Oral intake of added titanium dioxide and its nanofraction from food products, food supplements and toothpaste by the Dutch population.

Titanium dioxide (TiO2) is commonly applied to enhance the white colour and brightness of food products. TiO2 is also used as white pigment in other products such as toothpaste. A small fraction of the pigment is known to be present as nanoparticles (NPs). Recent studies with TiO2 NPs indicate that these particles can have toxic effects. In this paper, we aimed to estimate the oral intake of TiO2 and its NPs from food, food supplements and toothpaste in the Dutch population aged 2 to over 70 years by combining data on food consumption and supplement intake with concentrations of Ti and TiO2 NPs in food products and supplements. For children aged 2-6 years, additional intake via ingestion of toothpaste was estimated. The mean long-term intake to TiO2 ranges from 0.06 mg/kg bw/day in elderly (70+), 0.17 mg/kg bw/day for 7-69-year-old people, to 0.67 mg/kg bw/day in children (2-6 year old). The estimated mean intake of TiO2 NPs ranges from 0.19 µg/kg bw/day in elderly, 0.55 µg/kg bw/day for 7-69-year-old people, to 2.16 µg/kg bw/day in young children. Ninety-fifth percentile (P95) values are 0.74, 1.61 and 4.16 µg/kg bw/day, respectively. The products contributing most to the TiO2 intake are toothpaste (in young children only), candy, coffee creamer, fine bakery wares and sauces. In a separate publication, the results are used to evaluate whether the presence of TiO2 NPs in these products can pose a human health risk.

Effects of n-3 fatty acids on major cardiovascular events in statin users and non-users with a history of myocardial infarction.

AIMS: Recent secondary prevention trials have failed to demonstrate a beneficial effect of n-3 fatty acids on cardiovascular outcomes, which may be due to the growing use of statins since the mid-1990s. The aim of the present study was to assess whether statins modify the effects of n-3 fatty acids on major adverse cardiovascular events in patients with a history of myocardial infarction (MI). METHODS AND RESULTS: Patients who participated in the Alpha Omega Trial were divided into consistent statin users (n = 3740) and consistent statin non-users (n = 413). In these two groups of patients, the effects of an additional daily amount of 400 mg eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA), 2 g α-linolenic acid (ALA), or both on major cardiovascular events were evaluated. Multivariable Cox's proportional hazard models were used to calculate adjusted hazard rate ratios (HR(adj)). Among the statin users 495 (13%) and among the statin non-users 62 (15%) developed a major cardiovascular event. In statin users, an additional amount of n-3 fatty acids did not reduce cardiovascular events [HR(adj) 1.02; 95% confidence interval (CI): 0.80, 1.31; P = 0.88]. In statin non-users, however, only 9% of those who received EPA-DHA plus ALA experienced an event compared with 18% in the placebo group (HR(adj) 0.46; 95% CI: 0.21, 1.01; P= 0.051). CONCLUSION: In patients with a history of MI who are not treated with statins, low-dose supplementation with n-3 fatty acids may reduce major cardiovascular events. This study suggests that statin treatment modifies the effects of n-3 fatty acids on the incidence of major cardiovascular events.

Modelling approach to simulate reductions in LDL cholesterol levels after combined intake of statins and phytosterols/-stanols in humans.

BACKGROUND: To examine the effects on LDL cholesterol of the combined use of statins and phytosterols/-stanols, in vivo studies and clinical trials are necessary. However, for a better interpretation of the experimental data as well as to possibly predict cholesterol levels given a certain dosing regimen of statins and phytosterols/-stanols a more theoretically based approach is helpful. This study aims to construct a mathematical model to simulate reductions in low-density lipoprotein (LDL) cholesterol in persons who combine the use of statins with a high intake of phytosterols/-stanols, e.g. by the use of functional foods. METHODS AND RESULTS: The proposed model includes the cholesterol pool size in the liver and serum levels of very low-density lipoprotein (VLDL) cholesterol. Both an additional and a multiplicative effect of phytosterol/-stanol intake on LDL cholesterol reduction were predicted from the model. The additional effect relates to the decrease of dietary cholesterol uptake reduction, the multiplicative effect relates to the decrease in enterohepatic recycling efficiency, causing increased cholesterol elimination through bile. From the model, it was demonstrated that a daily intake of 2 g phytosterols/-stanols reduces LDL cholesterol level by about 8% to 9% on top of the reduction resulting from statin use. The additional decrease in LDL cholesterol caused by phytosterol/-stanol use at the recommended level of 2 g/d appeared to be similar or even greater than the decrease achieved by doubling the statin dose. CONCLUSION: We proposed a simplified mathematical model to simulate the reduction in LDL cholesterol after separate and combined intake of statins and functional foods acting on intestinal (re)absorption of cholesterol or bile acids in humans. In future work, this model can be extended to include more complex (regulatory) mechanisms.

Functional foods and dietary supplements: products at the interface between pharma and nutrition.

It is increasingly recognized that most chronic diseases of concern today are multifactorial in origin. To combat such diseases and adverse health conditions, a treatment approach where medicines and nutrition complement each other may prove to be the most successful. Within nutrition, apart from (disease-related) dietetic regimes, an increasing number of functional foods and dietary supplements, each with their own health claim, are marketed. These food items are considered to be positioned between traditional foods and medicines at the so-called 'Pharma-Nutrition Interface'. This paper encompasses aspects related to the regulatory framework and health claims of functional foods and dietary supplements. The use of functional foods or dietary supplements may offer opportunities to reduce health risk factors and risk of diseases, both as monotherapy and in combination with prescription drugs. Nevertheless, the potential caveats of these products should not be overlooked. These caveats include the increased risk for food-drug interactions due to the elevated amounts of specific functional ingredients in the diet, and the stimulation of self-medication potentially resulting in lower adherence to drug therapy. Health technology assessments should be used more to compare the cost-effectiveness and benefit-risk ratios of drugs, functional foods and dietary supplements, and to evaluate the added value of functional foods or dietary supplements to drug therapy.

Costs and health effects of adding functional foods containing phytosterols/-stanols to statin therapy in the prevention of cardiovascular disease.

The present modelling study aimed to evaluate if and by how much functional foods containing phytosterols/-stanols add to the benefits of statins in the prevention of cardiovascular disease in terms of cost-effectiveness. Long-term health effects, measured as quality-adjusted life-years gained, and costs for scenarios with additional phytosterol/-stanol use were compared to scenarios without extra use. Phytosterols/-stanols were given only to persons who were eligible for use according to their 10-year absolute risk of fatal cardiovascular disease (SCORE-risk). Intake levels and discontinuation rates as observed in daily practice were included in the model. Two situations were compared: 1) A real-life situation in which persons at high SCORE-risk were identified through clinical case-finding and, 2) A theoretical maximum situation where universal screening was implemented resulting in known SCORE-risks for the whole Dutch population aged 35-75 years (8.4 million people). Sensitivity analyses were performed for variations in the cholesterol-lowering effect and intake level of phytosterols/-stanols, indirect health care costs, time horizon and discount rates. At the model's start year, a total of 1.0 (real-life situation) to 3.3 (maximum situation) million persons qualified for phytosterol/-stanol use based on their SCORE-risk (both statin users and statin non-users). Over the model's time horizon, this resulted in a gain of 2700 to 16,300 quality-adjusted life-years, and yielded cost-effectiveness ratios that ranged between €92,000 and €203,000 per quality-adjusted life-year. This simulation study showed that the cost-effectiveness of phytosterols/-stanols as monotherapy and as add-on to statins is above thresholds for cost-effectiveness, generally ranging between €20,000 and €50,000, and is thus a non-cost-effective strategy to reduce cardiovascular disease.

Influence of the use of functional foods enriched with phytosterols/-stanols on adherence to statin therapy.

PURPOSE: Subjects using functional foods with approved health claims may be more likely to be non-adherent with prescribed drug therapy. This study aimed to assess the influence of the use of phytosterol/-stanol-enriched functional foods on adherence to statin therapy among patients initiating treatment. METHODS: We used data from the statin intervention research project, a randomized controlled trial aimed at improving adherence to statins. In the trial, new statin users were randomized to receive either usual care or extensive pharmaceutical care consisting of five individual counseling sessions. Customary use of phytosterol/-stanol-enriched products was identified by questionnaires filled out by all participants. Automated pharmacy-dispensing records were used to assess adherence in terms of discontinuation of therapy and the medication possession ratio. Analyses were performed for the overall population, as well as stratified for receiving pharmaceutical or usual care. RESULTS: The use of functional foods enriched with phytosterols/-stanols was not related to discontinuation of statin therapy, neither in the overall population (overall population adjusted hazard rate ratio (HR(adj)): 0.80 [95%CI: 0.59-1.08]), nor when stratified by randomization arm (pharmaceutical care HR(adj): 0.77 [95%CI: 0.49-1.23]); usual care HR(adj): 0.81 [95%CI: 0.54-1.21]). The median medication possession ratio was significantly lower in users of phytosterols/-stanols in the usual care group, but the difference was not clinically relevant. CONCLUSIONS: Customary use of phytosterol/-stanol-enriched functional foods did not affect adherence to statins in new users that are well informed on the beneficial effects of statin therapy. In daily medical practice, general practitioners and pharmacists should urge subjects not to take phytosterol/-stanol-enriched functional foods as replacement for their prescribed medication.

Dose-dependent cholesterol-lowering effects of phytosterol/phytostanol-enriched margarine in statin users and statin non-users under free-living conditions.

OBJECTIVE: To assess the effectiveness (extent to which an intervention works in daily medical practice) of the use of phytosterol/phytostanol-enriched margarines to lower total and non-HDL cholesterol levels in users and non-users of statins. DESIGN: Retrospective cohort study. SETTING: Data were obtained from questionnaires on health and food intake from a population-based longitudinal cohort linked to pharmacy-dispensing records. SUBJECTS: The analysis included 3829 men and women (aged 31-71 years) who were examined during 1998-2002 and re-examined at 5-year follow-up during 2003-2007. RESULTS: Recommended doses of margarines were consumed by only 9 % of the subjects. Serum total cholesterol decreased by respectively -0·16 (95 % CI -0·26, -0·05) mmol/l, -1·40 (95 % CI -1·51, -1·30) mmol/l and -1·64 (95 % CI -1·91, -1·37) mmol/l in subjects who started to use phytosterols/phytostanols only, statins only or a combination of both compounds at some point in time between examination and re-examination, compared with subjects who did not start using phytosterols/phytostanols or statins. Cholesterol-lowering effects of the phytosterols/phytostanols were similar in statin users and statin non-users and increased with increasing intake of enriched margarine (no intake, 0; low intake, -0·017 (95 % CI -0·16, 0·13) mmol/l; medium intake, -0·089 (95 % CI -0·22, 0·038) mmol/l; high intake, -0·32 (95 % CI -0·50, -0·14) mmol/l). CONCLUSIONS: Although recommended intake levels of the enriched margarines were not reached by all persons, these data show that under customary conditions of use phytosterols/phytostanols are effective in lowering cholesterol levels in both statin users and non-users.

Simultaneous intake of oat bran and atorvastatin reduces their efficacy to lower lipid levels and atherosclerosis in LDLr-/- mice.

The present study aimed to investigate the effects of separate and simultaneous dietary intake of atorvastatin (ATO) and the soluble fiber oat bran on serum and hepatic lipid levels and the degree of atherosclerosis. Ninety female LDL-receptor-deficient (LDLr-/-) mice were fed a Western-type diet containing either low dose (0.0025%), high dose (0.01%) or no ATO, with or without oat bran (27%) (n=15 per group) for 16 weeks. Both ATO and oat bran were effective in reducing serum total cholesterol levels (low ATO: -5.48, high ATO: -9.12, oat bran: -3.82 mmol/l, compared to control (no ATO/no oat bran), all p<0.0001). When oat bran was added to a low dose ATO, the cholesterol-lowering effects of this combination were 50% smaller compared to the low dose ATO diet alone (between-group difference: 2.77 mmol/l, p=0.002), whereas total cholesterol decreased to a similar extent in the groups fed a high dose ATO, with or without oat bran (between-group difference: 1.10 mmol/l, p=0.21). Serum LDL- and HDL-cholesterol, triglycerides, hepatic lipid levels and atherosclerotic lesion development showed a similar pattern. In conclusion, the efficacy of oat bran and atorvastatin to lower lipid levels and atherosclerosis is reduced after simultaneous intake. We hypothesize that oat bran inhibits the intestinal absorption of atorvastatin, and consequently its cholesterol-lowering effects. The effects are likely dependent on the type of statin and dietary fiber, and on the relative timing of intake of the statin and the dietary fiber. Future studies should focus on these aspects to provide further insight into the exact mechanism of this food-drug interaction.

A pharmaceutical care program to improve adherence to statin therapy: a randomized controlled trial.

BACKGROUND: Despite the well-known beneficial effects of statins, many patients do not adhere to chronic medication regimens. OBJECTIVE: To implement and assess the effectiveness of a community pharmacy-based pharmaceutical care program developed to improve patients' adherence to statin therapy. METHODS: An open-label, prospective, randomized controlled trial was conducted at 26 community pharmacies in the Netherlands. New users of statins who were aged 18 years or older were randomly assigned to receive either usual care or a pharmacist intervention. The intervention consisted of 5 individual counseling sessions by a pharmacist during a 1-year period. During these sessions, patients received structured education about the importance of medication adherence, lipid levels were measured, and the association between adherence and lipid levels was discussed. Adherence to statin therapy was assessed as discontinuation rates 6 and 12 months after statin initiation, and as the medication possession ratio (MPR), and compared between the pharmaceutical care and usual care groups. RESULTS: A total of 899 subjects (439 in the pharmaceutical care group and 460 in the usual care group) were evaluable for effectiveness analysis. The pharmaceutical care program resulted in a significantly lower rate of discontinuation within 6 months after initiating therapy versus usual care (HR 0.66, 95% CI 0.46 to 0.96). No significant difference between groups was found in discontinuation at 12 months (HR 0.84, 95% CI 0.65 to 1.10). Median MPR was very high (>99%) in both groups and did not differ between groups. CONCLUSIONS: These results demonstrate the feasibility and effectiveness of a community pharmacy-based pharmaceutical care program to improve medication adherence in new users of statins. Frequent counseling sessions (every 3 months) are necessary to maintain the positive effects on discontinuation. Although improvements are modest, the program can be applied easily to a larger population and have a large impact, as the interventions are relatively inexpensive and easy to implement in clinical practice.

Effects of the use of phytosterol/-stanol-enriched margarines on adherence to statin therapy.

PURPOSE: The use of margarines enriched with phytosterols or phytostanols is recommended as an appropriate adjunctive therapy for patients with certain lipid profiles, but may result in a behavioral modification leading to a change in person's adherence to lipid-lowering drug treatment. This study aimed to examine the influence of the use of margarines enriched with phytosterols/-stanols on adherence to statin therapy. METHODS: Retrospective data from food frequency questionnaires were used to assess phytosterol/-stanol-enriched margarine intake from a population based, longitudinal cohort between 1998 and 2007. Intake data were linked to pharmacy-dispensing records. Multivariate Cox proportional-hazards models were used to calculate hazard ratios for discontinuation of statin therapy. Drug-taking compliance was compared between users and non-users of enriched margarine using the Mann-Whitney U-test. Pre-defined subgroup analyses were performed to evaluate differences in adherence between prevalent statin users and starters of statins. RESULTS: Among 4848 subjects, 522 used statins only and 60 combined these drugs with phytosterol/-stanol-enriched margarine. Overall statin discontinuation rates were not significantly different between the users and non-users of enriched margarine, but more combination users discontinued statin therapy within 12 months in the subgroup of starters (HR(adj) : 2.52 [95%CI: 1.06-6.00]). Drug-taking compliance was high in both users and non-users of enriched margarine and was slightly lower in combination users (P<0.10). CONCLUSIONS: These results imply that persons who combine enriched margarines with statins may neglect taking their drug according to the prescription. Further investigations in larger populations are important, especially among patients susceptible to a low adherence to drug therapy.

Support of drug therapy using functional foods and dietary supplements: focus on statin therapy.

Functional foods and dietary supplements might have a role in supporting drug therapy. These products may (1) have an additive effect to the effect that a drug has in reducing risk factors associated with certain conditions, (2) contribute to improve risk factors associated with the condition, other than the risk factor that the drug is dealing with, or (3) reduce drug-associated side effects, for example, by restoring depleted compounds or by reducing the necessary dose of the drug. Possible advantages compared with a multidrug therapy are lower drug costs, fewer side effects and increased adherence. In the present review we have focused on the support of statin therapy using functional foods or dietary supplements containing plant sterols and/or stanols, soluble dietary fibre, n-3 PUFA or coenzyme Q10. We conclude that there is substantial evidence that adding plant sterols and/or stanols to statin therapy further reduces total and LDL-cholesterol by roughly 6 and 10 %, respectively. Adding n-3 PUFA to statin therapy leads to a significant reduction in plasma TAG of at least 15 %. Data are insufficient and not conclusive to recommend the use of soluble fibre or coenzyme Q10 in patients on statin therapy and more randomised controlled trials towards these combinations are warranted. Aside from the possible beneficial effects from functional foods or dietary supplements on drug therapy, it is important to examine possible (negative) effects from the combination in the long term, for example, in post-marketing surveillance studies. Moreover, it is important to monitor whether the functional foods and dietary supplements are taken in the recommended amounts to induce significant effects.

Integrated risk-benefit analyses: method development with folic acid as example.

With the introduction of novel and functional foods, there is increasing need for an integrated quantitative risk-benefit assessment of foods. Consensus about a quantitative risk-benefit assessment mirroring the risk assessment approach has been reached during a recent EFSA workshop. In line, we propose a risk-benefit model that consists of: (1) hazard and benefit identification, (2) hazard and benefit characterization through dose-response functions, (3) exposure assessment, and (4) risk-benefit integration. The DALY, which combines morbidity and mortality serves as common health measure. The overall health impact of bread fortified with folic acid in the Netherlands has been simulated. The case study showed how the risk-benefit approach may assist a policy maker in decisions on food fortification programs. It illustrates general problems regarding the data demands, the assumptions and uncertainties. A simple sensitivity analysis showed which assumptions were most crucial. Modest fortification (140 microg/100 g bread) seems reasonable to improve public health but the results hinge on the assumptions one makes for the association between colorectal cancer and high folate intake. A precautious policymaker may very well decide against folic acid fortification. The often debated increase in masked vitamin B(12)-deficiency appears negligible compared to the health gain resulting from prevented neural tube defects.

Comparison of five in vitro digestion models to in vivo experimental results: lead bioaccessibility in the human gastrointestinal tract.

This paper presents a multi-laboratory comparison study of in vitro models assessing bioaccessibility of soil-bound lead in the human gastrointestinal tract under simulated fasted and fed conditions. Oral bioavailability data from a previous human in vivo study on the same soil served as a reference point. In general, the bioaccessible lead fraction was significantly (P<0.05) different between the in vitro methods and ranged for the fasted models from 2% to 33% and for the fed models from 7% to 29%. The in vivo bioavailability data from literature were 26.2+/-8.1% for fasted conditions, compared to 2.5+/-1.7% for fed conditions. Under fed conditions, all models returned higher bioaccessibility values than the in vivo bioavailability; whereas three models returned a lower bioaccessibility than bioavailability under fasted conditions. These differences are often due to the method's digestion parameters that need further optimization. An important outcome of this study was the determination that the method for separating the bioaccessible lead from the non-bioaccessible fraction (centrifugation, filtration, ultrafiltration) is crucial for the interpretation of the results. Bioaccessibility values from models that use more stringent separation methods better approximate in vivo bioavailability results, yet at the expense of the level of conservancy. We conclude from this study that more optimization of in vitro digestion models is needed for use in risk assessment. Moreover, attention should be paid to the laboratory separation method since it largely influences what fraction of the contaminant is considered bioaccessible.

Safe addition of vitamins and minerals to foods: setting maximum levels for fortification in the Netherlands.

BACKGROUND: In 2004, the European Court of Justice decided that the prohibition of fortification with vitamin A, vitamin D, folic acid, selenium, copper, and zinc in the Netherlands conflicts with the principle of free movement of goods in the European Union. This decision led to a change in the Dutch policy, resulting in a more flexible handling of requests for exemption from this prohibition to fortify. Therefore, an investigation was proposed in which it would be determined whether a general exemption could be granted for food fortification with a certain maximum safe amount per micronutrient. AIM OF THE STUDY: To develop a risk assessment model to estimate maximum safe fortification levels (MSFLs) of vitamins and minerals to foods on the Dutch market, and to evaluate these levels to derive allowed fortification levels (AFLs), which can be used for a general exemption. METHODS: We developed a risk assessment model to estimate MSFLs of vitamins and minerals to foods on the basis of existing models. We used European tolerable upper intake levels in combination with national food consumption data to estimate MSFLs for fortification of foods for several age groups. Upon extensive stakeholder dialogue, the risk manager considered these estimated MSFLs and the final AFLs for a general exemption were set. RESULTS: For folic acid, vitamin A, and vitamin D, the MSFLs were calculated in the risk-assessment model. Children up to 6-years old were the group most sensitive to folic acid fortification, and they had an MSFL of 0 microg/100 kcal, but following a risk management evaluation, this was upgraded to an AFL of 100 microg/100 kcal. The MSFL for vitamin D was 3.0 microg/100 kcal (children 4-10 years old), and the risk manager increased this to an AFL of 4.5 microg/100 kcal. Children up to 10 years old, men, and postmenopausal women were the groups most sensitive to vitamin A fortification (MSFL = 0 microg/100 kcal). Because these groups represent a large part of the population and because of the seriously harmful effects of excessive vitamin A, the risk manager did not allow a general exemption. CONCLUSIONS: The combination of a risk assessment model and risk manager evaluation led to the setting of AFLs for general exemption of fortification with folic acid and vitamin D. This model is also applicable for other micronutrients, for which an UL is derived, and in other countries.

Consumer product in vitro digestion model: Bioaccessibility of contaminants and its application in risk assessment.

This paper describes the applicability of in vitro digestion models as a tool for consumer products in (ad hoc) risk assessment. In current risk assessment, oral bioavailability from a specific product is considered to be equal to bioavailability found in toxicity studies in which contaminants are usually ingested via liquids or food matrices. To become bioavailable, contaminants must first be released from the product during the digestion process (i.e. become bioaccessible). Contaminants in consumer products may be less bioaccessible than contaminants in liquid or food. Therefore, the actual risk after oral exposure could be overestimated. This paper describes the applicability of a simple, reliable, fast and relatively inexpensive in vitro method for determining the bioaccessibility of a contaminant from a consumer product. Different models, representing sucking and/or swallowing were developed. The experimental design of each model can be adjusted to the appropriate exposure scenarios as determined by the risk assessor. Several contaminated consumer products were tested in the various models. Although relevant in vivo data are scare, we succeeded to preliminary validate the model for one case. This case showed good correlation and never underestimated the bioavailability. However, validation check needs to be continued.

Potato glycoalkaloids and adverse effects in humans: an ascending dose study.

Glycoalkaloids in potatoes may induce gastro-intestinal and systemic effects, by cell membrane disruption and acetylcholinesterase inhibition, respectively. The present single dose study was designed to evaluate the toxicity and pharmacokinetics of orally administered potato glycoalkaloids (alpha-chaconine and alpha-solanine). It is the first published human volunteer study were pharmacokinetic data were obtained for more than 24 h post-dose. Subjects (2-3 per treatment) received one of the following six treatments: (1-3) solutions with total glycoalkaloid (TGA) doses of 0.30, 0.50 or 0.70 mg/kg body weight (BW), or (4-6) mashed potatoes with TGA doses of 0.95, 1.10 or 1.25 mg/kg BW. The mashed potatoes had a TGA concentration of nearly 200 mg/kg fresh weight (the presently recognised upper limit of safety). None of these treatments induced acute systemic effects. One subject who received the highest dose of TGA (1.25 mg/kg BW) became nauseous and started vomiting about 4 h post-dose, possibly due to local glycoalkaloid toxicity (although the dosis is lower than generally reported in the literature to cause gastro-intestinal disturbances). Most relevant, the clearance of glycoalkaloids usually takes more than 24 h, which implicates that the toxicants may accumulate in case of daily consumption.

Applicability of an in vitro digestion model in assessing the bioaccessibility of mycotoxins from food.

Food is considered a major route of exposure to many contaminants. Only the fraction of the contaminant that is released from the food (bioaccessibility) and is bioavailable can exert toxic effects. Insufficient knowledge on the bioavailability may hamper an accurate risk assessment of ingested contaminants in humans. This paper describes the applicability of an in vitro digestion model allowing for measurement of the bioaccessibility of ingested mycotoxins from food as an indicator of oral bioavailability. Bioaccessibility of aflatoxin B(1) from peanut slurry and ochratoxin A from buckwheat was high, 94% and 100%, respectively, and could be determined reproducibly. With the in vitro digestion model, the bioaccessibilities of aflatoxin B(1) and ochratoxin A in the presence of four different absorption modulators were in five out of six situations in accordance with the in vivo effects in humans and animals. By determining the effect of chlorophyllin on the transport of aflatoxin B(1) across the intestinal Caco-2 cells, also the sixth combination was in agreement with data in humans. Hence, the in vitro digestion model, combined with Caco-2 cells, is a powerful experimental tool, which can aid to a more accurate risk assessment of ingested contaminants.

Comparison of five in vitro digestion models to study the bioaccessibility of soil contaminants.

Soil ingestion can be a major exposure route for humans to many immobile soil contaminants. Exposure to soil contaminants can be overestimated if oral bioavailability is not taken into account. Several in vitro digestion models simulating the human gastrointestinal tract have been developed to assess mobilization of contaminants from soil during digestion, i.e., bioaccessibility. Bioaccessibility is a crucial step in controlling the oral bioavailability for soil contaminants. To what extent in vitro determination of bioaccessibility is method dependent has, until now, not been studied. This paper describes a multi-laboratory comparison and evaluation of five in vitro digestion models. Their experimental design and the results of a round robin evaluation of three soils, each contaminated with arsenic, cadmium, and lead, are presented and discussed. A wide range of bioaccessibility values were found for the three soils: for As 6-95%, 1-19%, and 10-59%; for Cd 7-92%, 5-92%, and 6-99%; and for Pb 4-91%, 1-56%, and 3-90%. Bioaccessibility in many cases is less than 50%, indicating that a reduction of bioavailability can have implications for health risk assessment. Although the experimental designs of the different digestion systems are distinct, the main differences in test results of bioaccessibility can be explained on the basis of the applied gastric pH. High values are typically observed for a simple gastric method, which measures bioaccessibility in the gastric compartment at low pHs of 1.5. Other methods that also apply a low gastric pH, and include intestinal conditions, produce lower bioaccessibility values. The lowest bioaccessibility values are observed for a gastrointestinal method which employs a high gastric pH of 4.0.

Utility of rat liver slices to estimate hepatic clearance for application in physiologically based pharmacokinetic modeling: a study with tolbutamide, a compound with low extraction efficiency.

Liver slice experiments were performed to determine the slice intrinsic clearance and to extrapolate this to the in vivo liver intrinsic clearance in a physiologically based pharmacokinetic (PBPK)-like approach. Precision-cut liver slices were incubated with different initial concentrations of tolbutamide, and the time series of parent and metabolite concentrations were measured in slice and incubation medium. A mathematical model was built that modeled the uptake of tolbutamide and its metabolism in the liver slice. In addition, binding of tolbutamide to cellular constituents and partition over the water and lipid phase were accounted for by the model. Model analysis imposed sampling of parent compound in slice and of metabolites pooled from slice and medium. The model was calibrated to the data, fitting the intrinsic clearance, the parent compounds' free fraction in liver material, and a diffusion parameter describing medium-slice exchange of tolbutamide. In addition, to ensure a meaningful application of the theoretical model, slice viability parameters were monitored before and during the experiment. For the different incubations, the intrinsic clearance per unit of volume of slice ranged from 0.035 to 0.086 min(-1) when not correcting for slice viability and from 0.044 to 0.11 min(-1) when correcting for slice viability. The results were extrapolated to a PBPK model for tolbutamide in the rat. The value for the intrinsic clearance found by calibrating the PBPK model to previous in vivo data was 0.090 min(-1). This result suggests that liver slices are a valuable tool for predicting in vivo intrinsic clearance of low-extraction compounds.