A new Australian study has found that improving diet and being more physically active can be as effective as therapy with a psychologist for treating low-grade depression (1). But what type of diet is best to help mood, and how do nuts fit in?

In the new trial, researchers from the Food and Mood Centre at Deakin University split the 182 adult participants, who had at least mild symptoms of depression, into two groups.

One group received ‘lifestyle’ therapy, provided by a dietitian and an exercise physiologist, and the other half took part in cognitive behavioural therapy sessions with psychologists.

After eight weeks, the average mental health scores had improved for both groups – by 42% and 37% for the lifestyle and psychotherapy groups, respectively.

A healthy lifestyle (food and exercise) and psychological therapy were as effective as each other in treating depression.

Importantly, the goals of the ‘lifestyle program’ group included:

• Eating a wide variety of foods
• Choosing high-fibre plant foods, including vegetables, fruit, nuts, whole grains, and legumes
• Including high-quality fats
• Limiting discretionary foods, such as those high in saturated fats and added sugars
• Doing enjoyable physical activity.

Did you know? Research suggests that greater adherence to several healthy dietary patterns, traditional diets (such as the Mediterranean diet) and other diets (such as the DASH diet) are associated with or can treat symptoms of depression (9).

Food and mood

Consistent evidence shows that a healthy dietary pattern promotes brain and mental health (2,9).

The ‘Supporting the Modification of lifestyle in Lowered Emotional States’, or ‘SMILES’ trial, was one of the earliest intervention studies to investigate the link between food and mood (3). 

It found a reduction in depressive symptoms, after a 12-week period, in people following a ‘modified Mediterranean diet’. In fact, one in three study participants, who changed their diet, no longer had significant symptoms of major depression.

The ‘ModiMedDiet’ used in the SMILES trial included a daily (30g) handful of nuts.

Figure 1: The ModiMedDiet Food Pyramid used in the SMILES trial

Diet interventions can lead to impressive reductions in depressive symptoms. And there is particularly compelling data to support the Mediterranean diet in improving symptoms of depression (9).

What does the research say about nuts and mood?

In a nutshell, more research is needed in this area. But some recent studies, all published in the past few years, have shed light on this question. Here are the key findings:

• A 2022 systematic review, of 10 previously-published studies, involving more than 66,000 people, across five countries, concluded: ‘Higher nut consumption is associated with a reduced risk of depression and better mood state in the general population’ (4).

• In a pooled analysis, looking at the findings from two earlier cohort studies of older adults (>65 years), nut consumption was linked with a lower risk of depression. Among the findings, the odds of depression were 8% lower in those consuming ≥3 (30g) servings of nuts/week, compared to <1 serving (5).

• In another study, of 13,504 middle-aged and older UK-based adults, without depression at baseline, who were tracked over an average of 5.3 years – eating nuts daily (>0 to 1 serve of 30g of nuts/day) was linked with a 17% lower risk of depression, compared with not eating nuts (6).

People who consumed a serving of nuts daily were less likely, at follow-up around five years later, to have developed depression (6).

• A recent study, which tracked more than 180,00 people for almost 12 years, found following the EAT-Lancet Planetary Health Diet, which prioritises plant foods, including nuts every day, may be linked with a reduced risk of depression and anxiety (7).

• A cross-sectional study, of 294 older Australians (≥ 60 years) showed that following a Mediterranean diet (MD) was inversely linked with severity of symptoms of anxiety and stress (8). And it found that certain foods within a MD, including nuts, fruit and legumes, were particularly beneficial. 

Nuts contain fatty acids, fibre, vitamins (like B vitamins), minerals (including zinc and magnesium) and antioxidants, which have essential roles in many aspects of brain and mental health.  

Just 2% of Australians meet the target of a 30g healthy handful of nuts a day.

How to include nuts in your diet:

• Keep a container of nuts in your car, bag or drawer for quick snack
• Blend nuts into smoothies, made of milk, yogurt and fruit
• Add nuts to your morning muesli, yogurt or fruit, or sprinkle over toast toppings
• Add nuts to ‘bowls’ alongside other foods like brown rice, vegetables and lean proteins
• Include nuts in salads, stir-fries, curries, pastas and risottos
• Make a batch of pancakes, using nut meal or flour, and top with fruit and nuts
• Serve nuts with a weekend fruit and cheese platter
• Coat fish or chicken with blitzed nuts before cooking, for a crunchy crust
• Spread nut butters on whole grain bread, stir through porridge, or use as a dip with carrot sticks
• Mix nuts with dried fruit, popcorn, and chocolate chips for movie night snack
• Make ‘nut mince’ (coarsely-ground nuts) to use in spaghetti bolognase or tacos.

The bottom line

A healthy diet and living an active lifestyle can go a long way towards supporting mental wellbeing. In fact, as this new Australian study shows, ‘lifestyle therapy’ can be just as effective as therapy with a psychologist for treating low-grade depression.

Research shows that healthy eating, centred around a variety of nutrient-dense foods, while limiting highly-processed foods rich in saturated fats and added sugars, benefits mood.

Many healthy dietary patterns, including the Mediterranean diet, follow these principles.

Further research is needed on exactly how nuts impact mood. In the meantime, enjoy a variety of nuts to benefit from the diverse range of nutrients they provide – and most importantly, aim for a 30g healthy handful every day!