Joanna McMillan explores the relationship between nutrition and mental health and if what we eat can have a big impact on how we feel, mentally as well as physically
If I were to ask you whether diet had an impact on your heart health, your risk of cancer, type 2 diabetes, your liver health or indeed any aspect of your physical health, I have little doubt your answer would be yes… but, what about your mental health?
The brain has until relatively recently been a rather mysterious organ of the body. What goes on in the brain has been a question of many from philosophers to neurosurgeons. It is couched in our sense of who we are and what we think and feel, and this intangible nature of the brain leads to romantic, spiritual and scientific interest. Yet, while we might believe our brains to simply ‘work’ regardless, the truth is that what you are eating has a significant impact on many brain functions.
Seafood provides such important nutrients for the brain
Let’s begin in infancy, or more precisely, while still in the womb. This is a crucial period of rapid brain development and the impact of nutrition starts here.
One key nutrient is iodine. We need only tiny amounts of this mineral, but a lack grossly affects brain development and leads to a lowering of IQ and, in severe cases, learning difficulties. We might think this is something that is only a problem in the developing world, but in fact iodine deficiency is increasingly diagnosed in developed, seemingly well-fed, countries.
We get iodine primarily from milk, dairy, fish and seafood. Including fish regularly in your diet will help boost your iodine intake.
Another group of nutrients key to both brain development and brain function throughout life are the long chain omega-3 fats called ‘DHA’ and ‘EPA’. The brain is about 60% fat and has a high proportion of these polyunsaturated fats. A higher intake of these essential fats has been associated with less depression and, importantly, high dose supplements have been shown to be useful in treating depression and some other mood disorders1.
The best dietary sources are oily fish such as salmon, trout, sardines and herring. It’s interesting that seafood provides such important nutrients for the brain and that may be because humans so often traditionally lived close to water, and that water provided much of our food.
Other sources include nuts and seeds (such as walnuts and pumpkin seeds), vegetable oils (such as rapeseed and linseed), soya and soya products (such as beans, milk and tofu), green leafy vegetables and enriched foods including some eggs, milk, yogurts and breakfast cereals.
Unless you eat oily fish you may be at risk of deficiency so you might consider taking a supplement.
These nutrients, along with many others, continue to be important throughout childhood and into adulthood. But diet is also key for kids to learn and to be able to concentrate at school. Diet influences their behaviour and their mental health.
An overall poor diet, characterised by a Western style diet of too much junk food and too little fresh, minimally processed food, has been associated with poorer mental health in children, adolescents and adults. A study from Norway linked poor diet in pregnant mothers and through infancy with mental health problems in children as young as five years old2.
When it comes to behaviour we so often blame discipline, boundaries or other environmental aspects of a child’s life. These are all undoubtedly important, yet diet has also shown to exert its influence.
You may well have read about the now infamous “Southampton Six” – not a wayward gang, but a list of six artificial colours that were shown in a study at the University of Southampton to have a negative effect on children’s attention, concentration and behaviour3. The study gained much international attention and many food companies have voluntarily removed these colours from food. In addition, labelling laws have been tightened to ensure clear labelling indicates their presence.
Diet is key for kids to learn and to be able to concentrate at school
As we get older, the risk of cognitive decline is higher with a diet high in saturated fat, but lower where the major fat is monounsaturated4. Saturated fats are largely found in animal foods and tropical oils, while monounsaturated fats dominate in extra virgin olive oil, most tree nuts, peanuts and avocado.
These foods are central to the traditional Mediterranean diet and there is good evidence that this dietary pattern is good for our mental health. A meta-analysis, pulling together results from 22 studies, found that eating a Mediterranean style diet reduced the risk of depression and cognitive impairment5.
Intervention studies give stronger evidence than observation type studies and here too we find support for a Mediterranean style diet. A European study that added either nuts or extra virgin olive oil into a Mediterranean diet, reported improved cognition in both Mediterranean diet groups and a strong trend towards less depression in the group supplemented with nuts6.
So what is it about this style of eating that might be protective for our brains? We don’t really know the answer to that yet, but the likelihood is that it is a combination of factors.
It may be that the high intake of vegetables and fruit provides a good daily dose of antioxidants that may be protective to brain cells. It may be that we need to eat legumes and wholegrains rich in fibre that take time to digest ensuring the carbohydrates present are absorbed slowly, providing a steady supply of glucose to fuel the brain. Or it may be that we need to eat only small amounts of processed and red meats, but plenty of omega-3 rich seafood and other good fats from extra virgin olive oil, avocado and nuts. Getting social and eating with others is an additional factor.
But it may also be that such a traditional diet does not include junk food. A British study found that the odds of having depression were significantly higher in those people that ate a diet high in junk foods – think too much added sugar, refined processed grains, processed meats and fried foods – than those that ate a whole food diet7.
What we eat affects the functioning of the brain
HOW TO EAT FOR BETTER MENTAL HEALTH
Looking at the big picture, it is clear that what we eat affects the functioning of the brain. Most people could benefit from eating more oily fish in addition to a plant-based diet (whether or not you also enjoy meat), with an abundance of vegetables in particular, fruit, nuts, seeds, wholegrains, legumes and other whole foods. Getting social and eating with others is an additional factor. This gives you the best chance of good mental health now and as you age, and the win-win is that this is also the kind of diet that is best for your physical health. To check out your diet seek expert advice from a Dietitian.