Free school lunch could cause improved grades

What you eat is as important as whether or not you've skipped a meal...
08 September 2023

Interview with 

Greta Defeyter, Northumbria University


An apple sitting on a stack of books.


London’s mayor, Sadiq Khan, has announced that all children in the city between the ages five and eleven will receive a free lunch when at school. It’s thought that around four million children in the UK don’t always get enough to eat. The plan to provide a free lunch to primary school kids in the capital has been welcomed by many. This is how the top celebrity chef, Jamie Oliver, responded to the announcement:

Jamie Oliver - This is a great day. In one of the greatest cities in the world, it means that we have a chance to apply measurement and actually prove that this is something not just for Londoners, but actually that's really relevant for the whole school food system across the whole country based on, on evidence of it being a good bang for the taxpayer's buck. I'm really pleased.

So, how might a good meal help our performance in school? James Tytko spoke to Greta Defeyter, professor of developmental psychology and director of the Healthy Living Lab at Northumbria University:

Greta - When your stomach is empty, a hormone called motilin causes it to contract causing hunger pangs, and your blood sugar level dips and your stomach produces another hormone called ghrelin, which activates neurons in the hypothalamus region of the brain that tells you you need to eat. And that actually divides attention between the learning tasks that the child or the adult is engaged in. The other part of that is, whilst the brain weighs only about 2% of the whole body weight, it uses 25% of the total body glucose. In other words, glucose that's absorbed into the blood is distributed to the brain cells to provide energy to the brain. So it's logical to follow that children who have not eaten either before school or skipped their school lunch, who may well be from food insecure households, are not able to concentrate, and do not have sufficient fuel, inhibiting working memory and sustained attention that are essential for learning.

James - So that's the theory. I suppose the question that follows is what's the evidence base that that is what's happening in schools across this country and indeed the world?

Greta - There's numerous sources of evidence in terms of breakfast clubs at school. There's quite robust evidence that skipping breakfast is detrimental to children's learning. And that's probably because that research is relatively easy because you can do it outside of the school system and you've fasted the night before. So you can actually have really good controls on what food is in the body. Breakfast - breaking the fast, it's actually in the term itself. The complication in terms of school food is it also depends, as well as actually whether you eat or don't eat, on the types of food that you're eating.

James - It's so interesting. So being hungry, first of all is not good for attainment, but being full doesn't mean being full of the food that's best for learning. I mean, the phrase school dinners in this country evokes the historical image of turkey twizzlers and chips, what we now refer to as ultra processed food or UPF. These sorts of foods are unlikely to be good brain food.

Greta - Correct. So you need to bear in mind here that the main macronutrients of food are carbohydrate, protein, and fat and carbohydrates are the sugars and starches found in bread, cereals, fruits and vegetables, and are the main constituents of most breakfast and often most packed lunches as well. In recent years, attention has been looking at what we call glycemic index. So high glycemic index carbohydrates - as seen in foods such as white potatoes, white bread - are often also referred to as simple or quick releasing carbohydrates. And they're quickly converted into glucose which results in a rapid and high increase in blood glucose with a corresponding rapid decrease; the so-called 'sugar high.' Whereas low glycemic index carbohydrates, such as found in green lentils, apples, full fat milk, are often referred to as complex or slow releasing carbohydrates that provide a smaller initial increase in blood glucose and a much longer gradual decline. Now this is interesting because when you actually map the intake of either high GI food or low GI food, it actually maps well onto cognitive tasks. If you consume a food that has mainly low glycemic index carbohydrates, your performance doesn't increase as quickly on cognitive tasks; it's roughly about the same. But your performance is sustained for a much longer period across the school day compared to if you eat foods that are high in GI.

James - This has the promise, doesn't it, of being an extremely important leveler in that we can use the science you've outlined today to reduce the gap in attainment that we see between the poorest and richest kids.

Greta - Yes, exactly that. But we have to remember that these options aren't cheap. And so I think the question is more of a political question in some ways. I think the evidence suggests in terms of stigma, in terms of increased uptake of the scheme through universalism, reducing bureaucracy costs, etc.. And knowing that we have a large proportion of families that are living in what we call household food insecurity, the scheme makes sense and the data definitely looks promising. I think the problem is that the cost of rolling out such a scheme, and especially when schools are facing so many additional costs, such as crumbling concrete, is high. So that's really a politician's job.


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