Whether you have childhood memories of the post-sugar-binge crash on halloween night or have noticed how caffeine makes you jittery, many of us have a direct, personal understanding of the impact of specific foods on our mood. As a former nutritionist who worked in a functional medicine-oriented medical practice prior to returning to graduate school to become a mental health counselor, I have always been interested in the relationship between diet and mental health.
As research has advanced in recent years, the link between nutrition and mental health is coming into focus. Studies have shown that following a diet rich in fruits, vegetables, nuts, and legumes, with moderate amounts of poultry, eggs, and dairy, and red meat can lower the risk of depression, and that a diet high in ultra-processed foods, such as artificially flavored snacks, chips, cookies and other packaged foods full artificial ingredients, is correlated with anxiety and depression.
The Gut-Brain Axis and the Role of Fiber
There has been a growing interest in gut microbiome (the bacteria in our digestive system) and its relationship to overall health and specifically to mental health, since 1998 when Michael Gerson’s book, “The Second Brain” popularized the burgeoning field of research on how the gut microbiome is related to mental health. One key to understanding the gut-brain connection is that diets that are rich in ultra-processed foods such as packaged foods designed for addictive taste and long shelf life (which contain hydrogenated oils, artificial sweeteners, emulsifiers, sugars, sodium, and preservatives) tend to be low in fiber, which is primarily found in whole, plant-based foods such as whole grains, fruits, vegetables, nuts, and seeds.
Fiber plays a crucial role in nurturing beneficial gut bacteria and is necessary for producing short-chain fatty acids. These fatty acids are produced when fiber breaks down in the digestive system, and they are vital for brain function. Studies have shown that individuals with mental health disorders often have significantly less diverse gut bacteria as well as lower levels of short-chain fatty acids in their digestive tracts.
In addition to increasing fiber intake through a diet rich in vegetables and fruits, a powerful way to boost your gut health is through consuming probiotic-rich foods such as yogurt, sauerkraut, kimchi, or kombucha.
It is widely believed that the gut microbiota communicates with the brain through nerves, hormones, and the immune system, influencing brain function. Research has shown that the gut microbiota plays a significant role in regulating anxiety, mood, thinking, and pain. This has led to the idea of a "microbiota-gut-brain axis," suggesting that changing the gut microbiota could be a new way to treat brain-related disorders.
Studies have also shown that gastrointestinal issues such as abdominal pain, diarrhea, constipation, and conditions like irritable bowel syndrome are more common in people with neuropsychiatric and neurodevelopmental disorders, including autism, ADHD, depression, OCD, and bipolar disorder. Additionally, a growing number of animal studies strongly support the link between the gut and the brain.
Blood Sugar Fluctuations and Mood
In clinical studies, diets rich in refined carbs have been found to directly impact mood, with healthy individuals reporting more depressive symptoms after consuming foods with a high-glycemic load. One theory is that rapid spikes and drops in blood sugar levels, triggered by a diet high in processed carbs, could lead to mood changes. When blood sugar levels rise quickly and then crash, the body releases stress hormones (cortisol and adrenaline), which can increase feelings of anxiety, irritability, and hunger. Studies have demonstrated that lowering blood sugar can cause these mood changes, while recurrent low blood sugar has also been linked to mood disorders.
This connection between blood sugar fluctuations and mental health seems to explain why high-sugar diets might affect mood so quickly. However, other factors may also be involved; for example, diets high in refined carbs are a known risk factor for diabetes, which often coexists with depression. Both conditions share common issues, such as insulin resistance and brain function problems, suggesting they may have overlapping causes. Additionally, the inflammation triggered by high-glycemic foods might link these diets to symptoms of depression through the body's immune system response. In addition to the impact of processed foods on blood sugar regulation, common chemical additives such as artificial sweeteners and emulsifiers found in ultra-processed foods may negatively impact gut health.
Key Takeaways
In thinking about the ways in which simple lifestyle changes can have a dramatic effect on our well-being, eating a fiber-rich diet that is low in sugar and processed foods is one of the best choices we can make for improving our day-to-day mood. Below are a few guidelines for changing your diet to have a positive impact on your mental health.
Add more fiber-rich foods to your meals, such as vegetables (broccoli, spinach, kale), fruits (berries, apples, bananas), whole grains (oats, quinoa, brown rice), and legumes (lentils, beans, chickpeas).
Try to cook more meals from scratch using whole, unprocessed ingredients.
Swap out packaged snacks for healthier options like nuts, fruits, hard-boiled eggs, or homemade energy bars.
Include whole grains to support stable blood sugar levels and improve mood and avoid refined carbohydrates such as candy, cookies, and sweet baked goods which can cause blood sugar spikes and crashes.
Add fermented foods like yogurt, kefir, kimchi, sauerkraut, or kombucha to your diet, aiming for at least one serving of a probiotic-rich food each day.
The above advice is provided for informational purposes only and is not intended as medical advice, nutrition therapy or individualized nutrition counseling. Please note that everyone has unique nutritional and lifestyle requirements and what works for one individual may not work for another. It is a good idea to consult a qualified healthcare professional before changing your diet.
Written by:
Laura Kraber
Mental Health Counseling Intern
References:
Gerson, M. (1998), The Second Brain : The Scientific Basis of Gut Instinct and a Groundbreaking New Understanding of Nervous Disorders of the Stomach and Intestines. Harper Collins
Tenchov, R., “How your gut microbiome is linked to depression and anxiety”. CAS Insights, February 2022.
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