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Nutritional Psychiatry: Mood, Anxiety, Depression and How Food Affects Your Brain

Think about it. Your brain is always “on.” It takes care of your thoughts and movements, your breathing and heartbeat, your senses — it works hard 24/7, even while you’re asleep. This means your brain requires a constant supply of fuel. That “fuel” comes from the foods you eat — and what’s in that fuel makes all the difference. Put simply, what you eat directly affects the structure and function of your brain and, ultimately, your mood.

Like an expensive car, your brain functions best when it gets only premium fuel. Eating high-quality foods that contain lots of vitamins, minerals, and antioxidants nourishes the brain and protects it from oxidative stress — the “waste” (free radicals) produced when the body uses oxygen, which can damage cells.

Feeling depressed or anxious? Can't focus? Sensitive to stress? Then read the following carefully. There is bi-directional communication between the gut and the brain. In fact, reputable scientists such as Dr. Michael Gershon, professor of Pathology and Cell Biology and father of neurogastroenterology, adamantly believe that we have a second brain in our gut.

The human gut is lined with more than 100 million nerve cells, more than in the spinal cord or in the peripheral nervous system. Yes, we have brain cells in our large intestines! This explains why antibiotics which disturb the gut microbial ecosystem might cause neuropsychiatric effects, interact with psychotropic medications, and/or influence our mood. This also explains why mood disorders are so prevalent in patients with irritable bowel syndrome.

Exposure and consumption of good bacteria are necessary for a balanced brain. Studies found that in germ-free sterile mice, there is an imbalance of depression-related brain chemicals in areas important for emotions and mood. Also, there are significantly more pro-inflammatory cytokines in depressed people compared to non-depressed ones. This effect on the inflammatory system may stem from interactions with a dysfunctional gut microbiome in depressed individuals.

Also, stress makes us more likely to develop mood disorders. And stress makes the gut more permeable to bacteria. Reciprocally, depression causes dysbiosis—an imbalance of good to bad gut bacteria. In sum, depression is maybe caused by dysfunctional gut-brain-immune system interactions.

Unfortunately, just like an expensive car, your brain can be damaged if you ingest anything other than premium fuel. If substances from “low-premium” fuel (such as what you get from processed or refined foods) get to the brain, it has little ability to get rid of them. Diets high in refined sugars, for example, are harmful to the brain. In addition to worsening your body’s regulation of insulin, they also promote inflammation and oxidative stress. Note: When we speak of refined sugars, this isn’t just candy, ice cream and baked goods. This is processed grain, dairy and sugar products. Multiple studies have found a correlation between a diet high in refined sugars and impaired brain function — and even a worsening of symptoms of mood disorders, such as anxiety and depression.

It makes sense. If your brain is deprived of good-quality nutrition, or if free radicals or damaging inflammatory cells are circulating within the brain’s enclosed space, further contributing to brain tissue injury, consequences are to be expected.

What’s interesting is that for many years, the medical field did not fully acknowledge the connection between mood and food. Today, fortunately, the burgeoning field of nutritional psychiatry is finding there are many consequences and correlations between not only what you eat, how you feel, and how you ultimately behave, but also the kinds of bacteria that live in your gut.

How does the foods you eat affect how you feel?

Serotonin is a neurotransmitter that helps regulate sleep and appetite, mediate moods, and inhibit pain. Since about 95% of your serotonin is produced in your gastrointestinal tract, and your gastrointestinal tract is lined with a hundred million nerve cells, or neurons, it makes sense that the inner workings of your digestive system don’t just help you digest food, but also guide your emotions. What’s more, the function of these neurons — and the production of neurotransmitters like serotonin — is highly influenced by the billions of “good” bacteria that make up your intestinal microbiome. These bacteria play an essential role in your health. They protect the lining of your intestines and ensure they provide a strong barrier against toxins and “bad” bacteria; they limit inflammation; they improve how well you absorb nutrients from your food; and they activate neural pathways that travel directly between the gut and the brain.

Scientists have found that gut bacteria produce many other neurotransmitters such as dopamine, norepinephrine, acetylcholine and GABA, which are critical for mood, anxiety, concentration, reward and motivation.

The gut microbiome can cause changes in how our brains react. Studies have shown that our microbiome does play a role in mental health and neurological conditions such as autism, and epilepsy by interacting with our nervous system and even releasing molecules that can make their way to the brain. Scientists have found that gut bacteria produce many other neurotransmitters such as dopamine, norepinephrine, acetylcholine and GABA, which are critical for mood, anxiety, concentration, reward and motivation.

Studies have compared “traditional” diets, like the Mediterranean diet and the traditional Japanese diet, to a typical “Western” diet and have shown that the risk of depression is 25% to 35% lower in those who eat a traditional diet. Scientists account for this difference

because these traditional diets tend to be high in vegetables, fruits, unprocessed grains, and fish and seafood, and to contain only modest amounts of lean meats and dairy. They are also void of processed and refined foods and sugars, which are staples of the “Western” dietary pattern. In addition, many of these unprocessed foods are fermented, and therefore act as natural probiotics. This may sound implausible to you, but the notion that good bacteria

not only influence what your gut digests and absorbs, but that they also affect the degree of inflammation throughout your body, as well as your mood and energy level, is gaining traction among researchers.

Nutritional psychiatry: What does it mean for you?

Start paying attention to how eating different foods makes you feel — not just in the moment, but the next day. Try eating a “clean” diet for two to three weeks — that means cutting out all processed foods and sugar. See how you feel. Then slowly introduce foods back into your diet, one by one, and see how you feel. When some people “go clean,” they cannot believe how much better they feel both physically and emotionally, and how much worse they then feel when they reintroduce the foods that are known to enhance inflammation.

The 7 Worst Foods for Your Brain

1. Sugary Drinks

2. Refined Carbohydrates

3. Foods high in trans fats (fast and processed food).

4. All highly processed foods

5. Aspartame

6. Alcohol

7. Fish high in mercury.

If you are someone who has taken several doses, or repetitive doses of antibiotics over the years, your digestion isn't healthy, and it will take time and attention to bring it back into balance. Antibiotics not only destroys all bad bacteria, some of which we need; it also destroys good bacteria that doesn't automatically return. If you or a family member must take an antibiotic, make sure you take a quality, appropriate dose of probiotic within two hours of taking the antibiotic. Do not take them together.

What has become evident is that patients with psychiatric disorders have different populations of gut microbes compared to microbes in healthy individuals. Also, stress and stress hormones such as cortisol can have a negative impact on our microbiome. And all of these factors interact in complex ways with the immune system.

As the knowledge of the exact nature of brain-gut interactions unfolds in relation to psychiatric disorders, treatments may include a probiotic instead of Prozac! What all of the above findings strongly suggest is this: Take care of your gut bacteria for good quality of life, better mental health, and a sharper brain.


(1) Sternbach H, State R. Antibiotics: neuropsychiatric effects and psychotropic interactions. (1997). Harv Rev Psychiatry; 5: 214–226.

(2) Harvard Medical School, Harvard Health Publishing, November 2015

(3) Psychology Today, Marwa Azab Ph.D, August, 2019

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