How Poor Gut Health Can Increase Anxiety and Depression Risk & What to Eat to Help

Even in grade school, you probably knew that there was some link between your stomach and your brain. Remember those butterflies you felt when you saw your crush? Or the stomach-in-knots feeling that flared up when you were in trouble?

"Stress can play a major role in tummy troubles, even initiating symptoms when there are no changes in diet. But people are often pretty surprised to learn that a whopping 90% of the communication between the brain and the gut is actually moving from the gut to the brain," explains Desiree Nielsen, RD, a Vancouver, Canada-based registered dietitian and the author of Good for Your Gut.

Read on to learn more about the extensive conversation between your gut and your brain (aka the "gut-brain axis"), how less-than-stellar gut health can impact your mood, plus the best foods to feed your brain and good gut bacteria all at once.

The Gut-Brain Axis and Mental Health

When most of us think of our nervous system, we think of our brain and spinal cord; however, the digestive tract has a complex nervous system of its own. The enteric (or gut) nervous system actually has more nerve cells than our spinal cord, Nielsen says. Those nerves come into play when we eat a meal. Stretch receptors in our stomach activate and relay messages to the brain that we are getting full.

It's not only nerves that play a role here, though. Our gut microbiota, the trillions-strong bacterial population that lives within our guts, is another major factor in the gut-brain connection, too.

"The type of bacteria living in our gut may impact motility, digestive secretions, inflammation and even neurotransmitter production in our digestive tracts," Nielsen adds.

There's one neurotransmitter, in particular, that's made in high supply in the gut: serotonin, often referred to as the "feel good" neurotransmitter. A whopping 95% of our body's serotonin is made in our guts, not our brains, says Mike Hoaglin, M.D., the San Francisco-based medical director of the telehealth company DrHouse.

When our healthy gut bacteria are fed well, they send signals to the brain that help influence our mood, confirms William W. Li, M.D., an internal medicine physician and scientist in Boston and the author of Eat to Beat Disease: The New Science of How Your Body Can Heal Itself. When our guts are happy, the brain responds by releasing mood-boosting hormones like the aforementioned serotonin, plus dopamine and oxytocin.

"These hormones are important for improving our mood, so what we feed ourselves literally influences how we feel," Li says.

In the short term, poor gut health interferes with signals sent to the brain. Over time, "dysbiosis," or an imbalance of gut bacteria, can also lead to chronic inflammation.

"When our body has high levels of inflammation, this can also affect the function of our brain, including cognition, mood and irritability," Li says.

While it's not the only factor or cause, a July 2020 study published in Neuron suggests that chronic inflammation plays a role in depression. Inflammation is an immune system response, and since 70% of the immune activity in the body happens in the gut, it stands to reason that when gut health is not so, well, healthy, our body responds in a wide variety of ways.

"In the 'leaky gut' model, the inflammatory response causes microscopic holes in the gut wall, thereby allowing toxins and microbes to enter the bloodstream. These toxins may directly irritate the brain or indirectly by improperly activating the immune system. Some of the compounds released by helpful gut bacteria nourish the blood-brain barrier," Hoaglin says.

Because your gut function depends on—and has effects on—your immune and nervous system function, long-term changes in gut health may impact your mental well-being, Nielsen summarizes.

It's challenging to tell if it's the chicken or the egg, Nielsen adds. Digestive conditions such as irritable bowel syndrome and inflammatory bowel disease have been associated with increased rates of anxiety and depression.

"While the mechanisms are not fully understood, it's likely a combination of the negative impact on quality of life, as well as inflammatory and nervous system effects in the gut itself," Nielsen says. "In one review, people who had both IBS and depression or anxiety had distinctly different microbiomes than those with IBS alone. People with undiagnosed celiac disease may experience brain fog from the significant inflammation and gut barrier changes that occur while the disease process is ongoing."

Everyday digestive symptoms such as bloating and constipation can affect your mood in smaller ways as well. Regardless of what's going on, "if you don't feel good or are worried about your health, your mood will suffer. Temporary changes in gut function can make you feel sluggish, lethargic or foggy but should resolve when the gut symptoms have passed," Nielsen says.

Since it's becoming so clear that what we eat can affect our mental health and increase the risk for anxiety, depression, brain fog, a down mood and so much more, there's now an entire field dedicated to what our mouths (and microbiomes and minds) consume: nutritional psychiatry, per a 2019 article published in European Neuropsychopharmacology.

What to Eat to Boost Your Mood

It's crucial to note that there's no one food or diet that can completely cure or prevent a mental health condition. Any treatment program for anxiety or depression should include guidance from a mental health provider.

What you eat can support your less-stressed, brighter-mood strategy, though.

"There are so many factors we don't have control over, such as stress. But many of us have the opportunity to make healthier food choices," Nielsen says. "Without a doubt, one of the most important things you can do to nourish the gut-brain connection is to eat more whole plant foods, which are rich in fiber and phytochemicals. Research hints that dietary fiber from whole plant foods can help to nourish the gut-brain connection in multiple ways: from boosting the growth of beneficial bacteria in the gut, to improving gut barrier function and minimizing inflammation."

Plants, probiotics (good bacteria) and prebiotics (which feed the good gut bacteria) are all smart choices for your stomach—and your spirits. So add these nine expert-recommended items to your next shopping list:

1. Blueberries
2. Pears
3. Kiwis
4. Jerusalem artichokes
5. Greek yogurt
6. Chia seeds
7. Lentils
8. Walnuts
9. Sauerkraut

The Bottom Line

There's a growing stack of scientific evidence to support the existence of a speedy interstate connecting the gut and the brain, so it's safe to say that the foods we eat can definitely affect our mental health. These best foods for gut health are not a magic pill to remedy depression, anxiety or a ho-hum mood, but eating more fruits, vegetables, nuts, seeds, probiotics and prebiotics certainly can't hurt as part of the Rx to help ease inflammation, tame stress and anxiety and potentially (eventually) boost your mood.

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