Depression is the most common mental health disorder affecting people with diabetes. Research has discovered that roughly a quarter of the diabetic population suffer with depression, and people with diabetes are at more than double the risk of developing depression compared to the general population.

For someone with diabetes, having depression can affect how they manage their condition. Studies have indicated that depression increases the risk of poor glycemic (blood sugar) and metabolic control, while poor glycemic control can also result in low mood, so it’s easy to see how this can become a vicious cycle.

Traditionally treatment for depression involves the use of medication and psychological therapy.  Whilst these methods can be effective, research has indicated that medication such as antidepressants can have hyperglycemic effects (meaning blood sugars climb higher) and could result in weight gain and an increased risk of developing type 2 diabetes.

Recently there has been a growing amount of research aiming to discover if changes in lifestyle could also be helpful.

The role of diet, specifically a diet low in carbohydrate, has already been shown to be beneficial for people with diabetes. There is also accumulating evidence to suggest that a diet low in sugar can also play in part in the prevention and management of depression. More specifically, a diet higher in fats and Omega 3, like the Mediterranean diet, can actually improve depressive symptoms.

The ‘SMILES’ trial

A group of researchers from the Food and Mood centre in Australia put treating depression with diet to the test. The SMILES (Supporting the Modification of Lifestyle in Lowered Emotional States) trial is the first of its kind to investigate whether a Mediterranean diet could be effective at reducing the symptoms of depression in comparison to social support.

The study took place over a 12-week period and participants were randomly assigned to either a diet or social support group. To meet the inclusion criteria, participants must have been diagnosed with depression and reported that they had poor diet quality, meaning that their diet was low in fruit, vegetables and lean protein and high in sugary foods and processed meats.

Participants randomised to the dietary condition were fed a modified Mediterranean diet with an emphasis on an increased consumption of olive oil, oily fish and nuts. Roughly 40% of their dietary intake would come from fat, 37% from carbohydrates, 18% from protein and the remainder from fibre/alcohol/other. They also received nutritional counselling support in the form of motivational interviewing and mindful eating techniques.

Participants in the social group received support from trained ‘befrienders’ who would spend the session talking to participants about their interests or playing board games with them to keep them engaged and positive.

At the end of the 12-week period the results showed that participants in the diet group reported lower depressive scores than in the social group and had an improved quality of diet.

These findings suggest that the Mediterranean diet could play a role in the prevention and management of depression. Whilst we can’t conclude that a Mediterranean diet cures depression, it does show that a diet lower in sugar and higher in fat can improve symptoms.

How can we explain the link?

There are a number of theories that could explain the relationship between sugar and depression. Firstly a diet high in processed foods and sugar has been linked to increased inflammation. Additionally, increased inflammation has been linked to a greater risk of depression. Meanwhile, evidence has suggested that foods containing poly-unsaturated fatty acids such as Omega-3 have been shown to have anti-inflammatory properties. So this might explain why a diet higher in foods containing Omega-3 could show improved symptoms.

What can we take from this?

This study adds to the growing amount of evidence linking the impact of diet on mood. It demonstrates that a diet high in sugar and processed foods can have a negative impact on mood. In order to maintain a positive wellbeing it might be beneficial to consider lowering your sugar and carbohydrate intake and increasing your intake of fat from foods such as oily fish, nuts and olive oil.

The researchers who implemented the trial are now looking at whether the diet can be feasibly prescribed in GP practices for patients suffering with depression.

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