Diet and Depression

How nutrition could be impacting your mood

By Rachael Hartley, RD, CDE, CLT

Everyone knows diet affects physical health, but did you know diet affects mental health too? Depression is sometimes thought to be rooted in emotions, however there is also a biochemical basis, and nutrition plays a critical role in brain health. Initially, it may be surprising to learn that diet affects emotions, but consider the fact that the brain is an organ, just like the heart or digestive tract, and just like any other organ, it needs a well-nourished body to function at its best. 

The brain is a highly metabolically active organ, meaning it uses large amounts of energy and micronutrients (vitamins and minerals) to function. Approximately 20 percent of the energy used by the human body is consumed by the brain, mainly in the form of glucose (carbohydrate). Fat also plays a role, as 60 percent of the brain’s structure comes from fat. Vitamins, minerals and protein play a role in the creation of neurotransmitters which are brain chemicals including serotonin, norepinephrine and dopamine, which regulate mood. 

Diet also affects mood by impacting digestive health. There are so many connections between the gut and brain that many scientists refer to the gut as “the second brain.” The gut is home to the enteric nervous system, which contains more neurons, or “brain cells,” than the spinal cord or peripheral nervous system. If you’ve ever had “butterflies in the stomach” or a “gut feeling,” then you’ve experienced this connection. In fact, the ancient Greeks thought that the stomach or gut was responsible for all thinking. 

Research on digestion and depression is in its infancy, but the field is growing and there’s already been interesting insight. Did you know 95 percent of the body’s serotonin, often called the happy hormone, is located in the gut? Research has also shown correlations between specific strains of gut bacteria and depression. Furthermore, researchers have been able to trigger or calm anxious behaviors in rats simply by changing their gut bacteria, leading to the hypothesis that probiotics could become a type of treatment for mental health disorders.

It’s important to note that nutrition is not a substitute for talk therapy or prescribed medication. However, building healthy eating habits and treating any underlying nutrient deficiencies can be a helpful adjunct treatment for depression, and at the very least, eating a little healthier may give you a boost of energy to get past a slump. 


Important Nutrients for 

Mental Health

Omega-3 fatty acids

Omega-3 fatty acids play a critical role in the development and function of the brain. The fatty acids are a critical part of its cellular structure, making its membrane more fluid and better able to transfer information between brain cells. Omega-3 fatty acids also decrease inflammation in the brain, and research has shown inflammatory markers to be associated with depression. 

A few studies have shown benefit in using fish oil supplements to reduce symptoms of depression, however this should be discussed with a doctor first. Supplements can interfere with certain medications and are not safe for everyone.  However, Omega-3 fatty acids are found in many foods, including walnuts, chia and flax seeds, winter squash and green leafy vegetables, but the type of omega-3 fatty acid that is most beneficial is found in animal foods, mainly fatty fish like salmon, tuna, mackerel and herring. 

To get more fatty fish, roast more salmon than you need for a meal and use the leftovers to top a lunch salad, in a morning omelet or stirred into soup. 


Vitamin D

Low vitamin D has been linked to many chronic conditions, including certain types of cancer, diabetes, cardiovascular disease, as well as Parkinson’s, dementia, depression and other conditions affecting the brain. Vitamin D is activated by sunlight exposure, and many researchers believe vitamin D deficiency plays a role in seasonal affective disorder. Although research is not conclusive that a vitamin D deficiency can cause depression, small studies have shown that vitamin D supplementation in people who are vitamin D deficient markedly improved symptoms of depression. 

Because vitamin D is activated by sunlight, most doctors recommend aiming for 15 minutes per day in the sun, without sunscreen. People with darker skin may need more time, while those with fairer skin that’s prone to burn may need less, so talk to your doctor for more specific recommendations. While you’re there, speak with your doctor about testing vitamin D levels. And make sure you have vitamin D levels checked before starting supplementation. 

There are few substantial food sources of vitamin D with the exception of fatty fish. It can also be found in smaller amounts in fortified dairy, eggs, cheese and mushrooms. 



Magnesium is a mineral that plays many roles in the body, including muscle and nerve function, blood pressure regulation, bone structure and energy production. Government surveys report that up to 70 percent of the population is deficient or suboptimal in magnesium. Signs and symptoms of magnesium deficiency include many of the symptoms of depression including insomnia, fatigue, poor appetite and irritability. There have been a few interesting case studies in which depression was successfully treated with magnesium supplementation. 

Green leafy vegetables are one of the best sources of magnesium. Add sautéed kale to a tomato sauce for spaghetti or swap spinach for lettuce leaves in a salad. Snack on nuts and seeds, especially pumpkin seeds and cashews, which are especially rich in magnesium. Beans are another good source. Try a couple vegetarian meals each week using beans as a source of protein like black bean soup, bean burritos, or red beans and rice.  



As previously mentioned, gut health is important for mental health. Part of gut health is maintaining diverse and plentiful microflora, or good bacteria, in the gut. To promote the growth of healthy bacteria, eat plenty of fiber rich whole foods, like beans, vegetables and whole grains. It’s also helpful to consume sources of healthy bacteria in the form of fermented foods. Many doctors and dietitians recommend fermented foods over probiotic supplements, as food contains a wider variety of strains and is better able to survive the acidic stomach environment. 

For probiotics, look beyond yogurt. Try kefir, a yogurt-like beverage that contains a wider variety of bacteria strains. It’s delicious blended into a smoothie. Miso paste is another fermented food, popular in Japanese cuisine. Blend equal parts butter and miso paste to make a topping for baked potatoes or roasted vegetables. Many grocery stores in Columbia sell a variety of fermented vegetable relishes, pickles and sauerkraut, which can be used in salads or grain bowls, sandwiches or served as a side dish. There are many online tutorials to make your own fermented vegetables, a tasty way to preserve extra produce from the garden or farmers market. 



Iron plays an important role in cognitive health throughout life. Inadequate iron during pregnancy has been linked to lower IQ, and children with lower iron stores score lower on cognitive testing. Iron is needed to create the mood-regulating brain chemicals serotonin and dopamine, and to produce energy in the brain. A common symptom of iron deficiency, which is especially prevalent among women, is depression. 

Although iron is found in many vegetarian foods, including beans, dried fruit and dark green leafy vegetables, it is difficult for the body to absorb iron when it comes from these plant-based sources. The body is better at absorbing iron from animal foods, and shellfish, red meat and liver are especially plentiful in iron stores. To enhance absorption, pair iron-rich foods with foods high in vitamin C, such as citrus, tomatoes and peppers. For example, try strips of beef sautéed with peppers and onions; spritz grilled shrimp with lemon or lime juice; and stew beans with tomatoes.


Vitamin B-12

Low levels of vitamin B-12 have been linked to cognitive decline, irritability and symptoms of depression. Vitamin B-12 and other B vitamins are needed to produce chemicals in the brain that regulate mood. It also supports myelin, a fatty substance that speeds communication between brain cells. 

Vitamin B-12 is only found in animal foods, so vegans and vegetarians may be at risk for deficiency and should speak to their doctor about supplementation. Also, a healthy stomach environment is needed to absorb vitamin B-12, so people with acid reflux or other digestive disorders may be at risk for deficiency and should have levels tested. 

Food sources of vitamin B-12 include seafood, beef, cheese and dairy. 


Suffering from depression?

Symptoms of depression include the following:

•    Difficulty concentrating

•    Fatigue

•    Irritability

•    Insomnia or excessive sleeping

•    Headaches, pains or digestive problems that do not ease with treatment

•    Feelings of guilt, worthlessness or 


•    Loss of interest in activities you once found pleasurable 

•    Loss of appetite or overeating

•    Thoughts of suicide

If you suspect you are suffering from depression, speak to your general practitioner. They can recommend a therapist and discuss medical treatment, as well as test for nutrient deficiencies. 

People most at risk for nutrient deficiencies and depression related to the deficiencies are those who do not obtain a wide variety of nutrients from their diet. This includes people who suffer from an eating disorder or have in the past, picky eaters and restrictive dieters. Those who suffer from digestive disorders that impair absorption, such as gastric reflux, irritable bowel syndrome, celiac disease and inflammatory bowel disease, may also be at risk. 


Nutrition Helps Combat Depression

The good news is there are no negative side effects to eating a healthy diet, so whether you’re struggling with depression or looking for a mood boost, here are some nutrition tips to help you feel more energetic, alert and positive:

•    Eat three balanced meals a day –– and a couple of snacks if hungry between meals. Low blood sugar and hunger can trigger fatigue and irritability. 

•    While there’s no need to eliminate all high sugar foods, which can boost mood because they are pleasurable to eat, excessive intake of added sugar has been linked to depression. Look for lower sugar snacks and beverages while saving room for the occasional sweet.  

•    Eat more fruits and vegetables, which are packed with nutrients that help your brain function at its best. Aim to cover half of your plate with fruits and vegetables. 

•    Eat fatty fish, like salmon, tuna, mackerel and herring, about twice to three times a week. Fatty fish are rich in brain boosting nutrients, like vitamin D, omega-3 fats and vitamin B-12. But beware of eating too much fish high in mercury, like tuna, so try to alternate.

•    Cook at home more frequently. Processed convenience food and fast food lacks the nutrients your brain needs to function well and can cause fatigue and blood sugar spikes that affect mood. 

•    Be wary of low carbohydrate diets. Fiber-rich sources of carbohydrates maintain healthy blood sugar levels, and low blood sugar can contribute to irritability and moodiness. Be sure to include a healthy source of carbohydrate, preferably a whole grain, bean, fruit or starchy vegetable, at each meal. 

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