No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Micronutrient bioavailability techniques: Accuracy, problems and limitations
Abstract
Within the scientific agricultural community it is widely known that the total micronutrient content of soils is not a useful measure of the amount of `available' micronutrients to plants. Thus, soil tests have been developed to determine the amounts of micronutrients in soils available to plants for growth. This same concept applies to plant foods eaten by humans because not all of the micronutrients in plant foods are available (i.e. bioavailable) for absorption and or utilization. Antinutrients and promoter substances within plant foods that can either inhibit or enhance the absorption and/or utilization of micronutrients when eaten. As a result, numerous techniques have been developed to determine the amounts of bioavailable micronutrients present in plant foods when consumed in mixed diets with other dietary constituents that can interact and affect the micronutrient bioavailability. Unfortunately, micronutrient bioavailability to humans fed mixed diets is still a confusing and complex issue for the human nutrition community. Our understanding of the processes that control micronutrient bioavailability from mixed diets containing plant foods is relatively limited and still evolving. It remains the subject of extensive research in many human nutrition laboratories globally. This article reviews some of the numerous methodologies that have arisen to account for the bioavailability of micronutrients in plant foods when eaten by humans.
... In addition, food processing methods, meal preparation, and individual's personal characteristics such as sex, age, genetic predisposition, ethnic background, economic status, physiological state, health status, etc. will determine micronutrient bioavailability in plant foods (House 1999 Graham et al. 2001). There is no single bioavailability evaluation method that is applicable for all micronutrients or for all plant foods in all the circumstances (Fairweather-Tait and Hurrell 1996), and micronutrient bioavailability data obtained through various model systems are always ambiguous (House 1999;Van Campen and Glahn 1999;Welch and Graham 2004). ...
... Different models have been suggested to assess the bioavailability of micronutrients in plant foods to human beings (House 1999;Van Campen and Glahn 1999). As bioavailability includes both bioaccessibility and bioactivity, assessment of these two phenomena will quantify the bioavailability of the nutrients from the foods. ...
... If the nutrient status is adequate, then there will be downregulation leading to minimum uptake by the body from a meal. Too severe deficiency state of the subject is also not preferred in clinical trials as intestinal malabsorption can occur resulting in artificial data that do not provide a true picture of the test meal on iron or zinc bioavailability in normal individuals (House 1999;Van Campen and Glahn 1999;Welch and Graham 2004). ...
... Numerous factors interact, ultimately to determine the bioavailability of a particular micronutrient to an individual eating a mixed diet within a given environment. Because of this complexity, the data obtained using various bioavailability model systems are always ambiguous (House, 1999 &Van Campen andGlahn, 1999). Only data from feeding trials in micronutrient-deficient test populations under free-living conditions can delineate the efficacy of using micronutrient-enriched varieties of plant foods as an intervention tool. ...
... Numerous factors interact, ultimately to determine the bioavailability of a particular micronutrient to an individual eating a mixed diet within a given environment. Because of this complexity, the data obtained using various bioavailability model systems are always ambiguous (House, 1999 &Van Campen andGlahn, 1999). Only data from feeding trials in micronutrient-deficient test populations under free-living conditions can delineate the efficacy of using micronutrient-enriched varieties of plant foods as an intervention tool. ...
... Numerous factors interact, ultimately to determine the bioavailability of a particular micronutrient to an individual eating a mixed diet within a given environment. Because of this complexity, the data obtained using various bioavailability model systems are always ambiguous (House, 1999 &Van Campen andGlahn, 1999). Only data from feeding trials in micronutrientdeficient test populations under free living conditions can delineate the efficacy of using micronutrient-enriched varieties of plant foods as an intervention tool. ...
... Many iron and zinc bioavailability techniques use either radioisotopes or stable isotopes of iron and zinc incorporated into a meal to determine bioavailability [2]. Intrinsic labelling of plants with either stable isotopes or radioisotopes requires growing plants in nutrient media labelled with an isotope of the micronutrient under study. ...
... This is a time-consuming and costly exercise, but it ensures that the micronutrient being tested in a meal will be in a form that occurs naturally in the food. Extrinsic labelling techniques (i.e., adding isotope labels during preparation of test meals) are easy and relatively inexpensive; however, the use of extrinsic isotope tags does not ensure that the added isotope will be fully equilibrated with all forms of the micronutrient in the plant food [2,3]. Thus, using intrinsic labels is the only way to obtain unequivocal results from bioavailability studies; this method was chosen in the studies reported here. ...
... Various in vitro and in vivo methods and animal models are available for determining the bioavailability of iron and zinc in plant foods [2][3][4]. Most in vitro methods cannot reproduce the interactions (e.g., release of intrinsic factors) that occur between intestinal mucosal cells lining the gut and the food constituents in the gut. ...
A rat model was used to determine the bioavailability of iron and zinc in bean seeds and rice grain from enriched genotypes of these globally important staple foods. Seed and grain from the genotypes tested (intrinsically radiolabelled with either ⁵⁹ Fe or ⁶⁵ Zn) were cooked, homogenized in water, and lyophilized to dryness. The dried, radiolabelled powder was fed to young male rats in single meals. Bioavailability was calculated from the amount of radiolabelled iron and zinc retained in the rats over a 10-day period as determined each day by whole-body gamma spectrometry assay. The data collected demonstrate that increasing the amount of iron or zinc in enriched rice grain and bean seed significantly increases the amount of iron or zinc bioavailable to rats.
Although a rat model is not ideal for determining iron and zinc bioavailability to humans, because rats are much more efficient at absorbing iron and zinc from plant foods than humans, rats can be used to give relative estimates of bioavailable iron and zinc in plant foods. These estimates can be used to rank promising genotypes of staple foods for use in later feeding trials with humans, greatly reducing the numbers of genotypes that would have to be tested in humans without use of the rat model. Ultimately, because of the complexities of determining the bioavailability to humans of iron and zinc in plant foods, human feeding trials performed under free-living conditions should be conducted with the most promising genotypes before these genotypes are released for distribution to breeding programmes worldwide
... The study showed that 9 months of consumption of Fe-biofortified rice improved the Fe stores in the blood of non-anemic Filipino women (171). However, examining the bioavailability of micronutrients from plants to humans is difficult because of the governing interactions of various factors, particularly in determining the bioavailability of a particular micronutrient to an individual with a diversified diet (172,173). The micronutrient status of test subjects affects the regulation of these nutrients within the body. ...
... The micronutrient status of test subjects affects the regulation of these nutrients within the body. It is suggested that, to maximize the response of subjects to a test meal, the subjects should be marginally depleted with micronutrients (172,173). Ideally, human trials should be conducted in a controlled environment to generate reliable and conclusive data. ...
The Philippines is one of the major rice-producing and rice-consuming countries of Asia. A large portion of its population depends on rice for their daily caloric intake and nutritional needs. The lack of dietary diversity among poor communities has led to nutritional consequences, particularly micronutrient deficiencies. Iron-deficiency anemia (IDA) and zinc deficiency (ZnD) are two serious nutritional problems that affect the health and economic sector of the country. Since rice dominates the Filipino diet by default, biofortification of rice will help improve the micronutrient status. The Philippine government has proactively initiated various programs and policies to address micronutrient deficiencies, particularly through fortification of basic food commodities. Biofortification, the fortification of rice with micronutrients through breeding, is considered the most sustainable and cost-effective strategy that can benefit large vulnerable populations. However, developing promising genotypes with micronutrient-enriched grains should be coupled with improving micronutrient bioavailability in the soil in order to optimize biofortification. This review documents the prevailing soil Zn-deficiency problems in the major rice production areas in the Philippines that may influence the Zn nutritional status of the population. The article also reports on the biofortification efforts that have resulted in the development of two biofortified varieties approved for commercial release in the Philippines. As nutritional security is increasingly recognized as a priority area, greater efforts are required to develop biofortified rice varieties that suit both farmers' and consumers' preferences, and that can address these critical needs for human health in a sustainable and cost-effective manner.
... Ultimately to determine the bioavailability of a particular micronutrient a number of factors interact in the body of an individual eating a mixed diet within a given environment. Because of this complexity, the data obtained using various bioavailability model systems are always ambiguous (House 1999;Van Campen and Glahn 1999). ...
... Various bioavailability models have been developed to determine the micronutrients in human plant foods (House 1999;Van Campen and Glahn 1999). Among these in wide use are in vitro models such as cultured human intestinal cells (i.e. ...
Micronutrients are essential minerals and vitamins required by humans in tiny amounts which play a vital role in human health and development. Over three billion people in the world are malnourished, particularly in the developing countries. Current food systems cannot provide sufficiently balanced micronutrients required to meet daily needs and to sustain the wellbeing of people in developing countries. Heavy and monotonous consumption of cereal-based foods which contain limited amounts of micronutrients is one of the major reasons for the significantly high prevalence of micronutrient deficiencies in many of the developing countries. The development of crops with enhanced micronutrient concentration is one of the most sustainable and cost-effective approaches to alleviate micronutrient malnutrition globally. In this chapter we focus on the research to improve mineral element concentration in crops through plant breeding strategies, especially in major cereal crops and a legume which are most widely cultivated and preferred in Africa and Asia. Biofortification is an appropriate strategy to increase the bioavailable concentrations of an element in edible portions of crop plants through traditional breeding practices or modern biotechnology to overcome the problem of micronutrient deficiencies. Therefore, conventional breeding with modern genetic engineering approaches are important for developing crop cultivars with enhanced micronutrient concentrations to improve human health. This chapter reports on biofortification research on rice, pearl millet, sorghum, maize, wheat and common bean.
... Absorption and/or retention of mineral nutrients are often used as indicators of bioavailability but they are not synonymous with bioavailability, which integrates the various processes whereby an ingested nutrient becomes available: digestion, absorption, transport, utilization and, elimination (Van Campen and Glahn, 1999; Wienk, et al., 1999; Hambidge, 2010). Bioavailability can be considered as an important factor in the nutrition field due to its variations with different foods, food components and gastrointestinal conditions. ...
... Nevertheless, these data were studied and collected by many different techniques and procedures and under a diversity of variable conditions. In many cases, these data cannot be compared as they were obtained by different methods and/or variables (Van Campen and Glahn, 1999). Iron is the only micronutrient for which there is a direct measure of bioavailability with 80-90% of the absorbed iron used to the hemoglobin synthesis and low daily metabolic excretion which allow the uses of measure of iron absorption as predictable bioavailability (Fairweather-Tait, 2001). ...
Iron deficiency anemia is the most common nutritional deficiency in humans. Not all dietary ingested iron, heme or non-heme, will be available to absorption and negative imbalance between iron requirements and absorption leads to iron deficiency and/or anemia. The recommended iron values usually are based on the genetic and on diet iron-bioavailability, which can be considered as the principal factor that change among the cultures and influences the distinct levels of recommendation among countries. Dietary changes present practical limitations due to be difficult to change food habits. The iron food fortification is considered more cost effective and economically more attractive than iron supplementation. There are many iron compounds available to be used in iron fortification. Cereals represent a target food group to iron fortification programs due high consumption and the in vitro studies can be useful to estimate the relative iron bioavailability in large number of products in short time and with a low cost. Wheat flour baked into bread or not was the main product tested in in vitro bioavailability studies and ferrous sulfate was the principal iron compound used in the fortification studies. However, iron bioavailability from ferrous sulfate is lower than from other compounds, such FeNaEDTA or ferric pyrophosphate. The variables level of fortification, storage, level of extraction, baking and also the association or not with other chemical compound seems to influence the results obtained.
... Açıklık-koyuluğun bir ölçüsü olan L* değeri 0 ila 100 arasında bir değer alır, 0'a yaklaştıkça koyuluk artarken, 100'e yaklaştıkça renk açılır. -a* değeri yeşil ve +a* değeri kırmızıyı, +b* değeri sarı veb* değeri maviyi temsil etmektedir ( Glahn, 1999;Diego Quintaes ve ark., 2017). Et, demir kaynağı olmasının yanı sıra tüketildiği besinlerin demirin emilimini de artırma özelliğine sahiptir (WHO, 2004;Harris, 2014). ...
Demir eksikliği ve demir eksikliği anemisi global ölçekte birçok insanı etkileyen besinsel bir problemdir. Bu çalışma kapsamında tüketimi yaygın, kolay erişilebilir tam buğday unlu galetalar yüksek demir ve protein kaynağı olan kırmızı et tozu ile %30 oranında zenginleştirilmiştir. Kimyasal analiz sonuçları; zenginleştirilen grubun kontrole göre yüksek oranda kül (%4.26±0.49) ve protein (%35.94±1.65) içeriğine sahip olduğunu göstermiştir. Ürünlerin nem miktarları kontrol ve et tozu içeren örneklerde sırasıyla %2.43 ve %16.03 olarak bulunmuştur. INFOGEST protokolü uygulanarak in vitro sindirim öncesi ve sindirim sonrası demir miktarı tespit edilerek biyoerişilebilir demir miktarı %56.84±0.42 olarak hesaplanmış ve zenginleştirilen grup kontrole göre (%10.20±0.15) önemli ölçüde artış göstermiştir. Kırmızı etin kendine has rengi örneklerin L*, a*, b* değerlerini etkilemiş ve toplam renk değişimi 11.46 olarak tespit edilmiştir. Kullanılan yüksek orandaki et tozunun örneklerin kırılganlığını azaltarak elastikiyeti arttırdığı, buna bağlı olarak kırılma için gerekli mesafenin azalmasına sebep olduğu görülmüştür. Panelistler tarafından örnekler görünüş, renk, lezzet, doku, genel beğeni açısından değerlendirildiği duyusal panelde, kontrol grubu tüm özellikler bakımından et tozu içeren gruba göre üstün bulunmuştur. Bu çalışmada günlük beslenmenin temelini oluşturan tahıl ürünleri ile demir ve protein içeriği yüksek kırmızı et bir araya getirilerek kolay ulaşılabilir, tüketimi yaygın tahıl bazlı atıştırmalık formuna dönüştürülmüştür. Bu yönü ile çalışma kapsamında demir ile zenginleştirilmiş ve demir biyoerişilebilirliği artırılmış, protein içeriği yüksek tam buğday unlu galeta eldesi sağlanmıştır. Ancak tüketici tercihini etkileyen fiziksel ve duyusal özelliklerde iyileştirmelerin faydalı olacağı düşünülmektedir.
... It describes the synergistic interactions where nutrients provided by the diet support the growth and activity of beneficial microorganisms, while these microorganisms, in turn, contribute to nutrient cycling, availability, and overall ecosystem health [23]. Given the prevalence of nutrient deficiencies we will discuss in this review, an emphasis on consuming bioavailable forms of micronutrients may assist in meeting our nutritional needs [24]. One example is that magnesium consumed in the form of leafy greens has a higher bioavailability than those obtained in grain products [25]. ...
Human nutrition, and what can be considered “ideal” nutrition, is a complex, multi-faceted topic which many researchers and practitioners deliberate. While some attest that basic human nutrition is relatively understood, it is undeniable that a global nutritional problem persists. Many countries struggle with malnutrition or caloric deficits, while others encounter difficulties with caloric overconsumption and micronutrient deficiencies. A multitude of factors contribute to this global problem. Limitations to the current scope of the recommended daily allowances (RDAs) and dietary reference intakes (DRIs), changes in soil quality, and reductions in nutrient density are just a few of these factors. In this article, we propose a new, working approach towards human nutrition designated “Foundational Nutrition”. This nutritional lens combines a whole food approach in conjunction with micronutrients and other nutrients critical for optimal human health with special consideration given to the human gut microbiome and overall gut health. Together, this a synergistic approach which addresses vital components in nutrition that enhances the bioavailability of nutrients and to potentiate a bioactive effect.
... If the appropriate conditions do not exist, the soil test aid in determining what must be done to provide the correct balance of nutrients and create the proper soil reaction (Collof et al. 2008). By conducting an analysis on chemical properties of soil, the amount of nutrients in the soil and the ability of the soil to supply the nutrients to plants can be assessed (Campen and Glahn 1999;Li et al. 2007;Sidari et al. 2008). Chemical property analyses include soil acidity, electrical conductivity, salinity nutrients and cation exchange capacity. ...
The rehabilitation of forest areas is not new to Malaysia as forest replanting activities have been carried out throughout the country for years to meet the demand for woody and non-woody products as well as to nurture degraded forestland. Thus it is important for a soil to be evaluated to ascertain the degree to which rehabilitation activities have succeeded in restoring forest health, particularly in sustaining soil quality in rehabilitated forests. This review article aims to provide a corpus of information for forest managers and related agencies who work closely with forestry. The aim is to provide an overview on the importance of soil quality in measuring the success of forest rehabilitation programs. Research articles on the evaluation of soil properties at selected rehabilitated forests in Peninsular Malaysia were included in the review. The impact of forest rehabilitation in relation to soil properties comprising soil compaction, moisture, acidity, macronutrients, cation exchange capacity, microbial count, microbial enzymatic activity, and microbial biomass is discussed. Natural forest is used as a benchmark to see the effect of forest rehabilitation programs. Our review indicates that rehabilitated forests that were established earlier and have gone through a longer period of time have better soil quality compared to the soil of forests established later. This shows that rehabilitated forests are able to restore their soil quality and achieve fertility on par with natural forests, if given longer periods of time for recovery. Soil quality analyses should be done regularly to measure the extent of success in rehabilitation programs.
... Pristupačnost je definisana kao sadržaj hraniva koji je lako dostupan biljkama i zavisi od tipa zemljišta, sadržaja organske materije, pH-vrednosti, fizičkih, hemijskih i bioloških osobina zemljišta itd. (White and Zasoski, 1999;Van Campen and Glahn, 1999). Pristupačnost mikroelemenata za biljke jedan je od bitnih problema biljne proizvodnje, jer pod uticajem mnogih fizičkih i hemijskih procesa u zemljištu može da dođe do njihovog nedostatka u ishrani biljaka. ...
Mikroelementi su zastupljeni u zemljištu u malim količinama i neophodni su za razne biohemijske i fiziološke procese biljaka, dok teški metali predstavljaju elemenate u tragovima od kojih su neki neophodni za mnoge funkcije u biljkama, ali su u većim količinama štetni. Takođe, postoje teški metali čije je prisustvo u bilo kojim količinama štetno po biljku. Značaj organske materije za zemljište je višestruk; ogleda se u očuvanju njegovih fizičkih svojstava; u organskoj materiji su rezerve ugljenika; i izvor je drugih elemenata neophodnih za ishranu biljaka. U ovom radu su prikazani načini dospevanja mikroelemenata i teških metala u zemljište; iz stajnjaka, komposta, digestata, industrijskog organskog otpada i kanalizacionog mulja. Prikazan je sadržaj mikroelemenata i teških metala u organskim đubrivima u različitim zemljama sveta i u R. Srbiji. Pozitivan uticaj đubrenja je značajan za raspoloživost esencijalnih elemenata i poboljšanje fizičkih, hemijskih i bioloških svojstava zemljišta, ali negativna posledica primene organskih materijala može da bude povećanje koncentracije pojedinih toksičnih teških metala. Da bi se izbegli negativni uticaji na životnu sredinu, neophodno je vršiti kontrolu kvaliteta organskih đubriva, kao preventivnu meru u cilju uspostavljanja održive
poljoprivredne proizvodnje.
... Iodine levels in human beings and life stock has also shown a marked improvement. [68]. Micronutrient bioavailability in seeds is ensured through plant breeding and transgenic methods so that the micronutrient deficiency is reduced in humans. ...
... Ideally, to study the bioavailability of Zn in crop grains should be evaluated through in vivo human studies. However, complexity to perform large-scale screening of sample and cost limit their applicability (Van Campen and Glahn 1999). In vitro digestion/Caco-2 cell model have been proposed as an alternative to in vivo methods for estimating mineral bioavailability in diets. ...
Rice is the staple food for more than half of the world’s population and, hence, the main
source of a vital micronutrient, zinc (Zn). Unfortunately, the bioavailability of Zn from rice is
very low and greatly varied by several inherent factors; therefore, it is important to evaluate the
bioavailability of Zn form different rice germplasm. A combined in vitro digestion and Caco-2
model was used to evaluate the Zn bioavailability from five rice genotypes differ in their grain
Zn concentration. Large variation in Zn bioavailability was observed among these selected rice
genotypes, varied up to 2 fold. These results suggest that Zn bioavailability should be assed for
cost-effective biofortification program to predict the amount of bioavailable Zn from polished
rice, consequently alleviate Zn deficnecy in targeted population.
... As an alternative to the difficult and expensive human absorption studies used to measure iron and zinc bioavailability, Miller, Schricker, Rasmussen, and Van Campen (1981) proposed an in vitro dialyzability assay, which involves a simulated gastrointestinal digestion followed by measurement of low molecular weight iron or zinc as bioavailability proxies. This method has been found to be in reasonable agreement with human absorption data, especially for iron (Aragón, Ortiz, & Pachón, 2012;Sandberg, 2005;Van Campen & Glahn, 1999). Since then, the dialyzability assay has been used extensively to understand the bioaccessibility of iron and zinc (meaning in vitro bioavailability) in foods. ...
The establishment of the INFOGEST in vitro static digestion method, a standardized international consensus, was an important milestone in the field of food digestion. We evaluated the contribution of iron and zinc in reagents used in the INFOGEST method in relation to sample iron and zinc and the potential interference of reagent-derived iron and zinc with bioaccessibility measurements. In most cases, reagent-derived iron and zinc contributed more than 50% of the total iron or zinc in the digesta containing selected cereals and legumes. Moreover, the chemical behaviour of reagent-derived iron and zinc was matrix dependent such that the application of a blanket blank correction was not appropriate. We therefore propose an improved approach involving isotopic labelling of reagent iron and zinc in order to discriminate between reagent-derived and sample-derived iron and zinc in each matrix. This stable isotope approach could improve the accuracy and reliability of iron and zinc bioaccessibility studies.
... Furthermore the in-vitro metal bioavailability technique has many problems and limitations, for example, human physiology of food digestion is quite complex, involves many biochemical reactions and varies from person to person. Also, the amount of soluble/digested metals is not fully accessible or absorbable to animal organs (Van Campen and Glahn, 1999). Therefore, further research is recommended and both in-vitro and in-vivo bioaccessibility models using a wide range of samples must be considered. ...
This study determines the bioaccessibility of toxic and carcinogenic arsenic (As) in composite food samples and evaluates potential exposure from food intake in Bangladesh children. Total As (tAs), inorganic As (iAs) and bioaccessible As (BAs) in food composite samples consumed by children were compared between an exposed and a control group (based on As in drinking water). Total As concentrations in composite food samples of children exposed to mean As level of 331 µg/l in drinking and cooking water ranged from 586 to 1975 µg/kg, dry weight over 76–90 µg/kg in the unexposed group. Average iAs in food composites was 73.9% (range: 49.3–90.8%). The fraction of BAs using gastric and gastrointestinal phases was 91 ± 13% and 98 ± 11%, respectively. Daily intake of iAs in the exposed group ranged from 0.41 to 6.38 µg per kg body weight (BW), which was much higher than the unexposed group (0.08–0.15 µg per kg BW). High iAs content and BAs in composite food samples indicated the elevated risk to exposed children. Further research should include both adults and children using larger sample size to determine overall As exposure from food intake in Bangladesh, attention must be given to lowering of As in food.
... The total amount of a micronutrient in plant food does not represent the actual micronutrient content of the food which is utilizable by the consumer. In human nutrition terms, bioavailability is commonly defined as the amount of a nutrient in a meal that is absorbable and can be utilized by the person eating the meal (Van Campen and Glahn, 1999). Micronutrients can occur in various chemical forms of differing proportions in plant foods and their amounts vary depending on numerous factors including the growth environment, plant species, genotype, and cultural methods and management practices used to grow the plant. ...
Micronutrient deficiencies have been identified as major public health problems affecting a large part of the world's population. Biofortification of staple crops like maize has been proposed as one of the most cost effective and feasible approaches to combat micronutrient deficiencies. Studies have shown that provitamin A from biofortified crops is highly bioavailable and has the capacity to improve vitamin A status of vulnerable groups. Most people in sub-Saharan Africa subsist on maize and many people may benefit from consumption of provitamin A carotenoid biofortified maize, especially women and children. With the exception of transgenic golden rice, biofortified crops have received considerable acceptance by most communities. Negative perceptions associated with yellow maize do not affect orange maize, which is, for example, well-liked in rural Zambia. With proper policy frameworks and full commercialization, provitamin A maize can address the problem of vitamin A deficiencies among poor nations with maize-based diets.
... Studies on iron (Fe) biofortification of the common bean were published as early as 2000, approximately a year or two before the term "biofortification" was coined [1]. Prior to 2000, experiments were primarily conducted in rodent models using intrinsically labelled crops, or in humans with extrinsically labelled foods and meals [2]. The cost and limitations of such in vivo studies often prevented the experimental approach from addressing important aspects of bean Fe bioavailability, such as the effects of polyphenols, phytate, and the influence of other foods consumed with beans. ...
This paper represents a series of in vitro iron (Fe) bioavailability experiments, Fe content analysis and polyphenolic profile of the first generation of Fe biofortified beans (Phaseolus vulgaris) selected for human trials in Rwanda and released to farmers of that region. The objective of the present study was to demonstrate how the Caco-2 cell bioassay for Fe bioavailability can be utilized to assess the nutritional quality of Fe in such varieties and how they may interact with diets and meal plans of experimental studies. Furthermore, experiments were also conducted to directly compare this in vitro approach with specific human absorption studies of these Fe biofortified beans. The results show that other foods consumed with beans, such as rice, can negatively affect Fe bioavailability whereas potato may enhance the Fe absorption when consumed with beans. The results also suggest that the extrinsic labelling approach to measuring human Fe absorption can be flawed and thus provide misleading information. Overall, the results provide evidence that the Caco-2 cell bioassay represents an effective approach to evaluate the nutritional quality of Fe-biofortified beans, both separate from and within a targeted diet or meal plan
... Samples were analyzed for iron (Fe), zinc (Zn), calcium (Ca), potassium (K), phosphorus (P), magnesium (Mg), sodium (Na) and aluminum (Al) by inductively coupled plasma-optical emission spectrophotometry (ICP-OES) using and ARL 3580 ICP. Aluminum (Al) was included to provide an indication of possible iron contamination from soil particles (Darrell and Glanh, 1999). Mineral determination was done on boiled samples because this is how potato tubers and traditionally freezedried chuño are consumed and therefore the results are more appropriate for estimation of the contribution of native potato cultivars and chuño to the human diet. ...
The potato in its Andean center of origin is commonly freeze-dried to assure long-term storability and consequent availability of food during periods of scarcity. The final product is known as chuño. Depending on the process and cultivars used, different kinds of chuño are prepared: white chuño (moraya, tunta) and black chuño. This paper explores the nutritional value of chuño using data from research in the Peruvian Andes. The paper specifically investigates the effect of regionally different processes on the mineral content of chuño: Zn, Fe, Ca, K, P, Mg and Na. First, the effect of 4 processes (P), resulting in 2 types of white and black chuño respectively, for 4 cultivars (C) belonging to distinct botanical species (P*C interaction). Second, the influence of locality, cultivar and process on nutrient concentrations (L*C*P interaction). Specifically, the effect of 3 contrasting growing environments on the mineral content of 4 cultivars processed into 2 types of white chuño. Results of the first experiment show that the mineral content of chuño, independent of the mineral analyzed, is significantly influenced by P*C interaction. Results of the second experiment show that particularly the dry matter, Ca, Mg and Na content of white chuño is significantly affected by L*C*P interaction. The zinc, potassium, phosphorus and magnesium content of all 'types' of chuño decreases in comparison with boiled (unprocessed) tubers. White chuño generally contains stable to high iron and high calcium concentrations.
... Maize is a staple crop in many parts of the word, and is often targeted for micronutrient "biofortification" (Xia et al., 2013). Suitable micronutrient concentration in crop plants is not only a crucial issue in agricultural technology, but also a key quantitative indicator in the standards of food and fodder consumption (Fageria et al., 2008;Van Campen and Glahn, 1999). As said by Quzounidou et al. (1995), maize is one of the most important cereal cropsrelatively sensitive to copper. ...
The paper demonstrates the influence of different mineral fertilization with phosphorus and potassium on the concentration of copper (Cu) and manganese (Mn) in the ear leaf of maize at the stage of flowering (BBCH 65) as well as the contents and accumulation of the nutrients studied in maize when fully ripe (BBCH 89). A single factor experiment was carried out in 5-year-cycle (2007-2011), in the randomized complete block design. The experiment was conducted as a part of a long-term stationary trial. The investigation comprised 8 different P and K treatments: the absolute control, exclusive of one of the main nutrients (P - WPN or K - WKN), reduced amount of phosphorus and potassium (to 25% - W25 and to 50% WP50, WK50) as well as recommended amounts of basic nutrients (NPKMg - W100 and NP*KMg, P* - P* as PAPR - W100 PAPR). Evaluation of the nutriational status, performed in the ear leaf of maize at flowering stage, showed that regardless of fertilization treatment applied, the concentration of copper was lower than normative values, whereas that of manganese ranged within the optimal scope. At the same time, there was found a significant relationship between the grain yield obtained and acquisition of both copper and manganese by maize at flowering stage (stronger for manganese, r = 0.614). The total accumulation of copper and manganese in fully ripe maize was significantly differentiated as a result of mineral fertilization. The total uptake of Cu and Mn was reduced under the conditions of 10-year lack of P fertilization. Uptake reduction was considerably more advanced when K fertilization was absent for 10 years. Regardless of the experimental factor effects, more than 50% of the total copper uptake was accumulated in grain, whereas the majority of manganese was accumulated in maize leaves (50-64% of the total uptake). Correlation analysis showed a significant relationship between maize grain yield and the total accumulation of copper, whereas that of manganese was observed only in 3 of 8 treatments tested (WPN, WP50 and W100 as PAPR).
... Cu was not detected. As the changes in mineral concentrations in the liver, heart, plasma, bone and bile, are indicative of their bioavailability [46][47][48], we believe that the hepatic content of Cu, Fe and Zn did not suffer from the action of chelating substances, such as brown-melanoidin-like polymers derived from chlorogenic acids, sugars, proteins [22], and fibers in the coffee powder (4% w/w) or the neoplastic action of DMH. ...
... To understand the bioactivity of DF and the polyphenolic compounds associated with it, a static in vitro gastrointestinal digestion systems appear to provide a useful alternative to animal and human models for rapidly screening of food ingredients; additionally in vitro techniques are ethically superior, faster and less expensive than in vivo techniques (Minekus et al., 2014). Thus, in vitro gastrointestinal digestion followed by the determination of bioactive compound concentrations as well as the bioaccessibility when they are able to cross a semipermeable membrane with a specific pore size, have been well correlated to animal and human studies (Van Campen & Glahn, 1999). ...
The aims of this work were to evaluate the effect of in vitro gastrointestinal digestion (GID) on (i) the recovery and bioaccessibility indexes, (ii) the changes on antioxidant activity and (iii) the short chain fatty acid (SCFA) production of two DF rich extracts (date pits flour (DPF) and apple bagasse flour (ABF)) obtained from agro-industrial co-products. At the end of GID process, the bioaccessibility of phenolic compounds present in DPF and ABF was 78.54 and 91.58%, respectively. With regard to antioxidant activity, GID increased the chelating activity and reducing power. However, the scavenging properties were reduced. Fermentation of DPF and ABF by colonic bacteria generated SCFA such as formiate, succinate, acetate, propionate and butyrate. These findings suggest that DPF and ABF might be used as potential food ingredients due to GID produced that bioactive compounds released from the matrix which exerts antioxidant activity.
... In human nutrition terms, bioavailability can be defined as the amount of a nutrient in a meal that is absorbable and utilisable by the person eating the meal (Van Campen & Glahn, 1999). Se is well absorbed (generally 73-93%) from most sources, with selenomethionine and selenate usually absorbed more efficiently than selenite (Raghib et al, 1986; Stewart et al. 1987; Moser-Veillon et al, 1992; Van Dael et al, 2002). ...
The metalloid selenium (Se) is ubiquitous in soils, but exists mainly in insoluble forms in high-iron, low pH and certain leached soils, and hence is often of limited availability to plants. Consequently, it is often supplied by plants to animals and humans at levels too low for optimum health. Se deficiency and sub-optimality are manifested in populations as increased rates of thyroid dysfunction, cancer, severe viral diseases, cardiovascular disease, and various inflammatory conditions. Se deficiency probably affects at least a billion people. Optimal cancer protection appears to require a supra-nutritional Se intake, and involves several mechanisms, which include promotion of apoptosis, and inhibition of neo-angiogenesis. Evidence suggests that in some regions Se is declining in the food chain, and new strategies to increase its intake are required. These could include education to increase consumption of higher-Se foods; individual supplementation; food fortification; supplementation of livestock; Se fertilisation of crops, and plant breeding for enhanced Se accumulation. Se levels in Australian residents and wheat appear to be above a global estimated mean, but few studies have been conducted. Wheat is estimated to supply nearly half the Se utilised by most Australians. Increasing the Se content of wheat represents a food systems approach that would increase population intake, with consequent likely improvement in public health, and health cost savings. The strategies that show most promise to achieve this are biofortification by Se fertilisation and breeding wheat varieties that are more efficient at increasing grain Se density. Research is needed in Australia to determine the most cost-effective fertilisation methods, and to determine the extent of genetic variability for grain Se accumulation. Before recommending large-scale fortification of the food supply with Se, it will be necessary to await the results of current intervention studies with Se on cancer, HIV/AIDS and asthma.
... Although much of the emphasis is on macronutrients [nitrogen (N), phosphorus (P) and potassium(K)], the micronutrients boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni, a micronutrient for legume N fixation) and zinc (Zn) are common metals of concern from an environmental perspective. Perhaps the most interesting aspect of nutrient management as an analogue is that, in agronomic application, it has been assumed for many decades that measuring total concentration of a metal or nutrient in soil has very little predictive power for estimation of plant uptake and plant growth response (Van Campen and Glahn 1999). Similarly, measurement of concentrations in solution in the soil pore water underestimates what the plants can access. ...
The assessment of the health and environmental impacts of metal contamination in soils is complicated, and in different ways than is the assessment of many other contaminants. One of the foremost problems is that the metals are often relatively immobile, so that it is necessary to verify predictions of mobility and impact far into the future. One approach is to seek analogue information: information from studies that may not have set out to measure attributes related to metal behaviour, but that none the less provide useful insights. One example would be the information on the mobility of natural clays and pedogenic metals such as iron and aluminum in soils. It is well accepted that clay particles will move downward in soils; what is less commonly inferred is that any contaminants associated with the clays will also move downward. For mobility of some metals, this may be a dominant process. Similarly, bioturbation has proven to markedly outpace leaching for many metals. This paper considers analogues related to cesium from bomb-fallout and Chernobyl, other natural radionuclide inputs to the soil, soil pedogenesis, pollen and non-metal industrial-age inputs, ancient metal works, and soil fertility management. Related to biological transfers and toxicity, it considers analogy among elements and among biota, and analogy to ecotoxicology of metals to freshwater biota. Where possible, limiting values for parameters of assessment models have been derived.
... soil-based) micronutrient sources, leading to better estimation of dietary intake. The change in extrinsic bioaccessibility due to modification of agricultural practices (biofortification, pH adjustment) could also be evaluated, resulting in more comprehensive dietary intake information and potentially greater control over exposure to extrinsic sources of micronutrients [21]. ...
BGS 102, a guidance material for bioaccessible arsenic (As) and lead (Pb), was produced during validation of the in vitro Unified Bioaccessibility Method (UBM). This paper reports a compilation of reproducible bioaccessible guidance values for fifty-five additional elements in BGS 102, providing guidance for analysts to broaden the scope of UBM analyses for a wider range of elements based on data collected over an average of 60 separate analytical batches per element. Data are presented in categories for both gastric (STOM) and gastrointestinal (STOM + INT) extraction phases, where reproducibility, measured as relative standard deviation (RSD) was; ≤ 10% RSD for 27 elements (Mg, Al, Si, P, Ca, Cr, Mn, Co, Ni, As, Rb, Sr, Y, Ba, La, Ce, Pr, Nd, Sm, Eu, Tb, Gd, Dy, Ho, Er, Tm, Yb); between 10-20% RSD for 10 elements (Li, K, V, Fe, Cu, Zn, Cd, Lu, Pb, U); and ≥ 20% RSD for 19 elements in the gastric phase (Be, B, S, Ti, Ga, Se, Zr, Nb, Mo, Ag, Sn, Sb, Cs, Hf, Ta, W, Tl, Bi, Th). Two elements (Mg, Rb) met the ≤ 10% RSD criteria in the UBM gastrointestinal extraction phase due to the alkaline conditions of this phase precipitating out the majority of determinands. Certain elements, including Na, K, Zn and Se, were found to be a significant component of the extraction fluids with proportionally higher concentrations compared to the guidance material. Bioaccessible fractions (%BAF) were also calculated, but were found to be a less reproducible format for confirming the accuracy of measurements. The low concentration of some elements of interest in BGS 102, such as antimony (Sb), justifies the preparation of an alternative certified reference material (CRM). This paper presents an opportunity to broaden the scope of the UBM method to address food security issues (e.g. Fe and Zn micronutrient deficiencies) and contributions to dietary intake from extraneous dust or soil through evidence of the analytical possibilities and current limitations requiring further investigation.
... After differentiation, they develop microvilli and in several ways work similarly to small intestinal epithelial cells. 25 Evaluations by different laboratories showed that the expressions of transporters by Caco-2 cells monolayers and the small intestine were similar. 26 This in vitro model is currently considered as the best approach, in terms of cost and time, to investigate the bioavailability of different food components as a prelude to in vivo study. ...
... But, the nutrient is absorbed in a form that is physiologically useful. In the case of Se, changes in plasma or serum concentrations are generally considered good indicators of bioavailability (Van Campen, 1999). Knowledge about the absorption of Se from foods or supplements does not predict its utilization, because bioavailability depends on the conversion of absorbed Se into a biologically active form and tissue retention (King. ...
Korean ginseng (Panax ginseng C.A. Meyer) was tested to demonstrate that production of this plant with a nutritionally important selenium (Se) is possible, making it a functional ginseng with concentrated Se supplement and the Se incorporated into the enriched Korean ginseng occurs in a soluble, metabolically available form. Sequential extraction was used to assess the degree of solubility of Se. Se content of Korean ginseng represented linear accumulation tendencies in proportion to the increase of Na2SeO 4 concentration and duration in the nutrient solution. Results from this solubility experiment indicate that the accumulated Se achieves very soluble form, consequently this Se-enriched plant can economically supply 100 % of Se content in it to human. Two-year-old Korean ginseng containing an anti-carcinogenic Se compound can be recommended for growth in a hydroponic system.
... Retention of radiolabeled iron was assessed in the whole body of the rats for 7 consecutive days at 5 h, 24 h, and every subsequent 24-h interval after ingestion of the test diets [13]. The value at 5 h can serve as the reference value for assessing retention at the 7th day, when excretion rates stabilize [14,15]. ...
... A cultura de tecidos mais comumente usada nos estudos de absorção de ferro é a de células Caco-2, uma linha celular isolada a partir de um adenocarcinoma do cólon humano. Essas células, sob condições apropriadas, se diferenciam em monocamadas polarizadas, desenvolvem microvilosidades e, de várias formas, agem de maneira similar às células do epitélio do intestino delgado GLAHN, 1999). ...
Brazil is amongst the ten countries that mostly waste food, with about 35% of agricultural production going to the trash. The agro-food processing is one of the activities which generate high amount of residues, with approximately 50% of raw material being discarded. The lack of information on the nutritional quality of agroindustrial byproducts does not enable its potential use in the manufacture of food products. In this context, the aim of this study was the chemical characterization of the by-products of industrial processing of fruits and vegetables and grain processing. The chemical elements Br, Ca, Co, Cr, Cs, Fe, K, La, Na, Rb, Sc e Zn were determined by instrumental neutron activation analysis. The proximate composition was evaluated by methods recommended by AOAC. The antinutritional factors, through the determination of phytic acid and tannins. The availability of nutrients in vitro for Ca, Fe, K and Zn and through the Caco-2 cells for Fe. Most samples contain high fiber and protein and low lipid content and calorific value. Rice bran, the peel of cupuaçu seed, the cupuaçu seed and the raspberry bagasse had the highest concentrations of phytic acid, between 19.9 and 10.7 mg g-1. The grape peel showed the highest amount of tannins (23.8 mg / g of catechin). The samples showed good in vitro availability for Ca and Zn, but the values for K and Fe were below 10% available for most samples. In the analysis of bioavailability through the Caco-2 cells system, the sample that showed the highest amount of ferritin was the peel of cucumber (ferritin 56.8 ng/'mü'g protein). It could be observed that the by-products generally exhibit similar or larger amounts of the nutrient than the food usually consumed, and nutrients availability compatible with other plant origin food. The data suggest that the agroindustrial byproducts are potential ingredients for the food industry and can add nutritional value to new products. Future studies more specific to each by-product should be considered like sensory analysis and ways to increase the nutritional quality of by-products
... Besides the rat model used here, in vitro screening models have also been used to qualitatively rank foods as sources of bioavailable Fe. One such in vitro model is the caco-2 cell method (Van Campen and Glahn, 1999 ). However, because of the complexities of determining the bioavailability of Fe in plant foods to humans, ultimately, human feeding trials performed under free-living conditions should be conducted with the most promising genotypes before these genotypes are released for distribution to breeding programs worldwide. ...
The bioavailability of Fe from 24 select genotypes of bean (Phaseolus vulgaris L.) seeds containing a range of concentrations of Fe, myo-inositol pentaphosphate plus phytic acid (IP5+IP6), and tannins was studied using a rat model. Bean accessions, selected from field trials for their variations in Fe, phytate, and tannin seed concentrations, were grown in a greenhouse in nutrient solutions radiolabeled with (59)Fe. Mature seeds were autoclaved and lyophilized. Test meals (containing 1 g of dried bean, 0.5 g of sucrose, and 1 g of basal Fe-deficient diet) were fed to marginally Fe-depleted weanling rats over a 3-h period; rats were radioassayed in a gamma-spectrometer immediately after feeding and daily thereafter for the next 10 d. Radioiron retention data were used to calculate percent Fe absorption (i.e., Fe bioavailability) from the meals. Seed Fe concentrations ranged from 52 to 157 mu g g(-1) dry weight. There was a tendency to also select for higher Zn concentrations in the beans when selecting for high Fe concentrations. The Fe bioavailability to rats from test meals depended on the genotype and varied from 53% to 76% of the total Fe. Bean genotypes with higher seed Fe concentrations resulted in increased amounts of bioavailable Fe to rats. There was no significant correlation between the Fe concentration in different bean genotypes and Fe bioavailability to rats attributable to variations in IP5+IP6 or tannins, even though these antinutrients varied widely (i.e., from 19.6 to 29.2 mu mol of IP5+IP6 g(-1) and from 0.35 to 2.65 mg of tannins g(-1)) in the test meals. Other unknown seed factors (i.e., antinutrients or promoter substances) may be contributing factors affecting Fe bioavailability from bean seeds.
The interaction between nitrogen (N), phosphorus (P), and potassium (K) fertilizers significantly impacts the uptake of micronutrients in corn, influencing their availability in soil and uptake by plants. Understanding the interaction of macro‐ and micronutrients is a prerequisite to targeting nutrient balance in crop production. Therefore, a 2‐year field experiment was conducted to determine the effect of NPK fertilization on micronutrient uptake of rain‐fed corn (Zea mays L.). A randomized complete block design was employed with 12 treatments replicated three times. Different combinations of N, P, and K fertilizer rates were investigated for micronutrient concentration and uptake in rain‐fed corn. Findings revealed the order of nutrient accumulation in corn plants: iron (Fe) > manganese (Mn) > zinc (Zn) > copper (Cu). Nitrogen application influenced nutrient concentrations and uptake. Increasing N rates increased micronutrient concentrations in corn grain, except for Cu. Interestingly, Cu content in grains exhibited no correlation with nutrient supply, biomass, or other concentrations. As the N application rate increased, micronutrient content increased at early growth stage and physiological maturity. Phosphorus application showed negligible impact on grain micronutrient concentration and uptake. However, K application notably increased Mn, Fe, and Cu uptake in grains. This study underscores the need to consider not only grain yield but also nutritional quality when determining optimal NPK rates in rain‐fed corn cultivation.
Bioavailability is the fraction of a nutrient in the food that is absorbed upon digestion and available for utilization in normal physiological functions. Bioavailability of nutrients especially that of micronutrients from plant based foods is a complex issue and is a concern to the nutritionists and plant breeders who are undertaking nutrient enrichment in the staple crops called “biofortification.” It depends on a number of factors of the food like food structure, food processing, chemical form of nutrient and interaction between nutrients, as well as the consumer like age, sex, ethnicity, physiological factors, and health status. Presence of natural factors in the food grains such as phytate, tannin, fiber, etc. affects the availability of minerals. The micronutrient bioavailability from commonly consumed cereal foods is generally low. Several traditionally used household food preparation techniques like soaking, germination, hydrothermal treatment, etc. enhance the micronutrient bioavailability. Different bioavailability models are being adopted to screen large numbers of promising genotypes developed under breeding programs to study the efficacy of the biofortified products in alleviating micronutrient malnourishment. Genetic transformation is also being attempted to develop more nutritious sorghum grains along with enhanced iron and zinc bioavailability to ensure nutritional security of millions of African sorghum consumers. The micronutrient bioavailability has been enhanced in the transformed lines due to reduction in phytate up to 85%. Enhanced availability of nutrients in these grains is to be ascertained further through clinical trials along with risk assessment and appropriate biosafety regulations in place before farmer release.
Beans have high phenolic content and antioxidant activity, so it is important to know how much of these compounds is released from the food matrix and is used in the body. Therefore, the objective of this work was to determine the antioxidant compounds bioavailability on different bean varieties (Phaseolus vulgaris L.) through an in vitro gastrointestinal system. Quantification of phenolic compounds, flavonoids and antioxidant capacity (DPPH, ABTS and FRAP) of 6 cultivars (Black, Flor de Mayo, Patol, Pinto Saltillo, Teapa and Peruvian) was carried out, before and after cooking. Additionally, in vitro gastrointetinal digestion in cooked beans was evaluated. The results obtained from the Teapa and Peruvian bean varieties showed a higher yield of crude extract and an increase in phenolic content. Cooked beans showed an increase in flavonoid content in the Teapa, Peruvian and Pinto Saltillo varieties, as well as greater antioxidant capacity, in the Negro, Flor de Mayo, Teapa and Peruvian varieties. The mean inhibitory concentration (IC50) was reached by Teapa, Pinto Saltillo and Flor de Mayo (106.45, 154.72 and 127.16 μg/mL respectively). The gastrointestinal digestion in vitro resulted in greater bioavailability for phenolic compounds, highlighting the Teapa, Pinto Saltillo and Flor de Mayo varieties.
The rapid advancements in molecular marker technologies followed by genomics, and next-generation sequencing technologies in major crops like rice, maize, and wheat have given opportunities for their use in the minor, but highly valuable future crops, including finger millet (Eleusine coracana (L.) Gaertn.). Finger millet, an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Calcium (Ca), considered to be the most essential macronutrient, is required in relatively large quantities in the diet for maintaining healthy state of body. The unavailability of sufficient markers and genome sequence information in finger millet has resulted in limited breeding efforts for nutritional quality improvement through marker-assisted breeding. Nonetheless, advances in large-scale genomics technology have now streamlined production of genome-wide markers which can be used for large-scale identification of candidate genomic loci. The availability of NGS-based approaches with high resolution has enhanced the pace, precision, and efficiency of trait mapping. At present, trait-associated markers, cost-effective genotyping platforms and expertise are available for deploying genomics-assisted breeding in finger millet. High-throughput genotyping technology and phenotyping platforms have enabled genome-wide association studies, to precisely dissect the genetic architecture of complex traits such as calcium nutrition in finger millet. Large-scale mapping of agronomically important quantitative trait loci would not only help in the identification of molecular markers linked to grain calcium content in finger millet but also help in gene cloning and characterization, mining of elite alleles, exploitation of natural variations, and genomic selection paving the way toward genomics-assisted breeding, which ultimately will lead to genetic enhancement of finger millet. Therefore, marker-assisted breeding and selection is gradually evolving into ‘genomics-assisted breeding’ for crop improvement.
Static digestion in vitro is a commonly used technique for investigating micronutrient availability which allows the nutrients or foods of interest to be exposed to conditions that simulate those found within the stomach and small intestine. The activity of these digestive enzymes throughout their respective simulated digestion phases has been reported to decline due to the autolytic activity of the proteases and therefore incomplete digestion may result. The degree of protease inactivation under commonly simulated digestion conditions requires further quantification. Pepsin and pancreatic protease activities were assessed throughout a simulated digestion protocol in vitro over multiple time points using stop-rate spectroscopy. The protease activity of both pepsin and pancreatin decreased significantly during their respective digestion phases. Results suggest that gastric and intestinal proteases are destroyed or inactivated during their respective digestive phase. For this reason, prolonged digestion protocols may require protease supplementation throughout digestion to correctly simulate physiological conditions.
In an experiment to study the effect of basal and foliar application of zinc on antinutrient and pronutrient compounds in rice grains (Oryza sativa) the observed results showed that a combination of basal and foliar application resulted in an increase in the zinc content of rice plants by almost 58% during 2009 and up to 55% during 2010, which was confirmed by the measurement of acid phosphatase, grain and straw zinc content of the rice genotypes. Moreover, phytic acid content was found to be reduced and methionine content was enhanced. In general it was observed that rice genotypes respond to zinc application positively and zinc availability was found to increase. Hence, it can be concluded that proper zinc fertilization can enhance the availability of zinc in rice grains. © 2017, Indian Council of Agricultural Research. All rights reserved.
Calcium is an essential macronutrient for plants and animals and plays an indispensable role in structure and signaling. Low dietary intake of calcium in humans has been epidemiologically linked to various diseases which can have serious health consequences over time. Major staple food-grains are poor source of calcium, however, finger millet [Eleusine coracana (L.) Gaertn.], an orphan crop has an immense potential as a nutritional security crop due to its exceptionally high calcium content. Understanding the existing genetic variation as well as molecular mechanisms underlying the uptake, transport, accumulation of calcium ions (Ca²⁺) in grains is of utmost importance for development of calcium bio-fortified crops. In this review, we have discussed molecular mechanisms involved in calcium accumulation and transport thoroughly, emphasized the role of molecular breeding, functional genomics and transgenic approaches to understand the intricate mechanism of calcium nutrition in finger millet. The objective is to provide a comprehensive up to date account of molecular mechanisms regulating calcium nutrition and highlight the significance of bio-fortification through identification of potential candidate genes and regulatory elements from finger millet to alleviate calcium malnutrition. Hence, finger millet could be used as a model system for explaining the mechanism of elevated calcium (Ca²⁺) accumulation in its grains and could pave way for development of nutraceuticals or designer crops.
Manganese (Mn) deficiencies are common in soils on the Loess Plateau of China. This research provided essential information on improving Mn availability in semiarid soils through agricultural practices. Twelve cropping system and fertilization treatments were designed in a 28-year experiment. The cropping systems included long-term fallow, continuous winter wheat cropping, pea (1 year)-winter wheat (2 years)-millet (1 year) rotation (crop-legume rotation) cropping, and continuous alfalfa cropping. The fertilizer treatments under the cropping systems included no-fertilizer control (CK), application of P fertilizer (P), application of N and P fertilizers (NP), and application of N and P fertilizers and manure (NPM), but the NP treatment was excluded in the continuous alfalfa cropping system. Available Mn and Mn fractions of soil samples (0–20 and 20–40 cm depths) were measured and further analyzed quantitatively using path analyses. Results showed that the crop-legume rotation and continuous alfalfa cropping systems significantly increased available Mn compared with the fallow soil. Compared with the no-fertilizer control, manure application increased available Mn in soil of the continuous wheat cropping system. Across all treatments, the averaged content of mineral-, oxide-, carbonateand organic matter-bound and exchangeable Mn accounted for 42.08%, 38.59%, 10.05%, 4.59%, and 0.09% of the total Mn in soil, respectively. Cropping significantly increased exchangeable Mn in soil and the highest increase was 185.7% in the continuous wheat cropping system at 0–20 cm depth, compared with the fallow soil. Fertilization generally increased exchangeable and carbonate-bound Mn in soil. Carbonate-bound Mn was the main and direct source of available Mn in soil, followed by exchangeable and organic matter-bound Mn. These results indicated that crop-legume rotation cropping, continuous alfalfa cropping and application of manure, have the potential to promote Mn availability in soils of rainfed farmlands.
One sustainable agricultural approach to reducing micronutrient malnutrition among people at highest risk (i.e., resource-poor women, infants and children) globally is to enrich major staple food crops (e.g., rice, wheat, maize, beans and cassava) with micronutrients through plant-breeding strategies. These target groups are dependent on these staples for their sustenance. Available research has demonstrated that micronutrient-enrichment traits are available within the genomes of these major staple food crops that could allow for substantial increases in the levels of Fe, Zn and provitamin A carotenoids (as well as other nutrients and health-promoting factors) without negatively impacting crop yield. Furthermore, Fe- and Zn-dense seeds can increase crop yields when sowed to soils deficient in these nutrients ensuring their adoption by farmers in these regions once they are developed. Importantly, micronutrient bioavailability issues must be addressed when using a plant-breeding approach to eliminating micronutrient malnutrition. The reduction of antinutrient substances that inhibit micronutrient bioavailability or the increase in substances that promote micronutrient bioavailability from staple plant foods are both options that could be pursued in breeding programs, although care needs to be taken not to compromise agronomic performance and sufficient attention paid to possible beneficial roles of compounds which reduce the bioavailability of trace minerals. The time has come to invest in agricultural technologies to find sustainable solutions to micronutrient malnutrition. Plant breeding is one such technology that should be adopted by the world's agricultural community and that should be supported by the world's nutrition and health communities.
Microwave digestion method was used to preparing selenium samples from food supplements for selenium (Se) determination by spectrophotometric methods. This digestion method provides acid digestion of the samples in a closed vessel device using temperature control microwave heating for the selenium determination by spectrophotometric methods. Two simple, sensitive and specific spectrophotometric methods for the determination of selenium at trace levels were validated and compared on the basis of their performance characteristics. The spectrophotometry method using 3,3'diaminobenzidine hydrochloride was based on the formation of stable yellow-colored piazselenol complex by reaction of Se (IV) with 3, 3'-diaminobenzidine hydrochloride, which is then extracted in toluene and detected spectroscopically at 420 nm. The method using Thionin (TN) was based on the reaction of Se (IV) with potassium iodide in an acidic medium to liberate iodine. The liberated iodine bleaches the violet color of Thionin (TN), and which was measured at 600 nm. The limit of detection and quantitation for Thionin (TN) were 0.18 μg/ml and 0.56 μg/ml, respectively, and for 3,3'DABH were 0.008 μg/ml and 0.027, respectively. The optimum assay conditions were investigated and the average recovery from spiked samples was 99.7% -100.9%. Good values of precision were obtained, interday RSD% for Thionin (TN) was 1.41% and for 3,3'DABH was1.62%.The validated methods were used for estimation trace amount of Se(IV) in food supplements.
Several in vitro methods have been developed to simulate the physiological conditions of the human gastrointestinal digestion, the simplest being the static methods. The following chapter clarifies the concepts of bioaccessibility and dialyzability, and describes the conditions (pH, enzymes, agitation, etc.) to be applied in oral, gastric and intestinal phases when assessing a food component (nutrient, bioactive or toxin) or a food product, in a single or multi-phase model. The advantages and disadvantages of the static models vs. dynamic and in vivo models are discussed, and a review of specific conditions applied on nutrients (minerals, vitamins, proteins, fatty acids, etc.) and bioactive compounds (carotenoids, plant sterols, etc.) from recent studies is provided. Currently, it must be considered that, although the static digestion conditions must be adapted according to the component or food sample to be studied, a harmonization and standardization of the models are needed in order to establish suitable correlations among in vitro and in vivo assays, as it has been defined for some food components (carotenoids, proteins and minerals).
The bioavailability of ingested components is an extremely important area of food and pharmaceutical research. The main issue is to determine which fraction of ingested nutrients or food pollutants can be truly used by the body and exert its healthy or deleterious effects. In this sense, knowledge of bioavailability is essential to estimate the quantity of a mineral that must be supplied to satisfy the requirements, since low intake from diet and deficiencies (with negative consequences for health) are found worldwide, and also to evaluate the toxicological risk of contaminant minerals. Physiological and dietetic factors, as well as food processing, can have an impact on mineral bioavailability. Accordingly, this chapter reviews the bioavailability of minerals of nutritional interest (Ca, Fe, Zn and Se) and with toxicological risk (As, Hg, Cd and Pb).
Evolution of nutrient-rich food systems to calorie-focused production agriculture has created serious agricultural and human health issues: marginalization of traditional agricultural crops, greater dependence of agricultural inputs, and creation of both energy and micronutrient malnutrition. To date more than half of global human populations are suffering numerous health problems associated with excess calories and lack of essential micronutrients. Pulse crops, in particular lentils, are promising crops not only to improve human health but also to reduce agricultural inputs toward greater agricultural sustainability. In this book chapter, human micronutrient malnutrition issues, suggestions to reduce micronutrient deficiencies, promise of pulse crops using lentil as an example, lentil’s micronutrient and antinutrient profiles, nutrient analytical procedures, and the needs to shift our thinking from calorie-focused to nutrient-focused approaches are also presented.
Residues of supercrit. extn. of raspberry, strawberry, blackcurrant and linen seeds were satd. with Zn2+ ions by adsorption from aq. soln. of ZnSO4, analyzed for elemental compn. and used as new biocomponents of micronutrients in plant growing. Their applicability was studied in vivo germination tests on garden cress (Lepidium sativum) to det. the Zn transfer factors from substrate to the plant mass. The plant length was the highest in the case of raspberry seeds. No toxic effects were obsd.
In the present paper, new environmental-friendly fertilizer components were produced
in biosorption process by the enrichment of the biomass with zinc, essential in plant
cultivation. The obtained new preparations can be used as controlled release micronutrient
fertilizers because microelements are bound to the functional groups present in the cell wall
structures of the biomass. It is assumed that new fertilizing materials will be characterized by
higher bioavailability, gradual release of micronutrients required by plants, and lower leaching
to groundwater. The biological origin of the material used in plant fertilization results in the
elimination of toxic effect towards plants and groundwater mainly caused by low biodegradability
of fertilizers. Utilitarian properties of new formulations enable to reduce negative
implications of fertilizers for environmental quality and influence ecological health. In this
work, the utilitarian properties of materials such as peat, bark, seaweeds, seaweed postextraction
residues, and spent mushroom substrate enriched via biosorption with Zn(II) ions
were examined in germination tests on Lepidium sativum. Obtained results were compared
with conventional fertilizers—inorganic salt and chelate. It was shown that zinc fertilization
led to biofortification of plant in these micronutrients. Moreover, the mass of plants fertilized
with zinc was higher than in the control group.
This chapter discusses the potential of biotechnology to improve the health and nutrition of consumers in developing countries. In the relatively wealthy countries of Europe, North America and elsewhere, consumers spend perhaps 10% of their income on food. For the most part consumers in developed countries are free of classical nutrient deficiencies, although over-consumption is a problem for some. Also in relatively wealthy countries there is, in general, good access to affordable medical care to meet health needs and most consumers in rich countries have access to a relatively inexpensive supply of safe and healthy food.
The effect of enzyme amounts used in gastrointestinal in vitro digestion upon the solubility and Caco-2 cell uptake of calcium, iron and zinc from infant formulas (IFs) was studied. Different amounts of enzymes (g enzyme/g IF), pepsin (0.002 and 0.048), pancreatin (0.0005, 0.002 and 0.01) and bile extract (0.003, 0.125 and 0.0625) were assayed. Mineral soluble contents and mineral uptakes by Caco-2 cells were affected by the enzyme amounts used in digestion. Although the highest mineral solubility (Ca 98.6 vs 46.2%; Fe 98.1 vs 83.9%; Zn 98.4 vs 83%) was obtained when the lowest enzyme (pepsin 0.002 vs 0.048; pancreatin 0.0005 vs 0.01g/g IF) and bile extract (0.003 vs 0.0625g/g IF) amounts were used, under these conditions uptake decreased with respect to that obtained when the highest amounts were used (Ca 0.4 vs 1.8%; Fe 0.3 vs 4.8%; Zn 1.7 vs 37%), that indicated a lack of relationship between solubility and absorption. Interactions among different products resulting from the proteolytic activity of digestive enzymes and minerals can modify the physicochemical forms in which minerals are available for absorption after gastrointestinal digestion.
Recently, there has been a renewed interest in better defining the metabolism of chromium (Cr) with respect to both its absorption and cellular action. In the current study we investigated the absorption/retention of 3 Cr(III) compounds (Cr chloride [CrCl], Cr nicotinate [CrNic], Cr picolinate [CrPic]) over a 12 h period in a rat model. Male rats (150 - 170 g) were gavaged with 44 μCi (2.7 nmoles) 51Cr as CrCl3 x 6H2O, CrNic or CrPic. Rats were killed at 1, 3, 6, and 12 h post-gavage. Cardiac blood was collected and liver, kidneys, pancreas, testes, and gastrocnemius were removed, weighed and assayed for 51Cr. The amount of 51Cr in these tissues, along with that in urine (collected for the 6 and 12 h groups), was used to calculate 51Cr absorbed/retained. Urine, followed by muscle and blood, had the highest percent of absorbed/retained counts. For the majority of the time points and tissues, the average percent 51Cr retained was higher in CrNic-gavaged rats than in CrCl- or CrPic-gavaged rats. Tissues collected 1 h post-gavage from CrNic rats had retention percentages that were 3.2 to 8.4- fold higher than in the CrPic or CrCl groups. Three h post-gavage, CrNic rats had blood, muscle, and pancreatic 51C tentions that were 2.4 to 8 times higher than CrPic-gavaged rats. By 6 and 12 h post-gavage, the 'absorbed/retained' tissues were 1.8 to 3.8 times higher in CrNic than in CrPic rats. It is evident from the above that when investigating the absorption/retention of Cr, it is critical to evaluate urinary 51Cr activity, which reflects absorbed Cr, and early time points. The results show that there can be significant differences in the bioavailabillty of different Cr compounds.
This study was undertaken to develop an assay for biologically active chromium suitable for determining the best form of chromium for human supplementation studies. The assay involved monitoring the decrease in fasting serum glucose for 1-3 hours in normal human subjects following ingestion of 100 μg of chromium. The maximum decline occurred 1-2 hours after taking the chromium. The average maximum per cent decrease for 7 subjects was 6.0% for inorganic chromium, 5.7% for conventional brewer's yeast chromium and 16.8% for a high chromium yeast. A chromium-EDTA complex decreased serum glucose an average of 19.6% in 3 subjects. A placebo yeast and dose-response study demonstrated that the chromium in the high chromium yeast was the factor responsible for the serum glucose lowering effect. The high chromium yeast and CrEDTA had a significantly greater biologically active chromium than inorganic chromium. These findings demonstrate that inorganic chromium is biologically active in man, but chromium in the form of synthetic complexes or high chromium yeast is much more active.
1. The first part of this study was designed to determine the increase in the amount of iron absorbed by hypothetical groups of subjects on the border-line of Fe deficiency when they were given meals fortified with ferrous sulphate. Two levels of Fe fortification were used (1.6 and 8.9 mg/meal) and the increase in the amount of Fe absorbed by the ‘border-line’ groups was 0.13 and 0.7 mg respectively.
2. Subjects which are on the border-line of Fe deficiency may be considered the target group of an Fe-fortification programme. Therefore the experimental model used can provide valuable information on the effects on the prevalence of Fe deficiency which can be expected when such a programme is introduced.
3. In the second part of the study, the bioavailability in man of reduced Fe with different physico-chemical properties was measured. Special emphasis was given to the relationship between the values obtained in vitro and in vivo.
4. The bioavailability was expressed as absorbability relative to that of ferrous sulphate. In four samples of hydrogen-reduced Fe the bioavailability ranged from 90 to 13%. The reduced-Fe products differed considerably with respect to solubility in hydrochloric acid (8–94% dissolved after 30 min), particle size distribution (91–1% < 7 μm) and reactive surface area (< 0.1–2.7 m ² /g).
5. The relationships found between physico-chemical information and bioavailability indicated that reactive surface area and dissolution rate were better predictors of the bioavailability than the particle size.
The influence of drinking tea on copper bioavailability is unclear, particularly when tea is consumed with food. A breakfast meal containing white bread, margarine, strawberry jam, cheese and tea, with or without milk, was digested in; vitro and the dialysis of copper investigated. Reference breakfasts were prepared with water and water with milk. Copper dialysability (percentage of copper dialysed) was markedly increased by tea. The influence of adding milk to tea was not significant. A second study was carried out in rats using the breakfasts containing tea and water. They were spiked with 64Cu and given orally to the animals in a single dose. Whole-body 64Cu retention was measured over a 4-day period after administration. In order to determine the true absorption of 64Cu a control group of rats received the dose intraperitioneally. The results in vivo indicate a tendency to higher absorption and retention of 64Cu with tea. Liver 64Cu retention was significantly elevated by tea. Therefore, the presence of tea in a breakfast meal favours the formation of soluble low-molecular-weight ligands which can be absorbed and retained by rats. The concomitant increase in liver copper retetition may be associated with higher bioavailability and/or lower copper mobilisation.
Biliary/pancreatic (B/P) secretions are a major component of endogenous secretions, and endogenously secreted Zn is a primary
means of Zn homeostasis. This study examined whether B/P fluid alters the absorption/reabsorption of Zn and, in doing so,
whether this contributes to homeostatic control of Zn. Animal experiments utilized rats fed 10 or 300 μg Zn/kg diet. An open-ended
gut perfusion study in which65Zn-labeled B/P fluid or67Zn-labeled and digested diet found significantly decreased Zn absorption from B/P fluid. Although Zn absorption from both
sources was less in animals fed diets higher in Zn, there was no interaction of treatment and diet. Further studies utilizing
cultured human colon carcinoma cells (CACO-2) as in vitro models of gut enterocytes found that the presence of B/P fluid significantly
decreased Zn retention and/or transport and resulted in a redistribution of cellular Zn after 1200 min of incubation. These
studies show that a substance in B/P fluid can decrease the absorption of Zn and also suggest that dietary Zn and Zn associated
with B/P secretions are absorbed from distinct pools. However, the lack of an interactive effect with diet, and the amount
of time required to see differences in CACO-2 cells, suggest that differences in absorption are not a major contributor to
Zn homeostasis.
An in vitro method for the estimation of iron bioavailability was subjected to an interlaboratory trial. The method involved a simulated gastrointestinal digestion using pepsin for the gastric stage followed by pancreatin and bile salts for the intestinal stage. The proportion of iron diffused through a semi-permeable membrane (molecular mass cut-off 10 kDa) was used to measure the iron dialysability. An interlaboratory trial between nine laboratories was conducted to evaluate the repeatability and reproducibility of the agreed method. The reproducibility of the method among the participating laboratories was 20–30% and depended on the content of dialysable iron. Several factors contributing to the variation in the in vitro dialysability among laboratories are discussed. The pH adjustment in the intestinal digestion was identified as one of the critical parameters. The present in vitro method was used to evaluate the iron dialysability from three meals. The dialysability data were in reasonable agreement with human absorption data. The usefulness of the in vitro dialysability method is discussed.
The iron absorption from ferritin and hemosiderin biosynthetically labeled with radioiron was studied in 108 subjects. The geometric mean absorption of ferritin iron in both normal and iron-deficient subjects was 1.9 percent. Its mean absorption ranged from 0.9 percent in normal subjects to 2.5 percent in subjects with moderate iron deficiency and 5.7 percent in subjects with marked iron deficiency. The administration of this iron compound with vegetals in a meal showed distinctly lower absorption values than the absorption from either maize, wheat, or soybean. Ferritin iron absorption was also different from that of ferric chloride when they were administered together as a drink or mixed with maize or liver. The iron absorption from ferritin was markedly increased when it was administered with either meat or liver, but it did not reach the absorption level of these foods. It is still to be elucidated whether the difference in iron absorption between ferritin and vegetable foods administered together reflect that this iron is incompletely miscible with a nonheme iron pool or that it really forms a third iron pool.
Iron bioavailability was determined by the extrinsic label method in seven diets consumed by low, middle, and high socio-economic strata of the Venezuelan population. The results were compared with physiologic iron requirements and the prevalence of iron deficiency according to age and sex of others in the same strata. The iron metabolic balance obtained by comparing the iron absorption from diets with the physiologic iron requirement was negative in subjects consuming the low-bioavailability diets, being more marked in children below four years of age, and in adolescents and adult females. These groups also showed the highest prevalence of iron deficiency with and without anaemia. The metabolic iron balance in subjects consuming high iron-bioavailability diets was less negative among vulnerable groups consuming low-bioavailability diets and positive in the age and sex groups less vulnerable to iron deficiency. This information was used to identify the principal categories of dietary iron bioavailability in various regions of the world and their effect on the prevalence of iron deficiency.
Trace elements are essential for a wide range of body functions and diet is the main source of trace elements to meet human's daily requirements. Since most of the trace elements belong to transition group of elements, they possess characteristic chemical properties like low solubility in the alkaline pH of the duodenum, which limit their absorption from the gut. Thus, their bioavailability from foods, which is effected by a number of dietary factors, is an important consideration in trace element nutrition. The methods available for the determination of bioavailability of trace elements, their basis, reliability and sensitivity are critically reviewed. The need for developing appropriate in vitro methods for other trace elements, including both essential and toxic elements has been stressed.
Iron bioavailability was determined by the extrinsic label method in seven diets consumed by low, middle, and high socio-economic strata of the Venezuelan population. The results were compared with physiologic iron requirements and the prevalence of iron deficiency according to age and sex of others in the same strata. This information was used to identify the principal categories of dietary iron bioavailability in various regions of the world and their effect on the prevalence of iron deficiency. -from Author
The authors assessed the bioavailability of cadmium and selenium in lettuce leaves fed to male, zinc-depleted rats. Leaves were harvested after 68 days of growth from plants (Lactuca sativa) that were supplied varying levels of cadmium and selenium in nutrient solutions. Leaves labeled either intrinsically or extrinsically with 109Cd and 75Se were fed in a single meal to rats. Depending on the meal, absorption of the dose ranged from about 2 to 8% for 109Cd and from about 26 to 40% for 75Se. Absorption of 109Cd increased with increased selenium level in the meal, particularly in rats fed intrinsically labeled leaves. Neither the source of 109Cd nor the selenium level in the meal affected the biological half-life of 109Cd. Absorption of 75Se decreased with increased cadmium level in the meal. The biological half-life of 75Se was longer in rats fed intrinsically labeled leaves than in those fed extrinsically labeled leaves.
Retention of /sup 51/Cr was measured in rats fed 3-g test meals containing 63% sucrose, 10% corn oil, and 27% of a test food radiolabeled intrinsically or extrinsically. The test foods were egg yolk, kale, and wheat radiolabeled intrinsically and egg yolk, kale, wheat, and casein radiolabeled extrinsically. Five-week-old male rats were fed a Cr-deficient semisynthetic diet for 2 weeks prior to and 9 days following the 3-g test meals containing /sup 51/Cr-labeled foods. By day 9, only 1.1-2.3% of the /sup 51/Cr in the test meal remained in the animal. Retention of /sup 51/Cr from casein (2.3%) was not significantly different from retention from egg yolk (1.7%) but was significantly higher than that from kale (1.1%) and from wheat (1.5%). These differences may have reflected dietary Cr content rather than a difference in form. There were no significant differences in the retention of /sup 51/Cr due to method of labeling. Preparation of foods intrinsically labeled with /sup 51/Cr was difficult because of a root-shoot barrier in the case of plants and poor absorption or tissue retention by animals. Several approaches to endogenous labeling were attempted. An aqueous extract of kale subjected to gel permeation chromatography showed a low molecular weight chromium complex similar to that found in alfalfa. (M/sub r/ 2900).
Six men were fed a diet composed of conventional foods with all bread as whole wheat bread. Intrinsically labeled â¶âµCu bread (containing 6.5 ppm Cu and 48 atom % â¶âµCu) was substituted for unlabeled bread for 3 days, and stools were collected for 24 days. Extrinsically labeled bread was then substituted for 3 days and another 24-day stool collection made. â¶âµCu excretion was measured by mass spectrometry. Mean Cu intake was 1.10 mg of Cu/day. Average Cu balance was /minus/0.06 /+-/ 0.08 mg/day. Average absorption of the intrinsic copper was 72.2 /+-/ 9.3% and of extrinsic Cu 64.2 /+-/ 5.8%. The ratio of extrinsic to intrinsic absorption was 0.906 /+-/ 0.164. Absorption of intrinsic and extrinsic tracers did not differ significantly (p > 0.05) by a paired t-test, and the ratio (E/I) was not significantly different from 1. Use of extrinsic Cu tracers to assess Cu absorption is supported by these results.
The response of plasma zinc concentrations to oral doses of cooked beef were studied in healthy adult subjects as a prospective new model for studying dietary zinc bioavailability. The areas under the curve of change in plasma zinc, corrected for the downward drift in the fasting state, (cAUCs) for doses of 100, 200 and 300 g of cooked beef, containing 4, 8 and 12 mg intrinsic zinc, respectively, were identical, but the response to 400 g of beef with 16 mg of zinc was non-significantly greater. In 44 studies with 400 g of cooked beef, the mean cAUC was 38.9±3.8 ug/dl.h (range: −18 to 90 ug/dl.h) for the 4 h study. The corrected peak change in plasma zinc concentration was significantly correlated with the cAUC (r=0.88, p<0.001). On a group basis, the first and second beef-response tests in 11 subjects repeating the test on two occassions were identical, but on a individual subject bases, the test-retest reproductibility of the response was of low order. Four-hundred grams of cooked ground beef represents a feasible oral challenge for plasma zinc appearance tests of zinc bioavailability in humans, in spite of within-subject variability.
The study of the chemistry of iron in food materials undergoing digestion can increase our knowledge of the basis of iron bioavailability. Apotransferrin has been used as a probe of iron reactivity following the in vitro enzymatic digestion of pinto beans at pH 3.0 and pH 5.0 in the presence and absence of additives such as ascorbic acid, citric acid, a combination of ascorbic and citric acids, phosvitin, tea, and orange juice. Electron paramagnetic resonance spectroscopy was used to monitor and quantitate the exchange reactions. The effects of additives were similar when either the digestive slurry or its supernatant was reacted with apotransferrin. Although citric acid caused a two-fold increase in the digestive solubilization of pinto bean iron when compared to control, the amount of iron donated to transferrin was similar. The addition of ascorbic acid did not increase digestive solubilization of iron, however the iron exchange to transferrin increased 1.6 times. A maximum reactivity of pinto bean iron was observed when orange juice or ascorbic plus citric acids were included in the digestion. A strong inhibitory effect of tea on iron reactivity was seen. The order of additives in terms of their enhancement of the reaction of pinto bean supernatant with apotransferrin is: ascorbic plus citric acids > orange juice > ascorbic acid > citric acid > control > phosvitin > tea. This order parallels that expected for the effect of the additives on human iron bioavailability.
A model for the rapid assessment of iron availability was developed that combines in vitro digestion with iron uptake by Caco-2 cell monolayers. In this method, samples (beef, ascorbic acid, or citric acid) were adjusted to pH 2, labeled with 59Fe, and subjected to pepsin digestion (pH 2, 37°C) for 1 h to simulate gastric digestion. Next, a dialysis bag (12,000–14,000 molecular weight cutoff) containing 150 mM PIPES buffer (pH 6.7) was placed in the digest and incubation continued for 30 min. Then, a pancreatin-bile mixture was added, and incubation was continued for an additional 2 h. The contents of the dialysis bag were removed and an aliquot applied to Caco-2 cell monolayers. After a 60 min incubation, iron that was non-specifically bound to the surface of the monolayer was removed by rinsing with a solution containing bathophenanthrolinedisulfonic acid and sodium dithionite. Cells were then counted for 59Fe activity to measure uptake. Beef and ascorbic acid enhanced Caco-2 cell iron uptake, whereas citric acid had no effect. These results compare favorably with literature reports of human studies and suggest that a dialyzable factor(s) less than 14,000 daltons, released during beef digestion, was responsible for the iron absorption-enhancing properties of beef. We believe that this system will be useful for studying basic mechanisms of iron absorption and for in vitro estimation of iron bioavailability.
The validity of the use of extrinsic labeling for studies of manganese absorption in man was evaluated using a test meal containing Beta vulgaris intrinsically labeled with ⁵⁴Mn to which ⁵²Mn was added extrinsically. Whole body retention of the two isotopes was measured in a whole body counter during days 7–25 after administration of the test meal to six subjects. No difference in level of retention or rate of excretion was observed for the two isotopes. The calculated absorption (X = SD) was 6.0 ± 3.4% and 6.2 ± 2.9% for ⁵⁴Mn and ⁵²Mn, respectively, resulting in a ⁵⁴Mn : ⁵²Mn ratio for fractional absorption from the test meal of 0.95 ± 0.14 (X ± SD). These results demonstrate that extrinsic labeling with radioisotopes of manganese is a valid method for measurement of manganese absorption from vegetables when studied in humans.
Artificially produced radioactive iron is an extremely sensitive agent for use in following iron in the course of its changes
in body metabolism, lending itself to studies of absorption, transport, exchange, mobilization, and excretion.
The need of the body for iron in some manner determines the absorption of this element. In the normal dog when there is no
need for the element, it is absorbed in negligible amounts. In the anemic animal iron is quite promptly assimilated.
The plasma is clearly the means of transport of iron from the gastrointestinal tract to its point of mobilization for fabrication
into hemoglobin.
The speed of absorption and transfer of iron to the red cell is spectacular. The importance of the liver and bone marrow in
iron metabolism is confirmed.
An in vitro equilibrium dialysis test for estimating the strength of zinc binding to protein foods was developed for predicting zinc bioavailability. Soy flour, soy concentrate, casein, and dried egg white were labeled with 65ZnCl2 before dialysis. The conditions included 24-h dialysis at pH 7.4 against 0.05 M tris(hydroxymethyl)aminomethane buffer (Tris), Tris plus 0.01 M L-histidine hydrochloride (Tris-His), and Tris plus 0.01 M Na2EDTA (Tris-EDTA). Dialyzate and retentate 65Zn were measured. The protein foods retained 65Zn in the following decreasing order according to treatment: Tris > Tris-His > Tris-EDTA. The bioavailability of residual 65Zn in casein, egg white, soy concentrate, and soy flour after each buffer treatment was determined by giving single doses of the protein foods to young Japanese quail. For these protein foods, the best agreement between in vitro and in vivo data was with Tris-His-dialyzable 65Zn values and the whole-body 65Zn retentions from the labeled casein and egg white (no treatment). The data suggest that this in vitro test could be useful for preliminary assessment of zinc bioavailability of protein foods.
Kinetics of zinc metabolism are described for weanling piglets fed casein-based diets that contained 12–14 (marginal) or 100–104 (recommended) mg Zn/kg. After 10–11 days 61Zn was given to each animal intravenously as a bolus dose of 4 μg/kg body weight. Anticoagulated blood was withdrawn at timed intervals until 1, 24, or 120–144 h after label administration in short, intermediate, and long-term studies, respectively, at which times piglets were euthanized and liver, spleen, and kidney were excised. Zinc concentrations of diets, erythrocytes, plasma, spleen, liver, and kidney were determined by atomic absorption spectrophotometry, and 70Zn/61Zn was measured by inductively coupled plasma mass spectrometry. Data for label enrichments and total zinc content at all time points were fitted simultaneously for both dietary treatments by modification of a compartmental model previously developed for zinc metabolism in adult humans. Mean plasma and liver zinc concentrations were significantly lower (24% and 76%, respectively) in the marginal dietary group. Adjustments in values of model parameters that gave the best fit for the marginal group relative to the recommended group were 1) 5.52-fold higher fractional zinc absorption; 2) 30% lower release of zinc from erythrocytes; and 3) spleen accounting for a larger fraction (30% vs. 20%) of a smaller compartment that turns over in 3.6 h. Normal piglets compensate for marginal zinc intake primarily through increase in fractional zinc absorption. Differences in liver and plasma zinc caused by difference in dietary zinc correspond with calculations of their zinc pool sizes. © 1996 Wiley-Liss, Inc.
Two assays measuring iron bioavailability were compared. The absorption of a radioiron test meal given to iron depleted rats before and after partial repletion was compared to hemoglobin regeneration in the same animals. Ferrous sulfate, low fat soy flour, spinach, hemoglobin and ferrous sulfate with added ethylenediamine-tetraacetic acid (EDTA) were the iron sources selected based on their known wide variability in iron availability. The relative biological value (RBV) determined by the hemoglobin bioassay ranged from 100 to 30 percent (FeSO4=100) and the percent absorption of 39Fe ranged from 92 to 29 for these sources of iron. The correlation coefficients for the two assays ranged between r=0.98 and 0.73. A standard protocol for conduct of the radioiron assay in rats in suggested. Intrinsic and extrinsic labeling techniques were compared for rats fed the soy diet and found to be insignificant (p>0.05).
We evaluated the effect of increased dietary fiber (DF) content in weaning cereals based on wheat/soy (8.0 and 1.8% DF) and wheat/milk (5.3 and 2.0% DF) in healthy, formula-fed infants 7-17 weeks old. The study had a cross-over design, each infant acting as his or her own control. Stool characteristics and anthropometry were monitored over 4-week periods in groups of 34 (wheat/soy) and 23 (wheat/milk) infants. Absorption of zinc (Zn) and calcium (Ca) was studied by measuring the fecal excretion of stable isotopes during 72 h (70Zn and 42Ca) in a subgroup of the infants consuming wheat/soy cereals. Iron (Fe) bioavailability was evaluated by analysis of the incorporation of 58Fe into erythrocytes 14 days after administration. Fractional absorption (X +/- SD: 8.0 versus 1.8% DF) was 45.3 +/- 27.5 versus 41.2 +/- 19.4% of 70Zn and 63.4 +/- 15.8 versus 64.4 +/- 10.6% of 42Ca. Bioavailability of 58Fe varied between 1.0% and 5.4% (8.0% DF) and from <0.9% to 9.1% (1.8% DF). No significant difference in energy (95.3 +/- 2.0% versus 95.7 +/- 1.2%) or nitrogen (92.6 +/- 2.3% versus 93.0 +/- 1.6%) apparent absorption from the total diet was found during consumption of cereal with 8.0 and 1.8% DF. The intake of cereal decreased with higher DF content in the wheat/soy product: 34 +/- 23 g/d (8.0% DF) versus 42 +/- 23 g/d (1.8% DF), p < 0.01. While consuming the 8.0% DF product, 11 infants were reported to have "gritty stools"; no other differences were observed between different groups in stool characteristics or anthropometry. These results demonstrate no negative effect on the absorption of energy and nutrients with higher dietary fiber intake in primarily formula-fed infants. The impact of increased dietary fiber levels remains unknown in less well-nourished infants.
Es wurde geprft, ob die Verringerung des molaren Phytinsure/Zink-Quotienten in Vollkorn- oder Knckebrot mit einem hohen Phytinsuregehalt durch Anreicherung mit Zink die gleiche gnstige Wirkung auf die Zinkverfgbarkeit hat wie die Reduzierung der Phytinsure in Vollkornprodukten. In einem dreiwchigen Versuch wurden 5 Diten (3 Schrotbrot- und 2 Knckebrotproben) an wachsende Ratten verfttert. Die Proben, in denen der Phytinsure/Zink-Quotient durch Anreicherung mit Zink oder durch Reduzierung der Phytinsure (enzymatische Hydrolyse durch Einstellung des pH-Wertes des Teiges mit Milchsure) verringert war, bewirkten eine signifikante Erhhung der Zinkeinlagerung im Femur und der Aktivitt der alkalischen Phosphatase im Serum der Tiere im Vergleich zu unbehandelten Brotproben. Das Wachstum der Tiere zeigte nur geringe Unterschiede zwischen den 5 Gruppen. Die Ergebnisse lassen erkennen, da eine Verbesserung der Zinkverfgbarkeit in Getreidevollkornprodukten mit hohem Phytatgehalt durch Anreicherung mit Zink erzielt werden kann.A study was untertaken to determine whether the reduction of the molar phytic acid/zinc ratio by enrichment of wholemeal and crispbread with zinc improves zinc availability to the same extent as does the reduction of phytic acid in whole meal cereal products. For three weeks, five diets (three samples of wholemeal bread and two samples of crispbread)) were fed to growing rats. Significant increases in bone-zinc deposition and activity of serum alkaline phosphatase were induced by those bread samples in which the phytic acid/zinc ratio had been lowered either by enrichment with zinc or by reduction of phytic acid (enzymatic hydrolysis by adjusting the pH-value of the dough with lactic acid) when compared with untreated bread samples. Weight gain of the animals differed little between the groups. The results suggest that it is possible to improve zinc availability in wholemeal cereal products high in phytate by enrichment with zinc.
Aufgrund des hohen Phytatgehaltes ist die Bioverfgbarkeit von Zink in Getreidevollkornprodukten im Vergleich zu tierischen Nahrungsmitteln deutlich herabgesetzt. In dreiwchigen Ftterungsversuchen an wachsenden Ratten wurde geprft, wie sich eine Reduzierung des Phytatgehaltes in Vollkornprodukten aus Roggen und Weizen auf Wachstum, Zinkgehalt in Femur und Blutserum sowie auf die Aktivitt der alkalischen Phosphatase im Blutserum auswirkt. Die Reduzierung des Phytats erfolgte mit Hilfe der getreideeigenen Phytaseaktivitt. Durch die getroffenen Manahmen verringerte sich der molare Phytinsure/Zink-Quotient in den Vollkornprodukten von 27–37 auf 3–18. Alle 4 untersuchten Parameter zeigten eine signifikante Verbesserung der Zinkverfgbarkeit mit abnehmendem Phytinsure/Zink-Quotienten. Die bertragbarkeit dieser Ergebnisse auf den Menschen sowie die Eignung des Phytinsure-Zink-Quotienten als Indikator fr die Zinkverfgbarkeit in Nahrungsmitteln werden diskutiert.Due to its high phytate content, the bioavailability of zinc in whole meal cereal products is distinctly lower as compared to foods of animal origin. The effect of reducing the phytate content of cereal products made from rye and wheat on growth, zinc content of femur and blood serum, as well as on the activity of serum alkaline phosphatase was investigated during a 3-week feeding trial in growing rats. The reduction of phytate was achieved by controlling the phytase activity originally present in cereals. By these treatments, the molar phytic acid/zinc ratio in the cereal products was reduced from 27–37 to 3–18. The four parameters under investigation showed a significant improvement in zinc bioavailability with decreasing phytic acid/zinc ratios. The relevance of these results for man and the value of the molar phytic acid/zinc ratio as an indicator of the bioavailability of zinc in foods are discussed.
One self-selected study (study A) and one laboratory-controlled study (study B) were conducted to investigate the effect of tea consumption on zinc bioavailability in healthy humans. The 14-day study A consisted of two 7-day experimental periods, while the 28-day study B consisted of two 14-day experimental periods. In study A eight subjects and in study B ten subjects were participated. Subjects of study A consumed self-selected diets and kept a record of foods eaten. In study B, subjects ate a constant and weighed laboratory controlled diet. In both studies, subjects consumed 8 g of instant tea during tea supplementation periods. Complete urine and fecal collections were made by subjects of both studies. Zinc contents of urine, fecal and food samples were determined by using Atomic Absorption Spectrophotometer. Mean zinc intakes of humans consuming self-selected diets were below the RDA. Mean urinary zinc excretion, fecal zinc excretion and zinc balance were unaffected by the tea consumption. Negative zinc balances in study A and positive zinc balances in study B were observed in both tea and no tea dietary treatments. Tea consumption showed a small but not statistically significant adverse affect on zinc bioavailability in humans.
The purpose of this 2 factorial designed study was to investigate the influence of citric acid on the availability of zinc from diets containing 140 g corn germs as a native phytate source (0.5% phytate in diet).
Growing male rats with an average initial weight of 42 g were divided into 8 groups of 8 animals each. After a 7 d depletion period (2.4 μg Zn/g diet) the animals were fed ad libitum for 21 d a diet on the basis of egg white solid and corn germs. The diets were supplemented with zinc in order to obtain phytate:zinc molar ratios of 31, 20, 14, and 0 (control without corn germs, 11 μg Zn/g diet). Each diet was fed with and without a supplementation of 1 % citric acid.
A phytate∶Zn molar ratio of 31∶1 resulted in typical symptoms of zinc-deficiency like anorexia, alopecia and a significant depression of growth. These effects were apparently reduced by citric acid. The zinc concentration in serum and organs followed the graded levels of phytate:zinc molar ratios. Primary significant effects of the phytate∶Zn molar ratio but also effects of citric acid and interactions between the 2 factors phytate∶Zn and citric acid could be detected. Only total liver zinc but not liver zinc based on fresh matter was affected by the phytate∶Zn molar ratio. In serum and tissues the activity of alkaline phosphatase showed a significant response to the phytate⪍inc molar ratio. Furthermore the supplementation with citric acid increased the femur alkaline phosphatase and slightly reduced it in the liver. The concentrations of metallothionein in liver duodenum, jejunum and ileum were significantly affected by the phytate∶Zn molar ratio.
The effect of phytate reduction, fat extraction, and addition of Ca in the form of skim or whole milk on Ca and Zn bioavailability
from a breakfast containing bran muffins was studied in vitro and in vivo. Ca and Zn solubility were measured after in vitro
simulated peptic and pancreatic digestion under pH conditions resembling those in the human GI tract. Absorption of Ca and
Zn was measured in rats fed test meals tagged with45Ca and65Zn. Radioactivity in the femur and liver relative to levels found in rats injected with the isotopes served as criteria for45Ca and65Zn absorption, respectively.
In vitro solubility was significantly depressed by the presence of phytate and inversely correlated with the phytate: Zn and
the (phytate)(Ca): (Zn) ratios. Ca solubility was enhanced by extraction of fat and markedly increased by reduction in both
fat and phytate. None of these effects was seen in vivo. However,65Zn absorption was significantly decreased by fat extraction and phytate reduction although this treatment increased in vitro
Zn solubility. Possible reasons for these discrepancies are discussed.
A whole-body radioassay method was used to assess effects of supplemental dietary amino acids on absorption by rats of zinc in two varieties of corn kernels labeled either intrinsically or extrinsically with 65Zn. Corn genotypes were a normal type (Nor-corn) with one row of cells in the aleurone layer of the kernel and a variety (Mal-corn) that had multiple rows of cells in the aleurone. In experiment 1, rats fed a basal diet containing 15% soy protein absorbed 64% of the 65Zn provided extrinsically in test meals. When provided test meals that contained intrinsically labeled Nor-corn or Mal-corn kernels, the rats absorbed 64 and 57% of the intrinsic 65Zn, respectively. In rats fed diets that contained supplemental lysine, methionine, or both lysine and methionine, absorption of extrinsic 65Zn averaged 69, 82 and 86% of the dose, respectively. In experiment 2, rats fed the basal diet absorbed 57 and 53% of the intrinsic 65Zn in Nor-corn and Mal-corn kernels, respectively, but rats fed supplemental methionine or cysteine absorbed 73% of the intrinsic 65Zn in either the Nor-corn or Mal-corn kernels. Supplemental methionine or cysteine fed to rats that were marginally zinc deficient enhanced the absorption of 65Zn provided in test meals in the form of either intrinsically labeled corn kernels or as 65Zn-labeled zinc sulfate.
Objectives of this research were to compare iron bioavailabilities from infant rice cereals fortified with either electrolytic iron (EI) or ferrous sulfate (FS) and to evaluate the piglet as a model for iron bioavailability studies. Iron bioavailability was assessed by hemoglobin repletion assay. Yorkshire piglets were weaned at 21 days of age and assigned to 2 groups of 8 on the basis of hemoglobin (Hb) concentration, litter, and sex. Iron depletion was achieved by simply withholding the iron injections normally given to newborn pigs. Repletion diets contained 780 g of iron fortified rice cereal per kg diet and new formulated to meet the nutrient requirements of piglets. The diets were identical except for the form of iron used to fortify the cereal (iron concentrations in the EI and FS diets were 118 and 127 mg/kg diet, respectively). The piglets were fed the repletion diets for 10 days. Means of initial/final Hb concentrations were 7.0/6.5 and 7.0/8.8 g/dL for the EI and FS groups, respectively. mean Hb iron gain (total Hb iron on day 11 minus total Hb iron on day 1) was significantly lower (P<0.001) in the group fed EI fortified cereal (20.62 versus 58.07 mg) Although the bioavailability of EI from commercial fortified infant cereals is low compared to FS, these products may supply a significant portion of the iron needs for many infants because of their high iron content. The piglet is a promising model for iron bioavailability studies.
The bioavailability of chromium was examined in three feeding studies using laboratory rats. Absorption of the mineral from extrinsically labeled potato preparations was compared to absorption of an intrinsic potato label and of chromate. Raw and cooked potato preparations were fed. Excretion of endogenous chromium was 6% of daily intake. True and apparent absorption of chromium were calculated as percent of intake and were apparently affected by both labeling and preparation methods used. True absorption from extrinsically labeled feedings was 33.4±4.7% and apparent absorption, 27.0±7.1%. No difference existed between raw and cooked feedings. These results differed significantly from absorption of intrinsic labels and of chromate. True absorption from raw intrinsically labeled potatoes was 13.3±5.9% of dose. Apparent absorption of raw intrinsically labeled feedings (11.1±7.9%) differed significantly from that of the cooked intrinsically labeled material (−0.7±2.8%). True absorption of inorganic chromium was 17.8% and apparent absorption, 11.5%.
Two experiments were conducted to study the effect of high dietary Cu and duration of feeding time on tissue mineral composition of sheep to establish a standard curve for future bioassay of supplemental Cu sources. In Experiment 1, 24 crossbred wethers were fed a basal diet (9.24 mg/kg Cu) supplemented with 15, 30 or 45 mg/kg added Cu as cupric acetate for 15 or 30 days. An additional four sheep were killed at day 0 to serve as controls. In Experiment 2, 30 crossbred wethers were injected i.v. with 50 mg ammonium tetrathiomolybdate (ATM) twice weekly for 3 weeks to reduce body Cu stores, then fed the basal diet (7.29 mg/kg Cu) or the basal plus 20, 40, 60 or 80 mg/kg added Cu as cupric acetate for 10 or 20 days. Treatment with ATM reduced liver Cu stores by 52%. In Experiment 1, liver and bone Cu concentrations were greater in sheep supplemented with Cu compared with controls, but there was no difference among sheep fed various added Cu concentrations. In Experiment 2, liver Cu concentration increased linearly in sheep fed 10 days and quadratically in sheep fed 20 days, but serum, spleen and kidney Cu concentrations were not affected by treatment. A bioassay for Cu bioavailability based on liver Cu uptake with a 10-day supplementation period appeared feasable.
Chromium and ascorbate depletion effects on 51chromium retention and excretion after a dose of 51CrCl3 were investigated in guinea pigs. Weanling animals were fed low chromium (−Cr, <0.15 μg/g diet) or chromium-adequate (+Cr, 2 μg Cr from CrCl3/g diet) casein-based diets and were restricted to 0.5 mg ascorbate/d (−C) or supplemented with 10 mg ascorbate/d (+C) for 23 weeks. Ascorbate depletion did not inhibit 51Cr uptake as evidenced by no difference in tissue retention and by a significant increase in urinary excretion in −C animals. Animals fed −Cr diets had higher 51Cr in blood and liver than those fed +Cr diets. An effect of previous dietary intake of chromium on 51Cr uptake has not been previously reported.
Little is known about factors affecting availability of many trace elements. If the trace element is widely distributed in foods and there are no signs of nutritional deficiencies in vulnerable groups of the population, it could be argued that such details are primarily of academic interest. If there are signs that requirements for a trace element are not being met - indicating nutritional deficiency - it is most important to have a thorough knowledge and understanding of factors affecting availability. This article attempts to detail these factors as well as methods for the examination of trace element bioavailability, such as chemical balance experiments, rate of hemoglobin repletion plasma tolerance curves, isotopic techniques and in-vitro techniques.
Artificially produced radioactive iron is an extremely sensitive agent for use in following iron in the course of its changes in body metabolism, lending itself to studies of absorption, transport, exchange, mobilization, and excretion. The need of the body for iron in some manner determines the absorption of this element. In the normal dog when there is no need for the element, it is absorbed in negligible amounts. In the anemic animal iron is quite promptly assimilated. The plasma is clearly the means of transport of iron from the gastrointestinal tract to its point of mobilization for fabrication into hemoglobin. The speed of absorption and transfer of iron to the red cell is spectacular. The importance of the liver and bone marrow in iron metabolism is confirmed.
An in vitro method for the determination of availability of nonheme iron from foods and diets was investigated. Food was extracted with pepsin-HCl at pH 1.35 and subsequently the pH was adjusted to pH 7.5 and filtered. Ionizable iron was determined in the pH 7.5 filterate by the alpha, alpha-dipyridyl method. The percent iron absorption from the same diets observed in the adult males. Ionizable iron at pH 7.5 was shown to increase in presence of ascorbic acid and meat extract while it decreased in presence of phytate and tannins, similar to the effects of these factors on iron absorption in human subjects. Based on these observations it is proposed that ionizable iron at pH 7.5 determined as described in this study can be used as a reliable measure of bioavailability of nonheme iron in foods.
Studies were performed in adult volunteer subjects to determine the effect on nonheme iron absorption of protein, carbohydrate, and fat. These constituents were administered as egg albumin, dextrimaltose, and corn oil, respectively, in a semisynthetic meal containing 700 kcal and 4.1 mg iron. Because any one of these ingredients are unpalatable when administered alone, their effect was determined by serially deleting or doubling their content in the basal semisynthetic meal. With both approaches, carbohydrate and fat had little influence whereas egg albumin had a significant inhibitory effect on the absorption of nonheme iron.
As ascorbic acid is known to enhance the absorption of dietary iron and to inhibit the absorption of dietary copper, studies were undertaken to examine the effect of ascorbic acid on the bioavailability of zinc in human subjects. The index of absorption was the change in plasma zinc concentration after a 110-mg aqueous dose of ZnSO4.7H2O (containing 25 mg of elemental zinc). Doses of 0.5, 1.0, and 2.0 g of ascorbic acid, representing a spectrum of Zn:ascorbic acid molar ratios from the dietary to the pharmacological range, failed to produce any significant change in the pattern of zinc absorption. Moreover, 2.0 g of ascorbic acid, equivalent to a Zn:ascorbic acid ratio of 0.145 failed to improve the absorption of 108 mg of elemental zinc incorporated into 120 g of black bean gruel. Ascorbic acid over a range of dosages commonly consumed by man had no demonstrable effect on the absorption of inorganic zinc.