By Sarah Berry – The Sydney Morning Herald
It can take antidepressants up to six weeks to kick in, but findings of one small study indicate improving diet can help to alleviate symptoms of depression in as little as three weeks.
The randomised controlled study, published in the peer-reviewed journal PLOS ONE on Wednesday, followed 76 Australian adults aged between 17 and 35 with moderate-to-severe depression symptoms and a diet high in processed foods and sugar.
The participants were split into two groups; one remained on their regular diet while the second was given meal ideas, a shopping list and tips on how to deal with challenges such as the cost of some fresh foods, or time pressure, and instructed to eat a Mediterranean-style diet and to limit junk foods.
This meant aiming to increase intake of vegetables, fruit, wholegrains, protein (lean meat, poultry, eggs, tofu, legumes), unsweetened dairy, fish, nuts and seeds, olive oil and spices known for their neurological benefits (turmeric and cinnamon). The intervention lasted three weeks.
“Part of the reason we suspect diet is involved in depression symptoms is that depression is associated with chronic inflammation,” explained lead author, Dr Heather Francis from Macquarie University. Previous research has found inflammation reduction takes two-to-four weeks. “Poor diet can increase inflammation … and on the flip side, that a healthy diet can reduce inflammation.”
After the three weeks, those in the intervention group reported significantly reduced symptoms of depression (dropping from clinical depression scores of 21 to an average score of 14.62, which is within the “normal” range) as well as lower levels of stress and anxiety. The control group did not experience any change in their symptoms. At a three-month follow-up, those who had maintained the diet also maintained the elevated mood.
As well as improved self-reported symptoms, the researchers used a spectrophotometer to measure the level of carotenoids (found in fruit and vegetables) in the skin. “The greater change in their scores on the spectrophotometer, which represents more fruit and veg intake, the greater improvement in their depression symptoms,” Francis says.
The results are in line with the SMILES trial from 2017, which followed 166 adults aged 40 on average for 12 weeks and found that those who made positive changes to their diet experienced greater reductions in depression than those in a social support group.
Professor Felice Jacka, lead author of the SMILES trial and director of the Food and Mood Centre at Deakin University said while a single study can’t be given too much weight, the results are “very encouraging”.
“They’re also concordant with our recent meta-analysis that shows that dietary interventions improve depressive symptoms in many different patient populations,” Jacka says.
“It also provides further support for the strong relationship between diet quality and mental health in adolescents that seems to be independent of family functioning, socioeconomic factors, adolescent dieting behaviours, and many other explanatory factors.”
Jacka adds that given three-quarters of mental disorders start before the age of 24, studies such as these show the promise of addressing modifiable risk factors like diet (as well as physical activity) to “help improve resilience and prevent at least some mental health problems” from developing.
“We certainly don’t propose that diet would replace antidepressants or would replace psychological therapy,” Francis explains. “I think the take-home is that diet can improve symptoms of whatever they are doing at baseline. It’s an adjunct.”
Sarah Berry is a lifestyle and health writer at The Sydney Morning Herald and The Age.