July 21, 2020

Diet Matters: The Food-Mood Connection

by Alison Brown, MSc

“Let thy food be thy medicine and thy medicine be thy food” – Hippocrates, 400 BC

We are generally aware that our diets affect our physical health—after all, “you are what you eat” is a fairly common idiom. However, it’s interesting that 2000+ years passed before the mental health field focused on one of Hippocrates’ great insights: food is medicine for our entire bodies, including the ever-important human brain.

Increasing evidence suggests that what you eat affects your mental health—in more ways than one. While more research needs to be done, several studies have found that eating a diet of whole, unprocessed foods may decrease your risk of depression and suicide, and a diet made up of refined carbohydrates, simple sugars, and processed meats can increase that risk. Diet may offer an additional modifiable tool in an integrative approach to mental health.

Scientists and clinicians have launched the relatively new field of nutritional psychiatry, where research builds a case that focusing on nutrients for the brain and a strategic diet can help to avoid, and even substantially improve, symptoms of depression, anxiety, and other conditions. Reinforcing the concept of mind-body connections, diet affects how your brain and body function to keep your mind healthy. In fact, researchers from the International Society for Nutritional Psychiatry Research claimed in an opinion piece in Lancet Psychiatry that, “the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology.”

Can your diet protect you from depression and suicide?

Mediterranean-style diets, popular in addressing many physical health conditions, have received increasing attention in the nutritional psychiatry field. As mentioned in the Harvard Health Blog, one study that surveyed dietary patterns suggested that the risk of depression is lower in those who follow ‘healthy’ dietary patterns rich in fruits, vegetables and fish, as compared to those consuming a diet rich in processed meat, chocolates, sweetened desserts, fried food, refined cereals and high-fat dairy products.

Furthermore, a meta-analysis of observational research surveying dietary patterns showed that consumption of whole, unprocessed foods was associated with less depression and that Western-style diets increased depression risks. The authors called for further studies and clinical trials to confirm and build upon these findings.

Crucial evidence that changing your diet can support your mental health comes from the SMILES trial, the first intervention study to test the therapeutic effect of food on the development of major depressive episodes. In this controlled study, adults with major depressive disorder reported significant improvements to their mood after following a Mediterranean-style diet for 12 weeks. Participants were asked to add 12 key food groups to their diets: whole grains, vegetables, fruit, legumes, low-fat and unsweetened dairy foods, raw and unsalted nuts, fish, lean red meats, chicken, eggs, and olive oil. In addition, they were asked to reduce their consumption of sweets, refined cereals, fried food, fast food, processed meats, and sugary drinks. In comparison with the control group, improvements were also shown in secondary measures of anxiety. The researchers pointed out that weight loss did not occur, and surmised that diet-induced changes in inflammation, oxidative stress, brain plasticity, or the microbiome might be influential factors.

Another trial recently found that young adults who followed a Mediterranean-style diet for only three weeks reported significant improvement in depressive symptoms and lower levels of anxiety and stress. Those who had a greater intake in fruits and vegetables showed the greatest improvement in depressive symptoms. These authors refer to diet as a modifiable risk factor for depression, meaning that it is something you can changethat reduces risk.

In meta-analysis of clinical trials published just last year, researchers reviewed 16 studies of dietary interventions and their effects on symptoms of depression and anxiety. They found that improving diet by increasing vegetable and fiber intake and decreasing consumption of fast food and sugar shows promise in providing a measurable benefit on depression and, to a lesser extent and more so in women, anxiety, and suggested a need for more research into mechanisms and approaches for dietary interventions.

As for diet’s relationship to suicide (beyond the overlaps with depression), there is some evidence that deficiencies of certain nutrients can influence suicidal behavior, but as of yet, there are no controlled studies assessing dietary interventions. This paper highlights nutritional features associated with depression and suicide and suggests that there are certain nutrients (fatty acids, vitamin C, zinc, magnesium, vitamin B12 and folic acid) that support key cellular functions and may have therapeutic benefits for depression and suicidal behaviors.

Researchers have made a case that a deficiency of Vitamin D can affect suicide risk. One study found that low Vitamin D levels in the blood samples of US service members were associated with an increased risk for suicide. In an investigation of patients with a recent suicide attempt, researchers found that as many as 90% of the patients who had made a suicide attempt had low levels of Vitamin D, and 60% had a clear deficiency as well as elevated markers of inflammation. A recent study of adolescents who had made suicide attempts revealed Vitamin D deficiency, and the authors suggested that those treating adolescents test for Vitamin D levels, as there is some support that treatment may reduce risk.

Fatty acid levels have also received some attention. A study of young Chinese males found that low levels of the omega 3 fatty acid EPA represented a risk factor for suicide attempts. Another study of US service members who died by suicide found that low levels of the omega 3 fatty acid DHA were a strong predictor of suicide, and service men with the lowest levels of DHA were 62% more likely to die by suicide. Dr. Arthur Ryan (who received the first James Kirk Bernard Foundation Award for Excellence in the Biological Exploration of Suicide) presented evidence to a conference from his study which found that individuals who later died by suicide were more likely to have particular combinations of fatty acid profiles.

It’s important to note that these studies cannot confirm that these nutrient deficiencies were caused by diet alone, as metabolism, genetics, and lifestyle may affect any individual’s results. However, sometimes nutritional imbalances can be supplemented or improved with diet, especially critical nutrients such as DHA and EPA that cannot be made by our bodies.

How does your diet regulate mental health?

There appear to be three mechanisms by which diet affects mental wellness. First, your diet provides your brain with nutrients, such as fatty acids and B vitamins, that it needs to grow, function, and generate new connections. Dozens of neurotransmitters affect brain function and mood, and many of the nutrients needed to make them come from your diet. Of note, serotonin is a major regulator of mood, appetite, pain, circadian cycles, and digestion and is so important in mental health that boosting it is the target of anti-depressant medications such as SSRIs. Dopamine regulates pleasure, energy, mood, focus, and sleep and norepinephrine is involved in learning, mood, and forming new brain cells. One lesser-known nutrient for brain growth is brain-derived neurotropic factor, or BDNF, which increases plasticity and primes your brain for learning, good moods, and clear thinking. In fact, increased BDNF levels are associated with effective treatment of clinical depression.

Another means by which diet may affect mental health is by regulating inflammation, a factor of interest in many chronic health conditions, both physical and mental. Inflammation can lead to distress signals in the brain that influence anxiety and depression. Studies have shown that people with major depression have higher levels of some inflammatory markers, including C-reactive protein. Inflammation is also associated with symptoms of suicidal behavior like aggression, hopelessness, and hostility, and of increasing interest in the suicide research field. While the exact mechanisms that link inflammation, and especially neuroinflammation, to suicide are not yet firmly established, there are multiple theories currently being researched.

The third mechanism by which diet may affect mental health is through your gut health. The gastrointestinal tract contains millions of nerve cells that send signals back and forth to the brain, so if your gut is feeling unwell, your cognition and mood can be affected too. Key to gut health and gaining increasing attention in both physical and mental health conditions, the microbiome is important for the production of neurotransmitters such as GABA and serotonin. While we think of serotonin as elemental to thought and emotions, and it’s important (and interesting!) to consider that 90% of serotonin is produced in the gut. Microbiome biodiversity is essential to gut health, and one study found that bacterial richness and diversity (influenced by what you eat!) was associated with decreased severity of depression and anxiety.

What should we be eating?

While consuming a diet including more whole, unprocessed food will likely also benefit your physical health, mental wellness is the target of these suggestions. That said, many chronic diseases raise the risk of suicide and psychological conditions, so what’s good for the body can be good for the mind. Of course, always consult your doctor before deciding which diet is right for you. Additionally, there’s a large body of research and an increasing number of experts on the food-mood connection, so we’ll just be highlighting a few recommendations here. The message is that what you eat can affect how you feel, so you may want to consider diet when thinking about mental health.

Seafood is especially important—according to the CDC, the majority of Americans fall short of the recommended amount of fish in their diet (the USDA recommends two servings of seafood per week). Meat from seafood, including fish, shellfish, and mollusks, is the most concentrated source of the important omega 3s DHA and EPA, and diets high in these omega 3s are associated with reduced  depression, obesity, cancer, and heart disease. This study showed that men with low seafood consumption were much more likely to be severely depressed. Along with the omega 3s, fish is full of other great mood-boosting nutrients like iodine, magnesium, vitamin D, and zinc.

As the Mediterranean-style diet has been the most extensively researched, many nutritional psychiatrists recommend following this or a similar meal plan, as popular press is starting to report. Dr. Lisa Masconi, the director of the Women’s Brain Initiative at the Weill Cornell Medical Center, said in a New York Times article, “imaging studies show that the brains of people who follow a Mediterranean-style diet typically look younger, have larger volumes, and are more metabolically active than people who eat a more typical Western diet.”

While following a traditional diet is a worthy goal, many experts agree that there’s no one food or one diet that is optimal for mental wellness. Instead, focusing on upping your intake of whole, unprocessed fruits, vegetables, fish, and meats and cutting out refined carbohydrates and sugar can make a difference.

Dr. Drew Ramsey, an assistant clinical professor of psychiatry at Columbia University and a leading expert in the nutritional psychiatry field, champions these top mood-boosting foods: wild salmon and shrimp, cherry tomatoes and watermelon, chile peppers, beets, and garlic. Dr. Ramsey has helpful tips and tricks to eating your way towards a healthy and happy brain in his book, The Happiness Diet, and in his TEDx talks, linked here and here

What shouldn’t we be eating?

First and foremost, one of the most important dietary changes to improve your mental health is to significantly reduce sugar consumption. In the past 200 years, we’ve increased our sugar intake by 3,000 percent, resulting in various metabolic changes.

Alarmingly, one investigation shows that countries with the highest intake of sugar per capita are the countries with the highest rates of depression. Sugar is one of the primary driving forces behind the obesity epidemic, and obesity-related diseases, such as diabetes, heart disease, and cancer, have much higher rates of depression. Not surprisingly, studies show that excessive consumption of energy drinks and sugary beverages increases the risk of depression and suicide ideation. Diets high in sugar decrease the amount of circulating BDNF, which is important for your brain to grow and make new connections. High blood sugar can also shrink the hippocampus and amygdala, affecting brain areas essential to regulating mood, memory, anxiety, and cognition.

Modern processed foods also wreak havoc on our mental health. Many nutrients that contribute to a happy brain have been stripped from our food supply, and in some cases, replaced with chemicals that may impair brain functioning. For example, to increase the shelf-life of flour, the naturally-occurring fiber is removed and replaced with chemical bleach. Vegetable oils (corn, soybean, sunflower) are particularly damaging, since they have high levels of pro-inflammatory omega 6 fats, in contrast to anti-inflammatory omega 3 fats found in fish. High levels of omega 6 fats and trans fats have been linked to an increased risk of depression.

Preliminary evidence shows that meat intake may have an association with depression, while one review suggests that grass-fed and grass-finished meats have a healthier nutritional profile of fats and antioxidants. Factory farmed cows, chickens, and even fish are usually fed diets of corn and soybeans which reduces the amount of mood-boosting omega 3s in their meat. The less-than-ideal conditions that the animals live in also increase their stress hormones, which lowers their concentration of B vitamins, zinc, and vitamins A, E and C. Furthermore, higher consumption of meats cured with added nitrates, such as hot dogs and beef jerky, has been associated with episodes of mania.

You Feel What You Eat

Experts in nutritional psychiatry, as well as medical doctors, are increasingly aware that what you eat truly affects how you feel. As Dr. Felice Jacka, president of the International Society for Nutritional Psychiatry Research, said in a twitter video, “we now have a very large and consistent evidence base… to say that the quality of your diet is linked to your risk of depression in particular.” The growing field of nutritional psychiatry reinforces the idea that mental health isn’t all in your head, but rather a part of a complex biological and psychological system that does not function in isolation. 

And while experts agree that there is consistent and compelling evidence that diet affects mental wellbeing, diet is not a silver bullet for treating mental health concerns or preventing suicide.  That said, healthy whole food coupled with professional support, as well as physical activity, carefully delivered  medication (when needed), adequate sleep, exposure to nature, social connectedness and a commitment to a balanced lifestyle can combine to help you feel your best each and every day.

Alison Brown, MSc., is a freelance writer with a background in cognitive science and evolutionary and comparative psychology. 



Reviewed 7/20 by Jian Zhang, MD, DrPH, MSc, Professor in the Department of Biostatistics, Epidemiology, and Environmental Health Sciences of Jiann-Ping Hsu College of Public Health at Georgia Southern University