foods.     

The adequacy of micronutrient concentrations in manufactured complementary foods from low-income countries

Iron, zinc, and calcium in complementary foods (CFs) are defined as problem micronutrients by the World Health Organization (WHO), as their concentrations in CFs fall below the calculated requirements for breast-fed infants of micronutrients obtained from CFs. Consequently, manufacturers often fortify plant-based CFs with these three micronutrients. We have analyzed concentrations of iron, zinc, calcium, and phytic acid (as hexa- and penta-inositol phosphates) in 57 cereal-based CFs purchased in five countries each in Africa and Asia. Molar ratios of phytate:iron, phytate:zinc, and phytate:calcium were also calculated. Intakes of iron, zinc, and calcium from these CFs were then calculated assuming breast-fed infants aged 9-11 months consume the recommended daily ration size of CF (40 g/d; dry weight), and compared with WHO estimated needs from CFs. Even though manufacturers claimed to fortify 84% (48/57) of the CFs, 79%, 10% and 32% had molar ratios for phytate:iron, phytate:zinc, and phytate:calcium, respectively, above desirable levels. Despite fortification, only ∼4% of the CFs met the WHO estimated needs for breast-fed infants aged 9-11 months for iron, 2% for zinc, and ∼4% for calcium. Appropriate fortification of cereal-based CFs is necessary to ensure they meet WHO estimated needs for iron, zinc, and calcium for breast-fed infants.