Babies who do not get enough zinc in the womb may become more likely to develop autism, according to a new study.
Scientists still do not have a definitive answer to the causes of autism, but the vast majority of research shows that it is a combination of "environmental factors" and genetic defects.
US and German scientists say in an article published today that they have evidence that zinc content may be one of the determining environmental factors that sews the seeds of behavioral disorder.
Further investigation is needed to confirm if there may be a causal link. The team states, however, that it has defined a possible mechanistic context.
US and German scientists say they have evidence that zinc levels may be one of the determining environmental factors that sew seeds of autism spectrum disorder
They found zinc forms, the connections or "synapses" between brain cells that form during early development, through a complex molecular machinery encoded by autism risk genes.
However, research is still at an early stage and the results do not mean that pregnant women should take zinc supplements to prevent autism.
The leading author Sally Kim of the Stanford University School of Medicine in California said: "Autism is associated with specific variants of genes involved in the development, maturation and stabilization of synapses during early development.
"Our findings link zinc levels in neurons through interactions with the proteins encoded by these genes with the development of autism."
Co-senior author Professor Craig Garner of the German Center for Neurodegenerative Diseases added: "There are currently no controlled studies on autism risk for zinc supplementation in pregnant women or babies, so the jury is still out.
"We can not really make any conclusions or recommendations for zinc supplementation at this point, but experimental work on autism models, also published in this Frontiers research topic, is promising.
"Nonetheless, our results provide a novel mechanism to understand how zinc deficiency – or malfunctioning of zinc in neurons – can contribute to autism."
Zinc helps in the production of new cells and enzymes, the processing of carbohydrates, fat and protein in food and wound healing.
Foods rich in minerals include meat, shellfish, dairy products such as cheese, bread and cereals.
According to the NHS, most people get enough zinc from their diet and should not take more than 25 mg of zinc supplements per day, unless advised by a doctor.
Too much reduces the amount of copper that the body can absorb, which can lead to anemia and weakening of the bones.
The study published in the journal Frontiers in Molecular Neuroscience found that a signal is transmitted via a synapse and zinc enters the target neuron, where it can bind two of these proteins – Shank2 and Shank3.
These proteins in turn cause changes in the composition and function ("maturation") of adjacent signal receptors, called AMPARs, on the surface of the neuron at the synapse.
Experiments demonstrated the mechanism of zinc-shank-mediated AMPAR maturation in the development of synapses.
Research author Dr. Stanford's Huong Ha stated, "In the developing rat neurons, we found that shank 2 and 3 accumulate at the same time as switching to mature AMPARs at synapses.
"The addition of extra zinc accelerated the switch – but not when the accumulation of shank 2 or 3 was reduced.
"In addition, our study mechanistically shows how Shank2 and 3 work with zinc to mature AMPAR, an important developmental step."
Co-senior author Professor John Huguenard, also from Stanford, in other words added that zinc affects the properties of synapse development via Shank proteins.
Prof. Huguenard concluded: "This suggests that zinc deficiency during early development may contribute to autism through impaired synaptic maturation and neuronal circuit formation.
"Understanding the interaction between zinc and shank proteins could therefore lead to diagnostic, treatment and prevention strategies for autism."
- Note to Readers: Talk to your doctor before changing your diet