In vitro dialyzability using meal approach as an index for zinc and iron absorption in humans

Comparison of the Potential Relative Bioaccessibility of Zinc Supplements-In Vitro Studies

The aim of this study was to determine the potential relative bioaccessibility of zinc (Zn) from selected dietary supplements during in vitro digestion. The bioaccessibility of Zn was evaluated in dietary supplements differing in the pharmaceutical form, content, dose, and chemical form of the element. The content of Zn was determined by flame atomic absorption spectrometry. The applied method was validated, and results were characterised by good linearity (R² = 0.998), recovery (109%), and accuracy (0.02%). As a result of the tests conducted, it was found that the bioaccessibility of Zn from dietary supplements varied and ranged from 1.1% to 9.4%. The highest bioaccessibility was found for zinc diglycinate and the lowest for zinc sulphate. In 9 out of 10 tested dietary supplements, the determined Zn content was higher than the one declared by the producer (up to 161%). The estimated tolerable upper intake level (UL) was exceeded by five of the analysed dietary supplements (123-146%). The analysed dietary supplements were assessed in terms of compliance with the information contained on the product packaging, based on current Polish and European legal regulations. The qualitative assessment was performed according to the United States Pharmacopoeia (USP) guidelines.

Dual-Fortified Lentil Products-A Sustainable New Approach to Provide Additional Bioavailable Iron and Zinc in Humans

BACKGROUND

Iron (Fe) and zinc (Zn) deficiencies are global health problems affecting 20% and 33% of the world's population, respectively. Lentil (Lens culinaris Medik.), part of the staple food supply in many countries, can be a potential vehicle for Fe and Zn fortification.

OBJECTIVE

We developed a dual-fortification protocol to fortify 3 milled lentil product types (LPTs) [red-football (RF), red-split (RS), and yellow-split (YS)], with NaFeEDTA and ZnSO4.H2O to increase the bioavailable content of Fe and Zn.

METHODS

Appropriate Fe and Zn doses were determined to fortify lentils based on RDAs. Relative Fe bioavailability (RFeB%) and phytic acid (PA) content were assessed using an in vitro Caco-2 cell bioassay and PA analysis, respectively. One-factor ANOVA determined the differences in colorimetric score; concentrations of Fe, Zn, and PA; and RFeB% among samples. The least significant difference was calculated with significance level set at P < 0.05.

RESULTS

Fe and Zn concentration and RFeB% increased and PA concentration decreased significantly in dual-fortified lentils. Dual-fortified lentil samples had higher RFeB% compared with Fe-fortified (single) samples in all 3 LPTs, whereas RFeB% decreased in Zn-fortified (single) RF and YS samples by 43.4% and 36%, respectively. The RF, RS, and YS samples, fortified with 16 mg Fe and 8 mg Zn/100 g of lentils, provided 27 mg Fe and 14 mg Zn, 28 mg Fe and 13.4 mg Zn, and 29.9 mg Fe and 12.1 mg Zn, respectively. RFeB% of RF, RS, and YS lentil samples increased by 91-307%, 114-522%, and 122-520%, respectively. Again, PA concentrations of RF, RS, and YS lentils were reduced by 0.63-0.53, 0.83-0.71, and 0.96-0.79 mg/g, respectively.

CONCLUSIONS

Dual-fortified lentil consumption can cost-effectively provide a significant part of the daily bioavailable Fe and Zn requirements of people with these 2 globally important micronutrient deficiencies.

Bioavailability of iron, zinc, and provitamin A carotenoids in biofortified staple crops

International research efforts, including those funded by HarvestPlus, a Challenge Program of the Consultative Group on International Agricultural Research (CGIAR), are focusing on conventional plant breeding to biofortify staple crops such as maize, rice, cassava, beans, wheat, sweet potatoes, and pearl millet to increase the concentrations of micronutrients that are commonly deficient in specific population groups of developing countries. The bioavailability of micronutrients in unfortified staple crops in developing regions is typically low, which raises questions about the efficacy of these crops to improve population micronutrient status. This review of recent studies of biofortified crops aims to assess the micronutrient bioavailability of biofortified staple crops in order to derive lessons that may help direct plant breeding and to infer the potential efficacy of food-based nutrition interventions. Although reducing the amounts of antinutrients and the conduction of food processing generally increases the bioavailability of micronutrients, antinutrients still possess important benefits, and food processing results in micronutrient loss. In general, biofortified foods with relatively higher micronutrient density have higher total absorption rates than nonbiofortified varieties. Thus, evidence supports the focus on efforts to breed plants with increased micronutrient concentrations in order to decrease the influence of inhibitors and to offset losses from processing.

Application of in vitro bioaccessibility and bioavailability methods for calcium, carotenoids, folate, iron, magnesium, polyphenols, zinc, and vitamins B(6), B(12), D, and E

A review of in vitro bioaccessibility and bioavailability methods for polyphenols and selected nutrients is presented. The review focuses on in vitro solubility, dialyzability, the dynamic gastrointestinal model (TIM)™, and Caco-2 cell models, the latter primarily for uptake and transport, and a discussion of how these methods have been applied to generate data for a range of nutrients, carotenoids, and polyphenols. Recommendations are given regarding which methods are most justified for answering bioaccessibility or bioavailability related questions for specific nutrients. The need for more validation studies in which in vivo results are compared to in vitro results is also discussed.

Bioavailability of insect growth regulator residues in citrus

The aim of this study was to increase the knowledge in the field of bioavailability of pollutants in agricultural food samples. Bioavailability of flufenoxuron, lufenuron, pyriproxyfen and fenoxycarb was studied in a common commodity as mandarin in vitro. Not only was it studied in fresh fruit but also in standards and canned mandarin to be able to establish matrix-related differences. Human gastric digestion, intestinal digestion and absorption were imitated. Porcine pepsin, porcine pancreatin, bile salts and semipermeable cellulose dialysis tubing were used. Dialysis values were lower than 15% and followed this order: standards > processed samples > fresh samples. The highest dialyzable values were observed for fenoxycarb and pyriproxyfen. The higher the digested amount of pesticide, the higher the dialysed amount.

Statistical model for predicting non-heme iron bioavailability from vegetarian meals

Availability of non-heme iron has been extensively discussed when meals comprise heme as well as non-heme iron, but seldom so for exclusively vegetarian meals. The present study aimed to develop a statistical model for predicting non-heme iron availability from a composite vegetarian meal. Radioisotopic measurements of in vitro iron dialyzability of 208 out of 274 meals representing vegetarian diets from Asia, Africa, Europe and Latin America and the meal contents of iron, zinc, copper, ascorbic acid, beta-carotene, riboflavin, thiamin, folic acid, tannic acid, fiber and degraded phytate forms (IP6-IP1) were used for development of the model. A multiple regression model weighted for calorie contents was developed for the percentage iron dialyzability with the possible predictors as meal contents along with plausible interaction terms. The model was validated with in vitro iron dialyzability of 66 meals and in vivo iron absorption in five ileostomized adults. Application of the model was demonstrated using data on the daily dietary intake of 215 young adults whose hemoglobin levels were estimated twice in 3 weeks. Weighted multiple regression model was: ln(% Fe dialyzability)=1.340-0.259xln(IP2 [mg])+0.188xln(IP3 [mg])-0.278xln(IP5 [mg])+0.0912xln(ascorbic acid [mg])+0.06693xln(tannins [mg])+0.09552xln(beta-carotene [microg])+0.137xln(hemicellulose [g]) (P<0.01, R2=0.51). Good agreement was seen between observed and predicted dialyzability (r=0.90) and human absorption (r=0.89). The model would be useful to estimate bioavailable iron intakes of vegetarian populations and to identify at-risk individuals.

Predicting Bioavailable Zinc from Lower Phytate Forms, Folic Acid and Their Interactions with Zinc in Vegetarian Meals

OBJECTIVE

To develop a statistical model for predicting zinc bioavailability from cereal-based vegetarian meals using relative proportion of nutrients, non-nutrients and their interactive effects.

METHODS

A database on in vitro zinc dialysability (by isotopic tracer, 65Zn) of vegetarian meals (266 out of 326) from Asia, Africa, Europe /US and Latin America was used to develop a model for estimating zinc bioavailability. A multiple regression analysis adjusted for energy content was carried out for net bioavailable zinc from a meal with the predictor variables as meal contents of iron, zinc, copper, ascorbic acid, beta-carotene, riboflavin, thiamine, folic acid, tannic acid, fiber, phytate degradation products (IP6 to IP1), along with their interaction terms. Reproducibility of the model was tested with remaining 60 meals. Validation of the model was done with zinc absorption data of i) 12 young adults on 24 meals and ii) 5 adults with ileostomy on 7 meals.

RESULTS

Folic acid, IP3 and IP5 were significant influencing factors for bioavailable zinc. Weighted multiple regression equation was: ln (bioavailable zinc in mg) = -1.701 + 1.285 x ln [(IP5 in mg] x (Zn in mg)] -1.222 x ln(IP5 in mg) -0.0078 x folic acid in microg -0.137 x ln [(IP3 in mg) x (Zn in mg)] with adjusted R--[2] = 0.64, p = 0.0001. The correlation between predicted and observed dialysability of meals was found to be 0.96 (p < 0.01). A significant correlation between observed and predicted amount of absorbed zinc (r = 0.85, p < 0.01) was obtained for the human data of zinc absorption in 12 healthy and 5 subjects with ileostomy.

CONCLUSIONS

Bioavailable amount of zinc from vegetarian meals was influenced by IP3, IP5 and folic acid content and their interactive effect with zinc content.

Effect of protein hydrolysis on the dialysability of amino acids and minerals in infant formulas

The objectives of this study were to evaluate the dialysed quantities of amino acids and minerals (calcium, phosphorus, magnesium, iron and zinc) in two types of infant formulas, one with a basis of native cow milk proteins and the other highly hydrolysed, to evaluate the possible application of Miller's in vitro method in amino acid and mineral availability studies. The percentage of dialysis differed between proteins. The hydrolysis treatment applied to the proteins significantly increased the dialysis percentage of almost all the amino acids. The dialysability of all the minerals was statistically greater in the formula made with a basis of hydrolysed proteins. Miller's method was seen to be of use for showing the effect which the hydrolysis treatment has on the availability of amino acids. Despite its limitations of having to be carried out in vitro, the study suggests that the nutritional value in relation with amino acids, minerals and trace elements differs between the both types of formulas.

In vitro availability of calcium, iron, and zinc from first-age infant formulae and human milk

BACKGROUND

Variation in the bioavailability of calcium (Ca), iron (Fe), and zinc (Zn) occurs because of interactions of food components in the gastrointestinal microenvironment. Bioavailability is preferably determined by in vivo tests, but these are expensive, labor-intensive, time consuming, and often unethical. As an alternative, in vitro methods can be used to predict bioavailability of nutrients from foodstuffs.

METHODS

A continuous-flow dialysis model with preliminary intraluminal digestive phase, adapted to the gastrointestinal conditions of infants younger than 6 months, was used. Human milk was the reference standard. Ca, Fe, and Zn content of samples and dialysates after digestion were analyzed by atomic absorption spectrometry.

RESULTS

Ca availability is similar in human milk (13.1%+/-0.8%), whey (13.3%+/-1.2%), and soy-based formulae (13.0%+/-1.2%; P > 0.05), and higher in casein-predominant formula (21.2%+/-0.6%; P < 0.05). Availability of Fe is highest in human milk (8.12%+/-0.27%: P < 0.05). Fe availability in whey (1.28%+/-0.28%) and soy formulae (1.48%+/-0.28%) is similar (P > 0.05), but availability is lower in casein-predominant formula (0.48%+/-0.22%; P < 0.05). Zn availability is also highest in human milk (13.1%+/-0.7%; P < 0.05). However, Zn availability is similar in whey (6.7%+/-0.6%) and casein formulae (8.5%+/-1.6%; P > 0.05), but lower in soy formula (2.3%+/-0.4%; P < 0.05).

CONCLUSIONS

Our observations are in agreement with previous data from in vivo studies in term infants. This in vitro procedure is an inexpensive, simple, rapid, and reliable method that predicts the bioavailability of Ca, Fe, and Zn in foods.