Eating junk food is shrinking your kid’s brain 

Alison’s son, Harry, started primary school this year. He was one of those kids who was ready for school and took to it with enthusiasm. There was no clinging to mum’s leg in the morning and his teacher reported he was fitting into his new routine beautifully.

But later in term two, Alison noticed a few changes. His teacher reported that Harry was struggling with his reading and his ability to focus and concentrate was not strong. Alison had seen the signs at home too. When she sat down with Harry to do his reading each night, she suspected he was guessing his way through the books. 

His teacher then revealed she was monitoring his behaviour in the classroom. He hadn’t really clicked with any of his classmates and told his mum that he felt a “scaredness and sadness” and did not know why. 

Like everyone, Alison is busy. She doesn’t love cooking and often uses convenience foods to get through the week. The family does a McDonalds or KFC run on nights that the children have sports on and lunchboxes are filled with packet foods, chocolate biscuits and nutella or jam white bread sandwiches. As Alison puts it, they’re quick, cost-effective and fill growing tummies.

Like many parents, Alison was unaware of the connection between Harry’s diet and the learning, mood and behavioural challenges she was seeing. Connecting the two things was a lightning-bolt moment.

There have been animal and human studies which examined what a processed-food diet does to our brains, and the results are astounding. Researchers discovered that when people (kids included) eat a junk food diet their hippocampus shrinks!

Yep, you read that right. A part of your brain actually shrinks. 

What your hippocampus does 

The hippocampus is located in the medial temporal lobe of the brain. It plays an important role in learning, memory and it helps us move information from our short term to long term memory. The hippocampus also forms part of the limbic system that is involved in emotions and mood regulation.

What we also know is that people with depression have a smaller hippocampus than those that don’t. 

Professor Felice Jacka and others conducted a groundbreaking, longitudinal study in 2015. It was the first human trial to find there were brain changes directly related to poor quality of diet. When depressed patients ate a high processed food diet they saw a 60% shrinkage in hippocampal volume. Scary stuff! 

What happens to you when your hippocampus is shrinking? 

What we see when hippocampal volume drops is a reduction in brain plasticity, a drop in brain derived neurotrophic factor (BDNF) and a reduction in learning, memory and executive function. 

BDNF is important for protecting existing neurons from oxidative stress and promoting the growth of new neurons. Low BDNF is what leads to dementia and cognitive decline as we age. 

This is where Harry comes in. He’s at an age where his brain is growing rapidly.

Eating too many processed foods is a large part of the explanation for why we are seeing kids like Harry struggle with inattention, lack of focus and learning difficulties in the classroom. Mood and behavioural challenges kids face at school and home is being caused, to some extent, by their diet quality. 

How to regrow your brain 

The good news is human beings are amazing creations. Studies show that we can reverse this damage to the hippocampus.

Here are some ways that you can restore hippocampal volume: 

1. Eat a good quality diet 

The Mediterranean diet has by far the largest and most consistent evidence for health benefits and studies in Nutritional Psychiatry find that eating a mostly plant-based, whole food diet helps patients overcome depression and anxiety and improves learning outcomes.

Aim to eat the following: 

  • High fibre foods: e.g. whole grains, legumes, fruits and vegetables 

  • They increase short chain fatty acids that are crucial for reducing inflammation and oxidative stress

  • Vegetables: You want to aim for five to seven serves of vegetables a day. Eat lots of garlic, onions, artichokes, leafy greens. A serve is about a handful or a cup.

  • Fruits: two to three serves a day is perfect. Red grapes and berries are the best.  

  • Dairy: one to two serves a day (if well tolerated) 

  • Legumes: Aim for a serve daily 

  • Nuts and seeds: one serve a day 

  • Fish: Aim to eat fish at least two to three times a week

  • Red meat: Two to three palm size serves a week is great 

  • Poultry: Two to three serves a week 

  • Eggs: Eating six to ten eggs a week is good 

  • Olive oil: Aim to have 50ml of olive oil (preferably extra virgin olive oil) daily to help with brain function 

2. Zinc 

Zinc plays a leading role in brain regeneration after eating a poor diet for a long period. It assists in reversing brain shrinkage. It is also a mineral that helps address picky and fussy eating. 

3. Fish oil 

Cod liver oil is fantastic for improving brain development and function and a must for growing brains. 

4. Regular Exercise 

Numerous studies have been done into the role of exercise and brain function and we know it has a BIG role to play in increasing BDNF in the brain to create new neurons. 

What happened to Harry?

This was great news for Alison. She had a possible solution for helping Harry.

Harry wasn’t so sure. When he saw carrots and cheese appearing in his lunchbox instead of chips and biscuits there were protests. Alison said many of those vegetables went to school and came home with him again, but he adapted. The chips didn’t disappear altogether, they just became a treat.

That was a middle ground they could both live with.

Months later Alison reported improvements in Harry’s ability to focus on a book from start to finish and he had stopped saying he felt sacred. His teacher said he was less anxious in the classroom, too.

With some simple, common-sense dietary changes, his mum had changed the trajectory of that all-important first year at school. And in the process, she said her own diet had improved too. We call that a win-win.