Neurobehavioral effects of low dose exposure to chemical mixtures: a review

Neurological disorders have become the leading cause of disease and disability worldwide, with 80% of these conditions being recorded in low- and middle-income countries. Scientific evidence has increasingly associated these disorders with exposure to xenobiotics, such as pesticides, heavy metals and endocrine-disrupting chemicals (EDCs). Recent studies have focused on the consequences of exposure to chemical mixtures and their potential neurotoxic effects. As reported, such exposures can adversely affect cognitive and motor skills, particularly when they occur prenatally or during the early stages of development. Long-term exposure to mixtures of these substances has been strongly related to oxidative stress, inflammation and neurodegeneration. This review aims to explore the neurobehavioral effects of low-dose xenobiotic combinations, stressing the potential long-term neurological damage from such exposure. The in vivo and epidemiological studies reviewed indicate that early-life exposure to chemical mixtures is linked to motor and cognitive disorders, increased anxiety prevalence and behavioral dysregulation. Mechanistic evidence suggests that these exposures may exacerbate oxidative stress, immune activation, and neuronal dysfunction, ultimately leading to neuroinflammation. Chemical interactions greatly affect neurotoxicity, often deviating from simple dose addition. Synergistic effects can arise at both low and high doses, while some studies also report antagonistic outcomes. The specific impacts depend on the chemicals involved, their ratios, and the biological endpoints assessed. Since pollutants like heavy metals can persist in the environment due to their resistance to natural degradation processes, innovative strategies are necessary to mitigate the detrimental effects of exposure to chemical mixtures on human health and the environment.

Food additive mixtures and type 2 diabetes incidence: Results from the NutriNet-Santé prospective cohort

BACKGROUND

Mixtures of food additives are daily consumed worldwide by billions of people. So far, safety assessments have been performed substance by substance due to lack of data on the effect of multiexposure to combinations of additives. Our objective was to identify most common food additive mixtures, and investigate their associations with type 2 diabetes incidence in a large prospective cohort.

METHODS AND FINDINGS

Participants (n = 108,643, mean follow-up =  7.7 years (standard deviation (SD) =  4.6), age =  42.5 years (SD =  14.6), 79.2% women) were adults from the French NutriNet-Santé cohort (2009-2023). Dietary intakes were assessed using repeated 24h-dietary records, including industrial food brands. Exposure to food additives was evaluated through multiple food composition databases and laboratory assays. Mixtures were identified through nonnegative matrix factorization (NMF), and associations with type 2 diabetes incidence were assessed using Cox models adjusted for potential socio-demographic, anthropometric, lifestyle and dietary confounders. A total of 1,131 participants were diagnosed with type 2 diabetes. Two out of the five identified food additive mixtures were associated with higher type 2 diabetes incidence: the first mixture included modified starches, pectin, guar gum, carrageenan, polyphosphates, potassium sorbates, curcumin, and xanthan gum (hazard ratio (HR)per an increment of 1SD of the NMF mixture score = 1.08 [1.02, 1.15], p = 0.006), and the other mixture included citric acid, sodium citrates, phosphoric acid, sulphite ammonia caramel, acesulfame-K, aspartame, sucralose, arabic gum, malic acid, carnauba wax, paprika extract, anthocyanins, guar gum, and pectin (HR = 1.13 [1.08,1.18], p < 0.001). No association was detected for the three remaining mixtures: HR =  0.98 [0.91, 1.06], p = 0.67; HR =  1.02 [0.94, 1.10], p = 0.68; and HR =  0.99 [0.92, 1.07], p = 0.78. Several synergistic and antagonist interactions between food additives were detected in exploratory analyses. Residual confounding as well as exposure or outcome misclassifications cannot be entirely ruled out and causality cannot be established based on this single observational study.

CONCLUSIONS

This study revealed positive associations between exposure to two widely consumed food additive mixtures and higher type 2 diabetes incidence. Further experimental research is needed to depict underlying mechanisms, including potential synergistic/antagonist effects. These findings suggest that a combination of food additives may be of interest to consider in safety assessments, and they support public health recommendations to limit nonessential additives.

TRIAL REGISTRATION

The NutriNet-Santé cohort is registered at clinicaltrials.gov (NCT03335644). https://clinicaltrials.gov/study/NCT03335644.

Biochemical Alterations and Motor Dysfunctions in Corpus Striatum of Rats Brain Exposed to Azo Dyes

Azo food dyes are prohibited in most countries, but their injudicious use is still reported particularly in the developing Nations. Continuous use of contaminated food raises health concerns and given this the present study designed to investigate the effects of 3 non-permitted azo dyes (metanil yellow - MY, malachite green - MG, and sudan III - SIII) on neurobehavioral, neurochemicals, mitochondrial dysfunction, oxidative stress, and histopathological changes in the corpus striatum of rats. Rats were grouped and treated with MY (430 mg/kg), MG (13.75 mg/kg), SIII (250 mg/kg) & mixture (YGR) (MY 143.33 + MG 4.52 + SIII 83.33 mg/kg) p.o. for 60 days showed a significant decrease in grip strength and motor activity, the activity of acetylcholinesterase (AChE), monoamine oxidase - B (MAO-B), and mitochondrial complex I and II compared to the control. The treated groups showed a significant increase in lipid peroxidation and a decrease in the level of reduced glutathione, superoxide dismutase, and catalase as compared to the control. Histopathology of the corpus striatum revealed immense damage. Data from the present study correlate between azo dyes and changes in the behavior of rats which have been associated with the altered biochemicals and neurochemicals activities. In conclusion, exposure to azo dyes caused neurotoxicity involving motor impairments associated with enhanced oxidative stress, mitochondrial dysfunctions, AChE and MAO-B inhibition, and neuronal damage in the corpus striatum of rats.

Exposure to Sunset Yellow FCF since post-weaning causes hippocampal structural changes and memory impairment in the adult rat: The neuroprotective effects of Coenzyme Q10

BACKGROUND

This study aimed to investigate whether exposure to Sunset Yellow FCF (SY) since post-weaning can lead to hippocampal structural changes and memory impairment in adult rat and whether the Coenzyme Q10 (CoQ10) can protect against these adverse effects.

METHODS

The weanling rats were randomly divided into six groups and were treated daily by oral gavage for 6 weeks, as follows: (I) control group, administered distilled water (0.3 mL/100 g/day); (II) CoQ10 group, received 10 mg/kg/day CoQ10; (III) low SY group, received 2.5 mg/kg/day SY; (IV) high SY group, received 70 mg/kg/day SY; (V) low SY + CoQ10 group; and (VI) high SY + CoQ10 group. At the end of the sixth week, the novel object recognition (NOR) test was conducted to evaluate memory. Then, after sacrificing animals, the cerebral hemispheres were removed for stereological study and evaluation of MDA levels.

RESULTS

The low and high doses of SY led to significant neuronal loss and a decrease in the volume of the hippocampus (CA1 and DG subregions), as well as increased the MDA level, which was associated with short- and long-term memory impairment. Although, administration of CoQ10 prevented the hippocampal neural loss and volume, and caused a reduction in MDA and improved memory in the low and high SY groups.

CONCLUSION

It seems that CoQ10 could prevent the neuronal loss and hippocampal atrophy caused by post-weaning exposure to SY through preventing oxidative stress, ultimately improving memory impairment in rats.

Sunset Yellow induced biochemical and histopathological alterations in rat brain sub-regions

Sunset Yellow, a synthetic orange azo food dye was examined in this study for its impact on the Wistar rat brain sub-regions. The dye was administered orally to weanling rats at the Acceptable Daily Intake level (4 mg/kg/bw) for 40 days, and brain sub-regions viz., frontal cortex, cerebellum and hippocampus were examined for biochemical and histopathological changes. The results showed a significant decrease in tissue protein levels, superoxide dismutase, and catalase activity, as well as a significant increase in lipid peroxide levels in all brain sub-regions. Glutathione-S-transferase and Glutathione Reductase activities decreased, while Glutathione peroxidase activity increased. The biogenic amine levels and Acetylcholinesterase activity were also altered, with the frontal cortex and hippocampus being the most affected. Additionally, the dye caused histopathological damage in all brain sub-regions examined. This study indicates that the ADI level of Sunset Yellow may adversely affect brain tissue by causing oxidative damage.

Exposures to FD&C synthetic color additives from over-the-counter medications and vitamins in United States children and pregnant women

BACKGROUND

Food and Drug Administration (FDA) Food Drug and Cosmetic (FD&C) synthetic color additives (SCAs) have been associated with attentional and behavioral problems in children. Efforts to quantify exposure have focused on foods, while the contribution of medications and supplements remains unknown.

OBJECTIVE

To estimate exposures to SCAs in children (2-16 years) and pregnant women from intake of common over-the-counter (OTC) medications and vitamins.

METHODS

We estimated single-day exposure (mg/kg/day) to FD&C SCAs based on measurements of 25 different products and recommended dosages on product labels. Exposures were compared to SCA exposure estimates from food we previously developed and acceptable daily intakes (ADIs) established by FDA and the World Health Organization.

RESULTS

The highest exposure was found for FD&C Red No. 40 in a children's cold/cough/allergy syrup. A child aged 12-16 years consuming the maximum daily dosage would have an exposure of 0.221 mg/kg/day, which is twice this age group's typical exposure to this additive from food. No estimated exposures exceeded the ADIs.

SIGNIFICANCE

Some children's OTC medications and vitamins may cause daily SCA exposures comparable to those from foods. OTC medications and vitamins should be considered in efforts to quantify population exposure to FD&C SCAs.

IMPACT

Exposure to synthetic color additives (SCAs) from foods has been associated with behavioral problems in children. Exposures from over-the-counter (OTC) medications and vitamins remain unquantified despite widespread use. We estimated exposures in children and pregnant women for 25 different OTC medication and vitamin products sold in the United States. While exposures were below acceptable daily intakes (ADIs) established by the US Food and Drug Administration and the World Health Organization, some were comparable to typical daily exposures from foods. This work critically informs future SCA exposure assessments and provides valuable information for parents concerned about the health effects of SCAs.

Status of food colorants in India: conflicts and prospects

Food colorants are imperative ingredients for attracting consumers and in deciding their preferences. Here we discuss the current status of natural colorants and synthetic food colorants on the Indian market by appraising the growth of the food colorant market both globally and nationally, based on published case studies on synthetic food colorants (SFCs), rules, and regulations implemented by Food Safety and Standards Authority of India on natural food colorants and SFCs. The substantial lacunae in the research on the impacts of SFCs in the Indian population identified through our literature survey signify the scope and need for appraisal of the issues prevailing in the Indian food colorant market as well as the necessity of renewing the food colorant policies. The illegal use of banned food colorants, the adulteration of natural food colorants, mislabelling of SFCs as natural colorants, and the permitted use of internationally banned food colorants, as well as the unawareness among consumers are serious issues recognized. Appropriate labelling to denote natural food colorants' presence, renewed standards of policy to determine the permitted use of food colorants, comprehensive regulations for the production and use of natural food colorants, stringent rules to constrain the production of toxic SFCs are obligatory to breakdown the dilemma on the Indian food market. Most importantly, awareness and responsiveness should be generated among consumers regarding the illegal use and adulteration of colorants and the need to use natural colorants. We also recommend a logo to designate the presence of natural colorants which will aid the consumers to make the right choice.

Dietary Exposure to United States Food and Drug Administration-Approved Synthetic Food Colors in Children, Pregnant Women, and Women of Childbearing Age Living in the United States

The Food and Drug Administration (FDA) regulates artificial food colors (AFCs) in the United States. Exposure to AFCs has raised concerns about adverse behavioral effects in children. We quantified AFC exposure in women of childbearing age, pregnant women, and children and compared them to FDA and World Health Organization acceptable daily intakes (ADIs). We estimated the “typical” and “high” single-day and two-day average dietary exposure to each AFC (mg/kg/day) based on laboratory measurements and food consumption data from the 2015−2016 National Health and Nutrition Examination Survey (NHANES). We also examined whether AFC intake differed by income, education, and ethnicity. Exposure tended to be higher in children and the highest AFC exposure was found for Red No. 40. Children’s mean and 95th percentile FD&C Red No. 3 estimated intakes exceeded the ADIs in some instances. Juice drinks, soft drinks, icings, and ice cream cones were major foods contributing to children’s (<16 years old) AFC exposure. AFC intake was higher in participants with lower incomes and education and of African American ethnicity. The findings indicate widespread AFC exposure including in very young children. Research is needed on the sociodemographic determinants of exposure and AFC toxicokinetics to better describe the absorption and organ-specific exposure.

Potential impacts of synthetic food dyes on activity and attention in children: a review of the human and animal evidence

Concern that synthetic food dyes may impact behavior in children prompted a review by the California Office of Environmental Health Hazard Assessment (OEHHA). OEHHA conducted a systematic review of the epidemiologic research on synthetic food dyes and neurobehavioral outcomes in children with or without identified behavioral disorders (particularly attention and activity). We also conducted a search of the animal toxicology literature to identify studies of neurobehavioral effects in laboratory animals exposed to synthetic food dyes. Finally, we conducted a hazard characterization of the potential neurobehavioral impacts of food dye consumption. We identified 27 clinical trials of children exposed to synthetic food dyes in this review, of which 25 were challenge studies. All studies used a cross-over design and most were double blinded and the cross-over design was randomized. Sixteen (64%) out of 25 challenge studies identified some evidence of a positive association, and in 13 (52%) the association was statistically significant. These studies support a relationship between food dye exposure and adverse behavioral outcomes in children. Animal toxicology literature provides additional support for effects on behavior. Together, the human clinical trials and animal toxicology literature support an association between synthetic food dyes and behavioral impacts in children. The current Food and Drug Administration (FDA) acceptable daily intakes are based on older studies that were not designed to assess the types of behavioral effects observed in children. For four dyes where adequate dose-response data from animal and human studies were available, comparisons of the effective doses in studies that measured behavioral or brain effects following exposure to synthetic food dyes indicate that the basis of the ADIs may not be adequate to protect neurobehavior in susceptible children. There is a need to re-evaluate exposure in children and for additional research to provide a more complete database for establishing ADIs protective of neurobehavioral effects.

Post-weaning exposure to Sunset Yellow FCF induces behavioral impairment and structural changes in the adult rat medial prefrontal cortex: protective effects of Coenzyme Q10

Sunset Yellow FCF (E110) is a water soluble synthetic dye that has adverse neurobehavioral effects. Coenzyme Q10 (CoQ10) is known as a neuroprotective agent. The present study aimed to evaluate the effects of post-weaning exposure to Sunset Yellow FCF on behavioral and structural changes in the adult rat medial prefrontal cortex and the protective effects of CoQ10. The weanling rats were randomly divided into six groups: distilled water, CoQ10 (10 mg/kg/day), and low (2.5 mg/kg/day), and high (70 mg/kg/day) doses of Sunset Yellow FCF with or without CoQ10 consumption for six weeks. A battery of behavioral tests including open field and Morris water maze tests were done at the end of the 6th week, and then the animals' brains were removed for stereological methods. Our finding indicated that the high dose of Sunset Yellow FCF led to a reduced total volume of mPFC (15.16%), especially in the anterior cingulate cortex (ACC) region (21.96%), along with loss of neurons (32%) and glial cells (37%), which was associated with higher anxiety behavior and loss in spatial memory. However, CoQ10 prevented the neural loss and glial cells, improved anxiety like behaviors and memory impairment. On the other hand, the acceptable daily dose (low dose of Sunset Yellow FCF) did not show a discernible effect on the same parameters. This study showed that the CoQ10 can protect the alteration in mPFC structure and behavioral changes of the rats exposed to high dose of Sunset Yellow FCF.

Perinatal diet and offspring anxiety: A scoping review

Health behaviors during pregnancy have an impact on the developing offspring. Dietary factors play a role in the development of mental illness: however, less is known about the impact of diet factors during pre-conception, gestation, and lactation on anxiety levels in offspring. This scoping review sought to systematically map the available research involving human and animal subjects to identify nutritional interventions which may have a harmful or protective effect, as well as identify gaps. Studies investigating an association between any perinatal diet pattern or diet constituent and offspring anxiety were included. The number of studies reporting an association with increased or decreased levels of anxiety were counted and presented in figures. A total of 55,914 results were identified as part of a larger scoping review, and 120 articles met the criteria for inclusion. A greater intake of phytochemicals and vitamins were associated with decreased offspring anxiety whereas maternal caloric restriction, protein restriction, reduced omega-3 consumption, and exposure to a high fat diet were associated with higher levels of offspring anxiety. Results were limited by a very large proportion of animal studies. High quality intervention studies involving human subjects are warranted to elucidate the precise dietary factors or constituents that modulate the risk of anxiety in offspring.

Using High-Throughput Screening to Evaluate Perturbations Potentially Linked to Neurobehavioral Outcomes: A Case Study Using Publicly Available Tools on FDA Batch-Certified Synthetic Food Dyes

There is growing evidence from human and animal studies indicating an association between exposure to synthetic food dyes and adverse neurobehavioral outcomes in children. However, data gaps persist for potential mechanisms by which the synthetic food dyes could elicit neurobehavioral impacts. We developed an approach to evaluate seven US FDA-batch-certified food dyes using publicly available high-throughput screening (HTS) data from the US EPA's Toxicity Forecaster to assess potential underlying molecular mechanisms that may be linked to neurological pathway perturbations. The dyes were screened through 270 assays identified based on whether they had a neurological-related gene target and/or were mapped to neurodevelopmental processes or neurobehavioral outcomes, and were conducted in brain tissue, targeted specific hormone receptors, or targeted oxidative stress and inflammation. Some results provided support for neurological impacts found in human and animal studies, while other results showed a lack of correlation with in vivo findings. The azo dyes had a range of activity in assays mapped to G-protein-coupled receptors and were active in assays targeting dopaminergic, serotonergic, and opioid receptors. Assays mapped to nuclear receptors (androgen, estrogen, and thyroid hormone) also exhibited activity with the food dyes. Other molecular targets included the aryl hydrocarbon receptor, acetylcholinesterase, and monoamine oxidase. The Toxicological Prioritization Index tool was used to visualize the results of the Novascreen assays. Our results highlight certain limitations of HTS assays but provide insight into potential underlying mechanisms of neurobehavioral effects observed in in vivo animal toxicology studies and human clinical studies.

Acute effects of tartrazine (E102) exposure on behavior, and histology of land snail Helix aspersa biological model

Introduction. Tartrazine is an azofood additive widely used in the pharmaceu-cal, cosmetic, food, and other industries. Objective. To assess the effects of tartrazineon the attitude to move and to eat, and histological changes in digestive, and renal sys-tem, after an acute treatment on a biological model the snail Helix aspersa. Material and Methods. Snails were exposed orally, and by contact to flour contaminated with this dye for 24 hours. Adult snails were divided into two groups of 20 animals each. The control group fed flour alone. The experimental group was administered orally with flour treated with tartrazine (200mg/g flour). Results. The observation of behaviour revealed inhibitory effects of tartrazine on locomotion, and nutrition of snails. Histolo-gical examination of intestines, hepatopancreas, and kidney of treated animals showed altered tissue structures, with advanced degeneration of digestive tubules, connective tissue, and smooth muscle fibers of the walls surrounding the three organs, in response to tartrazine, compared to controls. Conclusion. This study suggests that acute exposure to tartrazine may lead to disorders in locomotor, and nutritional behavior, in addition to tissue alterations. Therefore, this study on behavior, supported by histological changes in H. Aspersa can be used as potential biomarkers of exposure to other azodyes.

Prenatal exposure to artificial food colorings alters NMDA receptor subunit concentrations in rat hippocampus

Exposure to artificial food color additives (AFCAs) has been implicated in the etiology of certain childhood hyperactivity and learning disabilities. N-methyl-D-aspartate receptors and alpha-7 nicotinic acetylcholine receptor (α7 nAChR) are involved in learning and memory. We administered a mixture of AFCAs (erythrosine, ponceau 4R, allura red AC, sunset yellow FCF, tartrazine, amaranth, brilliant blue, azorubine, and indigotine) to female rats during gestation to investigate the effects of prenatal exposure to AFCAs on neurobehavior, spatial learning, and memory in their offspring. We also investigated whether AFCAs modulate NR2A, NR2B, and α7 nAChR protein levels in their offsprings' hippocampi. Although spatial learning and memory were not altered, the offspring of rats exposed to AFCAs exhibited decreased motivation and increased despair-related behavior. NR2A and NR2B protein levels were significantly reduced in female offspring in the experimental group (p < 0.05), whereas α7 nAChR level was not significantly altered. Our results suggest that prenatal exposure to AFCAs may lead to sex-dependent alterations in glutamatergic signaling which may continue into adolescence.