OpEd- Have you ever wondered why when we experience emotions such as sadness, anxiety, boredom or stress it can trigger a desire to eat something we enjoy? Often referred to as ‘comfort eating’, we use food as a coping mechanism due to its association with happy feelings. By doing so we are engaging our brains in a pleasure reward system which encourages us to repeat this behaviour. When we reward ourselves or even in anticipation of receiving the reward, our brain releases a chemical called dopamine (the ‘happy’ hormone), which results in making us feel better.
It has been suggested that foods higher in fat and sugar give a more instant rush of dopamine, which may be why we are attracted to eating foods we know are less healthy when seeking comfort. However, this immediate ‘hit of happiness’ from the food we consume may be short lived and can later lead to feelings of guilt over a lack of self-control, fatigue and worsen feelings of depression and anxiety.
How our food choices impact our emotions.
The long-term impact of our dietary choices on our mood is a relatively new consideration. There is evidence to suggest that diets high in processed and sugary foods are a risk factor for developing depression, whilst diets that include higher levels of fruits and vegetables, legumes, whole grains, and lean protein lower this risk (1). An accumulation of studies investigating the effect of the Mediterranean Diet (which is often hailed as the gold standard dietary pattern) found that following this way of eating reduced the likelihood of developing depression by 30% (2) and a separate review of studies into mental health in children found that children who consumed diets high in saturated fat, refined carbohydrates and processed food were more likely to experience low mood, anxiety and depressive symptoms (3).
Can food change the structure of our brains?
As research into neuro-science has progressed we now understand that our brains have ‘plasticity’ throughout our lives, which means that they can be rewired based on our experiences, environment and lifestyle. The role that our diets play as a modifiable lifestyle factor is now a key area of interest, as something we have control over.
Diet may have a direct impact on the physical structure of our brain and studies have shown that what we eat may impact the size of the ‘hippocampus’ region of the brain, which is responsible for our mood, learning and memory. People who consumed a standard ‘western diet’ low in fruit and vegetables and high in sugar and saturated fat were found to have a smaller hippocampus. This is interesting when considering our mood, as people who experience depression have also been found to have a smaller hippocampus (4)
What about the gut/brain connection?
Serotonin is a chemical messenger, the majority of which is produced in our guts from an amino acid (protein) called tryptophan. Serotonin controls our mood, wellbeing and metabolism and the amount available for us to utilise can be influenced by the type of bacteria we have in our guts (5). Having an imbalance of gut bacteria (dysbiosis) has been associated with low mood and it is thought that some bacteria utilise serotonin themselves, reducing the amount available for our brains. Dysbiosis of gut bacteria has also been associated with ‘western diets’ low in fibre and one of the key ways to increase diversity is to consume higher quantities of fruit and vegetables.
The role of diet in treating depression.
Until recently, most of our understanding of how mood is influenced by diet has come from observational and animal studies. The ‘SMILES’ trial was a ‘first of its kind’ clinical trial investigating dietary therapy as a treatment for people suffering depression. For a period of three months participants were supported with implementing a Mediterranean Diet protocol, whilst a second group received social support.
The diet intervention was found to be four times more successful in helping the participants to reach remission from their symptoms, with the greatest degree of relief from symptoms experienced by participants who implemented the diet to the greatest degree. The framework for the Mediterranean Diet used in the study included 5-8 servings of wholegrains, 3 servings fruit and 6 of vegetables per day, along with 60ml of olive oil and 1 serving of nuts in addition to legumes, eggs, lean red meat, poultry and fish consumed several times a week.
