{"id":1366,"date":"2026-07-12T07:23:49","date_gmt":"2026-07-12T07:23:49","guid":{"rendered":"https:\/\/drshintani.com\/wordpress\/?p=1366"},"modified":"2026-07-12T07:23:51","modified_gmt":"2026-07-12T07:23:51","slug":"feeling-down-or-stressed-your-gut-flora-produces-90-of-your-serotonin","status":"publish","type":"post","link":"https:\/\/drshintani.com\/wordpress\/2026\/07\/12\/feeling-down-or-stressed-your-gut-flora-produces-90-of-your-serotonin\/","title":{"rendered":"Feeling Down or Stressed? Your Gut Flora Produces 90% of Your Serotonin"},"content":{"rendered":"
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When people feel persistently low, anxious, or unable to cope with stress, the first place most doctors look is the brain. Antidepressants, anti-anxiety medications, and mood stabilizers all target neurotransmitter activity in the brain \u2014 and for many people, they provide meaningful relief.<\/p>\n\n\n\n

But there is a dimension of mood regulation that conventional medicine has been slow to integrate into mainstream practice, despite a rapidly growing body of research pointing directly to it.<\/p>\n\n\n\n

Your gut.<\/p>\n\n\n\n

Specifically \u2014 the 100 trillion microorganisms living in your digestive tract, collectively known as the gut microbiome or gut flora. And the remarkable fact at the center of this emerging science is this: more than 90 percent of the body’s serotonin<\/a> is produced not in the brain, but in the gut \u2014 in direct conjunction with the gut flora that lives there.<\/p>\n\n\n\n

What Is Serotonin \u2014 and Why Does It Matter?<\/strong><\/p>\n\n\n\n

Serotonin is one of the most important neurotransmitters in the human body. Often called the “happy hormone,” it plays a central role in regulating mood, emotional stability, and the experience of calm and enjoyment. It helps modulate anxiety, supports healthy sleep cycles, and contributes to a general sense of wellbeing.<\/p>\n\n\n\n

Low serotonin levels have been associated with depression, anxiety, irritability, poor sleep, and difficulty managing stress. Most pharmaceutical antidepressants \u2014 including SSRIs (selective serotonin reuptake inhibitors), the most widely prescribed class of antidepressants in the world \u2014 work by preventing the breakdown of serotonin in the brain, effectively making more of it available.<\/p>\n\n\n\n

But here is what most people \u2014 and many doctors \u2014 don’t fully appreciate: the brain’s serotonin supply depends heavily on what is happening in the gut. The gut produces serotonin, and the gut flora plays a direct role in that production. When the gut microbiome is healthy, diverse, and well-nourished, serotonin production tends to be adequate. When the gut is dysbiotic \u2014 unbalanced, inflamed, or depleted of beneficial bacteria \u2014 serotonin production can be compromised, contributing to the very mood symptoms that are typically attributed to the brain alone.<\/p>\n\n\n\n

The Gut-Brain Connection<\/strong><\/p>\n\n\n\n

The gut and brain are in constant, bidirectional communication through what scientists call the gut-brain axis<\/a> \u2014 a complex network of neural, hormonal, and immune signals that flows in both directions between the digestive system and the central nervous system. The vagus nerve \u2014 one of the longest nerves in the body \u2014 serves as a primary highway for this communication, carrying signals from the gut directly to the brain.<\/p>\n\n\n\n

This means that what happens in the gut does not stay in the gut. Inflammation in the gut triggers inflammatory signals that travel to the brain, affecting mood, cognition, and stress response. A disrupted gut microbiome sends different signals than a healthy one \u2014 and the brain responds accordingly.<\/p>\n\n\n\n

Researchers studying the gut-brain axis have found that people with depression and anxiety tend to have less diverse gut microbiomes, lower levels of certain beneficial bacterial strains, and higher levels of inflammatory markers in the gut than people without mood disorders. While the direction of causality is still being investigated \u2014 does gut dysbiosis cause depression, or does depression cause gut dysbiosis? \u2014 the relationship is increasingly clear and almost certainly runs in both directions.<\/p>\n\n\n\n

How to Support Healthy Gut Flora for Natural Serotonin Production<\/strong><\/p>\n\n\n\n

The good news is that the gut microbiome is highly responsive to dietary change. Unlike the brain \u2014 which is protected by the blood-brain barrier and can be difficult to influence directly \u2014 the gut flora can begin to shift meaningfully within days of changing what you eat.<\/p>\n\n\n\n

Dr. Shintani identifies two key categories of foods for supporting a healthy gut microbiome:<\/p>\n\n\n\n

Probiotic Foods \u2014 Direct Sources of Beneficial Bacteria<\/strong><\/p>\n\n\n\n

Probiotics are live beneficial bacteria found in fermented foods. When consumed regularly, they contribute directly to the diversity and health of the gut microbiome.<\/p>\n\n\n\n

Miso<\/strong> \u2014 the fermented soybean paste central to Japanese cuisine \u2014 is one of the richest and most accessible probiotic foods available. It contains multiple strains of beneficial Lactobacillus bacteria and has been consumed for centuries in cultures with some of the world’s lowest rates of depression and anxiety.<\/p>\n\n\n\n

Sauerkraut<\/strong> \u2014 fermented cabbage \u2014 is one of the most studied probiotic foods in Western research. Its beneficial bacteria survive the digestive process and have been shown to colonize the gut and support microbiome diversity. Choose unpasteurized sauerkraut \u2014 the pasteurization process kills the beneficial bacteria.<\/p>\n\n\n\n

Kimchi<\/strong> \u2014 the Korean fermented vegetable dish \u2014 contains a rich diversity of beneficial bacteria along with powerful anti-inflammatory compounds from its chili, ginger, and garlic ingredients. Research has linked regular kimchi consumption to improved gut microbiome diversity and reduced inflammatory markers.<\/p>\n\n\n\n

Other excellent probiotic sources include tempeh, kombucha (low sugar), and plant-based yogurts with live active cultures.<\/p>\n\n\n\n

Prebiotic Foods \u2014 Fuel for Beneficial Bacteria<\/strong><\/p>\n\n\n\n

Prebiotics are the fiber-rich foods that feed and sustain the beneficial bacteria already living in the gut. Without adequate prebiotic fiber, beneficial bacteria cannot thrive \u2014 regardless of how many probiotic foods are consumed.<\/p>\n\n\n\n

Whole grains<\/strong> \u2014 brown rice, oats, barley, and whole wheat \u2014 provide the fermentable fiber that beneficial gut bacteria use for energy. The short-chain fatty acids produced when gut bacteria ferment this fiber also have direct anti-inflammatory effects throughout the body, including in the brain.<\/p>\n\n\n\n

Whole beans and legumes<\/strong> \u2014 chickpeas, lentils, black beans, mung beans \u2014 are among the most prebiotic-rich foods available. Their resistant starch and diverse fiber types feed a wide range of beneficial bacterial strains, supporting microbiome diversity.<\/p>\n\n\n\n

Cooked vegetables<\/strong> \u2014 particularly cruciferous vegetables, root vegetables, and leafy greens \u2014 provide multiple types of prebiotic fiber along with the antioxidants and anti-inflammatory compounds that support gut lining health.<\/p>\n\n\n\n

Whole fruit<\/strong> \u2014 particularly berries, apples, and pears \u2014 provide pectin and other soluble fibers that specifically support beneficial bacterial growth and serotonin-producing bacterial strains.<\/p>\n\n\n\n

The Bigger Picture<\/strong><\/p>\n\n\n\n

The connection between gut health and mental health is one of the most exciting and rapidly evolving areas of nutritional science. It reframes how we think about mood disorders \u2014 not as purely brain-based chemical imbalances, but as whole-body conditions that involve the gut, the immune system, and the food we eat every single day.<\/p>\n\n\n\n

This does not mean that diet alone can treat clinical depression or anxiety \u2014 and anyone experiencing significant mood symptoms should work with a qualified healthcare provider. But it does mean that what you eat is not irrelevant to how you feel emotionally. The gut flora that lives inside you responds to every meal you eat \u2014 and it responds by producing the very neurotransmitters that shape your mood, your calm, and your ability to handle the stresses of daily life.<\/p>\n\n\n\n

Feed your gut well. Your brain is listening.<\/p>\n\n\n\n

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Dr. Terry Shintani<\/a> is a Harvard-trained physician (MD, JD, MPH), a Living Treasure of Hawai’i, and the creator of the Waianae Diet and the Peace Diet. He continues to see patients at his Honolulu practice and shares daily health insights on YouTube.<\/em><\/p>\n\n\n\n

\ud83c\udf3f Learn more at PeaceDiet.org | Watch the video: https:\/\/www.instagram.com\/p\/DaryUGSTD8K\/<\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

When people feel persistently low, anxious, or unable to cope with stress, the first place most doctors look is the brain. Antidepressants, anti-anxiety medications, and mood stabilizers all target neurotransmitter activity in the brain \u2014 and for many people, they provide meaningful relief. But there is a dimension of mood regulation that conventional medicine has…<\/p>\n

Read More “Feeling Down or Stressed? Your Gut Flora Produces 90% of Your Serotonin”<\/span> »<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/posts\/1366"}],"collection":[{"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/comments?post=1366"}],"version-history":[{"count":1,"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/posts\/1366\/revisions"}],"predecessor-version":[{"id":1368,"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/posts\/1366\/revisions\/1368"}],"wp:attachment":[{"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/media?parent=1366"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/categories?post=1366"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/drshintani.com\/wordpress\/wp-json\/wp\/v2\/tags?post=1366"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}