The Gut-Brain Connection: How Diet and Mental Health Are Linked

The belief that “you are what you eat” is gaining more and more credibility through the emerging field of nutritional psychiatry. Researchers in this field — psychologists, dietitians, nutritionists, and more — are finding compelling evidence that your food choices and diet are directly linked to depression, anxiety, and other mental health issues. If you or someone you know has been struggling with constant feelings of melancholy and/or general sluggishness, an unhealthy diet may be the reason why.

This link between personal nutrition and mental health is commonly referred to as the “food-mood connection.” However, if we dive deeper, it has been found that the way food is processed in our guts — and maintaining a healthy gut bacteria — is what improves our mood and decreases feelings of mental health conditions. This “gut-brain connection” may be a more accurate way to describe the correlation between diet and mental health.

Nutritional psychiatry is a relatively new field of study that is gaining much ground. This is creating an opportunity for those with an Allied Health Studies degree to work with doctors in promoting individual wellness through nutrition, diet, and more — creating a healthy gut-brain connection to alleviate, or prevent, both the physical and mental ailments that can arise if not treated.

What Is the Gut-Brain Connection?

There is a reason why the gut is referred to as the second brain. Our gastrointestinal tract is lined with 100 million nerve cells and releases hormones that influence everything from when we are hungry to feelings of stress, anxiety, and depression. In other words, our guts heavily impact the way our brains think, how we feel, and our general well-being.

It is when the bacteria, or microbiota, in our digestive tract are improperly balanced that we may feel feelings of depression and anxiety, gain weight, and may develop more severe conditions such as diabetes and heart disease. Our microbiome, when disturbed, can affect the human body’s daily operations, as well as leave it susceptible to inflammation and disease. One major disruption to a microbiome is continuing to put foods into our bodies that are not gut-friendly. It is critical that we pay attention to our diet, and eat the foods necessary for our holistic health.

Food for Mental Health: Nutrients That Affect Your Mood Positively

Though there is no perfect mental health diet, there are many foods we can eat that contain the nutrients to make both our digestive tracts and brain happy. Look to implement the following foods into your diet in an effort to improve your mental health:


Omega-3s are not produced by our bodies, so we must get these fatty acids somewhere else. Omega-3’s are said to lower cholesterol and high blood pressure — promoting cardiovascular health. Additionally, Omega-3’s have been shown to improve the diversity of gut bacteria within the microbiome in a study done on middle-aged and elderly women. Omega-3s can calm you down, increase memory and cognitive function, and reduce sugar cravings, and can be found in:

  • Walnuts
  • Flax seeds
  • Salmon
  • Sardines
  • Mackerel

Vitamin D

Lack of vitamin D can cause seasonal affective disorder (SAD), cause inflammatory bowel disease, and may disrupt your microbiome as well. In fact, it is the lack of vitamin D which affects your microbiota that leads to inflammatory bowel disease. Getting vitamin D into your diet can help regulate your microbiome, and reduce gastrointestinal inflammation. Foods that contain vitamin D include:

  • Fortified milk
  • Shiitake mushrooms
  • Orange juice
  • Egg yolks
  • Salmon and tuna


Selenium has antioxidant properties that help prevent inflammation of the gut, may deter symptoms of Alzheimer’s, and boosts your immune system. Additionally, Selenium has been found to optimize gut microbiota for protection against intestinal dysfunctions. Good sources of selenium:

  • Chicken breast
  • Eggs
  • Sardines and tuna
  • Oysters
  • Halibut


Protein works in our guts in the opposite way that the other foods on this list do. Proteins contain nitrogen, which limits the number of bad bacteria in a microbiome. Lean proteins boost our mood by producing an off product, serotonin, which decreases feelings of depression. Good sources of protein include:

  • Eggs, milk, and yogurt
  • Lean beef, turkey, chicken, and fish
  • Broccoli and brussel sprouts
  • Oats and quinoa
  • Nuts


The intake of fiber has been said to reduce the risk of symptoms of depression, improve memory, and overall mood. Fiber also decreases inflammation and oxidative stress in your digestive tract by supporting its microbiota. Foods that are high in fiber include:

  •  Fruits and vegetables
  •  Beans and legumes
  •  Oats
  •  Nuts and seeds
  •  Dark chocolate

Foods That Can Negatively Affect Your Mood

If you are struggling with intestinal discomfort, mental issues, or more severe health conditions it may very well be that you regularly ingest one of the following foods (or beverages) as part of your diet. Consider cutting down on — or cutting out — the following foods to increase your gut health, and overall well-being.


Excessive alcohol consumption may lead to addiction, liver disease, and many more significant health problems. Alcohol also has been shown to alter gut microbiota and throw off the balance of your microbiome. Additionally, alcohol is a depressant, and while it may temporarily put you in a positive mood, alcohol can alter your brain chemistry and leave you with feelings of anxiety and depressive thoughts. Consider limiting your alcohol intake, or cutting alcohol out entirely, by drinking “mocktails,” or non-alcoholic drinks when you are out.

Fish High In Mercury

High levels of mercury can damage the gastrointestinal tract and may cause mood swings, and memory loss. Many fish contain omega-3 fatty acids and other nutrients that positively affect your gut health, so it is important to stay away from the fish that are high in mercury, yet understand which ones to include in your diet. Swordfish, king mackerel, tilefish, marlin, and orange roughy are all fish high in mercury and should be avoided. Salmon, tilapia, sardines, oysters, and shrimp are all kinds of seafood that are said to be low in mercury.

Processed Food

Foods containing artificial ingredients such as preservatives, colorants, flavors, and texturants can alter the mucus barrier and the microbes associated with it. In addition to having artificial sweeteners, trans fats, and being low and several nutrients, processed food can lead to a number of severe health conditions. It is advised to check the food label of what you are buying, cut out the junk food (and/or replace them with healthy alternatives), and consume fresh fish and meat, as well as uncanned fruits and vegetables.

Sugar and Artificial Sweeteners

Added sugars (those not found and fruits) can increase feelings of anxiety and irritability when a sugar crash hits. Additionally, artificial sweeteners such as aspartame can lead to thoughts of depression. Added sugars and artificial sweeteners can be found in processed foods, and may even be included in foods you may consider healthy such as various condiments, bread, and yogurt.

Added sugars and artificial sweeteners are also common in sodas, soft drinks, and juices. Again, it is advised to carefully read a food label for added sugars and/or artificial sweeteners, and replace these with natural sweeteners such as raw honey, stevia, or coconut sugar.

Trans Fats

High trans-fat diets can lead to a disruption of microbiota, causing inflammatory bowel disease, irritable bowel syndrome, and even gastrointestinal tumors. It is best to limit junk and fast food, as well as vegetable shortening and some kinds of margarine, crackers, cookies, frozen pies, and various baked goods. There are variations of these foods that come without trans fats, and it is essential that you read the ingredient list of what you are buying to avoid trans fats.

Diets for Mental Health

Certain diets are inherently good for your mental health simply because they include many of the good foods mentioned above, while cutting out the items that negatively affect your mental health. This may be due to a conscious effort in recognizing gut-healthy nutrients, or a geographical coincidence in the foods available.

The Mediterranean Diet

The Mediterranean diet is adopted from Greece, Crete, Southern France, and Italian regions. In seeing the heart-healthy, weight-managing, and mental health improving effects, many more areas of the globe have come to include the above regions’ food habits into their diets. The Mediterranean diet includes:

  • Fish
  • Nuts
  • Fruits and vegetables
  • Olive Oil
  • Moderate amounts of wine

These are all foods that positively impact your microbiome in addition to having cardiovascular and weight-reducing benefits. One main point of emphasis of the Mediterranean diet is the use of olive oil over many other oils that contain saturated or trans-fats. Oils from avocados, fish, and olive oil contain omega 3 fatty acids and monounsaturated fats which are desirable in a gut-healthy diet to improve mental health. Foods high in refined sugar, hydrogenated oils, and processed foods are all excluded from the Mediterranean diet.


The DASH diet is an acronym that stands for dietary approaches to stop hypertension. While it is a diet to help reduce high blood pressure, it does not go without its benefits to the gastrointestinal tract. The DASH diet encourages fruits and vegetables, fish, poultry and nuts while cutting out sugary drinks, saturated fat, foods high in cholesterol, and red meat. While it may not be designed for gut and mental health, it does contain many of the foods that will balance microbiota, and therefore contribute to the improvement of your mood and mental health. The DASH diet has even been combined with the Mediterranean diet as a way to have the best of both worlds.


Another variation of the DASH diet is the vegetarian DASH diet, and this will still be beneficial to your mental health. The vegetarian diet includes fruits and vegetables — which have been explained above to contain the nutrients necessary for good gut health, to improve mood, and to reduce mental and physical health diseases. Vegetarianism also includes many more gut-healthy foods such as:

  • Nuts and seeds
  • Eggs
  • Grains
  • Honey

Nutrition, gut health, and their connection to mental health is still an emerging science. As the gut-brain connection is becoming more of an accepted notion in healthcare, careers are opening up for those with a degree in Allied Health Studies to work improve patient and community health education, accommodation and food services, and more.