It’s hard to imagine that the baby you once cradled and comforted could one day become aggressive — hitting, kicking, biting, pushing, or throwing objects. For many parents, it’s both distressing and confusing, especially when it feels like your child’s anger is directed right at you.

While aggression in children is more common than we might think, it’s important to look beyond labels like Oppositional Defiant Disorder (ODD) and explore what might be driving these behaviours. From a functional medicine perspective, aggression isn’t just a behavioural issue — it’s often a sign that something deeper is out of balance.

Understanding the Roots of Aggression in Children

There’s rarely one single cause. Research shows that several factors can play a role — including what happens even before birth. Things like mum’s nutrition during pregnancy, exposure to toxins, stress, trauma, smoking or alcohol use, and even early pregnancy can all influence a child’s developing brain.

As children grow, factors such as ADHD, family stress, parenting style, and school environment can also contribute. When kids are surrounded by other children who are aggressive, for example, they’re more likely to mirror that behaviour.

How Nutritional Deficiencies Can Lead to Aggression

Nutrition is one of the biggest, and most overlooked, pieces of the puzzle. According to the Australian Bureau of Statistics, children today are eating fewer fruits and vegetables than they were just a few years ago:

• Only 4.6% of children meet the recommended vegetable intake.
• Just 4.3% meet both fruit and vegetable recommendations.
• And a quarter of children aged 2–17 consume sugary drinks daily.

Fruits and vegetables are rich in vitamins, minerals, and plant compounds that support healthy brain and nervous system function. When these are lacking, it can affect mood, energy, and behaviour.

For example:

• Calcium: Nearly three-quarters of girls and half of boys don’t meet their daily calcium needs.
• Iron: One in eight Australians aged two and over have low iron intake.
• Zinc: Most children over age nine don’t get enough zinc.

What the Research Shows about aggression and nutrients

An Australian study in 2017 looked at boys aged 4–14 who displayed ongoing aggression for at least six months. Many had behavioural diagnoses like ODD, ADHD, PTSD or ASD. The researchers found that:

• 45% were low in zinc, and many had signs of oxidative stress (a kind of internal inflammation).
• The children were given a broad-spectrum micronutrient formula containing vitamins C, E, B6, biotin, selenium, zinc, and chromium.

After 16 weeks, the results were striking — aggression levels dropped significantly, and over a third of the boys moved into the normal range for behaviour. Interestingly, there was a 95% increase in plasma zinc, and 81% decrease in copper.

And there were other benefits, all four domains on the Health Related Quality of Life scale – physical, social, school and emotional including relationships with peers and behaviours such as anger, anxiety, depressed mood and insomnia – improved significantly.

Why These Nutrients Were Selected

These nutrients play crucial roles in the brain’s chemistry and function:

• Vitamin B6, zinc and biotin help produce neurotransmitters like serotonin, dopamine and GABA.
• Vitamins C and E and selenium support antioxidant defences and protect brain cells.
• Chromium assists with neurotransmitter synthesis, fat metabolism and glucose regulation where glucose intolerance has been a potential exacerbating factor in violent outbursts.

When any of these are low — or when the body has difficulty using them — behaviour can be affected.

Other Nutrients That Can Be Implicated

• Iron – studies have shown that iron deficiency at crucial time points in an infant’s brain development can influence their social and emotional development and lead to aggression, as well as social anxiety, ADHD, PTSD, oppositional defiance and rule breaking. Deficiency is also linked to long term changes in the metabolism of key neurotransmitters dopamine, GABA
• Vitamin D – studies have shown that those with vitamin D deficiency in early childhood were 1.8 times more likely to display aggressive and rule-breaking behaviour as teenagers than those without Vitamin D deficiency.
• Copper excess – whilst our bodies need copper, when it’s in excess, it can cause a range of symptoms including aggression, agitation, anxiety and depression. There are many sources of copper exposure, including chlorinated pools, the oral contraceptive pill, farming pesticides and water pipes. The issue with copper is that when copper is high, zinc is low, so not only do we experience copper excess signs, we display zinc deficiency signs.

Nutrient levels can be determined via blood testing, hair tissue mineral analysis and thorough history taking.

Aggression in kids is a taboo issue. Which makes it hard for parents to seek help. Make an appointment with one of our team for a judgement free discuss on optimising your child’s wellbeing.