HOW DIET AND GUT BACTERIA MAY HELP BEAT LOW MOOD
RESEARCH increasingly suggests diet can also play an important role in tackling mental health disorders such as depression, and may be even more effective than medication or psychotherapy.
One of the pioneers in this area is Professor Felice Jacka, director of the Food and Mood Centre at Deakin University in Australia. Her ground-breaking SMILES study, published in 2017, compared dietary changes with social support (involving regular meetings with therapists) in patients with depression.
After three months, 38 per cent of those on a healthy diet no longer experienced depression, compared to 8 per cent in the social support group.
The diet group followed a plan similar to the Mediterranean diet — with 5-8 servings of wholegrains; six servings of veg, three of fruit; 3tbsp olive oil a day; 3-4 servings of legumes (such as beans); one serving of raw and unsalted nuts; and at least two portions of fish per week. It also involved reducing intake of ‘extras’, such as sweets, refined cereals and processed meats.
‘We could not believe what a huge impact these dietary changes had,’ Professor Jacka told Good Health.
In 2019, the Professor published a review of 16 studies, involving more than 45,000 people, which concluded that dietary interventions (e.g. switching processed foods for wholefoods) offer ‘profound benefit’ in reducing depressive symptoms.
What’s more, the diet interventions seem to work in as little as three weeks, while medication can take up to eight weeks to work, if at all.
So how can food have such a major impact? A key mechanism, it seems, involves our microbiota — the micro-organisms that live in our gut.
It appears that the microbiota struggle to function on a junk diet, but fed a high-fibre diet rich in plants, they make compounds that support the immune system, calm the stress response, and affect the action of brain chemicals that control mood.
Professor Jacka says the microbiota break down plant fibres and compounds and, in so doing, release thousands of beneficial molecules. For instance, a protein called tryptophan is essential for the creation of the ‘happy hormone’ serotonin – but tryptophan cannot be extracted from food without the microbiota.
Other researchers have focused on specific foods (e.g. oily fish) or tried to identify specific populations of microbiota with the aim of bolstering them with supplements.
Professor Ted Dinan, a psychiatrist at the University of Cork in Ireland, coined the term ‘psychobiotics’ ten years ago to describe a bacterium that, when ingested, has a positive effect on mental health.
He says good nutrition is ‘essential in the management of psychiatric disorders. Medication and social intervention have a place, but all patients with depression have a better outcome if they are given advice about nutrition’.
His research is focused on the potential use of a probiotic as an antidepressant. ‘Most probiotics are
not psychobiotics, but we have seen that one particular probiotic strain, Bifidobacterium longum, is,’ he says.
A new study, published in Nature Translational Psychiatry, found that taking a multi-strain probiotic for a month reduced symptoms in people with ‘depressive episodes’ more effectively than a placebo.
However, Professor Dinan warns against relying on readily available probiotic supplements, saying the market is ‘unregulated and most probiotics do nothing to improve mood’.
Professor Jacka is now running large trials to provide dietary guidance for clinical practice. ‘For now, we don’t advocate that diet replace medication or psychological therapy, but suggest that it be a focus alongside other treatments,’ she says.
Professors Jacka and Dinan agree on the mental health benefits of a traditional, preindustrial diet rich in a variety of plant foods, fish, unrefined grains and fermented foods, with only a little meat and little or no alcohol.