Healthy fats are necessary for healthy brain function, as the brain is made up of a significant amount of fat. "Omega-3 fatty acids, specifically DHA and EPA, support healthy brain function, and low levels can lead to unstable moods, depression, anxiety, poor focus and attention, and more," says Dr. Beurkens. The best food sources of omega-3 fatty acids are fatty cold water fish such as salmon, sardines, or mackerel. "But make sure they are wild caught and not farmed," she says. Other foods that contain omega-3s are grass-fed beef, chia seeds, flaxseeds, and walnuts.

Although most of us think of vitamin D when it comes to bone health and immune system function, it is also critical for mental health. "Vitamin D is needed for neurotransmitter production, and low levels have been linked to depression, anxiety, and a host of other mental health symptoms," says Dr. Beurkens. Foods that provide vitamin D include fatty fish (salmon and tuna), egg yolks, and fortified dairy foods like milk or cheese.

"Vitamin B12 insufficiency isn't likely to be noticeable to most people, but we know this nutrient has an important impact on mental health," Suzanne Dixon, MPH, MS, RDN tells Bustle. "Even in people with seemingly normal blood vitamin B12 concentrations, depression will improve with vitamin B12 supplementation. This observation supports the important role of vitamin B12 in mental health, even in people with seemingly normal levels of the nutrient." Although most adults eat enough vitamin B12-rich foods, vegetarians and vegans are at much higher risk of coming up short.

Although low-carb diets seem to be all the rage lately, this nutrient plays an important role in your mental health. "Low carbohydrates diets tend to hasten depression," Becky Kerkenbush, MS, RD-AP, CSG, CD tells Bustle. "Carbohydrate-rich foods trigger the production of serotonin and tryptophan, two brain chemicals. Serotonin helps regulate sleep and appetite, and mediate mood."

Protein is made up of amino acids, which are the precursors to neurotransmitters like serotonin that your body needs to regulate mood, says Kerkenbush. Tyrosine is the precursor to dopamine, and it is found in dairy products, meats, fish, eggs, nuts, beans, oats, and wheat. Tryptophan is used to make serotonin, melatonin and niacin, and it is found in foods such as nuts, seeds, tofu, cheese, red meat, chicken, turkey, fish, oats, beans, lentils, and eggs.

"Magnesium is necessary for many different processes in the brain and body, and it can be thought of as a calming nutrient," says Dr. Beurkens. "Research has shown that a high percentage of people in the U.S. have magnesium levels that are lower than they should be, which can lead to increased anxiety and panic, restlessness, poor sleep, and irritability." To get more magnesium in your diet, include foods such as almonds, avocados, bananas, spinach, dark chocolate, and pumpkin seeds.

Many people think of zinc as something to take when you have a cold or illness, but zinc is a very important nutrient for mental health. "Poor zinc levels can impact mood and anxiety levels, reduce appetite, and lead to people generally feeling like they have no energy or motivation to do things," says Dr. Beurkens. To include more zinc in your diet, eat foods such as red meat, chicken, oysters and crab, pumpkin seeds, chickpeas, cashews, and spinach.

"Low energy is the most common symptom people associate with reduced iron levels, but low iron is also linked to depression, anxiety, restlessness, sleep problems, and ADHD symptoms," says Dr. Beurkens. "This is especially the case in children, with research showing that many children who exhibit ADHD have suboptimal iron levels." Excellent food sources of iron include meat, fish, dark leafy greens such as spinach, beans, lentils, cashews, and quinoa.

"Folate is another B vitamin linked with mental health," says Dixon. "When someone experiences full-blown folate deficiency, depression is one of the most prominent symptoms." Good sources of folate include pinto beans, adzuki beans, chickpeas, lentils, kidney beans, soy beans, spinach, asparagus, broccoli, Brussels sprouts, avocado, and fortified breakfast cereals.

Since selenium is only found in significant amounts in a few select foods, there's a higher likelihood of people having insufficient intake. "[One study] on 50 healthy British adults found that selenium supplementation improved mood," says Dixon. "When the researchers assessed the magnitude of mood improvement, it was most pronounced in the participants with low dietary selenium intake." If you're looking to add more selenium to your diet, try Brazil nuts. "Brazil nuts are such an incredibly good source of selenium that just a single Brazil nut provides more than 100 percent of the RDA for this nutrient," she says.

If you believe you might have a nutrient deficiency that could be affecting your mental health, see a doctor, who can help test you and give you the most accurate diagnosis.