When we consider the dizzying high of a sugar rush and the crushing low of a sugar crash, or the irritability and anger that comes with being “hangry”, it’s hard to imagine that the food we consume is not linked to how we feel.
Poor glycaemic control has previously been linked to psychiatric conditions. However, studies on the relationship between food and depression and anxiety have been limited.
Susi Lodola, cognitive psychotherapist, notes that nutritious foods we consume provide the nutrients our brain requires to function optimally.
“A balanced diet rich in vitamins, minerals, and antioxidants supports brain health and can enhance mood,” she says. “Conversely, diets high in processed foods and sugars may contribute to mood disorders. The gut-brain axis, a communication network between the gastrointestinal tract and the brain, plays a crucial role in this interaction. A healthy gut microbiome, fostered by a nutritious diet, can positively influence mood.”
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Mental health is a complex issue with varying psychological, social and biological factors determining a person’s experience. Numerous randomised controlled trials have demonstrated that diet is one such biological factor that can significantly impact the risk for symptoms of depression and anxiety, suggesting that mental health treatment strategies should target every risk factor, including nutrition.
Research published in the Journal of Effective Disorders indicates there is a notable connection between our diet and our emotions, suggesting that blood sugar fluctuations are partly responsible.
The researchers noted that continuous hyperglycaemia and increased glycaemic variability may be related to the development of depression and anxiety symptoms, suggesting that routine examinations may assist in identifying individuals who are at elevated risk of developing such disorders and could benefit from timely interventions.
For young people and children, highly processed sugary and fried foods can be linked to hyperactivity and aggression. If you suffer from depression or anxiety, these foods need to be avoided
— Dr Gillian Moore Groarke
Dr Gillian Moore Groarke, consultant psychologist at Bon Secours Hospital, Cork, explains that the glycaemic index (GI) is a measure of how quickly food can make your blood sugar (glucose) rise. For instance, the Mediterranean diet recommends dark green, leafy vegetables, fruit, olive oil, whole grains, legumes and nuts, with small amounts of fish, meat and dairy products. This is a diet with a low glycaemic index – research published in Nutrition and Health notes its positive effect on mood, with decreased feelings of stress and mental distress.
“What you eat affects the structure and function of your brain and ultimately your mood,” she says. “Our brains require a constant supply of fuel. Good food with a lower GI has a more positive effect on brain function. High-quality foods that have lots of vitamins, minerals, and antioxidants nourish the brain. Diets high in sugar are harmful to the brain and can worsen your body’s regulation of insulin. They also cause inflammation and stress. Diets high in refined sugars worsen symptoms of mood disorders and lead to depression.”
Furthermore, Dr Moore Groarke suggests that alcohol, caffeine, processed foods, sugar, energy drinks, refined carbs, soda, white bread, refined cereals, trans fats, fried foods, gluten, and preservatives also affect mood.
“For young people and children, highly processed sugary and fried foods can be linked to hyperactivity and aggression,” she says. “If you suffer from depression or anxiety, these foods need to be avoided.”
[ Food and mood: Why nutritional psychiatry is attracting attentionOpens in new window ]
Lodola advises that a recent study published in British Journal of Nutrition showed that certain foods have been associated with increased anxiety and other mental health issues. Ultra-processed foods such as sugary snacks, fast food, and processed meats have been linked to higher rates of depression and anxiety. Refined sugars are also culprits, with a high intake of refined sugars leading to blood sugar fluctuations – which may contribute to mood swings and anxiety.
“Diets high in refined sugars have been linked to impaired brain function and worsening symptoms of mood disorders,” says Lodola, who also notes that “excessive caffeine consumption can cause restlessness, nervousness, and exacerbate anxiety symptoms. Reducing alcohol and caffeine can also help manage anxiety symptoms and promote better sleep, which is vital for mental health”.
“Using psychological techniques such as mindful eating, relaxation and CBT can all help to change the narrative around food to enable us to make better choices,” advises Dr Moore Groarke.
“When we change the narrative from ‘I can’t’, ‘I should’, ‘I have to’, ‘I must’, ‘what if’ and ‘but’ to ‘I choose to’ and ‘I choose not to’, it gives back control, leading to empowerment and greater self-esteem, which over time leads to weight loss and better weight management.”
Lodola recommends adopting a balanced diet. “Embrace a diet rich in fruits, vegetables, whole grains, lean proteins and healthy fats,” she says. “The Mediterranean diet, for instance, has been associated with reduced symptoms of depression and anxiety. I often say to clients ‘eat the rainbow’ or look at your plate and think ‘how could I make this meal a bit healthier?’.”
Balance means adding a few more vegetables, seeds, salads, and colour to a diet. Lodola also recommends including omega-3 fatty acids. “Foods like oily fish (for example, salmon, mackerel), flaxseeds, and walnuts are high in omega-3s, which have been shown to support brain health and improve mood,” she says.
She also recommends instilling the idea of maintaining positive and regular eating patterns and habits. “Eating regular, balanced meals helps stabilise blood-sugar levels, preventing mood swings and irritability.
“When you start your breakfast with sugary foods – and often those sugars can be hidden (read the labels) – you end up in sugar highs and sugar crashes, which often lead to mood swings, irritability, and tiredness.”
Finally, a balanced diet also includes staying hydrated. “Adequate water intake is essential for optimal brain function and can influence mood and energy levels,” says Lodola.
It’s important to note that not everyone is equally affected. A person will react differently to the same meal depending on their sex, genetics, and gut microbiome. The complexity of the mental health condition will also play a part.
However, a poor diet may have a negative impact on a person’s mood and is worth considering when managing symptoms of depression and anxiety.
