Diet and NutritionWellness

The Gut Bacteria and Depression Connection

Research is increasingly showing a mind-body connection. Did you know, for example, that depression could be a result of bacteria in your gut?

In 2012, scientists at University College Cork discovered that brain levels of serotonin, or the ‘happy hormone,’ are regulated by the amount of bacteria in the gut during early life. In other words, normal adult brain function depends on the presence of gut microbes from when you were a child.

But even as an adult, gut bacteria, or microbiome, seems to affect mood. It helps to maintain brain function and influences the risk of psychiatric and neurological disorders like depression.

The connection

To better understand how this works, Dr. Willa Hsueh, from the Division of Endocrinology, Diabetes and Metabolism at Ohio State University’s Wexner Medical Center, explains that gut microbiome produce enzymes that make metabolites, or small molecules that result from metabolism, from the foods we eat. Many of these metabolites affect brain, neuroendocrine, and neurological function.

“The species of bacteria that people develop are impacted by many factors including type of food ingested, environment, presence of obesity and other diseases, infections and treatment with antibiotics,” says Dr. Hsueh.

Got serotonin? Dr. Patrick Fratellone, MD, FIM, RH (AHG), an integrative MD and herbalist, says 90 percent of serotonin, or the ‘happy hormone,’ is made in the small intestines.

Multiple insults to the gut can cause low serotonin. An important one can be caused by certain food allergies or sensitivities, Dr. Fratellone says, like non-celiac gluten sensitivity or celiac disease. People who have a gluten sensitivity or allergy may experience depression, anxiety, insomnia, and lack of focus/concentration. “Each of these is caused by changes in the neurotransmitters caused by the low serotonin level,” he says, “accompanied by low levels of vitamin D3.”

Other causes include overgrowth of candida, accumulation of metals in the body, and chronic infections, Dr. Fratellone says.


It’s possible to test for gut flora and the presence of an overgrowth of certain bacteria strains, which are known to influence symptoms of anxiety and depression, says Dr. James Greenblatt, M.D., Chief Medical Officer and Vice President of Medical Services at Walden Behavioral Care and assistant clinical professor of psychiatry at Tufts University School of Medicine.

Dr. Fratellone recommends doing a blood test for allergies as well as starting a rotation and elimination dietary lifestyle. If the blood test is positive for celiac, then eliminating all gluten will result in a positive change in mood.

In addition to finding and treating the underlying cause, there are many supplements, vitamins, and herbs that help with digestion. “This will lead to changes in the neurochemistry, thus making the individual feel better,” says Dr. Fratellone. Some of these supplements include the amino acid glutamine and a probiotic. Herbs that have been shown to help alleviate gastrointestinal distress are Meadowsweet, Marsh mallow, Slippery Elm, and deglycerrhized licorice.

The bottom line is that it’s safe for women with depression to take high dose probiotics to help alleviate symptoms by maintaining a healthy gut balance, says Dr. Greenblatt.

Women’s risk

The University College Cork study showed that the serotonin-bacteria influence was sex dependent, with more effects in male compared with female animals.

Dr. Greenblatt cites a 2014 study published in Nature Communications. The study found that the microbes living in the guts of females and males react differently to diet, even if the diets are identical. “Genetics, lifestyle, diet and stress can affect the variety and abundance of certain strains of microbes in the gut, which can have a profound effect on mental health and well-being,” says Dr. Greenblatt. He says it’s unclear why women and men react differently to certain diets, but it could potentially be due to the different hormones produced by the different sexes, which affect the habitat of the gut microbiome. “Despite the differences, women are not necessarily more prone to this connection,” he says.

On the horizon

The good news is the more scientists learn about this phenomenon, the greater the benefit to our overall health. A Colorado professor is studying whether beneficial microbes can be used to treat or prevent stress-related psychiatric conditions, including depression. Ultimately, brain disorders may be treated through the gut, a much easier target for drug delivery than the brain.

Earlier this year, researchers gave 40 healthy young adults a powdered probiotic supplement every night for four weeks or a placebo, Dr. Greenblatt says. “The group that consumed the probiotic supplement began to see improvement in their moods and reported less reactivity to bouts of sadness, and had fewer depressive thoughts when compared to the non-probiotic group,” he adds. “Although preliminary, the results are promising in demonstrating the potential of probiotics as a safe and cost-effective therapy to help prevent and treat depression.”

Eventually, “the goal would be to measure bacteria and metabolites in a stool sample to determine whether there are microbiome and metabolite changes that predict or are causative of depression,” says Dr. Hsueh.

Experiencing the connection

Kim Rullo has irritable bowel syndrome (IBS) and depression/anxiety. She’s read about gut bacteria affecting overall health in terms of immunity issues, inflammation, and the like, so she says she wouldn’t be surprised if they were related somehow.

“I am always looking for ways to alleviate depression symptoms, whether it be exercise or other,” says Rullo. “I did a regimen of Activia and exercise when I was having severe stomach issues, and that seemed to positively affect my overall health.” She says with more research, she would probably explore a simple regimen once again to help her general wellness.

Another woman who has depression (and asked for her name to be withheld) says she definitely agrees with the gut-mental connection. “It’s very real,” she says. She’s been using a magnesium supplement every day for a year, and it has totally helped her get over depression. She never realized the connection before. Sure enough, magnesium is necessary for serotonin production.

She only heard about the supplement because she started seeing an acupuncturist, as traditional therapy wasn’t helping. Even though she went to the acupuncturist for depression, she was asked about how often she goes to the bathroom. The supplement was one of the first things recommended.

Of course, she did her own research as well. She read a lot of reviews and talked to her doctor. “[The supplement] has become a necessity for me,” she says. “For me, what I eat, my weight, constipation, and depression are all connected. Taking constipation out of the mix has helped break a vicious cycle.”

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Lisa A. Goldstein

Lisa A. Goldstein

Lisa A. Goldstein is a freelance journalist with a Master’s in Journalism from UC Berkeley. She has two kids, a love of books and sweets, and wishes her metabolism is what it used to be.