There's a Connection Between Gut Health and Depression

Everybody's into guts these days. Well, not having a gut, but promoting intestinal health as a solution to a wide variety of health problems. On the other side of the coin, everybody's depressed! Depression and anxiety are on the rise, so doctors are beginning to look beyond the brain to learn what might be causing this wave of sadness.

For years, doctors found that patients with depression often suffered from constipation, diarrhea, and other poop-related problems. Now some scientists think that the bowel issues might not be an effect of depression—but the cause.

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My gut's making me depressed?

At first, this sounds crazy: How can your stomach and intestines make you depressed? Is my stomach telling me that I'm a failure and I'll disappoint my family and friends? Are my intestines controlling my Facebook feed to show another governmental horror, making me wonder if there's any good left in the world? These might be, ahem, slightly personal examples, but they're still legit.

Although your thoughts and emotions are controlled in the brain, the brain and gut actually have a very powerful connection. "The gut and brain are intimately connected by a bi-directional pathway called the gut-brain axis," says Boston-based registered dietitian and gut health expert Kate Scarlata. This axis is connected through the vagus nerve. "The vagus nerve is the longest nerve in the body—it is the key route for communication between the gut microbes and our brain."

All the millions of microbes in the intestines have a direct line to the brain—which is why people actually refer to the gut as the "second brain." You know how you might pee yourself if you get really scared? That's emotion having a direct effect on your digestive system. But the calls aren't always from the brain to the gut. In fact, the gut might hog the line more often than we thought.

"We've long known that the neurotransmitter serotonin plays a crucial role in the biology of anxiety and depression," says Donald N. Tsynman, M.D., a gastroenterologist at Manhattan Gastroentorology. "Furthermore, we know that the gut has a higher concentration of serotonin receptors than the brain does. That being said, we have hypothesized for years that the connection between the gut and depression is a real and strong one."

And this hypothesis is proving to be a sound one—studies about the gut/brain connection are being published regularly (and we'll get into some of these below).

What do I do to change my gut?

As with most gut problems, the answer doesn't lie in a pill or a shot, but in the scariest medicine of all—dietary changes!

Sadly, a steady dose of Taco Bell and raw cookie dough is not the diet of choice to heal intestinal issues—so while they might make you feel better in the moment, these foods won't do much to help with gut-related depression. But you don't necessarily have to do a total dietary 180 and do the Whole30 to feel a difference—and there's growing evidence that even moderate dietary changes do relieve depression.

"From my clinical experience working with IBS patients, diet changes that result in a calmer gut appear to impact overall quality of life," Scarlata says. A study from the University of Michigan found this exact idea to be true. As patients ate a low FODMAP diet, their self-reported anxiety and depression went down, while quality of life went up.

The SMILES trial, published in BMC Medicine, found that a healthy diet (lots of fruits and vegetables, increased intake of fish and whole grains) had a significant impact on depression. For the study, patients were treated with either social support or a healthy diet. In the healthy diet group, more people stayed to finish the study, and in a number of patients, depression went into remission—a marked difference from the results of the control group. 

It's important to note that these were both very small studies and the results don't prove a direct connection between gut health and depression. Eating healthy food does generally make you feel better, but that doesn't necessarily mean that your gut was causing the problem in the first place. And maybe people who don't have to run to the bathroom all the time are generally happier and less anxious.

I'm not trying to rain on the gut parade. Between these studies—and the fact that the intestines are a primary producer of serotonin—make a real case for a gut-depression connection. We'll just have to wait for more studies (and BMC alone has quite a few more in the works) before there's a solid scientific foundation.

In the meantime, it might be worth trying a modified diet if you're looking to decrease depression and anxiety.

OK—so what delicious foods do I have to give up?

With no definitive proof of gut-induced depression, there's no definitive answer for which diet works best. But there is something that all the experts said to avoid.

You've probably heard it a million times by now: Avoid processed food. Yes, Pop-Tarts are extremely tasty. And yes, it's so much easier to heat up a Stouffer's Mac and Cheese than to make an actual meal. But the high salt, fat, and sugar content in most processed foods is really just the worst for you.

"Several studies have shown that eating foods high in sugar and fat can change the chemical activity of the brain, making it more dependent on such foods," says colorectal surgeon Lynn O'Connor, M.D. "When those foods are withheld, people can suffer from withdrawal symptoms, have difficulty dealing with stress, and feel depressed."

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O'Connor isn't saying that junk food causes depression, but it does cause something close to addiction, which makes depressive and anxious symptoms even worse.

In addition to cutting out junk food, Tsynman recommends lowering alcohol intake (since alcohol is a depressive, it's only going to make you more depressed in the long run) and moderating caffeine (and possibly eliminating it, for people with heightened anxiety).

O'Connor says you should eat sources of selenium, which has been demonstrated to reduce depression and improve mood. Selenium can be found in whole grains, fish, and Brazil nuts—fish pull double duty because they're also sources of omega-3 fatty acids, a nutrient that helps protect the coverings of the brain's nerve cells, which can improve cognition and reduce depression, according to O'Connor.

Of course, depression isn't all in the gut—getting enough exercise is also a critical part of mental health. But if you want to boost your gut health, a study from the University of Wales Swansea suggests that probiotics might improve your mood too: Participants drank a probiotic-filled drink, and by the end of three weeks, people who rated themselves towards the depressive end of the scale jumped up towards the "elated" end of the scale. That's not to say they were filled with constant glee, but the drink did seem to improve their moods, especially among people who were initially depressed.

Thankfully, these dietary recommendations aren't crazily strict—mostly, you should eat vegetables, whole grains, omega-3s, kefir or other probiotics... and maybe throw in some Brazil nuts for good measure.

Though you should avoid eating a bunch of processed food, not drink a ton of alcohol, and watch your caffeine, the experts mostly recommend moderation. According to Tsynman, "Moderation is the goal when it comes to healthy food choices to ensure that people can continue to have well-balanced meals."

Any other weird gut stuff I should know?

Yep! Depressed people could one day eat poop to feel better.

I realize that's a wild sentence. But fecal transplants (i.e., eating a capsule of a healthy person's poop) has been shown to relieve intestinal problems. And if relieving intestinal problems reduces depression, using a fecal transplant instead of Prozac isn't such a crazy idea.

There haven't been any human tests to show the efficacy of fecal transplants as a depression treatment yet, but a paper published in the Clinical Psychopharmacology and Neuroscience Journal shows the potential of fecal transplants to treat neurological disorders. If you're worried that your doctor's going to hand you a prescription for poop the next time you're feeling down—don't stress. Fecal transplant studies aren't there yet, and it'll be quite a while before any such treatment would be approved, especially for depression.

On the flip side, if you're thinking of taking a little bit of a happy person's poop and doing an at-home transplant, please, please don't. Oh for the love of God, please don't do that. It won't work, and it'll be ever-so-gross.

Though there isn't hard proof to show that depression and gut health are connected, it's pretty likely that what you eat does affect how you feel.

I know that's a real "no duh" statement, but we're not talking about, "I just ate a salad and I feel so great." We're talking about diet reversing the dread, apathy, and pain that depression and anxiety can cause. And if we can relieve some of the most common mental health issues through eating healthier food, that's pretty good news.

Amber Petty is a freelance writer in Los Angeles. If you like easy crafts and Simpsons gifs, check out her blog, Half-Assed Crafts.