The link between autism and zinc deficiency in the early stage of a child’s development

The link between autism and zinc deficiency in the early stage of a child’s developmentMore and more people get autism. The disease is linked to, among other things, lack of zinc in the childhood. Although it has still not been proved, whether zinc deficiencies during pregnancy can cause autism, scientists have discovered a link between zinc, genes, and the abnormal neurological connections that are associated with autism. The scientists therefore see a whole new potential for treating the condition, but one must also take into account other factors in the environment.

Autism occurs in different forms and is characterized by grave disturbances in a person’s social imagination, behavior, communication, and interaction with others. Over the course of the last three to four decades, the number of autistic people in the Western countries has increased ten-fold from around one in a thousand to one in a hundred. Experts are not entirely certain what the underlying cause of this increase is, as genes as well as environmental factors are at play. Although it is still uncertain how a zinc deficiency contributes to autism, the scientists seem to have found a possible connection.

Zinc is the mineral that is involved in most enzyme processes – even in the brain

It is already established that zinc is a cofactor of more than 1,000 enzyme processes, and the nutrient is bound to around 10 percent of our proteins. Zinc supports a host of different transport proteins in our cell membranes and is needed for more than 2,000 different transcription factors – which are proteins that make sure that the right genes are expressed at the right time in our cells. For that reason, zinc is highly important for a list of cellular processes that control our nervous system and a host of other functions.

The brain contains around 125 billion nerve cells (neurons) that are connected in an intricate network. One single neuron can be connected to 10,000 other neurons. The communication between adjacent neurons is carried out in a process that involves exchanging chemical signaling substances (neurotransmitters) between the surfaces of the nerve cells (synapse).

Zinc is important for our brain cells

The new research reveals how zinc forms synapses between the different neurons. This is also the case with neurons that may be disturbed during the early stages of a child’s development, and that increases the risk of autism. According to senior researcher, Dr. Sally Kim from Stanford University School of Medicine, the United States, autism is linked to specific gene variants that, during the early development stages, are involved in the formation, maturation, and stabilization of synapses. The zinc level in the neurons is therefore of importance for the risk of developing autism by means of gene-coding proteins.
Kim and her research colleagues noted that when a signal is transmitted via a synapsis, zinc enters the target neuron, where it binds to two proteins: Shank2 and Shank3. These zinc-containing proteins are responsible for the maturation of adjacent signaling receptors called AMPARs on the surface of the neurons.
In other words, zinc is important for the maturation and development of synapses via these two Shank proteins.
Therefore, a zinc deficiency during the early stage of the brain‘s development may contribute to the risk of autism through impaired maturation of neurons and synapses in the complicated circulatory system of the brain. Their study is published in the science journal Frontiers in Molecular Neuroscience. According to Professor John Huguennard, who co-authored the article, a better understanding of the interaction between zinc and the Shank proteins may lead to new strategies for preventing and treating autism.

The development of the brain

The brain develops in accordance with a genetic code. Up until the age of around one to one-and-a-half years, more and more neurons develop. Afterwards, the brain begins to repair and sort neurons and dismiss the neurons that are no longer needed. We humans have the highest number of neurons during the first years of life. From that point on, the brain needs to be stimulated so it can specialize and develop neural networks in order to function normally.

Are zinc supplements able to prevent autism?

Professor Craig Garner, one of the other authors, underlines that there are still no controlled studies to show if zinc supplements given to expecting mothers or babies can prevent autism. Nonetheless, the results of the new study suggest that being zinc deficient may increase the risk of autism. It is therefore important for pregnant and breastfeeding women to get enough zinc from their diets or from supplements. At the same time, it is important to avoid prolonged overconsumption of zinc, at this may lower the body’s uptake of copper, and that can lead to impaired immunity, anemia, and a weakening of the bones.

Good zinc sources and things that deplete your zinc levels

We get zinc from fish, shellfish, meat, dairy products, nuts, kernels, and beans. Zinc from animal sources is absorbed far more easily in the body than zinc from plant sources. According to the European Food Safety Authority (EFSA), the upper safe intake level for zinc (adults and pregnant women) is 25 mg daily.
The body’s uptake of zinc is impaired by e.g. sugar, birth control pills, inorganic iron supplements, and diuretics.

Choose inorganic zinc supplements, which the body can absorb and utilize

Many zinc preparations contain inorganic zinc sources such as zinc sulfate or zinc oxide, which the body does not absorb all that well. On the other hand, the body can easily absorb organic sources like zinc gluconate and zinc acetate. Always look at the label before buying a zinc preparation.

Other factors that increase your risk of autism

  • Lack of vitamin D (very common)Lack of folic acid
  • Environmental toxins, including mercury, aluminum, and pesticides
  • Hereditary factors
  • Becoming parents after the age of 35 years
  • Complications during pregnancy and delivery
  • Overdiagnosing (after the autism criteria were changed in 1994)
  • Having too high copper levels (copper blocks the uptake of zinc)
Autism is believed to be a congenital ailment, but studies suggest that it may also be a result of toxic exposure to aluminum that is found in the environment and in certain vaccines. For instance, scientists have discovered that children with autism have higher aluminum levels in their brain compared with children without the condition.

References

Huong T.T. Ha et al. Shank and Zink Mediate an AMPA Receptor Subunit Switch in Developing Neurons. Frontiers in Molecular Neuroscience. 2018.

Frontiers. Autism and zinc deficiency in early development. ScienceDaily November 2018

Nutrition insight. Taking Folic Acid Throughout Pregnancy May Increase Children´s Emotional Intelligence. 12 May 2017

Rebecca J. Schmidt et al. Combines Prenatal Pesticide Exposure and Folic Acid Intake in Relation to Autism Spectrum Disorder. Environmental Health Perspectives. 2017

Bjorklund G. The role of zinc and cobber in autism spectrum disorders. Acta Neurobiol Exp 2013a

Ann-E. Knudsen. Udvikling af barnets hjerne 0-18 år. Artikel til Tænketanken 2008

Min Barsel. Børn med autisme har mest aluminium i hjernen. 30. april 2018