Introduction
The Present Study
Method
Inclusion and Exclusion Criteria
Search Strategy
Selection of the Studies
Analysis of Bias Risk
Tabulation and Data Analysis
Data Synthesis
Author/country | Objective | Sample Size/%sex ASD | Age (Years) | Duration | Outcome measures | Significant outcomes |
---|---|---|---|---|---|---|
(Uğur & Gürkan, 2014) Turkey | -Investigate serum levels of vitamin D, calcium (Ca), phosphorus (P), alkaline phosphatase (ALP) and folate in 54 young children, ages 3 to 8, with autism spectrum disorders (ASD) and in 54 normal control children paired in age and sex | 54 ASD 87% male 54 CG | 3–8 | 7 months | -Vitamin D levels -Folate levels | -They did not establish significant differences between vitamin D and folate levels between ASD and CG group: vitamin D: ASD: 25.12 ± 11.28; CG: 21.11 ± 9.65 Folate: ASD: 12.46 ± 5.84; CG: 12.68 ± 4.37 |
(Gong et al., 2014) China | -Evaluate vitamin D levels in sample of Chinese children with ASD | 48 ASD 40% male 48 CG | 3–8 | 12 months | -Vitamin D levels | -Vitamin D levels obtained were lower in the ASD group than in healthy controls: 19.9 ± 3.8 vs 22.6 ± 4.5 |
(Bener et al., 2014) Qatar | -Determine the association between vitamin D and autism -Determine difference in vitamin D levels between controls and autistic children | 254 ASD 65% male 254 CG | 3–8 | 2 years | -Vitamin D levels | -Lower vitamin D levels in ASD group than in CG. 18.39 ± 8.2 vs 21.59 ± 8.4 |
(Fernell et al., 2015) Sweden | -Address the emerging hypothesis that low levels of vitamin D increase the risk of ASD | 29 ASD 89% male 29 CG | 14–32 months | 6 months | -Vitamin D levels | -Vitamin D deficiency more accentuated in ASD group than in CG. 24(19.6) vs 31.9(27.7) |
(Farid et al., 2016) Egypt | -Determine dietary intake of vitamin D and sun exposure and its impact on vitamin D level | 49 ASD 81% male 40 CG | 3–15 years | 6 months | -Vitamin D levels | -Lower vitamin D levels in ASD group than in CG. 46.5(14–120) vs 70.89 (16–149) |
(Parletta et al., 2016) Australia | -Compare PUFA levels in erythrocytes in children with ADHD, ASD, and typical developing controls, and investigate correlations between PUFA levels and respective symptoms | 85ASD 80% male 79 CG 401TDAH | 3–17 years | March 2004 December 2010 | -Blood levels of fatty acids: DHA, AA, EPA + DHA | -Lower levels of EPA, DHA, and AA in ASD and ADHD versus CG. DHA: ASD: 0.557 ± 0.524; CG: 1.798 ± 0.5894 AA: ASD: 0.557 ± 0.524: 0.851 ± 0.564; CG: 4.715 ± 1.020. EPA + DHA: ASD; CG: 10,522 ± 2056 |
(Bala et al., 2016) Turkey | -Analyze thyroid hormones and antibodies, ferritin, vitamins B12 and D, adrenal and gonadal steroid levels, and celiac antibodies in children diagnosed with ADHD and ASD | 16 ASD 62.5% male 27 CG 34 TDAH | 2–17 years | February 2014 July 2014 | -Vitamin D levels -Folate levels | -Vitamin D levels lower in ASD than in CG. ASD; CG: 28.73 ± 9.04 -Slightly lower folate levels in CG; CG: 8.52 ± 3.75; ASD |
(Liu et al., 2016) China | -Determine whether growth, eating behaviors, and gastrointestinal symptoms of children with ASD differ from those of controls; whether biochemical nutrition index levels are lower in children with ASD compared to Chinese standards; and possible relationship between nutritional status (vitamin A (VA), VD, vitamin B12 (VB12), ferritin (FER), hemoglobin (Hb), and folate (FOL) and ASD symptoms | 154 ASD 91.6% male 73 CG | 3–7 years | August 2013 October 2014 | -Vitamin D levels -Folate levels | -Vitamin D values in ASD group: 22.55 ± 7.43 -Folate levels in ASD: 9.07 ± 3.84 -They did not establish significant results between levels and ASD symptoms |
(Bener et al., 2017) Germany | -Investigate iron deficiency anemia and vitamin D deficiency in children with autism and assess the importance of risk factors (determinants) | 308 ASD 43.7% male 308 CG | 8 years | June2011 May2014 | -Vitamin D levels | -Vitamin D values in ASD lower than in CG. ASD: 18.79 ± 8.35; CG: 22.18 ± 9.00 |
(Garipardic et al., 2017) Turkey | -Evaluate mean platelet volume (MPV) values in children with ADHD and ASD to determine the risk of cardiovascular disease in these 2 groups of disorders | 18 ASD 61.1% male 25 CG 36 ADHD | 2–18 years | February 2014 July 2014 | -Vitamin D levels -Folate levels | -Vitamin D levels in ASD were lower than in CG. ASD: 14.3 ± 7.25, CG: 29.42 ± 9.07 -Folate values in ASD: 9.09 ± 3.91; CG: 8.43 ± 3.85. No significant relationships were established in this hematological parameter |
(Altun et al., 2018) Turkey | -Examine serum levels of vitamin D, vitamin D receptor (VDR), homocysteine, vitamin B6, vitamin B12, and folate in ASD | 60ASD 86.6% male 45CG | 3–12 years | March September Year N/A | -Vitamin D levels -Folate levels | -Lower vitamin D values in ASD than in CG. ASD: 13.79 ± 1.03; CG: 16.58 ± 1.06 -Folate values lower in ASD than in CG. ASD: 121.16 ± 8.04; CG: 172.31 ± 17.19 |
(Wu et al., 2018) China | -Estimate the prevalence of ASD in Chinese children 3 years of age and examine the association between neonatal vitamin D status and the risk of ASD | 310 ASD 77.4% male 1240 CG | 3 years | 2008–2010 | -Vitamin D levels | -Vitamin D levels in ASD group significantly lower than in CG. ASD: 17.6 Z: 11.997; CG: 40.2 Z: 12.986 |
(El-Ansary et al., 2018) Saudi Arabia | -Determine possible relationship between vitamin D levels, proven biomarkers, and the presence and severity of ASD | 28 ASD 100% male 27 CG | 7 years | N/A | -Vitamin D levels | -Vitamin D levels in ASD were lower than in CG. ASD: 95.63 ± 26.63; CG: 140.43 ± 17.68 |
(Arastoo et al., 2018) Iran | -Assess the serum level of vitamin D among children with ASD in the city of Ahvaz, Iran | 62 ASD 84% male 31 CG | 9 years | 1 year | -Vitamin D levels | -Establish significant differences between ASD and CG levels. ASD: 9.04 ± 4.14, CG: 15.25 ± 7.89 |
(Bičíková et al., 2019) Czech Republic | -Determine calcidiol levels in a group of autistic children and compared with healthy children of the same age as controls | 45ASD 100% male 40 CG | 4–7 years | N/A | -Vitamin D levels | -No significant differences were found between ASD and control groups. ASD: 65.22 ± 25.950; CG: 64.46 ± 20.7 |
(Guo et al., 2019) China | -Investigate vitamin A (VA) and vitamin D (VD) levels in children with autism spectrum disorders (ASD) -Determine whether VA and VD co-deficiency exacerbates clinical symptoms | 332 ASD 48.5% male 197 CG | 3–6 years | N/A | -Vitamin D levels | -Vitamin D levels were lower in the ASD group than in CG -Differences in vitamin A and vitamin D accentuated the symptoms of ASD |
(Şengenç et al., 2020) Turkey | -Investigate the relationship between autism spectrum disorder (ASD) and vitamin D levels in children and adolescents | 100 ASD 100 CG 1529 ASD 80% male | 3–18 years | N/A | -Vitamin D levels | -Lower vitamin D levels in ASD group than in CG. ASD100: 42 ± 19.8; ASD1529: 44.60 ± 18.62; CG: 48.57 ± 22.36 |
(Petruzzelli et al., 2020) Italy | -Evaluate the serum concentration of 25-hydroxyvitamin D (25 (OH) D) in children with ASD (ASD group, n = 54) compared to children affected by other neurological and psychiatric disorders (group without ASD, n = 36) | 54 ASD 81.5% male 36 CG | < 18 years | 2014–2018 | -Vitamin D levels | -The ASD group showed significant levels lower than the CG. ASD: 18.61 ± 8.33; CG: 24.62 ± 13.18 |
(Alzghoul et al., 2020) China | -Assess the correlation between vitamin D deficiency and autism spectrum disorder in Jordan | 83 ASD 100% male 106 CG | < 8 years | N/A | -Vitamin D levels | -A relationship is established between low vitamin D levels and the onset of ASD. The ASD group had more gastro-intestinal complaints. ASD: 23.4; CG: 37.5 |
(Zhu et al., 2020) China | -Compare the nutritional status and symptoms of preschoolers with autism spectrum disorder from two regions of China -Analyze the association between nutritional status and symptoms of ASD | 738 ASD 85.15% male 302 CG | 2–6 years | N/A | -Vitamin D levels | -The ASD group presents a higher risk of nutrient deficiencies than the CG group; low levels of vitamin D and folate were associated with worsening ASD symptoms and the development of ASD |