Risk of vitamin A toxicity from candy-like chewable vitamin supplements for children

Vitamin A - discovery, metabolism, receptor signaling and effects on bone mass and fracture susceptibility

The first evidence of the existence of vitamin A was the observation 1881 that a substance present in small amounts in milk was necessary for normal development and life. It was not until more than 100 years later that it was understood that vitamin A acts as a hormone through nuclear receptors. Unlike classical hormones, vitamin A cannot be synthesized by the body but needs to be supplied by the food as retinyl esters in animal products and ß-carotene in vegetables and fruits. Globally, vitamin A deficiency is a huge health problem, but in the industrialized world excess of vitamin A has been suggested to be a risk factor for secondary osteoporosis and enhanced susceptibility to fractures. Preclinical studies unequivocally have shown that increased amounts of vitamin A cause decreased cortical bone mass and weaker bones due to enhanced periosteal bone resorption. Initial clinical studies demonstrated a negative association between intake of vitamin A, as well as serum levels of vitamin A, and bone mass and fracture susceptibility. In some studies, these observations have been confirmed, but in other studies no such associations have been observed. One meta-analysis found that both low and high serum levels of vitamin A were associated with increased relative risk of hip fractures. Another meta-analysis also found that low levels of serum vitamin A increased the risk for hip fracture but could not find any association with high serum levels of vitamin A and hip fracture. It is apparent that more clinical studies, including large numbers of incident fractures, are needed to determine which levels of vitamin A that are harmful or beneficial for bone mass and fracture. It is the aim of the present review to describe how vitamin A was discovered and how vitamin A is absorbed, metabolized and is acting as a ligand for nuclear receptors. The effects by vitamin A in preclinical studies are summarized and the clinical investigations studying the effect by vitamin A on bone mass and fracture susceptibility are discussed in detail.

Dietary Vitamin A Intake and Circulating Vitamin A Concentrations and the Risk of Three Common Cancers in Women: A Meta-Analysis

BACKGROUND

According to relevant clinical research, dietary and circulating antioxidants vitamin A are connected with the risk of breast, cervical, and ovarian cancer in women. However, there was inconsistency between the findings. We completed this meta-analysis at the right moment to address this contradiction of the problem.

METHODS

Web of Science, Embase, and PubMed databases were searched using the proposed search strategy and filtered using the inclusion and exclusion criteria as well as the NOS quality score. As of May 2022, low intake or low concentration was used as a control, and odds ratio (OR) or relative risk (RR) and ninety-five percent confidence intervals (95% CI) were extracted for high intake. Stata 12.0 was used to process the data.

RESULTS

Our meta-analysis included a total of 49 studies, 29 on breast cancer, 10 on ovarian cancer, and 10 on cervical cancer. There were 38 case-control studies included, with 25,363 cases and 42,281 controls; there were 11 cohort studies included, 1,334,176 individuals were followed up, and finally 9496 obtained cancer. The pooled OR value results were as follows: diet or supplements (OR = 0.83, 95% CI 0.76-0.90, I ² = 56.1%) and serum or plasma (OR = 0.96, 95% CI 0.86-1.09, I ² = 29.5%). Subgroup analyses were performed according to cancer type, diet or supplements, serum or plasma, study type, and geographic regions.

CONCLUSIONS

In North American and Asian populations, high dietary consumption of vitamin A or supplements decreases the incidence of three cancers in women, with breast and ovarian cancers being more significant. However, high circulating vitamin A concentrations were not significantly connected with the risk of the three malignancies.

Assessing Vitamins, Minerals and Supplements Marketed to Children in Canada

Given the growth of supplements specifically designed for children in Canada, this study examines the nutrient levels of these products, and evaluates them in light of the US Health and Medical Division (HMD)—formerly the Institute of Medicine—and Health Canada’s recommendations. Content analysis was used to document the nutrient levels of child-targeted vitamins, minerals and fish oils/omega-3s (n = 80) in Calgary, Alberta, Canada. Products were assessed according to HMD and Health Canada dosage recommendations for children, and the percentage of Estimate Average Requirements (EAR), Adequate Intakes (AI), and Tolerable Upper Intakes Level (UL) calculated. Median EAR/AI/UL percentages and quartiles were calculated for each nutrient, and estimates for the adequate intake recommendations plotted with box plots. Sixty five percent of the products assessed were multivitamins; the median dose was higher than AI recommendations for vitamins A, B6, B12, and C, as well as thiamin, riboflavin, pantothenic acid, and biotin. Substantial variation in vitamin, mineral, or fish oil dosage was found between similar supplements—with nutrients such as vitamin B12 ranging from 83% to 5557% of AI. Such findings matter because the very existence of these products suggests that children should be taking them, yet more research is needed on their potential (adverse) effects over both the short and long term. The substantial variation in dosages between products also raises questions about the (perhaps unnecessary) fortification of our children, as well as the expectations that parents know—or are even aware of—appropriate nutrient levels for their kids.

Compliance of Parenting Magazines Advertisements with American Academy of Pediatrics Recommendations

This study examined 3218 advertisements from the two parenting magazines with highest circulation in the United States. The authors compared each advertisement for a product for use by children, against all the published recommendations of the American Academy of Pediatrics (AAP) on topics such as toy safety, helmet use, age-defined choking hazards, infant sleep safety, and others. Any advertisement with images or products which went against a published AAP recommendation was deemed as non-adherence and was categorized according to the statement it contradicted. Nearly one in six (15.7%) of the advertisements contained example(s) of non-adherence to AAP recommendations, with twelve categories of offense represented. Categories ranked by overall share from most to least include: non-Food and Drug Administration (FDA) approved medical treatments, age-defined choking hazards, vitamins, cold medicine, formula, oral care, screen time, toy/playground safety, infant sleep, nutrition, water safety, and fall risk. Given that repeated exposure to messages in advertisements has been associated with changes in health decision-making, and parents often turn to parenting magazines for advice and ideas regarding their children, the publishers might consider screening the content in order to prevent confusing and potentially dangerous messages from being disseminated in the media.

Vitamin D and Risk for Vitamin A Intoxication in an 18-Month-Old Boy

An 18-month-old boy presented with abdominal pain, vomiting, diarrhea, and poor appetite for 6 days. He had been given a multivitamin preparation once daily, containing 50.000 IU of vitamin D and 10.000 IU of vitamin A for a wide anterior fontanelle for about three months. He presented with hypercalcemia, low levels of parathyroid hormone (PTH), and very high serum 25-hydroxyvitamin D (25-OHD) levels. Renal ultrasound showed nephrocalcinosis. He did not have sign or symptom of vitamin A intoxication. Patient was successfully treated with intravenous hydration, furosemide, and prednisolone. With treatment, serum calcium returned rapidly to the normal range and serum 25-OHD levels were reduced progressively. In conclusion the diagnosis of vitamin D deficiency rickets without checking 25-OHD levels may cause redundant treatment that leads to vitamin D intoxication (VDI).

An examination of product packaging marketing strategies used to promote pediatric multivitamins

The purpose of this study was to describe the nature of marketing strategies for multivitamin and multimineral (MVM) supplement packaging and to assess the extent to which these supplements are marketed as food products. A cross-sectional study of children's supplement packaging was conducted. Descriptive statistics identified common marketing practices. Websites of the three largest retail chain pharmacies in the United States and MVM manufacturers were accessed. The study's sample consisted of packaging for 52 children's MVM supplements. Child-targeted marketing included reference to trademarked characters on 42.3% of MVM packaging (n = 22). More than 80% of the sample (n = 42) listed fruity flavors and almost all packaging included descriptive words related to the MVMs' shape and/or flavor (88.5%, n = 46). Nearly one-fifth of the packaging (n = 10) pictured a food item. With respect to parent-targeted promotional language, almost 83% of the supplement packages (n = 43) included text on the support of bodily structure/function. More than half of the sample (53.8%, n = 28) had promotional language related to dietary practice (e.g. organic, gluten-free). Pediatricians can play a role in ensuring that parents are aware of (1) possible risks associated with MVM overconsumption, and (2) the importance of deriving vitamins and minerals from a balanced diet. Given the high number of exposures to pediatric MVMs among youth and established influence of food marketing on shaping children's perceptions and behaviors, further research is necessary to determine the extent to which children's MVMs are marketed as a food product and perceived as such by children.

Vitamin A supplementation modifies the antioxidant system in rats

BACKGROUND/OBJECTIVES

It has been shown that vitamin A supplementation has different effects on skeletal health and the antioxidant system. Deficiency or excess of this vitamin can lead to health problems. Vitamin A can work as either an antioxidant or prooxidant depending on its concentration. The present study was conducted to investigate the effects of different doses of vitamin A supplementation on the antioxidant system in rats.

MATERIALS/METHODS

Forty Spargue-Dawley male rats were divided into four groups according to the dose of vitamin A received: 0 (A0), 4,000 (A1), 8,000 (A2), and 20,000 (A3) IU retinyl palmitate/kg diet. After a feeding period of 4 wks, lipid peroxide levels, glutathione concentration, antioxidant enzyme activities, and vitamins A and E concentrations were measured. Histopathological changes were observed in rat liver tissue using an optical microscope and transmission electron microscope.

RESULTS

Lipid peroxide levels in plasma were significantly decreased in the A1 and A2 groups compared to the A0 rats. Erythrocyte catalase and hepatic superoxide dismutase activities of the A2 group were significantly higher than those of the A0 group. Hepatic glutathione peroxidase activity was significantly lower in the A3 group compared to the other groups. Total glutathione concentrations were significantly higher in the A1 and A2 groups than in the A0 group. Histological examination of liver tissue showed that excessive supplementation of vitamin A might lead to lipid droplet accumulation and nuclear membrane deformation.

CONCLUSIONS

These results indicate that appropriate supplementation of vitamin A might have a beneficial effect on the antioxidant system in rats.

The neurotoxic effects of vitamin A and retinoids

Vitamin A (retinol) and its congeners - the retinoids - participate in a panoply of biological events, as for instance cell differentiation, proliferation, survival, and death, necessary to maintain tissue homeostasis. Furthermore, such molecules may be applied as therapeutic agents in the case of some diseases, including dermatological disturbances, immunodeficiency, and cancer (mainly leukemia). In spite of this, there is a growing body of evidences showing that vitamin A doses exceeding the nutritional requirements may lead to negative consequences, including bioenergetics state dysfunction, redox impairment, altered cellular signaling, and cell death or proliferation, depending on the cell type. Neurotoxicity has long been demonstrated as a possible side effect of inadvertent consumption, or even under medical recommendation of vitamin A and retinoids at moderate to high doses. However, the exact mechanism by which such molecules exert a neurotoxic role is not clear yet. In this review, recent data are discussed regarding the molecular findings associated with the vitamin A-related neurotoxicity.

Fortification of foods with vitamin D in India: strategies targeted at children

Vitamin D deficiency is endemic in India, despite abundant sunshine, due to several socioeconomic and cultural constraints. Fortification of staple foods with vitamin D is a viable population-based strategy for the general population in India. These strategies are discussed in the review article entitled, "Fortification of Foods With Vitamin D in India" [1]. The quantity of foods consumed by children is much smaller compared to adults. Therefore, children need energy-dense and micronutrient-dense foods to meet their daily nutritional requirements. Targeted food fortification programs are needed to meet the special needs of children. This review explores potential strategies that could be used for fortification of foods with vitamin D for children in India. Sattu has the potential to be a valuable vehicle for vitamin D fortification in India. The salient characteristics and merits of sattu as an ideal food to be fortified with micronutrients, especially vitamin D, are reviewed here. Key teaching points: • Fortification of foods with vitamin D, specifically targeted towards the nutritional requirements of infants and children, is a viable strategy in the Indian scenario. •Government programs targeting the nutritional needs of children in India, especially via midday meal programs in schools, should incorporate indigenous ready-to-eat foods fortified with micronutrients including vitamin D. These foods would need to have longer shelf life, require minimal preparation, and have economic and technological feasibility. • Sattu, a protein rich Indian fast food, comprised of roasted flour made from cereals and legumes, has immense potential to serve as an economically and technologically feasible fortification vehicle for vitamin D fortification strategies.

An examination of marketing techniques used to promote children's vitamins in parenting magazines

More than a third of children and adolescents in the United States take vitamins even though professional medical organizations do not endorse their use in healthy children. Regardless of their efficacy, children's vitamin products are aggressively promoted. Therefore, the goal of this study was to describe and analyze advertisements related to vitamins in the following three popular parenting magazines, Parents, Parenting Early Years, and Parenting School Years. A total of 135 magazines across four years were reviewed.  There were 207 advertisements for children's vitamins, all in the form of chewy or gummy.  None of these advertisements included a dosage or a warning.  Almost all (92.3%) included a cartoon in the advertisement.  Almost a quarter (23.2%) of the advertisements promoted their product with the theme of prevention and more than half (51.2%) included the theme of peace of mind.  Parenting magazines are a popular medium for providing exposure to products geared towards children.  Companies that market children's vitamins in these magazines can increase awareness among parents of the risks by providing warning and dosage information in their advertisements.  Magazines can also play a role by encouraging responsible marketing and providing editorial content on children's vitamins and potential consequences of pediatric overdose.

Respiratory tract epithelial cells express retinaldehyde dehydrogenase ALDH1A and enhance IgA production by stimulated B cells in the presence of vitamin A

Morbidity and mortality due to viral infections are major health concerns, particularly when individuals are vitamin A deficient. Vitamin A deficiency significantly impairs mucosal IgA, a first line of defense against virus at its point of entry. Previous reports have suggested that CD11c(Hi) dendritic cells (DCs) of the gastrointestinal tract produce retinaldehyde dehydrogenase (ALDH1A), which metabolizes vitamin A precursors to retinoic acid to support normal mucosal immunity. Given that the upper respiratory tract (URT) and gastrointestinal tract share numerous characteristics, we asked if the CD11c(Hi) DCs of the URT might also express ALDH1A. To address this question, we examined both CD11c(Hi) test cells and CD11c(Lo/neg) control cells from nasal tissue. Surprisingly, the CD11c(Lo/neg) cells expressed more ALDH1A mRNA per cell than did the CD11c(Hi) cells. Further evaluation of CD11c(Lo/neg) populations by PCR and staining of respiratory tract sections revealed that epithelial cells were robust producers of both ALDH1A mRNA and protein. Moreover, CD11c(Lo/neg) cells from nasal tissue (and a homogeneous respiratory tract epithelial cell line) enhanced IgA production by lipopolysaccharide (LPS)-stimulated splenocyte cultures in the presence of the retinoic acid precursor retinol. Within co-cultures, there was increased expression of MCP-1, IL-6, and GM-CSF, the latter two of which were necessary for IgA upregulation. All three cytokines/chemokines were expressed by the LPS-stimulated respiratory tract epithelial cell line in the absence of splenocytes. These data demonstrate the autonomous potential of respiratory tract epithelial cells to support vitamin A-mediated IgA production, and encourage the clinical testing of intranasal vitamin A supplements in vitamin A deficient populations to improve mucosal immune responses toward respiratory tract pathogens and vaccines.

Vitamin a metabolism, action, and role in skeletal homeostasis

Vitamin A (retinol) is ingested as either retinyl esters or carotenoids and metabolized to active compounds such as 11-cis-retinal, which is important for vision, and all-trans-retinoic acid, which is the primary mediator of biological actions of vitamin A. All-trans-retinoic acid binds to retinoic acid receptors (RARs), which heterodimerize with retinoid X receptors. RAR-retinoid X receptor heterodimers function as transcription factors, binding RAR-responsive elements in promoters of different genes. Numerous cellular functions, including bone cell functions, are mediated by vitamin A; however, it has long been recognized that increased levels of vitamin A can have deleterious effects on bone, resulting in increased skeletal fragility. Bone mass is dependent on the balance between bone resorption and bone formation. A decrease in bone mass may be caused by either an excess of resorption or decreased bone formation. Early studies indicated that the primary skeletal effect of vitamin A was to increase bone resorption, but later studies have shown that vitamin A can not only stimulate the formation of bone-resorbing osteoclasts but also inhibit their formation. Effects of vitamin A on bone formation have not been studied in as great a detail and are not as well characterized as effects on bone resorption. Several epidemiological studies have shown an association between vitamin A, decreased bone mass, and osteoporotic fractures, but the data are not conclusive because other studies have found no associations, and some studies have suggested that vitamin A primarily promotes skeletal health. In this presentation, we have summarized how vitamin A is absorbed and metabolized and how it functions intracellularly. Vitamin A deficiency and excess are introduced, and detailed descriptions of clinical and preclinical studies of the effects of vitamin A on the skeleton are presented.

Liver abnormalities in drug and substance abusers

Drug and substance abuse remains a major medical problem. Alcohol use, abuse and dependence are highly prevalent conditions. Alcohol related liver disease can present as simple steatosis, steatohepatitis, alcoholic hepatitis or liver cirrhosis. Paracetamol hepatotoxicity secondary to accidental or deliberate overdose is another common problem. While the adverse cardiovascular, neurological, renal and psychiatric consequences of various illicit substance abuses are widely studied and publicized, less attention has been directed towards possible hepatotoxic effects. Illicit drug abuse can cause a range of liver abnormalities ranging from asymptomatic derangement of liver function tests to fulminant hepatic failure. This article reviews the epidemiology, risk factors, clinical manifestations, pathogenesis, investigations, management and prognostic factors of alcohol related liver disease and paracetamol hepatotoxicity as well as the current knowledge pertaining to hepatotoxicity of the more commonly used illicit substances including cannabis, amphetamine type stimulants, cocaine, khat chewing and complementary and alternate medicine.

Systematic review of the literature on vitamin A and memory

Background

Over the last 30 years, a variety of studies reporting the effects of vitamin A on memory have been published.

Objective

To perform a rigorous systematic review of the literature on vitamin A and memory in order to organize evidence-based data on the subject.

Methods

Four authors carried out the systematic review in accordance with strict guidelines. The terms "vitamin A" OR "retinol" OR "retinoic acid" AND "memory" OR "cognition" OR "Alzheimer" were searched in virtually all medical research databases.

Results

From 236 studies containing the key words, 44 were selected for this review, numbering 10 reviews and 34 original articles. Most studies used animal models for studying vitamin A and cognition. Birds, mice and rats were more frequently employed whereas human studies accounted for only two reports on brain tissue from autopsies and one on the role of isotretinoin in cognition among individuals taking this medication to treat acne.

Conclusion

Vitamin A may be an important and viable complement in the treatment and prevention of Alzheimer's disease. Clinical trials are imperative and, at present, there is no evidence-based data to recommend vitamin A supplementation for the prevention or treatment of Alzheimer's disease.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Increased receptor for advanced glycation endproducts immunocontent in the cerebral cortex of vitamin A-treated rats

Vitamin A, beyond its biological role, is an alternative choice in treating some life threatening pathologies, for instance leukemia and immunodeficiency. On the other hand, vitamin A therapy at moderate to high doses has caused concern among public health researchers due to the toxicological aspect resulting from such habit. It has been described hepatotoxicity, cognitive disturbances and increased mortality rates among subjects ingesting increased levels of vitamin A daily. Then, based on the previously reported data, we investigated here receptor for advanced glycation endproducts (RAGE) immunocontent and oxidative damage levels in cerebral cortex of vitamin A-treated rats at clinical doses (1,000-9,000 IU/kg day(-1)). RAGE immunocontent, as well as oxidative damage levels, were observed increased in cerebral cortex of vitamin A-treated rats. Whether increased RAGE levels exert negative effects during vitamin A supplementation it remains to be investigated, but it is very likely that deleterious consequences may arise from such alteration.

Impaired redox state and respiratory chain enzyme activities in the cerebellum of vitamin A-treated rats

Vitamin A is a micronutrient that participates in the maintenance of the mammalian cells homeostasis. However, excess of vitamin A, which may be achieved through increased intake of the vitamin either therapeutically or inadvertently, induces several deleterious effects in a wide range of mammalian cells, including neuronal cells. Vitamin A is a redox-active molecule, and it was previously demonstrated that it induces oxidative stress in several cell types. Therefore, in the present work, we investigated the effects of vitamin A supplementation at clinical doses (1000-9000IU/(kgday)) on redox environment and respiratory chain activity in the adult rat cerebellum. Glutathione-S-transferase (GST) enzyme activity was also measured here. The animals were treated for 3, 7, or 28 days with vitamin A as retinol palmitate. We found increased levels of molecular markers of oxidative damage in the rat cerebellum in any period analyzed. Additionally, vitamin A supplementation impaired cerebellar mitochondrial electron transfer chain (METC) activity. GST enzyme activity was increased in the cerebellum of rats chronically treated with vitamin A. Based on our results and data previously published, we recommend more caution in prescribing vitamin A at high doses even clinically, since there is a growing concern regarding toxic effects associated to vitamin A intake.

Retinoid-mediated regulation of mood: possible cellular mechanisms

Vitamin A and its derivatives, the retinoids, have long been studied for their ability to alter central nervous system (CNS) development. Increasingly, it is recognized that sufficient levels of retinoids may also be required for adult CNS function. However, excess dietary vitamin A, due to the consumption of supplements or foods rich in vitamin A, has been reported to induce psychosis. In addition, 13-cis-retinoic acid (13-cis-RA, isotretinoin), the active ingredient in the acne treatment Accutane, has been reported to cause adverse psychiatric events, including depression and suicidal ideation. Nevertheless, epidemiological studies have reported no consistent link between Accutane use and clinical depression in humans. Using an animal model, we have recently shown that 13-cis-RA induces an increase in depression-related behavior. Impairments in spatial learning and memory have also been demonstrated following 13-cis-RA treatment in mice. This review focuses on the behavioral and possible cellular effects of retinoid deficiency or excess in the adult brain in relation to altered mood. Specifically, we discuss the effect of retinoids on depression-related behaviors and whether norepinephrinergic, dopaminergic, or serotonergic neurotransmitter systems may be impaired. In addition, we consider the evidence that adult neurogenesis, a process implicated in the pathophysiology of depression, is reduced by retinoid signaling. We suggest that 13-cis-RA treatment may induce depression-related behaviors by decreasing adult neurogenesis and/or altering the expression of components of serotonergic neurotransmitter system, thereby leading to impaired serotonin signaling.

Therapeutic vitamin A doses increase the levels of markers of oxidative insult in substantia nigra and decrease locomotory and exploratory activity in rats after acute and chronic supplementation

Vitamin A is known to regulate some central nervous system (CNS)-associated functions. Vitamin A at high doses has been demonstrated to be beneficial in the treatment of some diseases, for instance acute promyelocytic leukemia. However, vitamin A and its naturally occurring metabolites (retinoids) are known to alter neuronal function, inducing behavioral disorders. Here we provide an evidence to indicate that vitamin A supplementation, at both therapeutic and excessive doses, induces oxidative stress in the rat substantia nigra. Vitamin A supplementation induced lipid peroxidation, protein carbonylation, and oxidation of protein thiol groups, as well as change in catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activity. Surprisingly, locomotory and exploratory activity of rats were decreased after acute and chronic vitamin A supplementation. Therefore, we may conclude from our results that vitamin A supplementation is prooxidant to the rat substantia nigra and effective in altering behavior.

Acute and chronic vitamin A supplementation at therapeutic doses induces oxidative stress in submitochondrial particles isolated from cerebral cortex and cerebellum of adult rats

Vitamin A is an essential micronutrient to the normal brain function. However, there is an increasing concern regarding the use of vitamin A at high doses even therapeutically. Here, we show that acute and chronic vitamin A supplementation induces oxidative stress to submitochondrial particles (SMP) isolated from rat cerebral cortex and cerebellum. Both chronic and acute vitamin A supplementation at therapeutic (1000 IU/kg or 2500 IU/kg) or excessive (4500 IU/kg or 9000 IU/kg) doses induced lipid peroxidation, protein carbonylation, and oxidation of protein thiol groups in cerebral cortex and cerebellum SMP. Furthermore, vitamin A supplementation induced an increase in the superoxide (O(2)(-)) anion production, indicating an uncoupling in the electron transfer chain (ETC). Locomotory and exploratory activity, which are associated to cerebral cortex and cerebellum, also were affected by both acute and chronic vitamin A supplementation. Vitamin A induced a decrease in both locomotory and exploratory behavior. Together, these results show that vitamin A could be toxic at the sub cellular level, inducing mitochondrial dysfunction and altering cerebral cortex and/or cerebellum-dependent behavior.