You’re back in the classroom after lunch break and one of your pupils is acting up. Maybe they’re wired after running around the playground for an hour. Perhaps they’re just tired, longing for the final bell to ring.

Or maybe you should be asking what they had for lunch, because research shows that the food we eat has repercussions for our mood, behaviour and cognitive performance.

This relationship between diet and learning is often overlooked: an EU-wide study found that 80 per cent of teachers and parents believe diet is an important part of children’s physical development, compared with just 67 per cent who saw a link with mental development (Egan, Gage, Williams et al, 2016). So, what do we need to know?

Meagre omegas

Dr Alex Richardson, founder-director of the charity Food and Behaviour Research and visiting senior research fellow at the University of Oxford’s department of physiology, anatomy and genetics, researches how nutrition - particularly omega-3 fatty acids - affects brain development, learning and mood in children.

“There are two fats that are essential to our diet: omega-3 and omega-6,” says Richardson. “There are both short-chain and long-chain omega-3s and -6s, and what matters for health, particularly for the brain, are the long-chain fatty acids.

“For omega-6, that’s meat, dairy and eggs; for omega-3, it’s fish and seafood, and the oilier the fish - such as salmon and mackerel - the better.

“But there’s a deficiency in the population, particularly among children, in long-chain omega-3 fatty acids, and these are essential for mood, behaviour and learning. They are an essential part of cell membranes and vital for blood circulation to the brain.”

In a 2013 paper, Richardson and colleagues found that low blood levels of long-chain omega-3 fatty acids in schoolchildren were associated with poor behaviour.

“If you’re in optimum health, those blood levels should be 8 per cent or higher; the average for the seven- to nine-year-old children we assessed was 2.5 per cent,” she says. “We found that the higher the blood levels, the better the behaviour measured on ADHD-type symptom scales - and these were general-population schoolkids.

“Learning was better, too. Some of our trials found improvement in reading in the poorest readers when we gave long-chain omega-3 supplements compared with the placebo.”

Time to dose up on oily fish, then, but what else can send children’s moods askew?

Surprise, surprise: sugar and refined carbohydrates are the enemy.

“If a child is heading into the classroom having had a soft drink and a chocolate bar, their blood sugar shoots up incredibly quickly,” says Richardson. “That’s the signal for the body to pump out insulin. The faster your blood sugar rises, the more insulin gets pumped out.

“The child is full of energy; he or she might even perform better in the classroom for the next 30-60 minutes. But then their blood sugar crashes and he or she starts pumping out adrenaline and the stress hormone cortisol. Suddenly, the child grows inattentive, disruptive, irritable, maybe they’re up and out of their seat.”

In other words, they’re on a one-way ticket to detention.

Going with the gut

Anything else? Well, our knowledge about the brain-gut connection is expanding fast, with new revelations emerging all the time.

Dr Uma Naidoo, nutrition educator at Harvard Medical School, is a nutritional psychiatrist, a practice that has developed over the last decade. She says the research is “getting more and more robust”.

While her patients are adults, Naidoo’s work provides a fascinating insight into how what’s going on in the gut is tied to how we feel.

“There’s a balance of good and bad bacteria in your gut,” explains Naidoo. “The good guys help with digestion and help you get the vitamins you need from your food. The bad guys cause trouble and disease.

“Processed foods feed the bad bacteria, so those bacteria get stronger and start contributing to disease, including depression. When you’re eating foods that contribute to a gut imbalance, your mood may be affected.

“Conversely, the good bacteria are fed by prebiotics and probiotics. Probiotics are foods like yoghurts. Prebiotics help to keep your gut stable and grow good bacteria - they’re the non-digestible parts of foods such as bananas, onions, garlic, Jerusalem artichokes and the skins of apples.”

Iron age

Meanwhile, low iron levels are also linked to poor concentration and mood in children.

“This is particularly important for teenage girls because National Dietary and Nutrition Survey data shows that almost half of 11- to 18-year-old girls don’t get enough iron,” says Richardson.

“From the moment they hit puberty and menstruation starts, their iron requirements go up relative to boys’. Quite a few studies show links between low iron and problems with attention and concentration, and research has also found low iron in children with ADHD.”

So what should an A-star lunch look like? Chicken nuggets, it ain’t.

“It should include a good source of protein such as eggs, meat or fish,” says Richardson. “It needs carbohydrates such as wholegrain bread or rice and a variety of fruit and vegetables to ensure they’re getting a good spread of nutrients.”

Ultimately, the message from Richardson is clear: “When it comes to mood, behaviour and learning, nutrition trumps all else. If children aren’t able to regulate their emotions, then they’re not in a position to learn. We need to sit up and pay attention.”

It seems Gillian McKeith was right all those years ago: we really are what we eat.

Christina Quaine is a freelance writer

This article originally appeared in the 3 May 2019 issue under the headline “We need food for thought…and for behaviour, too”