The study, funded by the National Natural Science Foundation of China, aimed primarily to assess links between maternal dietary patterns and ASDs, and secondarily to explore the relationship between maternal supplement intake and ASDs.
Diet and disorders
The researchers — from Central South University, Shandong Mental Health Centre, Beijing Huilongguan Hospital, and The State Key Laboratory of Medical Genetics — used a case-control design to enrol 354 children without ASDs (also called ‘typically developing’ or TD children) and 374 children of similar age with ASDs in the study, using data from the Autism Clinical and Environmental Database (ACED).
The children were aged three to six years old; those with ASDs had been diagnosed with autistic disorder, Asperger disorder, or pervasive developmental disorder not otherwise specified (PDD-NOS) at a local hospital. The diagnoses also had to be confirmed by a senior child psychiatrist, based on the Diagnostic and Statistical Manual of Mental Disorders.
Interestingly, 168 of the TD children were boys, while 324 of the ASD children were also boys.
The researchers then reported that unbalanced maternal dietary patterns prior to conception led to a “significant increased risk” of ASDs in offspring.
They further said that insufficient vegetable intake could result in deficiencies in micronutrients (including vitamins and minerals), while insufficient meat consumption could lead to dietary protein insufficiency.
In both cases, the risk of metabolic conditions related to nutrient deficiency would increase the risk of metabolic conditions associated with nutrient deficiency.
Besides affecting the baby’s health, unbalanced pre-natal dietary patterns may eventually lead to long-term metabolic conditions in mothers, such as obesity, diabetes and metabolic syndrome.
The researchers wrote: “These conditions have also been identified as environmental risk factors for ASD as well as other neurodevelopmental disorders”.
Supplementation and support
Additionally, maternal supplementation with calcium while preparing for pregnancy was linked to lowered ASD risk.
During pregnancy, calcium can be transferred from mother to foetus via the placenta, drawing a possible association between maternal and foetal calcium levels.
Women are encouraged to maintain optimal calcium levels as calcium plays an important part in neurodevelopment and “may provide preventive and therapeutic strategies for ASDs”.
The researchers added that calcium is crucial in regulating synaptic development and function, meaning it may support proper brain development. Furthermore, abnormal synaptic development has been associated with ASDs.
Children with ASDs tend to have markedly lower serum calcium levels and tend to consume less calcium than TD children, “suggesting calcium may be involved in the pathological process”.
The study also referenced earlier RCTs, which had reported that maternal calcium supplementation was linked to reduced blood lead levels and “may constitute an important secondary prevention effort to reduce circulating maternal lead through suppressing mobilisation of lead and, consequently, decrease foetal lead exposure”.
The relationship between ASDs and lead exposure led to the hypothesis that calcium supplementation could help to prevent ASDs by restricting lead exposure.
Rigour in research
The researchers acknowledged the study’s limitations, saying that since the children with ASD had been enrolled using a special hospital- and school-based design rather than from an epidemiological sampling method, the study sample “may not adequately represent the whole population”.
At the same time, they said the questions and items used to gather data on maternal dietary patterns were ‘ambiguous’, as they had focused on dietary patterns instead of the amount of nutrient intake. As such, it was unclear whether or not the mothers had consumed enough protein (meat) or micronutrients (vegetables).
Supplement dosage among the mothers was also unknown, despite a dose-response relationship being necessary in determining causal association.
The retrospective reporting of maternal diets may also have affected the accuracy of the information, with recall bias a possible factor in dietary patterns, supplement categories, and timing of exposure.
In addition, the maternal dietary patterns observed in China likely differ from those in other countries, limiting the generalisability of the results.
These observations led the researchers to state: “Future prospective investigations with a more rigorous study design are warranted to further study underlying links and to improve our understanding of the mechanisms. Replication studies in other countries are also encouraged.”
In conclusion, they wrote: “Our results provided preliminary evidence that maternal unbalanced dietary patterns before conception would increase risk of ASDs, (and) maternal supplementation of calcium during pregnancy preparation could reduce (the) risk of ASDs.
“However, those findings were preliminary and may not be conclusive. Future prospective studies with larger sample sizes and more detailed timing information should consider maternal nutritional status in association with ASDs in offspring.”
“Maternal dietary patterns, supplements intake and autism spectrum disorders: A preliminary case-control study”
Authors: Ya-Min Li, et al.