We often think happiness comes from a dream job, a great relationship, or just “good genes.” But according to renowned heart surgeon and bestselling author Dr. Steven Gundry, there’s a lesser-known source of joy that might be even more powerful: your gut.

In his new book, The Gut-Brain Paradox, Dr. Gundry unpacks the fascinating and often overlooked connection between gut health and emotional well-being. The truth? Many of the factors affecting our mood have less to do with external achievements—and more to do with what’s happening inside our microbiome. From the benefits of dirt to the power of fasting, here are some of the most surprising ways your gut could be the key to real, lasting happiness:

1. Dirt—Yes, Dirt: It turns out that our obsession with cleanliness may be making us sicker—and unhappier—than ever. We live in an age of antibacterial soaps, hand sanitizers, and sterilized environments. However, according to Dr. Gundry, this war on microbes has weakened our gut microbiome and, in turn, affected our brain’s defenses against stress and anxiety.

Microbes found in soil contain beneficial bacteria that help train the immune system and promote a balanced gut. Without exposure to these microorganisms, we lose essential bacteria that produce neurotransmitters like serotonin, which directly impact our mood. So the next time you’re hesitant about walking barefoot on the grass, letting your kids play in the dirt, or snuggling with your pet, you might want to reconsider. Your gut—and your happiness—may depend on it.

2. Bitter Foods: We tend to associate happiness with sweet treats, but one of the most important flavors for mental well-being is actually bitterness.

Bitter foods—like dark chocolate, extra virgin olive oil, and coffee—are packed with polyphenols that fuel gut bacteria and reduce inflammation. And when inflammation in the gut is reduced, inflammation in the brain calms down as well. Since chronic inflammation is linked to anxiety, depression, and even brain fog, increasing your intake of bitter foods may be an easy way to boost both your gut health and your mood.

3. Fasting—The Happiness Reset: It might sound counterintuitive, but skipping a meal could actually make you feel better. Dr. Gundry is a strong proponent of time-controlled eating—simply put, shortening your daily eating window, which not only improves gut health but also enhances mental clarity and mood.

When you limit your eating window or even go on a 5-day vegan diet, your gut bacteria go through a reset. Fasting triggers a process called autophagy, where the body clears out damaged cells and creates new, healthier ones—including brain cells. Research also shows that fasting increases BDNF (brain-derived neurotrophic factor), a protein that supports cognitive function and emotional well-being. So if you’re feeling sluggish or down, skipping breakfast (or dinner) might be the mental reset your body needs.

4. Socializing Feeds Your Gut—Literally: Your gut microbiome isn’t just influenced by what you eat—it’s also shaped by who you spend time with. Social interaction helps diversify gut bacteria because we naturally share microbes through touch, shared spaces, and even the air we breathe.

People who live in isolation or have limited social engagement tend to have a less diverse microbiome, which has been linked to mood disorders like anxiety and depression. Surrounding yourself with positive, health-conscious individuals can be especially beneficial—not only does it uplift your mood and mindset, but their healthy habits can also rub off on you, encouraging better dietary choices, an active lifestyle, and stress reduction. Plus, spending time with others—especially in nature or communal settings—exposes you to a wider range of microbes, strengthening your gut’s resilience.

Want to Learn More?

Dr. Gundry explores these surprising gut-brain connections in his new book, The Gut-Brain Paradox, where he reveals even more unexpected ways to boost happiness through gut health. You can pre-order your copy now here to discover how small changes in your diet and lifestyle can transform your mood—and your life.