Research backs up idea that better diet may help to beat depression

by Jennifer Bowden / 30 March, 2017

Photo/Getty Images

Bland, generic “eat a healthy diet” advice has long been dished out to people suffering from depression. But the marvellously named “Smiles Trial” has produced the first evidence that a Mediterranean-style diet may help to banish the blues.

According to the 2014/15 New Zealand Health Survey, more than a sixth of adults have been diagnosed with a common mental condition – depression, bipolar disorder and/or anxiety disorder. That’s a substantial increase on the one in eight adults who reported a mood or anxiety disorder in the 2006/07 survey. So, why is the incidence increasing?

Evidence collected in observational research from different age groups in many countries has long suggested that diet quality may be linked to depression. There are myriad definitions of a healthy diet, but those associated with a reduced risk of depression all include a high proportion of plant-derived foods, such as vegetables, fruits, legumes and whole grains, and lean protein content, including fish. A 2013 meta-analysis, for example, combined 22 studies and found a Mediterranean diet was associated with a 32% reduced risk of developing depression.

Of course, an “association” is only an observed connection: it doesn’t prove the diet caused the improvement in mental health. Randomised controlled trials are needed to test causal relationships. The Smiles (Supporting the Modification of lifestyle In Lowered Emotional States) test was a 12-week, randomised controlled trial conducted in Australia. Researchers enrolled 67 adults, of whom 69% were taking antidepressants and 45% receiving psychological therapy. Of the 67 participants, 31 were assigned to the diet support group and 25 to the control condition known as a social support group. (Data from the remaining 11 was excluded from analysis.)

The diet support group were given personalised dietary advice and nutritional counselling from a clinical dietitian to help them stick with a modified version of the Mediterranean diet (see box). The social support group had the same visit schedule and length but received no dietary advice.

After 12 weeks, the diet support group had improved their diet: they ate 1.2 more daily servings of wholegrain cereals; 0.46 more servings of fruit; 0.52 more servings of dairy; 0.42 more servings of olive oil; 1.4 more servings a week of pulses; and 1.12 more servings a week of fish. They also reduced their intake of unhealthy “extra” foods by a whopping 21.76 servings a week. No notable changes occurred in the control group’s consumption of these food groups.

The effect on mental health was pronounced: 32.3% of the diet support group showed remission of depressive symptoms, compared with just 8% of the control group.

The researchers concluded that improving diet may be an easy and effective option for major depressive episodes, alongside standard pharmacological and psychological treatments.

What’s more, the modified Mediterranean diet was a budget-friendly option: it cost just A$112 a week, less than the average A$138 a week the participants had been spending on food and beverages.

More clinical trials are needed to confirm these findings, but if you’re dealing with depression, there is nothing to lose, and potentially the joy of life to be regained, by adopting a Mediterranean-style diet.

Happy meals

The Smiles Trial diet support group were told to eat the ­following servings:

  • Whole grains, 5-8 a day
  • Vegetables, 6 a day
  • Fruit, 3 a day
  • Legumes, 3-4 a week
  • Low-fat, unsweetened dairy, 2-3 a day
  • Raw and unsalted nuts, 1 a day
  • Fish, 2 a week at least
  • Lean red meats, 3-4 a week
  • Chicken, 2-3 a week
  • Eggs, 6 a week maximum
  • Olive oil, 3 tbsp a day

Extras such as sweets, refined cereals, fried food, fast food, ­processed meats and sugary drinks were limited to 3 a week. Two standard drinks of red or white wine a day were allowed, but all other alcohol was ­considered an extra.

This article was first published in the April 8, 2017 issue of the New Zealand Listener. Follow the Listener on Twitter, Facebook and sign up to the weekly newsletter.


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