Folate bioavailability

An inadequate folate status is associated with increased risk of anaemia and neural tube defects. In many countries a folate intake below recommendations has been reported for women in childbearing age. However, data on folate intake and status are not always associated, since factors other than intake, e.g. bioavailability, affect folate status. This thesis studied the bioavailability of folate using in vivo and in vitro models. The effect of two pieces of Swedish nutritional advice on folate status of healthy women was assessed in a 12-week randomised controlled intervention trial. By combining a human plasma area under the curve (AUC)/ileostomy model with a stable isotope technique, the bioavailability of wholemeal bread fortified with reduced folate (5-CH3-H4folate) or folic acid was determined. In vitro effects of the food matrix on bioaccessibility and uptake of reduced folates were studied using a dynamic gastrointestinal model (TIM) and Caco-2 cells. The intervention breakfast diet (contributing ~1/3 of recommended daily folate intake) significantly improved folate status of the women, indicating a high folate bioavailability. The bread intervention diet (contributing ~1/5 of recommended daily folate intake) maintained folate and decreased homocysteine concentrations. Based on folate content in stomal effluent, the bioavailability of both folate fortificants tested was similarly high (~90%) but plasma kinetics differed significantly depending on ingested folate form. Data from in vitro TIM and Caco-2 cell experiments showed an inhibitory effect (~25%) of the bread matrix on bioaccessibility and uptake of reduced folates, which was higher than in vivo findings. Overall, data from these in vivo and in vitro studies suggest that the bioavailability of reduced folate is high and comparable to that of synthetic folic acid. Food matrix effects, e.g. of bread or a typical breakfast meal, on folate bioavailability seem negligible at physiological folate intake doses

Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

Hepcidin and iron homeostasis during pregnancy.

Hepcidin is the master regulator of systemic iron bioavailability in humans. This review examines primary research articles that assessed hepcidin during pregnancy and postpartum and report its relationship to maternal and infant iron status and birth outcomes; areas for future research are also discussed. A systematic search of the databases Medline and Cumulative Index to Nursing and Allied Health returned 16 primary research articles including 10 human and six animal studies. Collectively, the results indicate that hepcidin is lower during pregnancy than in a non-pregnant state, presumably to ensure greater iron bioavailability to the mother and fetus. Pregnant women with undetectable serum hepcidin transferred a greater quantity of maternally ingested iron to their fetus compared to women with detectable hepcidin, indicating that maternal hepcidin in part determines the iron bioavailability to the fetus. However, inflammatory states, including preeclampsia, malaria infection, and obesity were associated with higher hepcidin during pregnancy compared to healthy controls, suggesting that maternal and fetal iron bioavailability could be compromised in such conditions. Future studies should examine the relative contribution of maternal versus fetal hepcidin to the control of placental iron transfer as well as optimizing maternal and fetal iron bioavailability in pregnancies complicated by inflammation

Bioavailability of orange juice (poly)phenols: the impact of short-term cessation of training by male endurance athletes

Background: Physical exercise has been reported to increase the bioavailability of citrus flavanones. Objective: To investigate the bioavailability of orange juice (OJ) (poly)phenols in endurance-trained men before and after cessation of training for 7 days. Design: Ten fit endurance-trained males, with a maximal oxygen consumption of 58.2 ± 5.3 mL/kg/min, followed a low (poly)phenol diet for 2 d before drinking 500 mL of OJ, containing 398 µmol of (poly)phenols of which 330 µmol were flavanones. After the volunteers stopped training for 7 days the feeding study was repeated. Urine samples were collected 12 h pre- and 24 h post-OJ orange consumption. Bioavailability was assessed by the quantitative analysis of urinary flavanone metabolites and (poly)phenol catabolites using HPLC-HR-MS. Results: While training, 0-24 h urinary excretion of flavanone metabolites, mainly hesperetin-3-O-glucuronide, hesperetin-3´-sulfate, naringenin-4´-O-glucuronide, naringenin-7-O-glucuronide, was equivalent to 4.2% of OJ flavanone intake. This increased significantly to 5.2% when OJ was consumed after the volunteers stopped training for 7 days. Overall, this trend, although not significant, was also observed with OJ-derived colonic catabolites which after supplementation in the trained state were excreted in amounts equivalent to 51% of intake compared to 59% after cessation of training. However, urinary excretion of three colonic catabolites of bacterial origin, most notably, 3-(3´-hydroxy-4´-methoxyphenyl)hydracrylic acid, did increase significantly when OJ was consumed post- compared to pre-cessation of training. Data were also obtained on inter-individual variations in flavanone bioavailability. Conclusion: A 7-day cessation of endurance training enhanced, rather than reduced, the bioavailability of OJ flavanones. The biological significance of these differences and, whether or not they extend to the bioavailability of other dietary (poly)phenols, remains to be determined. Hesperetin-3´-O-glucuronide and the colonic microbiota-derived catabolite 3-(3´-hydroxy-4´-methoxyphenyl)hydracrylic acid are key biomarkers of the consumption of hesperetin-O-glycoside-containing OJ and other citrus products

Zinc accumulation and utilisation by wine yeasts

The present study has focused on the accumulation of zinc by wine yeast strains of Saccharomyces cerevisiae during fermentation of both grape juice and chemically defined medium with different carbohydrates and at varying levels of zinc. The results have shown that zinc accumulation by wine yeast was very rapid with all zinc being removed from the medium by yeast cells within the first two hours. Zinc uptake was stimulated by the presence of sucrose. Zinc affected fermentation progress at defined levels, with optimal concentrations at 1.5–2.5 ppm, depending on yeast strain and zinc bioavailability. The bioavailability of metal ions in grape must and the roles of metals in wine yeast physiology are aspects poorly understood by enologists. In brewing, it has long been recognized that malt wort may be zinc deficient and brewers often carry out zinc supplementations to avoid sluggish and incomplete fermentations. In winemaking, zinc levels in grape musts may be compromised depending on the bioavailability of zinc ions in vineyard soils as well as treatments with fertilizers and fungicides during grape growing. As a consequence, sub-optimal zinc levels in grape musts may negatively influence the fermentative performance of yeasts. We believe that optimization of metal ion bioavailability will improve yeast fermentation performance in industrial processes and this study addresses some issues relating to zinc in enology

Influence and interactions of multi-factors on the bioavailability of PAHs in compost amended contaminated soils

Compost amendment to contaminated soils is a potential approach for waste recycling and soil remediation. The relative importance and interactions of multiple factors on PAH bioavailability in soils were investigated using conjoint analysis and five-way analysis of variance. Results indicated that soil type and contact time were the two most significant factors influencing the PAH bioavailability in amended soils. The other two factors (compost type and ratio of compost addition) were less important but their interactions with other factors were significant. Specifically the 4-factor interactions showed that compost addition stimulated the degradation of high molecular PAHs at the initial stage (3 month) by enhancing the competitive sorption within PAH groups. Such findings suggest that a realistic decision-making towards hydrocarbon bioavailability assessment should consider interactions among various factors. Further to this, this study demonstrated that compost amendment can enhance the removal of recalcitrant hydrocarbons such as PAHs in contaminated soils

Validating the chronic Pb algae bioavailability model at high pH : single-species evaluation : final report, 12 June 2017

We investigated toxicity of Pb to Pseudokirchneriella subcapitata using the standard 72h-growth inhibition assays at 2 pH levels (pH 7.2 & pH 8.4) and 2 P (P 10 ug/L & P 100 ug/L) levels, i.e. at 4 treatments in total. This was done to test whether an existing algae Pb bioavailability model developed for pH≤8.0, can be used at higher pH>8.0. The algae Pb bioavailability model calibrated on Pb toxicity at pH 7.2 (P 100 µg/L) predicted filtered Pb toxicity(EC50 and EC20) at pH 8.4 (P 100 µg/L) with reasonable accuracy, i.e. within 2-fold error. Although the slope of the linear relationship between pH and log10(EC50 as Pb2+ acitivity) for the pH range between 7.2 and 8.4 (present study) was slightly lower than that of the pH range between 6 and 8 (existing model), our study suggests that the chronic algae Pb bioavailability model can be extrapolated to predict Pb toxicity up to pH 8.4

Gap analysis of nickel bioaccessibility and bioavailability in different food matrices and its impact on the nickel exposure assessment

The metal nickel is well known to cause nickel allergy in sensitive humans by prolonged dermal contact to materials releasing (high) amounts of nickel. Oral nickel exposure via water and food intake is of potential concern. Nickel is essential to plants and animals and can be naturally found in food products or contamination may occur across the agro-food chain. This gap analysis is an evaluation of nickel as a potential food safety hazard causing a risk for human health. In the first step, the available data regarding the occurrence of nickel and its contamination in food and drinks have been collected through literature review. Subsequently, a discussion is held on the potential risks associated with this contamination. Elevated nickel concentrations were mostly found in plant-based foods, e.g. legumes and nuts in which nickel of natural origin is expected. However, it was observed that dedicated and systematic screening of foodstuffs for the presence of nickel is currently still lacking. In a next step, published studies on exposure of humans to nickel via foods and drinks were critically evaluated. Not including bioaccessibility and/or bioavailability of the metal may lead to an overestimation of the exposure of the body to nickel via food and drinks. This overestimation may be problematic when the measured nickel level in foods is high and bioaccessibility and/or bioavailability of nickel in these products is low. Therefore, this paper analyzes the outcomes of the existing dietary intake and bioaccessibility/bioavailability studies conducted for nickel. Besides, the available gaps in nickel bioaccessibility and/or bioavailability studies have been clarified in this paper. The reported bioaccessibility and bioavailability percentages for different food and drinks were found to vary between < LOD and 83% and between 0 and 30% respectively. This indicates that of the total nickel contained in the foodstuffs only a fraction can be absorbed by the intestinal epithelium cells. This paper provides a unique critical overview on nickel in the human diet starting from factors affecting its occurrence in food until its absorption by the body

14C-Cobalamin Absorption from Endogenously Labeled Chicken Eggs Assessed in Humans Using Accelerator Mass Spectrometry.

Traditionally, the bioavailability of vitamin B-12 (B12) from in vivo labeled foods was determined by labeling the vitamin with radiocobalt (57Co, 58Co or 60Co). This required use of penetrating radioactivity and sometimes used higher doses of B12 than the physiological limit of B12 absorption. The aim of this study was to determine the bioavailability and absorbed B12 from chicken eggs endogenously labeled with 14C-B12 using accelerator mass spectrometry (AMS). 14C-B12 was injected intramuscularly into hens to produce eggs enriched in vivo with the 14C labeled vitamin. The eggs, which provided 1.4 to 2.6 μg of B12 (~1.1 kBq) per serving, were scrambled, cooked and fed to 10 human volunteers. Baseline and post-ingestion blood, urine and stool samples were collected over a one-week period and assessed for 14C-B12 content using AMS. Bioavailability ranged from 13.2 to 57.7% (mean 30.2 ± 16.4%). Difference among subjects was explained by dose of B12, with percent bioavailability from 2.6 μg only half that from 1.4 μg. The total amount of B12 absorbed was limited to 0.5-0.8 μg (mean 0.55 ± 0.19 μg B12) and was relatively unaffected by the amount consumed. The use of 14C-B12 offers the only currently available method for quantifying B12 absorption in humans, including food cobalamin absorption. An egg is confirmed as a good source of B12, supplying approximately 20% of the average adult daily requirement (RDA for adults = 2.4 μg/day)

Bioavailability of pesticides in freshwater sediments

In ecological risk assessment standardized sediment toxicity tests are used to predict the hazard of chemicals for sediment-living organisms. Feeding is a prerequisite in these long-term tests to avoid starvation of test organisms. Therefore, added food particles may act as vectors for the test compound. The importance of food particles as vectors, however, is dependent on several factors, for example, sorption and major uptake routes. In this thesis, laboratory experiments on the importance of pesticide sorption and uptake routes for the bioavailability to the midge Chironomus riparius in sediment toxicity test setups were performed. A feeding selectivity study showed that larvae almost exclusively fed on added food particles, and highly neglected sediment particles. Additionally, experiments on the sorption of the insecticide lindane, showed that food and peat particles (used in artificial sediment) efficiently sorbed lindane (>95% after 48 h). The binding strength of lindane was weak, facilitating particulate uptake. However, the uptake from dissolved lindane was higher than the uptake from particles. From this we concluded that toxicity may be underestimated in spiked-sediment scenarios, where hydrophobic pesticides sorb to the sediment and larvae to a large extent feed on uncontaminated food particles. Conversely, in a spiked-water scenario, the food particles may act as vector, resulting in a facilitated particulate uptake, in addition to the uptake from water. Sediment organic matter affects sorption, and thus bioavailability of pesticides. Pyrethroid toxicity was much higher in artificial sediment than in a natural sediment, indicating the simplicity and shortcomings of using artificial sediments. Interestingly, the sediment quality highly affected bioavailability in spiked-water. For example, C. riparus larvae in sediments with low organic matter content and exposed to spiked-water pyrethroids, showed lower survival, slower development, and increased adult size, than those in sediments with higher organic matter. The pyrethroid deltamethrin, showed an LC50-value (28 d) for C. riparius larvae in artificial sediment of 16 pg/L and 11 µg/kg for water- and sediment exposures, respectively, i.e. toxic effects occurred at concentrations lower than the detection limits for high-tech analytical methods. This thesis contributes to a wider understanding of processes affecting bioavailability in freshwater sediments, and in particular in standardized sediments used in toxicity testing. The understanding of test compound sorption and bioavailability is crucial for sound interpretations of toxicity tests and for the general credibility of such tests