• Food can influence chemicals in your brain; in fact, an estimated 95 percent of your serotonin is produced in your gastrointestinal tract.
• Some foods that can help relieve depression symptoms are fish like salmon and anchovies, turkey, cacao, probiotic foods, and fruits and vegetables. 
• Be sure to avoid processed foods or foods high in sugar, as these can cause inflammation and irritability.
• This story is part of Insider’s guide to Depression. 

Depression is usually treated with therapy or medication, but what you eat can also play a role in your mental health. Though more research is needed, some studies show that certain diets may prevent or reduce the severity of depression.

“The right kind of diet may give the brain more of what it needs to avoid depression, or even to treat it once it’s begun,” says Lisa Mosconi, PhD, Director of the Women’s Brain Initiative at Weil Cornell Medical College and author of The XX Brain.

Here’s what experts know about which foods are helpful and which may be harmful for depression. 

The connection between diet and depression

There are many different factors that contribute to depression. Some are out of your control, like genetics or a traumatic life event. But the foods you choose to eat can also play a role. 

Because food can influence certain chemicals in the brain, like serotonin, that help regulate mood. An estimated 95 percent of your serotonin is produced in your gastrointestinal tract. So, it makes sense that what you eat may influence mood.

For example, a 2014 review found that people who followed a Mediterranean diet of fruits, vegetables, fish, and whole grains were 16 percent less likely to experience depression compared to people who followed a typical high-carbohydrate Western diet. 

The Mediterranean diet is thought to be effective against battling depression because it's rich in anti-inflammatory foods like leafy greens and fish, while also cutting down on processed foods that can cause inflammation.

Inflammation is known to contribute to a number of diseases including heart disease, Alzheimer's, and certain cancers like liver and cervix. How strongly inflammation contributes to depression is still unclear. But some studies, like the 2014 review, suggest that keeping inflammation at bay through your diet may help prevent depression.

Foods that can help relieve depression

Your brain needs certain nutrients to produce the chemicals used to regulate your emotions, Mosconi says. Some of these helpful foods and nutrients include:

Small, oily fish (salmon, mackerel, anchovies, sardines, herring): These fish are all high in omega-3 fatty acids, a type of fat that has been shown to reduce the severity of depression symptoms by reducing inflammation.

Turkey: Eating turkey provides you with tryptophan, an amino acid that your body uses to produce serotonin.

Cacao: Certain compounds like flavanols and procyanidins, which are present in cacao in dark chocolate, can reduce inflammation in the body.

Probiotic foods: More research is needed to understand exactly how probiotics work and the different ailments they can treat. But what researchers have found is that probiotic-containing foods like yogurt and sauerkraut contain live bacteria that are helpful for balancing out your gut bacteria. That's important when it comes to depression because these bacteria can produce chemicals that regulate your mood, such as serotonin and gamma-Aminobutyric acid (GABA).

Fruits and vegetables: Eating foods like fruits and vegetables can be one of the most powerful ways to fight inflammation because they contain antioxidants, compounds that help protect your cells from the damage caused by inflammation. Here are some foods rich in antioxidants:

• Walnuts and pecans
• Berries
• Pomegranates
• Dark chocolate
• Coffee and green tea
• Herbs like mint and oregano 

Foods to avoid

Many of the foods that are bad for your physical health can also affect your mental health. Below are some foods to avoid to help prevent and fight depression.

Processed foods: "Processed or deep-fried foods often contain trans fats and a variety of chemicals that can promote inflammation," Mosconi says, adding that inflammation is a possible cause of depression, as well as other brain illnesses like dementia. 

Some examples of processed foods are:

• Meats, including bacon and sausage
• Pre-packaged baked goods like cookies
• Instant noodle meals
• White bread

Sugar: Eating a diet that includes a lot of sugary foods and drinks has been linked to higher rates of depression. This may be because sugar increases inflammation and can destabilize your blood sugar. When your blood sugar drops too low, you can have symptoms like nervousness and inability to concentrate, while high blood sugar can cause fatigue.

Getting treatment for depression often involves therapy or medication, but watching what you eat can also play an important role in your mood. Eating a Mediterranean style diet and avoiding processed foods may help you battle depression.

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