Foods can improve mood in some people, but can diet really affect depression? On the positive side, chocolate does seem to have a beneficial effect on mood, especially for women-but don’t overdo the chocolate and its calories. Caffeine also improves mood in some people. Some evidence suggests that tryptophan in the diet-from foods such as turkey or oatmeal-may increase levels of serotonin in the brain.
On the other hand, a diet high in junk food is associated with depression-and obesity-though it’s hard to know which comes first. When people are depressed, they often spend more time sitting in front of the TV and eating fatty, salty, sugary foods, instead of getting out to exercise and improving their diet. Several observational studies over the years have suggested that diet can indeed influence the risk for depression, independent of education, socioeconomic status, and other potential confounding factors.
Last year, the first controlled clinical trial on the link between diet quality and depression gave stronger support to this connection. Dubbed SMILES (Supporting the Modification of Lifestyle In Lowered Emotional States) and published in BMC Medicine, this Australian study enrolled people who had moderate to severe depression and poor diets at the start and randomized them into two groups:
- A diet group received ongoing personalized nutrition counseling on how to follow a modified Mediterranean diet. Participants were encouraged to eat whole grains, vegetables, fruits, legumes, low-fat and unsweetened dairy foods, nuts, fish, lean meats, and olive oil; reduce refined grains, sweets, fried or fast foods, processed meats, and sugary drinks; and consume moderate alcohol.
- A social support (control) group discussed neutral topics such as sports and music with a trained “befriender” or engaged in board games and other activities, over the same time frame.
After 12 weeks, the diet group had a greater reduction in depression and anxiety symptoms than the social support group, even with variables such as weight loss taken into account. Moreover, more participants in the diet group (32 percent versus 8 percent) achieved depression remission. These encouraging findings-which come out of the new field of nutritional psychiatry-provide preliminary evidence for dietary improvements as an “efficacious treatment strategy” for depression, the authors concluded.
Diet may influence depressive illness by affecting inflammatory and oxidative stress pathways, brain plasticity, and possibly the gut microbiota, according to the authors. “Moreover, behavioral changes associated with food (cooking/shopping/meal patterns) are an expected outcome of a nutrition intervention, and these changes in activity may also have a therapeutic benefit,” they wrote. As a bonus, improving diet may improve physical illnesses that often occur with depression.