Nutritional aspect of zinc availability

Use of granules and free salts for Fe and Zn fortification of leafy vegetables: Improvements in trace element bioaccessibility and fulfillment of Dietary Reference Intakes

BACKGROUND

Leafy vegetables represent an excellent dietary source of trace elements such as Fe and Zn. Nevertheless, Fe and Zn bioaccessibility can lessen due to a high concentration of anti-nutritional compounds. The encapsulation of Fe and Zn salts as granules could be used to fortify these leafy vegetables.

METHOD

Three leafy vegetables, spinach, Swiss chard and Ethiopian mustard were fortified with iron sulfate and zinc sulfate as granules and free salts in order to test the improvements in the bioaccessibility and fulfillments of DRIs. Fe and Zn granules were prepared in a fluidized bed granulator. A probabilistic analysis was performed, using experimental data, to assess bioaccessible intake and fulfillments of DRIs in European populations.

RESULTS

Fe contents ranged between 4.8 mg/100 g of Ethiopian mustard to 157.4 mg/100 g of spinach. Fe and Zn bioaccessibility percentages were low for Swiss chard and spinach without fortification. Fortification with granules improved Fe bioaccessibility of these latter vegetables (196 and 223 mg/100 g). Zn contents in samples without fortification ranged between 2.3 mg/100 g for Ethiopian mustard and 7.4 mg/100 g for spinach. Zn fortification as granules improved Zn bioaccessibility for the three vegetables studied. Thus, Zn bioccessible concentrations ranged between 17.4 and 108 mg/100 g for the solubility assay and between 5.9 and 31.1 mg/100 g for the dialyzability assay. Besides, the probability analysis showed that fortification had a better performance in meeting DRIs for those populations with higher consumption levels of leafy vegetables.

CONCLUSIONS

The probability analysis demonstrated that fortification can be a suitable strategy to meet DRIs for both trace elements, which was especially remarkable for Fe. Fortification with granule was more effective in most the cases, although for Ethiopian mustard, free salt of Fe showed a better performance.

Comparative study on the effects of micro- and nano-sized zinc oxide supplementation on zinc-deficient mice

BACKGROUND

Zinc (Zn) is an essential cofactor for physiological homeostasis in the body. Zn oxide (ZnO), an inorganic compound that supplies Zn, exists in various sizes, and its bioavailability may vary depending on the size in vivo. However, comparative studies on the nutritional effects of micro-sized ZnO (M-ZnO) and nano-sized ZnO (N-ZnO) supplementation on Zn deficiency (ZnD) animal models have not been reported.

OBJECTIVES

This study investigated the nutritional bioavailability of N-ZnO and M-ZnO particles in dietary-induced ZnD mice.

METHODS

Animals were divided into six experimental groups: normal group, ZnD control group, and four ZnO treatment groups (Nano-Low, Nano-High, Micro-Low, and Micro-High). After ZnD induction, N-ZnO or M-ZnO was administered orally every day for 4 weeks.

RESULTS

ZnD-associated clinical signs almost disappeared 7 days after N-ZnO or M-ZnO administration. Serum Zn concentrations were higher in the Nano-High group than in the ZnD and M-ZnO groups on day 7 of ZnO treatment. In the liver and testis, Nano-Low and Nano-High groups showed significantly higher Zn concentrations than the other groups after 14-day treatment. ZnO supplementation increased Mt-1 mRNA expression in the liver and testis and Mt-2 mRNA expression in the liver. Based on hematoxylin-and-eosin staining results, N-ZnO supplementation alleviated histological damage induced by ZnD in the testis and liver.

CONCLUSIONS

This study suggested that N-ZnO can be utilized faster than M-ZnO for nutritional restoration at the early stage of ZnD condition and presented Mt-1 as an indicator of Zn status in the serum, liver, and testis.

Zinc nutrition and dietary zinc supplements

As the second most abundant trace element in the human body, zinc nutrition is constantly a hot topic. More than one-third population is suffering zinc deficiency, which results in various types of diseases or nutritional deficiencies. Traditional ways of zinc supplementation seem with low absorption rates and significant side effects. Zinc supplements with dietary components are easily accessible and improve zinc utilization rate significantly. Also, mechanisms of maintaining zinc homeostasis are of broad interest. The present review focuses on zinc nutrition in human health in inductive methods. Mainly elaborate on different diseases relating to zinc disorder, highlighting the impact on the immune system and the recent COVID-19. Then raise food-derived zinc-binding compounds, including protein, peptide, polysaccharide, and polyphenol, and also analyze their possibilities to serve as zinc complementary. Finally, illustrate the way to maintain zinc homeostasis and the corresponding mechanisms. The review provides data information for maintaining zinc homeostasis with the food-derived matrix.

Monitoring bioaccessibility of iron and zinc in pearl millet grain after sequential milling

The present study was to understand the effect of sequential milling on the distribution of inhibitory factors and their relation to iron-zinc bioaccessibility in the two pearl millet cultivars differing in grain shape and size. The studies revealed that the yield of decorticated grain and bran fractions differed between the cultivars. The initial bran fractions had lower iron content, which increased on increase of decortication duration (2.33-25.14 mg/100 g), while zinc did not follow this pattern. Among the inhibitory factors, polyphenols and phytic acid were low in the initial stages of milling and subsequently increased as the milling duration increased. Microscopic studies further confirmed that iron-zinc and inhibitory factors coexist in the same tissues of the grain. The β- carotene was more concentrated in the middle layers of the pericarp. It was observed that iron bioaccessibility was the highest in the 4 min milling bran (7.7%, 3.34%) and final decorticated grain fractions (13.79%, 18.45%) of both the cultivars. Iron bioaccessibility could not be related to any particular inhibitory factors, in bran insoluble fibre and phytic acid were prominent while in decorticated grain galloyls, catechols and phytic acid were the maxima. In both the cultivars, zinc bioaccessibility was high in fractions with low phytic acid and insoluble fibre. The data presented suggest that 6 min decortication that removed around 10-15% of the bran had the highest iron and zinc bioaccessibility. The iron-rich bran fraction after appropriate processing can also be used in speciality food and thereby addresses the problem of micronutrient deficiency.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05072-x.

Effect of Enzymatic Hydrolysis on the Zinc Binding Capacity and in vitro Gastrointestinal Stability of Peptides Derived From Pumpkin (Cucurbita pepo L.) Seeds

Zinc is a crucial micronutrient for maintaining body immune system and metabolism function. However, insufficient intake from diet may lead to zinc deficiency and impair normal body function. In addition, conventional zinc salts supplementation has the disadvantage of low bioavailability since the zinc ions may be easily chelated by dietary fiber or phytate commonly found in diets rich in plants, and form precipitates that cannot be absorbed. Therefore, the objective of the present study is to prepare pumpkin seed derived peptides and to evaluate the effect of structure and surface properties on the zinc binding behavior of the pumpkin seed protein hydrolysate (PSPH), as well as their gastrointestinal stability. Briefly, different PSPHs were prepared using enzymatic hydrolysis method with bromelain, papain, flavourzyme, alcalase, and pepsin. The particle size, zeta potential, surface hydrophobicity, degree of hydrolysis, ATR-FTIR spectra, and zinc binding capacity were determined. The representative samples were chosen to characterize the binding energy and surface morphology of PSPH-Zn. At last, the in vitro gastrointestinal stability of PSPH and PSPH-Zn were evaluated. Our results showed that peptides hydrolyzed by papain had the largest average molecular weight, smallest particle size, highest hydrophobicity, and the greatest zinc binding capacity. Zinc showed better gastrointestinal stability in PSPHs chelates than in its salt. Meanwhile, PSPH-Zn with higher zinc binding capacity showed better stability. The result of this study indicated pumpkin seed hydrolyzed by papain may be used as a potential source for zinc fortification. The findings in this study may provide important implications for developing plant-based zinc chelating peptides.

Ferritin Nanocage: A Versatile Nanocarrier Utilized in the Field of Food, Nutrition, and Medicine

Compared with other nanocarriers such as liposomes, mesoporous silica, and cyclodextrin, ferritin as a typical protein nanocage has received considerable attention in the field of food, nutrition, and medicine owing to its inherent cavity size, excellent water solubility, and biocompatibility. Additionally, ferritin nanocage also serves as a versatile bio-template for the synthesis of a variety of nanoparticles. Recently, scientists have explored the ferritin nanocage structure for encapsulation and delivery of guest molecules such as nutrients, bioactive molecules, anticancer drugs, and mineral metal ions by taking advantage of its unique reversible disassembly and reassembly property and biomineralization. In this review, we mainly focus on the preparation and structure of ferritin-based nanocarriers, and regulation of their self-assembly. Moreover, the recent advances of their applications in food nutrient delivery and medical diagnostics are highlighted. Finally, the main challenges and future development in ferritin-directed nanoparticles’ synthesis and multifunctional applications are discussed.

Peptide-metal complexes: obtention and role in increasing bioavailability and decreasing the pro-oxidant effect of minerals

Bioactive peptides derived from food protein sources have been widely studied in the last years, and scientific researchers have been proving their role in human health, beyond their nutritional value. Several bioactivities have been attributed to these peptides, such as immunomodulatory, antimicrobial, antioxidant, antihypertensive, and opioid. Among them, metal-binding capacity has gained prominence. Mineral chelating peptides have shown potential to be applied in food products so as to decrease mineral deficiencies since peptide-metal complexes could enhance their bioavailability. Furthermore, many studies have been investigating their potential to decrease the Fe pro-oxidant effect by forming a stable structure with the metal and avoiding its interaction with other food constituents. These complexes can be formed during gastrointestinal digestion or can be synthesized prior to intake, with the aim to protect the mineral through the gastrointestinal tract. This review addresses: (i) the amino acid residues for metal-binding peptides and their main protein sources, (ii) peptide-metal complexation prior to or during gastrointestinal digestion, (iii) the function of metal (especially Fe, Ca, and Zn)-binding peptides on the metal bioavailability and (iv) their reactivity and possible pro-oxidant and side effects.

Isolation and identification of zinc-chelating peptides from sea cucumber (Stichopus japonicus) protein hydrolysate

BACKGROUND

Zinc is known to play an essential role in the biological activities in the human body. In this study, a zinc-chelating peptide (ZCP) produced by Alcalase-assisted hydrolysis of the body wall of sea cucumber was isolated and identified. The ZCP was purified stepwise by ultrafiltration, anion-exchange chromatography, and gel filtration chromatography, in conjunction with ultraviolet-visual (UV-visual) spectrophotometry, which was used to analyze each purified fraction.

RESULTS

Analysis of the purified ZCP revealed that its zinc-chelating ability was 33.31%. Analysis of isothermal titration calorimetry suggested that the binding of ZCP and zinc (N ≈ 2) was endothermic, with weak binding affinity. Fourier transform infrared spectroscopy spectra (FTIR) indicated that carboxylic and amide groups in ZCP were the primary binding sites of Zn. Sequencing the result by ultra-performance liquid chromatography-quadrupole/time of flight mass spectrometry (UPLC-Q-TOF-MS/MS) showed that a representative ZCP had the sequence WLTPTYPE with a molecular weight of 1005.5 Da.

CONCLUSION

These results provide a promising foundation for the production of zinc supplements from sea-cucumber-derived ZCPs. © 2019 Society of Chemical Industry.

Effect of decortication methods on the chemical composition, antinutrients, Ca, P and Fe contents of two pearl millet cultivars during storage

Purpose

The purpose of this paper is to evaluate the impact of modern and traditional decortication methods on the chemical composition, antinutrients, Ca, P and Fe contents during storage of two pearl millet cultivars (white and green) grown in Sudan.

Design/methodology/approach

The grains of each cultivar were either decorticated traditionally using traditional stone dehuller or by using modern dehuller. The chemical composition, antinutrients and Ca, P and Fe contents of the cultivars were evaluated during storage for six months.

Findings

The results showed that both methods of decortication (modern and traditional) employed significantly decreased ash, protein, oil and crude fiber contents but increased moisture and nitrogen free extract contents of the grains for both cultivars. Storage resulted in a slight and gradual decrease in the chemical composition of the treated and untreated grains of the cultivars. Modern decortication of the grains significantly (P=0.05) reduced tannin content in both cultivars compared to untreated and traditionally decorticated grains. Phytic acid content of the white cultivar was not affected by the method of decortication used but modern decortication reduced that of green cultivar. Decrease in tannin and phytic acid was observed as the storage continued in both treated and untreated cultivars. Decortication significantly (P=0.05) reduced the Ca, P and Fe contents in both cultivars grains. Lower P and Fe contents were found in modern decorticated grains compared to traditional decorticated ones. Storage of the cultivars resulted in gradual decrease in Ca, P and Fe contents.

Research limitations/implications

Processing methods such as decortication affect the quality attributes of pearl millet cultivars. The application of modern decortication method on pearl millet cultivars has better quality attributes than those treated with traditional decortication.

Originality/value

The study uses decortication methods (traditional and modern) to improve the quality attributes of pearl millet cultivars. Antinutrients such as tannin and phytic acid were observed to reduce the bioavailability of minerals like Fe. Decortication of the grains significantly reduced the level of such antinutrients and improved bioavailability of minerals.

Prospects of enhancing dietary zinc bioavailability with food-derived zinc-chelating peptides

Zinc is an essential micronutrient that strongly influences human health and nutrition through its involvement in several biological processes. Zinc functions as structural and functional component of many transcription factors and enzymes that regulate cell growth, gene expression, and immune response, and its deficiency can lead to retarded growth and impaired immune functions. The physiological functions of zinc are dependent on its bioavailability in tissues, which in turn depends on intestinal absorption of dietary zinc. The presence of dietary fibre and phytates impedes intestinal zinc absorption, as they can form insoluble complexes with zinc, decreasing its bioavailability. Peptides derived from food proteins can enhance zinc absorption and bioavailability. Peptides that contain amino acid residues such as cysteine, histidine, serine, aspartate and glutamate can chelate divalent metals, including zinc, forming soluble metal coordinate complexes. The structure-function relationship of zinc-chelating peptides and the stability of the peptide-metal complexes to gastrointestinal digestion are critical to their relevance in human nutrition and health promotion.

Assessment of inhibitory factors on bioaccessibility of iron and zinc in pearl millet (Pennisetum glaucum (L.) R. Br.) cultivars

The variations in iron and zinc bioaccessibility as influenced by inhibitory factors in 13 pearl millet cultivars were evaluated. The results indicated that iron and zinc contents ranged between 5.59-13.41 and 2.11-5.19 mg/100 g. Polyphenols, flavonoids and phytic acid were highest in GHB744 (781 mg/100 g), HHB223 (116 mg/100 g) and HHB226 (1.080 g/100 g) respectively. Insoluble fiber content range from 9.36 to 12.89 g/100 g. Iron and zinc bioaccessibility was the highest in local Anantapur (17.95%) and GHB744 (15.19%) cultivar with low phytic acid. HHB226 exhibited high β-carotene and phytase activity. In this study, the cultivars with high iron and zinc content also possessed high inhibitory factors which affected bioaccessibility. However, the bioaccessibility of iron did not seem to depend on the phytic acid: iron ratio alone. Further, a trend was observed in cultivars with low iron: zinc ratio had increased iron bioaccessibility. On the contrary, phytic acid: zinc ratio appears to play a significant role in zinc bioaccessibility. Certain cultivars with high iron content also had high phytase activity and β-carotene content which could be exploited for further technological treatments to enhance the bioaccessibility of iron and zinc.

Effect of mineral source and mannan oligosaccharide supplements on zinc and copper digestibility in growing pigs

This study aimed to compare the effects of organic (proteinate) and inorganic (sulphate) copper (Cu) and zinc (Zn) supplements, in presence or absence of a mannan oligosaccharide (MOS) supplement, on mineral solubility and digestibility in pigs. Twenty-eight barrows (25 ± 4 kg) assigned randomly to four treatment groups were fed a corn-wheat-soya bean meal diet with 10 mg/kg of Cu and 100 mg/kg of Zn supplied as organic or inorganic supplement, and supplemented or not with 0.1% MOS. After an adaptation period, total faeces and urine were collected for a period of 6-7 days. Pigs were then euthanatised and digesta from ileum and caecum were collected. Apparent digestibility was calculated in ileum and caecum using titanium dioxide. The organic mineral supplement improved total (faecal) digestibility and retained/ingested ratio of Cu (p < 0.05) while reducing apparent digestibility of Zn in the ileum (p < 0.05) without effect on total digestibility of Zn. Solubilities of Cu and Zn in liquid fraction of ileum and caecum were not affected by mineral sources. Although MOS supplement increased Cu solubility in the ileum (p < 0.05), it had no effect on digestibility of Zn and Cu in ileum, caecum and faeces, retained/ingested ratio of Zn and Cu, or pH and volatile fatty acid concentration in ileal and caecal digesta. In conclusion, organic mineral supplement improved total digestibility and retained/ingested ratio of Cu in pigs but this cannot be attributed to its solubility in ileal and caecal digesta. The MOS supplement did not interfere with digestibility or dietary utilisation of Zn and Cu in pigs fed above the Zn and Cu requirements.

Pharmacokinetics and biodistribution of zinc-enriched yeast in rats

Zinc-enriched yeast (ZnY) and zinc sulfate (ZnSO4) are considered zinc (Zn) supplements currently available. The purpose of the investigation was to compare and evaluate pharmacokinetics and biodistribution of ZnY and ZnSO4 in rats. ZnY or ZnSO4 were orally administered to rats at a single dose of 4 mg Zn/kg and Zn levels in plasma and various tissues were determined using inductively coupled plasma-optical emission spectrometry. Maximum plasma concentration values were 3.87 and 2.81 μg/mL for ZnY and ZnSO4, respectively. Both ZnY and ZnSO4 were slowly eliminated with a half-life of over 7 h and bone had the highest Zn level in all tissues. Compared to ZnSO4, the relative bioavailability of ZnY was 138.4%, indicating that ZnY had a significantly higher bioavailability than ZnSO4.

A novel calcium supplement prepared by phytoferritin nanocages protects against absorption inhibitors through a unique pathway

The consumption of milk is declining in industrialized countries, leading to inadequate calcium intake. Therefore, it is important to explore a new class of Ca-enriched nutrient for the fortification of food. In this work, we prepared a novel class of soluble and edible Ca-protein complexes where approximately 140 calcium ions were encapsulated within a phytoferritin nanocage. As an alternative to other organic and/or inorganic carriers, protein nanocages were found to provide a unique vehicle of biological origin for the intracellular delivery of calcium ions for supplementation. Such encapsulation can protect calcium ions within protein cages against dietary factors such as tannic acid (TA), oxalic acid (OA), and other divalent metal ions in foodstuffs. We demonstrated that the calcium-containing ferritin composites can be absorbed by Caco-2 cells through a process where a TfR1 receptor is involved, whereas the uptake of free calcium ions has been known to be associated with another receptor, DMT1, indicating that the calcium ions encapsulated in supramolecular protein cages can be internalized by the Caco-2 cells through a different pathway from its free analogs for calcium supplementation.

Trace element levels in whole blood of riparian villagers of the Brazilian Amazon

Monitoring the nutritional status of essential elements is of critical importance in human health. However, trace element concentrations in biological fluids are affected by environmental and physiological parameters, and therefore considerable variations can occur between specific population subgroups. Brazil is a large country with much food diversity. Moreover, dietary habits differ from north to south. As an example, the traditional populations of the Brazilian Amazon basin are heavily dependent on fish, fruits, vegetables and manioc for their daily sustenance. However, very few studies have examined to what extent these diets reflect adequate nutritional status for essential elements. Then, in the present study we have evaluated the levels of some trace elements (Cu, Co, Zn Sr, and Rb) in the whole blood of a riparian Brazilian Amazonian population and estimated the influence of age and gender on levels and inter-element interactions in the same population. For this, 253 subjects, aged 15 to 87, from 13 communities situated on the banks of the Tapajós, one of the major tributaries of the Amazon, were randomly selected. The values found for cobalt, copper and strontium in whole blood are in the same range as in other populations. On the other hand, the levels of rubidium and zinc may be considered higher. Moreover, gender was shown to influence Zn and Cu levels while age influenced the concentrations of Sr and Rb in men and Cu in women. Given the scarcity of studies examining nutritional status in traditional communities of the Amazon, our study is the first to provide relevant insight into trace element values in this region and inter-element interactions. This paper is also of particular importance for future studies looking at the possible protective effects of traditional Amazon riparian diets against mercury intake from fish consumption.

Iron bioavailability in fortified fruit beverages using ferritin synthesis by Caco-2 cells

The bioavailability of iron from fortified fruit beverages was estimated by an in vitro system including enzymatic digestion, iron uptake by Caco-2 cells, and ferritin formation determined via an enzyme immunoassay (ELISA). Thus, the aim of the present study was to assess iron bioavailability as influenced by the presence of known dietary promoter and inhibitory factors in fortified fruit beverages containing iron and/or zinc and/or skimmed milk. No negative effect ( p > 0.05) derived from micronutrient interaction can be ascribed to zinc supplementation on iron availability. Besides, the presence of caseinophosphopeptides derived from casein hydrolysis during digestion may confer enhancing effects on iron absorption in samples with milk added with respect to nonadded samples ( p < 0.05). Therefore, from a nutritional point of view, individuals in need of optimal iron absorption may choose dairy samples to ensure optimal iron bioavailability.

Clinical evaluation of the bioavailability of zinc-enriched yeast and zinc gluconate in healthy volunteers

Zinc (Zn)-enriched yeast and gluconate are considered two of the more biologically available supplements. However, there have been few reports comparing the bioavailability of these supplements. The objective of this study was to demonstrate whether Zn was absorbed better by healthy male volunteers when given supplements where the mineral is found organically bound in yeast or as a salt gluconate form. The trial used a randomized, two-way crossover design. Urine, blood, and fecal samples were collected and analyzed over a 48-h period after a single dose of supplement. The net Zn balance and the relative bioavailability were calculated. No differences were observed in urine excretion of the two supplements. Zinc gluconate gave higher Zn concentrations in the blood in the first 6 h but also showed greater losses in the feces. Zinc yeast also increased in blood with time but showed significantly less loss in the feces. Thus, the net Zn balance after 48 h for Zn yeast was 9.46 but for Zn gluconate it was -2.00, indicating that Zn gluconate supplementation contributed to a net loss of Zn. It was concluded that organic Zn yeast supplements are more biologically available than Zn gluconate salts.

Fortification of milk with calcium: effect on calcium bioavailability and interactions with iron and zinc

Calcium solubility, dialysability, and transport and uptake (retention + transport) by Caco-2 cells as indicators of calcium bioavailability have been estimated in the in vitro gastrointestinal digests of milk and calcium fortified milk. A significant linear correlation (p < 0.05) was obtained between calcium uptake and the amount of soluble calcium added to the cells, and also between percentage calcium uptake and the calcium measured in the analyzed samples. The solubility, dialysis, transport, and uptake values are higher (p < 0.05) for calcium fortified milks than for nonfortified milks; that is, calcium fortification increases not only calcium content but also its bioavailability. An inhibitory effect of calcium from fortified milks upon iron absorption was found. The observed effect of calcium from fortified milks upon zinc bioavailability depends on the in vitro method used, zinc solubility and dialysis decrease in calcium fortified milks, and percentage zinc uptake remains unchanged.

Relative contribution of phytates, fibers, and tannins to low iron and zinc in vitro solubility in pearl millet (Pennisetum glaucum) flour and grain fractions

In vitro digestions were performed on pearl millet flours with decreased phytate contents and on two dephytinized or nondephytinized pearl millet grain fractions, a decorticated fraction, and a bran fraction with low and high fiber and tannin contents, respectively. Insoluble residues of these digestions were then incubated with buffer or enzymatic solutions (xylanases and/or phytases), and the quantities of indigestible iron and zinc released by these different treatments were determined. In decorticated pearl millet grain, iron was chelated by phytates and by insoluble fibers, whereas zinc was almost exclusively chelated by phytates. In the bran of pearl millet grain, a high proportion of iron was chelated by iron-binding phenolic compounds, while the rest of iron as well as the majority of zinc were chelated in complexes between phytates and fibers. The low effect of phytase action on iron and zinc solubility of bran of pearl millet grain shows that, in the case of high fiber and tannin contents, the chelating effect of these compounds was higher than that of phytates.