The Brain-Gut Connection: Your Stress & Anxiety could be Causing Your IBS Symptoms...and Your Diet could be Causing Your Stress & Anxiety! ↔️

The relationship between the brain and the gut is an emerging area of research, highlighting the importance of diet in mental and digestive health.

It sounds a little farfetched, right? But, have you ever felt that gut-punch feeling when someone says something incredibly hurtful; or have you felt "butterflies" in your stomach when you're nervous or excited about something?

Those are examples when you can actually PHYSICALLY FEEL the brain-gut connection!

The gut and brain communicate bidirectionally through the gut-brain axis ↔️, involving the nervous system, immune system, and gut microbiota.

When dietary choices negatively impact gut health, this can lead to increased anxiety, depression, and irritable bowel syndrome (IBS). Here, we explore the science behind this connection and the role of nutrition in mental and digestive well-being.

The Gut-Brain Axis: A Complex Communication Network

The gut-brain axis is a communication system between the gastrointestinal (GI) tract and the central nervous system (CNS). It involves:

• The vagus nerve, which transmits signals between the brain and gut.

• Neurotransmitters, including serotonin and dopamine, which influence mood.

• The immune system, which responds to gut inflammation.

• Gut microbiota, the trillions of microbes that regulate digestion and brain function.

  
  

The gut produces approximately 90% of the body's serotonin, a neurotransmitter crucial for mood regulation (Carabotti et al., 2015). Disruptions in gut health can therefore significantly impact mental well-being.

How Poor Diet Fuels Anxiety and Depression

1. Inflammation and Mental Health

A diet high in ultra-processed foods, refined sugars, and unhealthy fats contributes to chronic inflammation, which has been linked to mood disorders.

Inflammation affects the production of key neurotransmitters such as serotonin and dopamine, increasing the risk of anxiety and depression (Miller & Raison, 2016).

Foods that contribute to inflammation include:

• Refined sugars 

• Trans fats 

• Artificial additives 

  
  

A nutrient-deficient diet can also lead to oxidative stress, further impairing brain function and mood stability. Oxidative stress occurs when there is an imbalance between free radicals (unstable molecules that can damage cells) and antioxidants (which help neutralize these harmful molecules) in the body.

Antioxidants include:

• Vitamin C

• Vitamin E

• Carotenoids including beta-carotene (a precursor to Vitamin A) and lycopene

• Selenium

• Zinc

When free radicals accumulate due to factors like poor diet, stress, and pollution, they can damage cells, proteins, and DNA, contributing to inflammation, aging, and various diseases, including anxiety, depression, and IBS.

For example, eating a diet high in processed foods and low in antioxidants (from fruits and vegetables) can increase oxidative stress, leading to brain fog, fatigue, and worsened mental health (Berk et al., 2018).

2. Gut Dysbiosis and Mental Health

Gut dysbiosis, an imbalance of gut bacteria, is common in individuals with depression and anxiety. Research shows that people with depression often have a less diverse microbiome compared to healthy individuals (Jiang et al., 2015).

This imbalance can:

• Increase inflammation

• Disrupt neurotransmitter production

• Alter the stress response

  
  

3. Blood Sugar Fluctuations and Mood Swings

Diets high in processed carbohydrates and sugars cause rapid spikes and crashes in blood sugar levels, leading to irritability, fatigue, and anxiety. Stabilizing blood sugar with complex carbohydrates and protein helps maintain balanced energy and mood.

Complex carbohydrates' fiber remains intact (unlike simple carbohydrates such as white rice which has been processed and fiber has been removed).

Examples:

• Whole grains (quinoa, brown rice, oats, barley)

• Legumes (lentils, chickpeas, kidney beans)

• Non-starchy Vegetables (broccoli, asparagus, Brussels sprouts, spinach)

• Starchy Vegetables (sweet potatoes, butternut squash)

• Fruits (apples, berries, grapes)

• Nuts and Seeds (sunflower seeds, almonds, walnuts, pumpkin seeds)

Diet and IBS: Stress and Anxiety could be causing IBS and Your Gut Health Could be Causing your Stress and Anxiety!

IBS is a common digestive disorder characterized by:

• Bloating

• Abdominal pain

• Diarrhea and/or constipation

  
  

1. Trigger Foods for IBS

Sometimes foods can trigger IBS symptoms, however, people often find that they have inconsistent responses. One day they eat onions and garlic with no problem; they eat it another day and have diarrhea 15 minutes after eating!

This is when it may be time to assess how your mind is affecting your gut (and vice versa!).

Some common foods that people experience issues with:

• High-FODMAP foods, which are fermentable carbohydrates that can cause gas, bloating, and discomfort in sensitive individuals. These include:

  • Onions and garlic

  • Legumes (beans, lentils)

  • Wheat-based products

  • Certain fruits (apples, pears, cherries)

  • Dairy products high in lactose

• High fat foods (fried, greasy)

• Dairy (for those who are lactose intolerant or those with issues tolerating milk proteins)

• Gluten (for some individuals with sensitivity)

  
  

A low-FODMAP diet is an elimination diet that has been shown to reduce IBS symptoms by limiting foods that ferment in the gut and cause digestive distress (Peters et al., 2021). However, it is best followed under the guidance of a registered dietitian nutritionist to ensure nutritional adequacy.

2. The Stress-Gut Connection

Chronic stress impacts gut function by:

• Reducing beneficial gut bacteria

• Altering gut motility, leading to diarrhea and/or constipation

• Increasing gut sensitivity, making digestion more uncomfortable

  
  

Since mental health and gut health are interconnected, stress management techniques such as mindfulness, exercise, and proper sleep can help improve IBS symptoms. Additionally, dietary interventions like increasing fiber and incorporating gut-friendly foods can support overall digestive health.

How to Improve Mental and Gut Health Through Diet

1. Increase Fiber Intake

Fiber supports gut health by feeding beneficial bacteria and reducing inflammation. Excellent sources include:

• Fruits (apples, berries, pears)

• Vegetables (broccoli, leafy greens, carrots)

• Whole grains (quinoa, oats, brown rice)

• Legumes (lentils, chickpeas, black beans)

  
  

2. Incorporate Probiotics and Fermented Foods

Probiotics introduce beneficial bacteria into the gut, improving both digestion and mental health. Include foods such as:

• Yogurt (with live cultures)

• Kefir

• Sauerkraut

• Kimchi

• Miso

  
  

Studies show that probiotics have the potential to reduce symptoms of depression and anxiety (Wallace & Milev, 2017).

You may have heard, "Happy wife, happy life!" but maybe it should really be, "Happy gut bacteria, happy life!"

3. Reduce Processed Foods and Sugar

Limiting ultra-processed foods and added sugars can decrease systemic inflammation and stabilize blood sugar levels, both of which are linked to improved mental well-being and reduced IBS symptoms.

4. Prioritize Omega-3 Fatty Acids

Omega-3s have anti-inflammatory properties and support brain function. Include sources like:

• Fatty fish (salmon, sardines, mackerel)

• Flaxseeds

• Chia seeds

• Walnuts

• Pumpkin seeds

• Hemp seeds

  
  

Omega-3 supplementation has been associated with reduced symptoms of depression and anxiety (Su et al., 2018).

5. Stay Hydrated and Manage Stress

Dehydration and chronic stress can negatively affect gut motility and microbiome balance. Strategies to improve stress resilience include:

• Mindfulness meditation

• Yoga and deep breathing exercises

• Regular physical activity

• Quality sleep

  
  

Conclusion

Stress and anxiety could be causing IBS and your gut health could be causing your stress and anxiety!

The brain-gut connection underscores the importance of dietary choices in mental AND digestive health.

A poor diet disrupts gut bacteria, increases inflammation, and alters neurotransmitter function, contributing to anxiety, depression, and IBS.

By focusing on a nutrient-dense, whole-food diet, individuals can support their gut microbiome and improve overall well-being.

References

• Berk, M., et al. (2018). So depression is an inflammatory disease, but where does the inflammation come from? BMC Medicine, 11(1), 200.

• Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: Interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology, 28(2), 203-209.

• Dinan, T. G., & Cryan, J. F. (2017). Gut instincts: Microbiota as a key regulator of brain development, ageing and neurodegeneration. Journal of Physiology, 595(2), 489-503.

• Holscher, H. D. (2017). Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut Microbes, 8(2), 172-184.

• Jiang, H., Ling, Z., Zhang, Y., Mao, H., Ma, Z., Yin, Y., ... & Ruan, B. (2015). Altered fecal microbiota composition in patients with major depressive disorder. Brain, Behavior, and Immunity, 48, 186-194.

• Miller, A. H., & Raison, C. L. (2016). The role of inflammation in depression: From evolutionary imperative to modern treatment target. Nature Reviews Immunology, 16(1), 22-34.

• Peters, S. A., et al. (2021). Gut-directed hypnotherapy vs. low FODMAP diet for IBS: A randomized controlled trial. The Lancet Gastroenterology & Hepatology, 6(2), 91-104.

• Su, K. P., et al. (2018). Omega-3 use and changes in anxiety severity. JAMA Network Open, 1(5), e182327.

• Wallace, C. J. K., & Milev, R. (2017). Probiotics and depressive symptoms: A systematic review. Annals of General Psychiatry, 16, 14.

Emily Conyers, MS, RDN, LD/N

Registered Dietitian Nutritionist in Jacksonville, Florida