No doubt most of us know that a diet of junk food won't do wonders for our waistlines. But how many of us are aware of what all those chocolate-chip breakfasts and supermarket ham sandwiches are doing to our brains? Or to our children's brains?
The evidence, as collected by chartered psychologist Kimberley Wilson in her book, Unprocessed: How The Food We Eat Is Fuelling Our Mental Health Crisis, is alarming. Britain's taste for sugary, processed foods is leaving our most nutrient-hungry organ - the brain - severely undernourished. The result is that we're more depressed, more antisocial and more prone to conditions such as dementia. We might even be stupider, too - IQ levels have been falling over the past couple of decades.
'If you're living in a state of chronic under-nutrition, then your brain is going to be in a constant state of stress,' Wilson says. Her aim is to make her readers feel empowered and informed to make better choices - but also a little angry at how successive governments have ignored the evidence and allowed the food industry to mess with our heads.
Men's Health: What is it about processed foods in particular that concerns you? Surely most food is processed in some way, including a lot of the stuff we would see as good for us: tinned sardines or dried fruit, say?
Kimberley Wilson: It's a controversial area in nutrition research. But the NOVA system of food classification sorts food into four groups, starting with natural or minimally processed foods that have been dried or frozen. At the other end of the spectrum are ultra-processed foods, where all of the constituent products have been through several processes. These are usually foods that are ready to eat or ready to heat. When you process a food, you strip it of its nutrients. You lose 80% of the magnesium, almost all of the omega-3s. And we know that in the UK, 55% of our diets consist of these foods. So, we're going to be struggling to meet the nutritional RDAs for good health.
MH: What is this doing to our brains?
KW: To take one example, there was a study where scientists took about 100 people and said: 'For four days of the week, I want you to have a couple of Belgian waffles for breakfast, and then on two days of the week, I want you to have a takeaway.' After just one week, they found impairments in the hippocampus - a part of the brain that's crucial for consolidation of memories and which becomes damaged by Alzheimer's disease.
We also know that hypoglycaemia - diabetes or prediabetes - confers two to three more times the risk of developing dementia: it can increase oxidative stress, it can increase inflammation. So high blood sugar is a real threat to brain health.
MH: Okay, so what should we all be eating more of?
KW: My biggest concern for individuals is around omega-3s. Professor Michael Crawford has been talking about the low population intakes of omega-3 fatty acids since the 1970s. If we don't sort this out, we're going to see a rise in mental health conditions. The guidelines say that you should be eating two portions of fish per week, one of which should be oily fish. If you don't eat fish, then you should consider a pre-formed omega-3 supplement - EPA and DHA, not ALA.
The other thing is fibre. There isn't a single age group in the UK that is meeting the fibre recommendations. Fibre is so boring. We think bran and prunes. But when your gut microbes break down fibre, they produce short-chain fatty acids. And one of the things that short-chain fatty acids do is protect the blood-brain barrier - which prevents toxic compounds from your bloodstream crossing into your brain. So I would be thinking about switching your white carbs to brown, eating your potatoes with the skins on. And beans! We should be eating beans and pulses four times a week.
MH: You make it clear that these deficiencies go all the way back to childhood, pregnancy, even before we were conceived. There's not a whole lot that any of us can do about the fact that our parents weren't eating enough mackerel 40-odd years ago. Does that mean it's too late?
KW: Yes! But I don't want to overstate that and I don't want to be alarmist. If you have children yourself, then ideally, your partner would've been eating mackerel through pregnancy. But if she wasn't, there are strategies. You find a food that the child really likes - say mashed potatoes - and you mash in a tiny bit of mackerel. That makes it more acceptable to the child over time. Also, you need to be eating mackerel. The biggest influence on what a child eats is what they see their parents eating. We like what we eat, rather than eat what we like.
MH: One of the parts of your book that surprised me was the link between diet and violence. Could you unpack that a little?
KW: Nutrition certainly leads to shifts in behaviour. There was one study where the scientists took a set of couples, measured their cortisol levels, gave them a voodoo doll of their partner, and said: 'Whenever you get angry with your partner, stick pins in this doll.' I mean, scientists, right? They found a correlation between higher levels of cortisol and a greater number of pins poked into these dolls.
We think of cortisol as a stress hormone. But actually, what cortisol does is release glucose and fats into the bloodstream to prepare you for that fight-or-flight response. We know that your cortisol goes up when you're hungry. So if your blood sugar drops, you have a rise in this hormone of arousal, agitation and stress.
Again, we come back to the question of child nutrition and the behavioural impact of children being hungry. And then we have the outcome of the prison studies: when they gave prisoners supplements of micronutrients versus placebos, there were 30% fewer violent incidents in the prisons.
MH: But nutrition is often confusing - go vegan, go carnivore, butter is bad, butter is good, etc. Isn't the advice changing all the time?
KW: The official advice doesn't change that much. What we get is a lot of conflicting information from disparate belief systems. It's not that the NHS has said, 'Everyone needs to go vegan.' Various social media influencers have decided that it's important. The national dietary recommendations get updated from time to time - but largely, it's eat whole grains, make sure you're getting plenty of fruit and vegetables, eat some meat and some fish in reasonable quantities and keep added sugars low. That's consistent across nations.
MH: But isn't it understandable that people don't trust these guidelines? If you look at the food served up in the nation's institutions - schools, hospitals, prisons - it's generally highly processed crap. Why is there such a discrepancy between what the government says and does?
KW: Now that's a really good question. One problem is that the NHS Eat Well recommendations are different from the food standards that are set for places such as prisons, schools and hospitals. Certainly, in prisons, there aren't really any standards for the nutritional density of food. It just needs to be wholesome, well prepared and reasonably varied. But none of those words have a definable meaning, right? So that allows vested interests and profit-making companies to play fast and loose with quality without any risk of actually being hauled over the coals for the fact that children or patients or prisoners aren't getting the nutrients that they require. It's an absolute mess.
MH: The government has tended to the view that it's up to us citizens to make better choices - that it isn't their job to dictate what we have for dinner. What's your view on that?
KW: I think that it's ignorant as to the impact of the environment or the nature of food choice. Our food preferences begin in utero and are trained in early childhood when those decisions are made for us. And of course, we respond to our environments. If you're living in an area with a lot of adverts for fast food, that's going to shape the choices you make.
And even if you know everything there is to know about healthy eating, but don't have the money to afford healthy foods, then you don't have a choice - especially in a cost of living crisis. The idea that you're just choosing to have a poor diet is actually insulting.
MH: What would a better food strategy look like?
KW: School would be a perfect opportunity to introduce children to new flavours. If there was a national campaign to expand the food horizons or the taste preferences of young children, that could be hugely beneficial. You can change the way you eat as an adult, but it's harder. It takes so much more effort, consistency and motivation. Whereas if you could get that started at an early age, it becomes more natural and habitual - it would improve children's concentration, their mental health, their wellbeing and their general pleasure in eating. But it's just not considered a priority.
We need to be thinking about early life nutrition. That is the foundation of later physical and mental health, academic achievement, productivity and a prosperous society. So even if it's only for that economic rationale - even if you're not moved by the appeal of hungry children - that should still be enough of a reason for us to be concerned about the number of undernourished children we have in the UK.