A fetus must have all the nutrition during pregnancy. During pregnancy, certain substances can increase a child’s chance of having autism if it is too little – or too much – of those substances.
However, many of these studies are observational, and they are not designed to establish a causal link. A possible association between prenatal nutrition and supplements for autism recovery may be explained by unrelated lifestyle factors, such as frequent hand-washing and eating a healthy diet.
How does vitamin D affect autism?
One of the most comprehensively studied nutrients in autism is vitamin D. There is only modest evidence, and clinical trials undergoing deprivation of vitamin D to developing fetuses would be unethical.
An early 1930s study in London, England, found a link between halibut liver oil and decreased preeclampsia and preterm birth rates when given to pregnant women. Autism is associated with preeclampsia and preterm birth.
Research shows that having low vitamin D levels while pregnant increases the likelihood of having an autistic child. In the Netherlands, researchers found that pregnancies with low vitamin D levels resulted in more than twice as many autistic children as pregnancies without low vitamin D levels. This population has a relatively low incidence of autism – just 1.6 per cent – so doubling that rate would still represent only a small increase compared to the general population’s 1.4 per cent prevalence. Few low-vitamin D women had autistic children.
However, the use of vitamin D supplements later in pregnancy does not seem beneficial. There was no noteworthy difference in the neurodevelopmental outcome of children whose mothers take high doses of vitamin D during the third trimester than controls in a randomized clinical trial.
Because sunlight provides vitamin D to the body, some research has focused on the prevalence of autism in babies born in the winter, when sunlight is scarce. One study found that 1.3 per cent more children conceived during winter months had autism, intellectual disabilities, or learning difficulties in Scotland.
According to some experts, the increased risk of autism is related to the influenza season during the winter months. Pregnancy-related infections can trigger mothers’ immune response, which may increase the expression of autism-linked genes, among other things.
How about folate?
Several supplements for pregnant women and fortified foods, including cereals and pasta, contain synthetic folate, a B vitamin. The proliferation of cells is accelerated during pregnancy due to this factor. Spina bifida and anencephaly have long been associated with low folate consumption during pregnancy.
The benefits of prenatal folic acid supplementation appear to be associated with a reduced likelihood of autism, even when pregnant women take epilepsy medications.
There is also the possibility that too much folic acid can cause autism. The effects of excessive folic acid supplementation in one mouse study were similar to those of folic acid deficiency. Experimental mice consumed folic acid ten times more than control mice. Folic acid should not be avoided despite these results – only taken in recommended quantities.
Does iron supplementation cause autism?
A fetus’s growing brain needs oxygen carried by the blood, which this mineral carries. During pregnancy, pregnant women with anaemia are more likely to have children with autism, intellectual disability, and attention deficit hyperactivity disorder. By protecting against a class of immune molecules known as C-reactive proteins, iron may also counterbalance any negative effects from maternal immune activation.
Perhaps fatty acids are at play as well?
Fatty acids strengthen cell membranes and neuronal communication. Researchers aren’t certain whether fish oil supplements are helpful for children who are autistic, but some parents swear by them.
According to a recent mouse study, Omega-3 fatty acids, like Docosahexaenoic Acid (DHA), may mitigate the effects of maternal malnutrition and stress. These two factors affect gene expression and contribute to autism risk.
The effects of other fats may differ. One study found that a high-fat diet while pregnant can cause persistent, possibly harmful brain changes in pups. This study affected areas of the brain that have been associated with autism.