The results were striking for a number of reasons. The diet benefited mental health even though the participants did not lose any weight. People also saved money by eating the more nutritious foods, demonstrating that a healthy diet can be economical. Before the study, the participants spent on average $138 per week on food. Those who switched to the healthy diet lowered their food costs to $112 per week.
The recommended foods were relatively inexpensive and available at most grocery stores. They included things like canned beans and lentils, canned salmon, tuna and sardines, and frozen and conventional produce, said Felice Jacka, the lead author of the study.
“Mental health is complex,” said Dr. Jacka, the director of the Food & Mood Centre at Deakin University in Australia and the president of the International Society for Nutritional Psychiatry Research. “Eating a salad is not going to cure depression. But there’s a lot you can do to lift your mood and improve your mental health, and it can be as simple as increasing your intake of plants and healthy foods.”
A number of randomized trials have reported similar findings. In one study of 150 adults with depression that was published last year, researchers found that people assigned to follow a Mediterranean diet supplemented with fish oil for three months had greater reductions in symptoms of depression, stress and anxiety after three months compared to a control group.
Still, not every study has had positive results. A large, yearlong trial published in JAMA in 2019, for example, found that a Mediterranean diet reduced anxiety but did not prevent depression in a group of people at high risk. Taking supplements such as vitamin D, selenium and omega-3 fatty acids had no impact on either depression or anxiety.
Most psychiatric professional groups have not adopted dietary recommendations, in part because experts say that more research is needed before they can prescribe a specific diet for mental health. But public health experts in countries around the world have started encouraging people to adopt lifestyle behaviors like exercise, sound sleep, a heart-healthy diet and avoiding smoking that may reduce inflammation and have benefits for the brain. The Royal Australian and New Zealand College of Psychiatrists issued clinical practice guidelines encouraging clinicians to address diet, exercise and smoking before starting patients on medication or psychotherapy.
Individual clinicians, too, are already incorporating nutrition into their work with patients. Dr. Drew Ramsey, a psychiatrist and assistant clinical professor at the Columbia University College of Physicians and Surgeons in New York, begins his sessions with new patients by taking their psychiatric history and then exploring their diet. He asks what they eat, learns their favorite foods, and finds out if foods that he deems important for the gut-brain connection are missing from their diets, such as plants, seafood and fermented foods.