The potential developmental neurotoxicity of calcium cyclamate in CD rats.

The developmental neurotoxicity of calcium cyclamate was evaluated in Sprague Dawley [Crl:CD(SD)] rats, administered in drinking water, in comparison to a concurrent control group (water) and a positive control group given propylthiouracil (PTU). Calcium cyclamate was administered to F0 females for 4 weeks prior to pairing, throughout mating, gestation and lactation and to F1 offspring from weaning to 12 weeks of age, PTU was administered by gavage to F0 females from Day 6 of gestation up to Day 20 of lactation. Target calcium cyclamate doses were 0, 250, 500 and 1,000 mg/kg bw/day, while the PTU dose was 0.5 mg/kg bw/day. No treatment-related effects of cyclamate were observed in either the F0 or F1 generations on reproductive performance or neurobehavioral development. In comparison, PTU exposure resulted in developmental delays, memory impairment and a number of neuropathological and morphometric outcomes. The results from the unique developmental neurotoxicity study design, corroborate the absence of hyperactivity and any other neurotoxic effects following cyclamate administration at levels up to 878 mg/kg bw/day in F0 females and 784 mg/kg bw/day in F1 animals. This demonstrates the suitability of PTU as a positive control and confirms the safe use of cyclamate as a no-calorie sweetener.

Biological fate of low-calorie sweeteners.

With continued efforts to find solutions to rising rates of obesity and diabetes, there is increased interest in the potential health benefits of the use of low- and no-calorie sweeteners (LNCSs). Concerns about safety often deter the use of LNCSs as a tool in helping control caloric intake, even though the safety of LNCS use has been affirmed by regulatory agencies worldwide. In many cases, an understanding of the biological fate of the different LNSCs can help health professionals to address safety concerns. The objectives of this review are to compare the similarities and differences in the chemistry, regulatory status, and biological fate (including absorption, distribution, metabolism, and excretion) of the commonly used LNCSs: acesulfame potassium, aspartame, saccharin, stevia leaf extract (steviol glycoside), and sucralose. Understanding the biological fate of the different LNCSs is helpful in evaluating whether reports of biological effects in animal studies or in humans are indicative of possible safety concerns. Illustrations of the usefulness of this information to address questions about LNCSs include discussion of systemic exposure to LNCSs, the use of sweetener combinations, and the potential for effects of LNCSs on the gut microflora.

A proposal for an upper limit of leucine safe intake in healthy adults.

Based on recent research, an upper limit of safe intake (ULSI) for leucine is proposed for healthy adults: 0.53 g/(kg·d). Because leucine has been used as a dietary supplement for many years in people practicing exercise and sport, further study with long-term exposure to leucine in this specific subpopulation should be performed to eventually adjust the ULSI.

Sweet-taste receptors, low-energy sweeteners, glucose absorption and insulin release.

The present review explores the interactions between sweeteners and enteroendocrine cells, and consequences for glucose absorption and insulin release. A combination of in vitro, in situ, molecular biology and clinical studies has formed the basis of our knowledge about the taste receptor proteins in the glucose-sensing enteroendocrine cells and the secretion of incretins by these cells. Low-energy (intense) sweeteners have been used as tools to define the role of intestinal sweet-taste receptors in glucose absorption. Recent studies using animal and human cell lines and knockout mice have shown that low-energy sweeteners can stimulate intestinal enteroendocrine cells to release glucagon-like peptide-1 and glucose-dependent insulinotropic peptide. These studies have given rise to major speculations that the ingestion of food and beverages containing low-energy sweeteners may act via these intestinal mechanisms to increase obesity and the metabolic syndrome due to a loss of equilibrium between taste receptor activation, nutrient assimilation and appetite. However, data from numerous publications on the effects of low-energy sweeteners on appetite, insulin and glucose levels, food intake and body weight have shown that there is no consistent evidence that low-energy sweeteners increase appetite or subsequent food intake, cause insulin release or affect blood pressure in normal subjects. Thus, the data from extensive in vivo studies in human subjects show that low-energy sweeteners do not have any of the adverse effects predicted by in vitro, in situ or knockout studies in animals.

Using urinary solubility data to estimate the level of safety concern of low levels of melamine (MEL) and cyanuric acid (CYA) present simultaneously in infant formulas.

Melamine (MEL) and cyanuric acid (CYA) may occur simultaneously in milk products. There is no health based guidance value for the mixture of MEL+CYA. Limited toxicological data indicate that MEL+CYA toxicity occurs at levels lower than the toxic doses of the single compounds. The key adverse effect of MEL+CYA is the formation of crystals in the urinary tract, which is dependent on the solubility of the MEL+CYA complex. Urinary concentrations resulting from oral doses of MEL+CYA and MEL alone have been calculated from published data from animal studies. A human exposure scenario assuming consumption of infant formula contaminated at a level of 1 ppm of MEL and CYA each (2 ppm of MEL+CYA) was also analyzed. Margins of more than two orders or magnitude were observed between estimated urine concentrations known to be without detectable effects in rats and calculated human urine concentrations. Because the hazard is related to the physico-chemical characteristics of the mixture, there would be a negligible concern associated with crystal formation if the urinary concentration of the complex is within the solubility range. The solubility of MEL+CYA was higher in urine than in water. A strong pH-dependency was observed with the lowest solubility found at pH 5-5.5. The calculated human urinary concentration was about 30 times less than the solubility limit for MEL+CYA in adult human urine. Altogether, these data provide preliminary evidence suggesting that the presence of 1 ppm of MEL and CYA each in infant formula is unlikely to be of significant health concern.

Application of the Margin of Exposure (MOE) approach to substances in food that are genotoxic and carcinogenic.

This paper presents the work of an expert group established by the International Life Sciences Institute - European branch (ILSI Europe) to follow up the recommendations of an international conference on "Risk Assessment of Compounds that are both Genotoxic and Carcinogenic: New Approaches". Twelve genotoxic and carcinogenic chemicals that can be present in food were selected for calculation of a Margin of Exposure (MOE) between a point of departure on the dose-response for oral carcinogenicity in animal studies and estimates of human dietary exposure. The MOE can be used to support prioritisation of risk management action and, if the MOE is very large, on communication of a low level of human health concern. Depending on the approaches taken in determining the point of departure and the estimation of exposure, it is possible to derive very different values for the MOE. It is therefore essential that the selection of the cancer endpoint and mathematical treatment of the data are clearly described and justified if the results of the MOE approach are to be trusted and of value to risk managers. An outline framework for calculating an MOE is proposed in order to help to ensure transparency in the results.

The 7th workshop on the assessment of adequate intake of dietary amino acids: summary of general discussion.

Extensive discussion sessions were held at the end of each of the 2 d of the workshop. Through the course of the workshop, it became clear that there were different opinions on how to use uncertainty factors to obtain upper levels of intake from no observed adverse effect levels of a particular nutrient and that the selection of an appropriate uncertainty factor would be rather arbitrary. Much of the discussion centered around the potential for using metabolic limits, expressed as the level of intake at which the major pathway of metabolism may approach saturation and at which the amino acid is metabolized by alternative pathways, as a measurable early or surrogate marker for amino acid excess and possible toxicity. After extensive discussion on various conditions that would need to be satisfied for metabolic limits to be used as markers of excessive intake of amino acids, there was a general consensus that methods such as measuring oxidation limits are an attractive approach that merit future investigation. It was noted that there are many data on the clinical use of glutamine, whereas data for proline are very scarce. There was recognition that regardless of the available data, there is regulatory pressure for setting upper levels of intake for amino acids and that much more data are required.

Minimising the population risk of micronutrient deficiency and over-consumption: a new approach using selenium as an example.

BACKGROUND: At the present time the recommended daily intake or allowance (RDA) and the safe upper level (UL) of intake of micronutrients are given as single values. The recommended daily intake is considered to cover the requirements of 97.5% of the population while the safe upper level is a value for the whole population. These values provide only limited guidance to risk managers. AIM OF THE STUDY AND METHODS: A method has been developed recently which models the relationships between intake and risks of either deficiency or excess using an observed incidence for each effect and population distribution characteristics. Using this model it is possible to formulate advice to risk managers on the incidence (prevalence) of adverse effects, due to either deficiency or excess, at different levels of intake. Application of the model to the data used to derive the RDA and UL for selenium shows that it can predict the impact of changes in nutrient intake on the balance between benefit (absence of deficiency) and risk (development of toxicity). RESULTS AND CONCLUSIONS: Application of the model has illustrated the utility of this approach, but highlighted the need for a comprehensive evaluation of the data and a critical appraisal of the validity of the relationships that are analyzed. In addition, the derived incidences will usually relate to effects with different biological or health impacts, so that the final balance between benefit and risk should be developed by a dialogue between the risk assessor and the risk manager.

The intake of intense sweeteners - an update review.

Studies on the intakes of intense sweeteners in different countries published since the author's previous review in 1999 indicate that the average and 95th percentile intakes of acesulfame-K, aspartame, cyclamate and saccharin by adults are below the relevant acceptable daily intake (ADI) values. Fewer data are available for the newer sweeteners, sucralose and alitame, and because they are recent introductions to the market very low intakes were reported in those countries where they were available at the time of the intake study. Overall there has not been a significant change in the intakes of sweeteners in recent years. The only data indicating that the intake of an intense sweetener could exceed its ADI value were the 95th percentile intakes of cyclamate in children, particularly those with diabetes. This sub-group was identified as having high intakes of cyclamate in 1999, and recent studies have not generated reliable intake data to address this possibility.

Establishing the upper end of the range of adequate and safe intakes for amino acids: a toxicologist's viewpoint.

The safety assessment of high intake levels of individual amino acids cannot be based on data from nutritional studies with proteins. Routine toxicity tests designed to investigate a wide range of possible effects should be undertaken for hazard identification and characterization using studies selected to mirror the predicted pattern and duration of human exposure. The approach used to establish an acceptable daily intake level for additives and pesticides, based on defining a "no observed adverse effect" level in the experimental study and dividing by uncertainty factors that allow for species differences and human variability, has a long history of use for foreign compounds and would provide a suitable basis for determining health-based guidance values for single amino acids. The usual default uncertainty factors for toxicokinetics and toxicodynamics should be replaced by compound-specific values if suitable data are available. In addition, the usual uncertainty factors should be modified to more relevant default values based on species differences and human variability in the biodisposition of amino acids in general or of groups of metabolically interrelated amino acids. There would be no significant health concerns if the human intake levels were below a health-based guidance value developed using this approach. A population-distribution approach could be used to define the magnitude of any risk at intake levels above the guidance value.

The safety testing of amino acids.

The risk assessment of compounds added to foods or taken as supplements is usually based on hazard characterization studies performed in animal test species. A large default uncertainty factor, or margin or exposure, is usually required to allow for possible species differences and human variability in the toxicokinetics and toxicodynamics of the compound. The development of biomarkers offers the potential to rationalize the risk assessment of amino acids, and to refine the extrapolation of data from animals to humans. The use of high resolution nuclear magnetic resonance spectroscopy applied to readily accessible biological fluids, such as urine and plasma, offers great potential for the identification of toxicologically relevant biomarkers in animal studies that can then be applied to studies in humans.

Pesticide residue analysis and its relationship to hazard characterisation (ADI/ARfD) and intake estimations (NEDI/NESTI).

Over 800 pesticides are currently approved for use in one or more EU countries. The maximum residue levels (MRL) for agricultural pesticides are derived from field trials conducted under good agricultural practice (GAP). The MRL is a legally enforceable limit related to GAP. The results from field trials would only be used to establish MRLs if the estimated intake of residues did not exceed the acceptable daily intake (ADI) or acute reference dose (ARfD). However, the MRL is not linked to the ADI or ARfD, and could result in intakes considerably below the ADI/ARfD. This disconnection between hazard characterisation (ADI/ARfD) and potential exposure assessment (MRL) means that risk characterisation of pesticide residues is less transparent than for other chemicals present in human food. Residue levels at or below the MRL would not give intakes that exceed the ADI/ARfD but, despite this, there is public concern over such residues. Residue levels above the MRL have to be analysed on a case-by-case basis to determine if the intake could exceed the health-based limits. Other causes of public concern, such as the presence of multiple residues, are currently under investigation.

Aspartame: review of safety.

Over 20 years have elapsed since aspartame was approved by regulatory agencies as a sweetener and flavor enhancer. The safety of aspartame and its metabolic constituents was established through extensive toxicology studies in laboratory animals, using much greater doses than people could possibly consume. Its safety was further confirmed through studies in several human subpopulations, including healthy infants, children, adolescents, and adults; obese individuals; diabetics; lactating women; and individuals heterozygous (PKUH) for the genetic disease phenylketonuria (PKU) who have a decreased ability to metabolize the essential amino acid, phenylalanine. Several scientific issues continued to be raised after approval, largely as a concern for theoretical toxicity from its metabolic components--the amino acids, aspartate and phenylalanine, and methanol--even though dietary exposure to these components is much greater than from aspartame. Nonetheless, additional research, including evaluations of possible associations between aspartame and headaches, seizures, behavior, cognition, and mood as well as allergic-type reactions and use by potentially sensitive subpopulations, has continued after approval. These findings are reviewed here. The safety testing of aspartame has gone well beyond that required to evaluate the safety of a food additive. When all the research on aspartame, including evaluations in both the premarketing and postmarketing periods, is examined as a whole, it is clear that aspartame is safe, and there are no unresolved questions regarding its safety under conditions of intended use.

Botanical health products, positioning and requirements for effective and safe use.

Within the group of botanical products there is a large range of variation with regard to their properties. Some products are identical to foods while others come close to or are medicines. Botanical products are regulated differently within the different member states of the European Union (EU) and globally. They are regulated either as food or as medicinal products, and in the latter case often with simplified registration procedures. These differences are caused by differences in traditional use, in cultural and historical background, in scientific substantiation and in enforcement of current legislation. One may expect that in the future differences will remain, unless EU legislation is enacted with sufficient room for different approaches. The strengths and weaknesses of the different regulatory procedures have been reviewed and evaluated as well as the current methods for quality, efficacy and safety evaluation. Criteria to categorize botanical products have been defined, such that botanical products can be regulated under the current food and medicinal regulations. Furthermore, a decision tree has been developed as a tool to distinguish herbal medicinal products from botanical health products and vice versa, and to provide a stepwise framework for the assessment of safety and efficacy.