Vitamin D and Autism Spectrum Disorder: A Literature Review

Vitamin D deficiency in mothers, neonates and children

Vitamin D is produced in response to the exposure of skin to sunlight through UV-B synthesis. It can also be obtained from diet and dietary supplements. Vitamin D is essential for strong bones as it helps to absorb calcium from diet. Vitamin D deficiency mainly occurs if strict vegetarian diet is followed as mostly the source of vitamin D is animal based; therefore, exposure to sunlight is restricted or having dark skin color. Low vitamin D levels results in increased possibility of gestational diabetes among pregnant women, low birth weight and pre-eclampsia in infants, and mothers may suffer bone impairment, osteoporosis, hypocalcaemia, and hypertension. Vitamin D deficiency is directly linked with severe complication in mothers and neonates, causing rickets, poor fetal growth and infantile eczema in neonates. Higher prevalence rate of vitamin D deficiency has led professionals to emphasize on development of relevant precautionary measures.

Maternal early pregnancy vitamin D status in relation to low birth weight and small-for-gestational-age offspring

Maternal vitamin D deficiency is an independent risk factor for fetal growth. We examined the associations between maternal vitamin D status (defined by 25-hydroxyvitamin D [25(OH)D]) at the first prenatal visit and measures of newborn and placental weight, in a large China cohort of singleton, term, live births. From July 2015 to June 2016, women delivering singleton, term, live births with 25(OH)D measured at a first prenatal visit (N=747). Birth weight, placental weight, the placental to fetal weight ratio, and small for gestational age (SGA) were measured. The relationship between levels of 25(OH)D and SGA were evaluated using univariate and multivariate regression analysis. Vitamin D deficiency was defined as 25(OH)D less than 20ng/ml. In those women, 76.9% (95%CI: 74%-78%) were defined as vitamin D deficiency. Incidence of SGA was also high (13.3%; 95%CI: 10.8%-15.7%). We found a nonlinear relation between 25(OH)D and birth weight as well as head circumference (P<0.01). Birth weight and head circumference increased by 69 [95%CI: 38-122] g and 0.31 (0.22-0.40) cm, respectively, per 1ng/ml increase in maternal 25(OH)D up to 20ng/ml and then leveled off thereafter. The SGA distribution across the 25(OH)D quartiles ranged between 3.7% (fourth quartile) to 24.1% (first quartile). For each 1 unit decrease of plasma concentration of 25(OH)D, the unadjusted and adjusted risk of SGA increased by 19% (odds ratio 1.19 [95% CI 1.13-1.25], P<0.001) and 9% (1.08 [1.03-1.16], P=0.009), respectively. In a multivariate model using the vitamin D deficiency vs. other together with the clinical variables, the adjusted risk of SGA increased by 205% (odds ratio 3.05 [95% CI 2.24-4.40], P=0.001). Maternal vitamin D insufficiency is common during pregnancy and is independently associated with low birth weight and high risk of SGA in term infants.

Vitamin D status in chronic fatigue syndrome/myalgic encephalomyelitis: a cohort study from the North-West of England

OBJECTIVE

Severe vitamin D deficiency is a recognised cause of skeletal muscle fatigue and myopathy. The aim of this study was to examine whether chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is associated with altered circulating vitamin D metabolites.

DESIGN

Cohort study.

SETTING

UK university hospital, recruiting from April 2014 to April 2015.

PARTICIPANTS

Ninety-two patients with CFS/ME and 94 age-matched healthy controls (HCs).

MAIN OUTCOME MEASURES

The presence of a significant association between CFS/ME, fatigue and vitamin D measures.

RESULTS

No evidence of a deficiency in serum total 25(OH) vitamin D (25(OH)D₂ and 25(OH)D₃ metabolites) was evident in individuals with CFS/ME. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis revealed that total 25(OH)D was significantly higher (p=0.001) in serum of patients with CFS/ME compared with HCs (60.2 and 47.3 nmol/L, respectively). Analysis of food/supplement diaries with WinDiets revealed that the higher total 25(OH) vitamin D concentrations observed in the CFS/ME group were associated with increased vitamin D intake through use of supplements compared with the control group. Analysis of Chalder Fatigue Questionnaire data revealed no association between perceived fatigue and vitamin D levels.

CONCLUSIONS

Low serum concentrations of total 25(OH)D do not appear to be a contributing factor to the level of fatigue of CFS/ME.

Vitamin D deficiency: infertility and neurodevelopmental diseases (attention deficit hyperactivity disorder, autism, and schizophrenia)

The process of development depends on a number of signaling systems that regulates the progressive sequence of developmental events. Infertility and neurodevelopmental diseases, such as attention deficit hyperactivity disorder, autism spectrum disorders, and schizophrenia, are caused by specific alterations in these signaling processes. Calcium signaling plays a prominent role throughout development beginning at fertilization and continuing through early development, implantation, and organ differentiation such as heart and brain development. Vitamin D plays a major role in regulating these signaling processes that control development. There is an increase in infertility and an onset of neurodevelopmental diseases when vitamin D is deficient. The way in which vitamin D deficiency acts to alter development is a major feature of this review. One of the primary functions of vitamin D is to maintain the phenotypic stability of both the Ca²⁺ and redox signaling pathways that play such a key role throughout development.

A review of prevalence studies of Autism Spectrum Disorder by latitude and solar irradiance impact

Autism Spectrum Disorder (ASD) is a lifelong disability with no known cause or cure. Among the suggested etiologies, is Cannell's hypothesis of a deficiency in Vitamin D the main natural source of which is Solar Ultraviolet-B (UVB) radiation. The aim in this paper is to build on this hypothesis and explore the relationship of solar irradiance of which UVB is a component, by latitude with the prevalence rates of ASD. Twenty-five reports published between 2011 and 2016 using comparable diagnostic criteria were reviewed. The results suggest a tendency for the prevalence rates of ASD to be lowest in countries near the equator and for this rate to increase as the latitude increases. These findings provide some support not just for the Vitamin D hypothesis, but also for a new proposition that along with UVB radiation, the entire solar radiation spectrum which reaches the earth, may play a role in ASD. While these results are both novel and encouraging in terms of the potential efficacy of exposure to natural sunlight, further research is warranted before results can be considered definitive, and before the implications of the findings can be implemented clinically.

Vitamin D and mental health in children and adolescents

While vitamin D is known to be relevant for bone health, evidence has recently accumulated for an impact on mental health. To identify the potential benefits and limitations of vitamin D for mental health, an understanding of the physiology of vitamin D, the cut-off values for vitamin D deficiency and the current status of therapeutic trials is paramount. Results of a systematic PUBMED search highlight the association of vitamin D levels and mental health conditions. Here, we focus on children and adolescents studies as well as randomized controlled trials on depression in adults. 41 child and adolescent studies were identified including only 1 randomized controlled and 7 non-controlled supplementation trials. Overall, results from 25 cross-sectional studies as well as from 8 longitudinal studies suggest a role of vitamin D in the pathogenesis of mental disorders in childhood and adolescence. Findings from supplementation trials seem to support this hypothesis. However, randomized controlled trials in adults revealed conflicting results. Randomized controlled trials in childhood and adolescents are urgently needed to support the potential of vitamin D as a complementary therapeutic option in mental disorders. Study designs should consider methodological challenges, e.g., hypovitaminosis D at baseline, appropriate supplementation doses, sufficient intervention periods, an adequate power, clinically validated diagnostic instruments, and homogenous, well-defined risk groups.

Vitamin D-related genes are subjected to significant de novo mutation burdens in autism spectrum disorder

Vitamin D deficiency is a putative environmental risk factor for autism spectrum disorder (ASD). Besides, de novo mutations (DNMs) play essential roles in ASD. However, it remains unclear whether vitamin D-related genes (VDRGs) carry a strong DNM burden. For the 943 reported VDRGs, we analyzed publicly-available DNMs from 4,327 ASD probands and 3,191 controls. We identified 126 and 44 loss-of-function or deleterious missense mutations in the probands and the controls, respectively, representing a significantly higher DNM burden (p = 1.06 × 10^-5 ; odds ratio = 2.11). Specifically, 18 of the VDRGs were found to harbor recurrent functional DNMs in the probands, compared with only one in the controls. In addition, we found that 108 VDRGs with functional DNMs in the probands were significantly more likely to exhibit haploinsufficiency and genic intolerance (p < 0.0078). These VDRGs were also significantly interconnected and co-expressed, and also with other known ASD-risk genes (p < 0.0014), thereby forming a functional network enriched in chromatin modification, transcriptional regulation, and neuronal function. We provide straightforward genetic evidences for the first time that VDRGs with a strong degree of DNM burden in ASD and DNMs of VDRGs could be involved in the mechanism underlying in ASD pathogenesis.

Vitamin D and autism, what's new?

An increasing amount of evidence points to the possibility that gestational and early childhood vitamin D deficiency [25(OH)D < 40 ng/ml] cause some cases of autism. Vitamin D is metabolized into a seco-steroid hormone that regulates about 3% of the 26,000 genes in the coding human genome. It is also a neurosteroid that is active in brain development, having effects on cellular proliferation, differentiation, calcium signaling, neurotrophic and neuroprotective actions; it also appears to have an effect on neurotransmission and synaptic plasticity. Children who are, or who are destined to become, autistic have lower 25(OH)D levels at 3 months of gestation, at birth and at age 8 compared to their unaffected siblings. Two open label trials found high dose vitamin D improves the core symptoms of autism in about 75% of autistic children. A few of the improvements were remarkable. The vitamin D doses used in these children were 300 IU/KG/day up to a maximum of 5000 IU/day (highest final 25(OH)D level reached was 45 ng/ml). The other study used 150,000 IU/month IM as well as 400 IU/day [highest final 25(OH)D level was 52 ng/ml]. These two open label trials were recently confirmed with a randomized controlled trial (RCT) using 300 IU/kg/day with a maximum of 5000 IU/day and resulted in effects similar to the two open label studies. In terms of prevention, a recent small study showed vitamin D supplementation during pregnancy (5000 IU/day) and during infancy and early childhood (1000 IU/day) significantly reduced the expected incidence of autism in mothers who already had one autistic child from 20% to 5%. Vitamin D is safe; for example, over the last 15 years, Poison Control reports there have been approximately 15,000 cases of vitamin D overdose. However only three of these 15,000 people developed clinical toxicity and no one died. Given those facts, practitioners might consider treating autism with 300 IU/kg/day, and seek to prevent autism by supplementing pregnant and lactating women (5000 IU/day) and infants and young children (150 IU/kg/day) checking 25(OH)D levels every 3 months. These doses will increase 25(OH)D blood levels to those recommended by the Endocrine Society. As the American Academy of Pediatrics recommends vitamin D supplementation during infancy and childhood, pediatricians and family practitioners should evaluate the current evidence on autism and vitamin D and act accordingly.

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.

Vitamin D deficiency and diabetes

Vitamin D deficiency has been linked to the onset of diabetes. This review summarizes the role of Vitamin D in maintaining the normal release of insulin by the pancreatic beta cells (β-cells). Diabetes is initiated by the onset of insulin resistance. The β-cells can overcome this resistance by releasing more insulin, thus preventing hyperglycaemia. However, as this hyperactivity increases, the β-cells experience excessive Ca2+ and reactive oxygen species (ROS) signalling that results in cell death and the onset of diabetes. Vitamin D deficiency contributes to both the initial insulin resistance and the subsequent onset of diabetes caused by β-cell death. Vitamin D acts to reduce inflammation, which is a major process in inducing insulin resistance. Vitamin D maintains the normal resting levels of both Ca2+ and ROS that are elevated in the β-cells during diabetes. Vitamin D also has a very significant role in maintaining the epigenome. Epigenetic alterations are a feature of diabetes by which many diabetes-related genes are inactivated by hypermethylation. Vitamin D acts to prevent such hypermethylation by increasing the expression of the DNA demethylases that prevent hypermethylation of multiple gene promoter regions of many diabetes-related genes. What is remarkable is just how many cellular processes are maintained by Vitamin D. When Vitamin D is deficient, many of these processes begin to decline and this sets the stage for the onset of diseases such as diabetes.

Autism genes are selectively targeted by environmental pollutants including pesticides, heavy metals, bisphenol A, phthalates and many others in food, cosmetics or household products

The increasing incidence of autism suggests a major environmental influence. Epidemiology has implicated many candidates and genetics many susceptibility genes. Gene/environment interactions in autism were analysed using 206 autism susceptibility genes (ASG's) from the Autworks database to interrogate ∼1 million chemical/gene interactions in the comparative toxicogenomics database. Any bias towards ASG's was statistically determined for each chemical. Many suspect compounds identified in epidemiology, including tetrachlorodibenzodioxin, pesticides, particulate matter, benzo(a)pyrene, heavy metals, valproate, acetaminophen, SSRI's, cocaine, bisphenol A, phthalates, polyhalogenated biphenyls, flame retardants, diesel constituents, terbutaline and oxytocin, inter alia showed a significant degree of bias towards ASG's, as did relevant endogenous agents (retinoids, sex steroids, thyroxine, melatonin, folate, dopamine, serotonin). Numerous other suspected endocrine disruptors (over 100) selectively targeted ASG's including paraquat, atrazine and other pesticides not yet studied in autism and many compounds used in food, cosmetics or household products, including tretinoin, soy phytoestrogens, aspartame, titanium dioxide and sodium fluoride. Autism polymorphisms influence the sensitivity to some of these chemicals and these same genes play an important role in barrier function and control of respiratory cilia sweeping particulate matter from the airways. Pesticides, heavy metals and pollutants also disrupt barrier and/or ciliary function, which is regulated by sex steroids and by bitter/sweet taste receptors. Further epidemiological studies and neurodevelopmental and behavioural research is warranted to determine the relevance of large number of suspect candidates whose addition to the environment, household, food and cosmetics might be fuelling the autism epidemic in a gene-dependent manner.

Lower maternal serum 25(OH) D in first trimester associated with higher autism risk in Chinese offspring

OBJECTIVE

The aim of this study was to examine the association between maternal serum vitamin D status in first trimester and risk of ASD at age 3-7years in the offspring.

METHODS

Using a case-control design, 68 children diagnosed with ASD and 68 sex and age matched typically-developing children were included. Archived maternal blood samples from the first trimester of pregnancy (11-13weeks gestational age) were identified for those participants. Maternal serum levels of 25 hydroxyvitamin D3 [25(OH) D], unmetabolized folic acid (FA), vitamin B12, homocysteine (HCY) and High Sensitivity C Reactive protein (CRP) were measured from those samples. We examined the associations between those factors in pregnancy and diagnosis of ASD with logistic regression using SPSS.

RESULTS

Mothers in autistic group had significantly lower maternal serum levels of 25(OH) D than in typically-developing group [19.2(IQR: 15.8-22.9)ng/ml vs. 24.3(19.3-27.3)ng/ml, P<0.001], with 55.9% and 29.4% being vitamin D deficient, respectively (P<0.001). Levels of 25(OH) D increased with decreasing severity of ASD as defined by the CARS score (r=-0.302, P<0.001). Maternal first trimester serum levels of 25(OH) D in the lower 3 quartiles (quartile 1, 2, 3) (compared to the highest quartile) was associated with increased odds of ASD diagnosis in offspring [OR (95% CI) Q1: 1.36(0.84-2.58, P=0.25); Q2: 2.68(1.44-4.29, P=0.006); Q3:3.99(2.58-7.12, P<0.001)].

CONCLUSIONS

Lower first trimester maternal serum levels of 25(OH) D were associated with increased risk of developing autism in offspring. If these findings are confirmed, this may present an opportunity for prenatal intervention to reduce the risk for ASD.

Vitamin D and omega-3 fatty acid supplements in children with autism spectrum disorder: a study protocol for a factorial randomised, double-blind, placebo-controlled trial

Background

There is strong mechanistic evidence to suggest that vitamin D and omega-3 long chain polyunsaturated fatty acids (n-3 LCPUFAs), specifically docosahexaenoic acid (DHA), have the potential to significantly improve the symptoms of autism spectrum disorder (ASD). However, there are no trials that have measured the effect of both vitamin D and n-3 LCPUFA supplementation on autism severity symptoms. The objective of this 2 × 2 factorial trial is to investigate the effect of vitamin D, n-3 LCPUFAs or a combination of both on core symptoms of ASD.

Methods/design

Children with ASD living in New Zealand (n = 168 children) will be randomised to one of four treatments daily: vitamin D (2000 IU), n-3 LCPUFAs (722 mg DHA), vitamin D (2000 IU) + n-3 LCPUFAs (722 mg DHA) or placebo for 12 months. All researchers, participants and their caregivers will be blinded until the data analysis is completed, and randomisation of the active/placebo capsules and allocation will be fully concealed from all mentioned parties. The primary outcome measures are the change in social-communicative functioning, sensory processing issues and problem behaviours between baseline and 12 months. A secondary outcome measure is the effect on gastrointestinal symptoms. Baseline data will be used to assess and correct basic nutritional deficiencies prior to treatment allocation. For safety measures, serum 25-hydroxyvitamin D 25(OH)D and calcium will be monitored at baseline, 6 and 12 months, and weekly compliance and gastrointestinal symptom diaries will be completed by caregivers throughout the study period.

Discussion

To our knowledge there are no randomised controlled trials assessing the effects of both vitamin D and DHA supplementation on core symptoms of ASD. If it is shown that either vitamin D, DHA or both are effective, the trial would reveal a non-invasive approach to managing ASD symptoms.

Trial registration

Australian New Zealand Clinical Trial Registry, ACTRN12615000144516. Registered on 16 February 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1428-8) contains supplementary material, which is available to authorized users.

Vitamin D Deficiency in Adult Patients with Schizophreniform and Autism Spectrum Syndromes: A One-Year Cohort Study at a German Tertiary Care Hospital

INTRODUCTION

Vitamin D has many immunomodulatory, anti-inflammatory, and neuroprotective functions, and previous studies have demonstrated an association between vitamin D deficiency and neuropsychiatric disease. The aim of our study was to analyze the prevalence of vitamin D deficiency in a 1-year cohort of adult inpatients with schizophreniform and autism spectrum syndromes in a naturalistic inpatient setting in Germany.

PARTICIPANTS AND METHODS

Our study was comprised of 60 adult schizophreniform and 23 adult high-functioning autism spectrum patients who were hospitalized between January and December of 2015. We compared our findings with a historical German reference cohort of 3,917 adults using Pearson's two-sided chi-squared test. The laboratory measurements of 25-hydroxyvitamin D2/3 [25(OH)vitamin D] were obtained using a chemiluminescence immunoassay.

RESULTS

In the schizophreniform group, we found decreased (<20 ng/ml) 25(OH)vitamin D levels in 48/60 (80.0%) of the patients. In the autism spectrum group, decreased levels were detected in 18/23 (78.3%) of the patients. 25(OH)vitamin D deficiencies were found in 57.3% of the historical control group. Particularly, severe deficiencies (<10 ng/ml) occurred much more frequently in the schizophreniform (38.3%) and autism spectrum groups (52.2%), when compared to the control group (16.3%). The recommended 25(OH)vitamin D values of >30 ng/ml were observed in only 5% of the schizophreniform patients, 8.7% of the autism spectrum patients, and 21.9% of the healthy controls.

DISCUSSION

We found very high rates of 25(OH)vitamin D deficiencies in both patient groups and have discussed whether our findings might be related to alterations in the immunological mechanisms. Irrespective of the possible pathophysiological links between vitamin D deficiency and schizophrenia or autism spectrum disorders, a more frequent measurement of vitamin D levels seems to be justified in these patient groups. Further prospective, controlled, blinded, and randomized research should be conducted to analyze the effectiveness of vitamin D supplementation on the improvement of psychiatric symptoms.