Jodi Corbitt had been battling depression for decades and by 2010 had resigned herself to taking antidepressant medication for the rest of her life. Then she decided to start a dietary experiment.
To lose weight, the 47-year-old Catonsville, Md., mother stopped eating gluten, a protein found in wheat and related grains. Within a month she had shed several pounds — and her lifelong depression.
“It was like a veil lifted and I could see life more clearly,” she recalled. “It changed everything.”
Corbitt had stumbled into an area that scientists have recently begun to investigate: whether food can have as powerful an impact on the mind as it does on the body.
Research exploring the link between diet and mental health “is a very new field; the first papers only came out a few years ago,” said Michael Berk, a professor of psychiatry at the Deakin University School of Medicine in Australia. “But the results are unusually consistent, and they show a link between diet quality and mental health.”
“Diet quality” refers to the kinds of foods that people eat, how often they eat them and how much of them they eat. In several studies, including a 2011 analysis of more than 5,000 Norwegians, Berk and his collaborators have found lower rates of depression, anxiety and bipolar disorder among those who consumed a traditional diet of meat and vegetables than among people who followed a modern Western diet heavy with processed and fast foods or even a health-food diet of tofu and salads.
“Traditional diets — the kinds of foods your grandmother would have recognized — have been associated with a lower risk of mental health issues,” Berk said. Interestingly, that traditional diet may vary widely across cultures, including wheat for some people but not for others; the common element seems to be whole, unprocessed, nutrient-dense foods.
“There’s lots of hype about the Mediterranean diet (fruits, vegetables, whole grains, olive oil, nuts, fish) but the traditional Norwegian diet (fish, shellfish, game, root vegetables, dairy products, whole-wheat bread) and the traditional Japanese diet (fish, tofu, rice) appear to be just as protective” of mental health, he said.
It’s unclear how diet relates to mental health, said Rif El-Mallakh, a professor of psychiatry at the University of Louisville School of Medicine. “There seems to be a clear link, but it’s an association — it doesn’t tell you cause and effect,” he said. “We don’t know which is the chicken and which is the egg.”
It could be, he said, that mood disorders change how and what people choose to eat.
But an alternate theory is that the relationship works the other way: Certain foods, or their absence, may contribute to poor mental health. For example, studies in people and rats have linked zinc deficiency to depression. Also, illnesses that cause deficiencies — including celiac disease, an autoimmune disease in which the body reacts to gluten — have shown associations with mood disorders.
“There’s a two-way street between what’s going on in the gut and what’s going on in the brain,” said Linda Lee, director of the Johns Hopkins Integrative Medicine and Digestive Center — and recent research points to bacteria as possible middlemen in this back-and-forth. Gut bacteria are known to make most of the body’s serotonin, one of several chemicals that regulate mood, and the bugs may even have a hand in shaping behavior. A 2011 study in mice for example, showed that swapping the gut bacteria of two strains of mice — one known for its daring behavior, the other for its fearfulness and shyness — could make the timid mice more willing to explore and the bold mice more anxious and hesitant.