by Emily Reich, RD
Have you ever had butterflies in your stomach before an event? Have you noticed that after a few days of eating junk food, you feel fatigued or foggy? That is not a coincidence! Your gut and your brain are in constant communication, and the food you eat is very powerful for influencing how you think, feel, and function.
What Is the Gut-Brain Axis?
There is a physical communication highway connecting your gut to your brain called the vagus nerve, and it signals travel in both directions (from brain to gut, advise versa) [1].
Living inside your digestive tract is a vast community of bacteria, fungi, and other microorganisms collectively known as the gut microbiome. This community is made up of trillions of microorganisms and does far more than just help you digest food. It also helps to produce neurotransmitters (the chemical messengers your brain uses to regulate mood, memory, and focus), communicates with your immune system, and helps control inflammation throughout your body [2].
In fact, roughly 90-95%of the body’s serotonin is produced in the gut, not the brain [3]! So when your gut is out of balance, it can directly affect how you feel emotionally and mentally.
How Your Diet Shapes Your Gut and Your Mind
A diet rich in fiber, fermented foods, and a variety of plants is associated with a more diverse gut microbiome; and greater microbial diversity is consistently linked to better mental health outcomes, including lower rates of depression and anxiety [4].
On the flip side, diets high in ultra-processed foods, added sugars, and refined carbohydrates are linked to reduced microbial diversity and increased gut inflammation, both of which negatively affect mood and cognitive function [5]. Simply put, when you feed your gut poorly, your brain pays the price.
The Mood-Food Connection: What the Evidence Says
Research is building a compelling picture of how eating patterns relate to mental health. People who closely follow a Mediterranean-style diet, which is rich in vegetables, fruits, whole grains, olive oil, legumes, and fish, have shown to have lower rates of depression compared to those eating a typical Western diet [6].
A clinical trial put this to the test in people with moderate to severe depression. Participants who received dietary counseling and shifted to a healthier eating pattern showed greater improvement in depressive symptoms than those only in a social support control group [7].
The Foods That Support a Healthy Gut and a Sharper Mind
So what should you be eating? Here is the research on food that consistently supports gut and brain health:
Fiber-Rich Foods
Dietary fiber is the primary fuel source for the beneficial bacteria in your gut. Fruits, vegetables, legumes (beans, lentils, chickpeas), and whole grains all provide fiber that feeds your microbiome and helps it thrive. Adults eating higher amounts of dietary fiber show better diversity in their gut bacteria, improved mood and lower stress [8]. The goal for men is 35g per day and for women, 25g daily.
Fermented Foods
Fermented foods: yogurt, kefir, kimchi, sauerkraut, miso, and kombucha contain live bacteria that can temporarily populate the gut and support a healthier microbiome environment. A high-fermented-food diet has been shown to increase microbiome diversity and reduce inflammatory proteins, both of which benefit mental health [9].
Omega-3 Fatty Acids
These are found in salmon, sardines, walnuts, flaxseeds, chia seeds, and more – which are essential for brain health. They are structural components of brain cell membranes, and diets higher in omega-3s are associated with lower rates of depression and better preservation of cognitive function as we age [10].
Polyphenol-Rich Foods
Polyphenols are natural plant compounds found in berries, dark chocolate, green tea, olive oil, and colorful produce. Regular consumption of polyphenol-rich foods has been associated with improvements in memory, attention, and processing speed [11].
Prebiotic Foods
Prebiotics are specific types of fiber that selectively feed the most beneficial bacteria in your gut. Great sources include garlic, onions, leeks, asparagus, bananas, and oats. Prebiotic intake has been shown to lower stress hormones and improve emotional processing [12].
What to Reduce
Just as important as what you add, is what you reduce:
- Ultra-processed foods (packaged snacks, fast food, frozen meals with long ingredient lists): These reduce microbial diversity and raise inflammatory markers that reach the brain [5].
- Added sugars: Excess sugar feeds harmful bacteria in the gut and has been linked to higher rates of depression and anxiety [13].
- Alcohol: Regular alcohol consumption disrupts the gut lining and reduces beneficial bacteria which contributes to systemic inflammation. [14]
- Artificial sweeteners: Even sweeteners marketed as “healthier” alternatives may negatively alter the composition of gut bacteria, though research here is still evolving [15].
Summary
Your gut and your brain are not separate systems operating independently. They are intertwined, and what you put on your plate influences both! Feeling mentally sharp, emotionally steady, and energized is also influenced by what you are feeding the trillions of microorganisms working on your behalf every day.
At Princeton Longevity Center, our registered dietitians work with patients every day to build personalized nutrition strategies grounded in this kind of evidence. If you are ready to take a more proactive approach to how food affects your mood, mental clarity, and long-term health, we are here to help you build a plan that fits your life.
References
[1] Bonaz B, Bazin T, Pellissier S. The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis. Front Neurosci. 2018;12:49. https://pubmed.ncbi.nlm.nih.gov/29467611/
[2] Cryan JF, O’Riordan KJ, Cowan CSM, et al. The Microbiota-Gut-Brain Axis. Physiol Rev. 2019;99(4):1877-2013. https://pubmed.ncbi.nlm.nih.gov/31460832/
[3] Yano JM, Yu K, Donaldson GP, et al. Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell. 2015;161(2):264-276. https://pubmed.ncbi.nlm.nih.gov/25860609/
[4] Heiman ML, Greenway FL. A healthy gastrointestinal microbiome is dependent on dietary diversity. Mol Metab. 2016;5(5):317-320. https://pubmed.ncbi.nlm.nih.gov/27110483/
[5] Zinöcker MK, Lindseth IA. The Western Diet-Microbiome-Host Interaction and Its Role in Metabolic Disease. Nutrients. 2018;10(3):365. https://pubmed.ncbi.nlm.nih.gov/29562591/
[6] Lassale C, Batty GD, Baghdadli A, et al. Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Mol Psychiatry. 2019;24(7):965-986. https://pubmed.ncbi.nlm.nih.gov/30254236/
[7] Jacka FN, O’Neil A, Opie R, et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med. 2017;15(1):23. https://pubmed.ncbi.nlm.nih.gov/28137247/
[8] Swann OG, Kilpatrick M, Breslin M, Oddy WH. Dietary fiber and its associations with depression and inflammation. Nutr Rev. 2020;78(5):394-411. https://pubmed.ncbi.nlm.nih.gov/31750916/
[9] Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137-4153. https://pubmed.ncbi.nlm.nih.gov/34256014/
[10] Grosso G, Galvano F, Marventano S, et al. Omega-3 fatty acids and depression: scientific evidence and biological mechanisms. Oxid Med Cell Longev. 2014;2014:313570. https://pubmed.ncbi.nlm.nih.gov/24757497/
[11] Vauzour D, Camprubi-Robles M, Miquel-Kergoat S, et al. Nutrition for the ageing brain: Towards evidence for an optimal diet. Ageing Res Rev. 2017;35:222-240. https://pubmed.ncbi.nlm.nih.gov/27713095/
[12] Schmidt K, Cowen PJ, Harmer CJ, Tzortzis G, Errington S, Burnet PWJ. Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers. Psychopharmacology. 2015;232(10):1793-1801. https://pubmed.ncbi.nlm.nih.gov/25449699/
[13] Knüppel A, Shipley MJ, Llewellyn CH, Brunner EJ. Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Sci Rep. 2017;7(1):6287. https://pubmed.ncbi.nlm.nih.gov/28751637/
[14] Bishehsari F, Magno E, Swanson G, et al. Alcohol and gut-derived inflammation. Alcohol Res. 2017;38(2):163-171. https://pubmed.ncbi.nlm.nih.gov/28988571/
[15] Suez J, Korem T, Zeevi D, et al. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 2014;514(7521):181-186.