Share on Pinterest
Probiotics and prebiotics can be taken as supplements, but they can also be found in certain foods. Getty Images
  • Researchers in a new study say probiotics can help ease depression, especially if used in conjunction with prebiotics.
  • They say probiotics can be found in foods such as yogurt, and prebiotics can be found in high fiber foods such as bananas.
  • Both can also be taken as supplements.
  • The new study falls in line with other recent research that ties gut health and diet to mental health.

Probiotics — the microorganisms introduced to the human gut for their beneficial qualities — may also help relieve depression.

That’s according to a study released earlier this month.

Taking them with prebiotics can help as well, according to researchers involved in the study that was published in BMJ Nutrition, Prevention & Health.

The researchers also said the jury is still out on how probiotics might help with anxiety.

The study is part of a growing interest in recent years in what scientists call the gut-brain axis.

“Some literature study results indicate an association between gut health and mental health,” Dr. Leela R. Magavi, the regional medical director for Community Psychiatry, California’s largest outpatient mental health organization, told Healthline. “Depression and anxiety are intertwined. If probiotics and prebiotics improve depressive symptoms, many could experience an improvement in anxiety as well.”

The BMJ research looked at relevant studies published in England between 2003 and 2019 that examined the potential therapeutic contribution of prebiotics and probiotics in adults with depression and anxiety.

Researchers found 7 of 71 potential studies that met the criteria for inclusion. All seven looked at least one probiotic strain, while four looked at combinations of multiple strains.

All the studies varied in methods, clinical considerations, and design. But all of them concluded that probiotic supplements alone, or combined with prebiotics, may be linked to measurable reductions in depression.

The studies also showed a significant improvement in symptoms and clinically relevant changes in biochemical markers of anxiety.

“Studies have shown that depression is related with the constitution, amount, and species of intestinal microbiota,” Mahmoud Ghannoum, PhD, the co-founder of microbiome company BIOHM, told Healthline.

“It’s possible to distinguish between patients with depression and people without depression through the species of microbiota in their gut,” Ghannoum said. “Depressed patients have a reduced microbiome abundance degree and alpha diversity, and the amount of (probiotic strains) in the feces of patients with major depression was less than that of healthy people.”

“If a causal relationship between probiotics and depression is proven, then the use of probiotics as an adjunct therapy for depression is rational,” he added.

There were caveats to the BMJ study that made drawing conclusions difficult, researchers said.

None of the studies were of long duration, and the number of participants in each was relatively small.

“Further studies with appropriate controls and large-scale use of human subjects are needed before definitive statements can be made,” Dr. Carrie Lam from the Lam Clinic in Tustin, California, told Healthline. “This area of research is valuable because patients who suffer from mental health problems can benefit from alternative methods of alleviating those problems. There is also the suggestion that antidepressants may be influenced by the anti-inflammation effects of probiotics.”

Lam said dietary approaches may work well with depression because “there are a significant number of neurons in your gut system, as well as your brain. Serotonin, the neurotransmitter involved in both depression and anxiety, is in a high concentration in your gut system.”

The study itself speculates that “probiotics may help reduce the production of inflammatory chemicals, such as cytokines, as is the case in inflammatory bowel disease. Or they help direct the action of tryptophan, a chemical thought to be important in the gut-brain axis in psychiatric disorders.”

Whatever is going on in there, it’s likely the BMJ study will encourage more investigation.

“Clearly, there is an unmet need to understand these conditions, and it’s important we find ways to address them therapeutically and through dietary supplements,” said Ghannoum, who in addition to being co-founder of BIOHM, serves as director of the Integrated Microbiome Core and Center for Medical Mycology at Case Western and UH Cleveland Medical Center.

Probiotics are considered beneficial to your health in a number of ways.

Probiotics are in foods such as yogurt and sauerkraut and contain microorganisms intended to maintain or improve “good” bacteria (normal microflora) in the human body.

The prebiotics on which they feed are typically found in high fiber foods such as whole grains, bananas, greens, onions, garlic, soybeans, and artichokes.

Side effects are rare. Both probiotics and prebiotics can also be taken as supplements.

“People typically take them as a capsule by mouth, but they are also available as powders and chewable tablets,” Kristel Bauer, PA-C, a physician’s assistant and founder of the health and wellness website Live Greatly, told Healthline. “It’s really important to make sure you are getting a probiotic from a respectable source and are paying attention to the strains of bacteria because the kind you will want to use varies based on what you’re trying to address.”

“I think we need more research,” Bauer added. “Results may also vary based on the strain of probiotic used. Personally while in practice, I would always recommend a probiotic that also addressed lifestyle, nutrition, stress management, proper sleep, and exercise. I can say that I have seen some really wonderful responses with that approach.”