Autism study shows vitamin D and iron deficiencies affect up to 40% of children

New research highlights that nutrient deficiencies are widespread among children with autism in Singapore, with risks tied to age and ethnicity rather than picky eating, underscoring the need for routine screening and early intervention.

Study: Occurrence and Correlates of Vitamin D and Iron Deficiency in Children with Autism Spectrum Disorder. Image Credit: myboys.me / Shutterstock

In a recent study in the journal Nutrients, researchers conducted a retrospective study of 241 children with autism spectrum disorder (ASD) in Singapore to identify nutrient deficiencies in this cohort. ASD children are known to be exceptionally picky eaters (selective eating habits), but the nutritional impacts of these eating habits remain unverified, particularly in the Asian and multi-ethnic context.

Study findings revealed significant vitamin D (36.5% of the 222 participants tested) and iron (37.7% of the 236 participants tested) deficiencies, with iron deficiency anemia present in 15.6% of the 122 children with complete blood count data.

Older age and non-Chinese ethnicity were significant risk factors for vitamin D insufficiency/deficiency, while no significant correlates were identified for iron deficiency overall. However, older children had higher odds of iron deficiency anemia. Surprisingly, picky eating was not a reliable indicator for either deficiency. 

These findings underscore and support the inclusion of frequent nutritional screening as a part of an ASD child’s routine healthcare, though the results should be interpreted with caution due to sampling bias (only 23.8% of eligible children underwent testing).

Background

Autism spectrum disorder (ASD) is a neurobiological developmental condition characterized by patients’ difficulties in routine social communication and their demonstrations of restricted, repetitive behaviors. Children with ASD also frequently display significant dietary problems, such as strong sensory preferences and rigid food choices.

Termed “picky eating”, these traits are more than just behavioral quirks, with growing clinical concern about their nutrient outcomes. This concern is particularly directed towards vitamin D (essential for bone health and immune function) and iron (vital for cognitive development), two of the most critical nutrients for a developing child.

While previous studies have suggested a high prevalence of these deficiencies in children with ASD, their sample groups were overwhelmingly White (European or American ethnicity), with minimal information from other racial/ethnic groups.

About the study

The present study aims to address these knowledge gaps and inform ASD child healthcare by evaluating the occurrence of vitamin D and iron deficiencies in Singapore, a tropical, multi-ethnic country. The study further seeks to identify clinical or demographic factors that could help clinicians predict high-risk subgroups.

The study followed an observation, cross-sectional study design, leveraging retrospective medical records data from a tertiary developmental pediatric center in Singapore. The study included confirmed ASD patients between 1 and 10 years (n = 241 participants) between January 2018 and December 2022.

ASD diagnosis was confirmed using either the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria or the Autism Diagnostic Observation Schedule (ADOS-2). Data of interest included demographic details (age, sex, family education and income status, etc.), clinically documented feeding information (such as picky eating), and medical history (including the results of blood tests for vitamin D and iron).

Specifically, vitamin D status was determined by measuring serum 25-hydroxyvitamin D [25(OH)D] concentrations, while iron deficiency was defined using World Health Organization criteria for serum ferritin (<12 µg/L for children <5 years, <15 µg/L for children ≥5 years, or transferrin saturation <15%). Participants demonstrating <10 µg/L of the former or <12 µg/L of the latter were termed ‘deficient’ in the respective nutrient.

Statistical correlates were identified and evaluated using logistic regression analysis. Specifically, the study aimed to unravel patterns between demographics (age, gender, ethnicity), eating habits (picky eating), and observed deficiencies.

Study findings

The present study identified an alarmingly high occurrence of both vitamin D and iron deficiencies. Of the 222 children who had their vitamin D levels tested, 36.5% were either insufficient (32%) or deficient (4.5%). Iron status (deficiency) demonstrated similar overall prevalence, with 37.7% of the 236 children tested showing suboptimal iron stores. Furthermore, of the 122 children with complete blood count data available, 15.6% had progressed to iron deficiency anemia.

Risk factor analysis revealed that age and ethnicity were significant modifiers of vitamin D deficiency risk only. The odds of having low vitamin D were observed to increase by 4% for each additional month of age (Odds Ratio [OR] 1.04; 95% CI 1.03–1.06).

Similarly, compared to children of Chinese ethnicity, the odds of low vitamin D were significantly higher for children of Malay (OR 5.0), Indian (OR 20.9), and other ethnicities (OR 3.2). Iron deficiency did not show significant associations with demographics or eating habits, though older children were more likely to present with iron deficiency anemia.

While further case-control studies are required to elucidate the mechanisms behind these outcomes, the study authors hypothesize that differences in skin pigmentation likely affect the synthesis of vitamin D from sunlight.

Surprisingly, the study was unable to identify statistical associations between picky eating and either vitamin D or iron deficiency, suggesting that all ASD children, not just the majority picky eaters, require frequent nutritional screening for optimal development.

Conclusions

The present study reveals that vitamin D and iron deficiencies are alarmingly common in children with ASD in Singapore, affecting between 30% and 40% of those tested. While age and ethnicity were found to be associated with vitamin D deficiency and older age with iron deficiency anemia, picky eating was not a reliable clinical marker for these deficiencies. The findings challenge the clinical assumption that fussy eating is a reliable red flag for these specific deficiencies.

The study authors strongly recommend that clinicians consider routine nutrition (vitamin D and iron) screening in children with ASD, regardless of reported eating habits. They caution, however, that results may not reflect true prevalence due to sampling bias and the absence of a non-ASD control group.

Early detection and supplementation are simple, effective interventions that profoundly impact overall health and development.