Food you crave may not improve mood
New research field looks into mental wellness, diet links
As people across the globe grappled with higher levels of stress, depression and anxiety this past year, many turned to their favorite comfort foods: ice cream, pastries, pizza, hamburgers. But studies in recent years suggest that the sugar-laden and highfat foods we often crave when we are stressed or depressed, as comforting as they may seem, are the least likely to benefit our mental health. Instead, whole foods such as vegetables, fruit, fish, eggs, nuts and seeds, beans and legumes and fermented foods like yogurt may be a better bet.
The findings stem from an emerging field of research known as nutritional psychiatry, which looks at the relationship between diet and mental wellness. The idea that eating certain foods could promote brain health, much the way it can promote heart health, might seem like common sense. But historically, nutrition research has focused largely on how the foods we eat affect our physical health, rather than our mental health. For a long time, the potential influence of food on happiness and mental well-being, as one team of researchers recently put it, was “virtually ignored.”
But over the years, a growing body of research has provided intriguing hints about the ways in which foods may affect our moods. A healthy diet promotes a healthy gut, which communicates with the brain through what is known as the gut-brain axis. Microbes in the gut produce neurotransmitters like serotonin and dopamine, which regulate our mood and emotions, and the gut microbiome has been implicated in mental health outcomes. “A growing body of literature shows that the gut microbiome plays a shaping role in a variety of psychiatric disorders, including major depressive disorder,” a team of scientists wrote in the Harvard Review of Psychiatry last year.
Large population studies have found that people who eat a lot of nutrient-dense foods report less depression and greater levels of happiness and mental well-being. One such study, from 2016, that followed 12,400 people for about seven years found that those who increased their consumption of fruits and vegetables during the study period rated themselves substantially higher on questionnaires about their general levels of happiness and life satisfaction.
Large observational studies, however, can show only correlations, not causation, which raises the question: Which comes first? Do anxiety and depression drive people to choose unhealthy foods, or vice versa? Are people who are happy and optimistic more motivated to consume nutritious foods? Or does a healthy diet directly brighten their moods?
The first major trial to shed light on the foodmood connection was published in 2017. A team of researchers wanted to know whether dietary changes would help alleviate depression, so they recruited 67 people who were clinically depressed and split them into groups.
One group went to meetings with a dietitian who taught them to follow a traditional Mediterranean-style diet. The other group, serving as the control, met regularly with a research assistant who provided social support but no dietary advice.
Importantly, both groups were counseled to continue taking any antidepressants or other medications they were prescribed. The goal of the study was not to see if a healthier diet could replace medication, but whether it could provide additional benefits such as exercise, good sleep and other lifestyle behaviors.
After 12 weeks, average depression scores improved in both groups, which might be expected for anyone entering a clinical trial that provided additional support, regardless of which group you were in. But depression scores improved to a far greater extent in the group that followed the healthy diet; roughly a third of those people were no longer classified as depressed, compared with 8% of people in the control group.
The results were striking for a number of reasons. The diet benefited mental health even though the participants did not lose weight. People also saved money by eating the more nutritious foods, demonstrating that a healthy diet can be economical.
“Mental health is complex,” said Dr. Felice Jacka, the lead author of the study. “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.
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 around the world have started encouraging people to adopt lifestyle behaviors — such as exercise, sound sleep, a hearthealthy diet and avoidance of smoking — that may reduce inflammation and have benefits for the brain.