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The use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated with exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally low. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the transcriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention, plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP.

This study evaluates the potential of strains of Lactobacillus and Saccharomyces cerevisiae to reduce inorganic arsenic [iAs, As(III)+As(V)] bioavailability. Removal of iAs from aqueous solutions by these strains was evaluated and their effect on iAs bioaccessibility was analyzed by in vitro gastrointestinal digestion. The effect of the strains on iAs absorption was also tested, using intestinal cells. The results showed that iAs removal by the yeast strains was low (<10%). In contrast, some lactobacilli substantially reduced As(V) concentration in solution (25–40%) but only when the concentration of phosphate was ≤1 mM. Both microorganisms were able to reduce cellular transport of iAs added as aqueous solution (11–58%). Moreover, a strain of Lactobacillus plantarum reduced cellular transport of iAs from rice by up to 45%. We conclude that, in vitro, some lactobacilli and yeasts could reduce intestinal absorption of inorganic As present in water and food, and consequently reduce its bioavailability.

It is estimated that approximately 200 million people are exposed to arsenic levels above the World Health Organization provisional guideline value, and various agencies have indicated the need to reduce this exposure. In view of the difficulty of removing arsenic from water and food, one alternative is to reduce its bioavailability (the amount that reaches the systemic circulation after ingestion). In this study, dietary components [glutathione, tannic acid, and Fe(III)] were used to achieve this goal. As(III) or As(V) (1 mg/kg body weight) was administered daily to BALB/c mice, along with the dietary components, for 15 days. The results confirm the efficacy of Fe(III) and glutathione as reducers of arsenic bioavailability and tissue accumulation. Also, these treatments did not result in reductions of Ca, K, P, and Fe contents in the liver. These data suggest that use of these two compounds could be part of valid strategies for reducing inorganic arsenic exposure in chronically exposed populations.

Mushrooms can accumulate toxic trace elements. The objectives of the present study are to evaluate levels of mercury, cadmium, lead, and arsenic in dried mushrooms, to determine the effect of cooking on the contents of these elements, and to evaluate their bioaccessibility in the mushrooms ready for consumption. The results showed that Hg levels in Amanita ponderosa, Boletus edulis, Marasmius oreades, and Tricholoma georgii, as well as Cd levels in some samples of Amanita caesarea and T. georgii, exceeded the legislated limits. Cooking significantly reduced the levels of As (26–72%), whereas the reduction in levels of Hg, Cd, and Pb was much lower. However, the bioaccessibility of As (63–81%) was higher than the values obtained for the metals (<40%). Taking the effects of cooking and gastrointestinal digestion into account gives a more realistic estimate of the risk associated with the consumption of mushrooms.

The main route of human exposure to inorganic arsenic (As) is through the consumption of food and water. Continued exposure to inorganic As [As(III) and As(V)] may cause a variety of diseases, including various types of cancer. The removal of As from these sources is complex, especially for food. One way to decrease As exposure could be by reducing intestinal absorption of it. The aim of this study is to seek dietary strategies (pure compounds, extracts, or supplements) that are capable of reducing the amount of As that is absorbed and reaches systemic circulation. Standard solutions of As(III) and As(V) and bioaccessible fractions of food samples with or without the dietary strategies to be tested were added to colon-derived human cells (NCM460 and HT-29MTX) to determine the apparent permeability (Papp) of As. Results show that transport across the intestinal monolayers is substantial, and the passage of As(III) (Papp = 4.2 × 10–5 cm/s) is greater than that of As(V) (Papp = 2.4 × 10–5 cm/s). Some of the treatments used (iron species, cysteine, grape extract) significantly reduce the transport of both inorganic As standards across the intestinal monolayer, thus decreasing absorption of them. In food samples, the effect of the dietary compounds on inorganic As bioavailability was also observed, especially in the cases of curcumin and cysteine. Compounds that proved effective in these in vitro assays could be the basis for intervention strategies aimed at reducing As toxicity in chronically exposed populations or regular consumers of food products with high As contents.

Swordfish tend to accumulate mercury (Hg), but they are rich in selenium (Se), an element that can counteract the toxic effects of Hg. The aim of the present study was to evaluate the concentrations and bioaccessibility of Hg and Se in cooked swordfish and to identify the digestion parameters (pH, residence time, and enzyme concentrations) that may influence their bioaccessibility. The Hg concentrations ranged between 0.17 and 2.82 mg/kg wet weight (ww) and the bioaccessibility between 14 and 92%. The range for Se concentrations was narrower (0.29–1.17 mg/kg ww), with a bioaccessibility that was generally greater than that of Hg (59–103%). Most of the solubilization took place in the gastric step, where acidic pH and the increase in the pepsin concentration led to greater bioaccessibility, especially for Hg. In the intestinal stage, the most notable effect was the decrease in the bioaccessibility of Hg in the presence of bile salts.

The main route of exposure to arsenic (As) is the consumption of water and foods, in which the forms with greatest toxicity are inorganic As and dimethylarsinic acid, DMA(V). The objective of this study was to search for dietary components that reduce the bioaccessibility of As from food and water, in order to reduce the amount of As available for absorption. For this purpose, 35 compounds were assayed by use of a static in vitro model of gastrointestinal digestion. Sulfates of Fe(II) and Fe(III) reduced the solubility of inorganic As (86–99%) and DMA(V) in aqueous solution (40–66%). This reduction was also observed in rice (100%) and seaweed (60%). Aluminum, titanium, and tannic acid also reduced the bioaccessibility of As from food (42–70%). These data show that the use of dietary components may be a good strategy to reduce the entry of As into systemic circulation.

Total arsenic, inorganic arsenic, lead and cadmium contents were determined in 112 samples of seaweed preparations sold in Spain (seaweed packed in plastic or cardboard box, seaweed in the form of tablets and concentrates, foods containing seaweed, and canned seaweed). The concentration ranges found, expressed in mg/kg, dry weight, were: total As (0.031-149), inorganic As (<0.014-117), Pb (<0.050-12.1) and Cd (<0.003-3.55). For all the contaminants there were failures to comply with legislated values. In particular, all the samples of Hizikia fusiforme exceeded the inorganic As limit established in some countries, and a considerable number of species exceeded the Cd limit set by international regulations. With respect to food safety, consumption of 3 g/day of the samples analysed could represent up to 15% of the respective Tolerable Daily Intakes (TDI) established by the WHO. The situation is especially alarming for intake of inorganic As from H. fusiforme, which can be three times the TDI established.

The total arsenic, inorganic arsenic, lead, cadmium, and mercury contents of 18 algae food products currently on sale in Spain were determined. The suitability of the analytical methodologies for this type of matrix was confirmed by evaluating their analytical characteristics. The concentration ranges found for each contaminant, expressed in milligrams per kilogram of dry weight, were as follows: total arsenic, 2.3-141; inorganic arsenic, 0.15-88; lead, <0.05-1.33; cadmium, 0.03-1.9; and mercury, 0.004-0.04. There is currently no legislation in Spain regarding contaminants in algae food products, but some of the samples analyzed revealed Cd and inorganic As levels higher than those permitted by legislation in other countries. Given the high concentrations of inorganic As found in Hizikia fusiforme, a daily consumption of 1.7 g of the product would reach the Provisional Tolerable Weekly Intake recommended by the WHO for an average body weight of 68 kg. A more comprehensive study of the contents and toxicological implications of the inorganic As present in the algae food products currently sold in Spain may be necessary, which might then be the basis for the introduction of specific sales restrictions.