A Food to Lift Your Mood?

Probiotics, the live bacteria and yeast found in yogurt, fresh sauerkraut, and other fermented foods—as well as dietary supplements—have long been known to support digestive health and immunity. Now, researchers have discovered that probiotics may also ease mood-related disorders, like anxiety and depression.

About the Research

Probiotic supplements reduced participants’ responses to sad feelings and aggressive and obsessive thoughts, according to a 2015 Dutch study from Leiden University and Leiden Institute for Brain and Cognition. Reducing these reactions to sadness and stress may, in turn, reduce the risk of deep and prolonged anxiety and depression.

The supplements used in the Dutch study contained two grams (2,000 mg) of multiple types of probiotic bacteria, including Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus casei, Lactobacillus salivarius, Lactoccocus lactis, Bifidobacterium bifidum, and Bifidobacterium lactis. Participants took the supplements every day for four weeks. These same probiotics were also found to reduce anxiety and depression in earlier studies.

"We used multi-species probiotic supplements because we already know that the combination of specific strains can have a more positive effect than any one strain alone," says Laura Steenbergen, lead researcher on the Dutch study. "The specific strains we used have also previously been found to work, both individually and in combination, to protect the lining of the intestinal tract, contributing to the beneficial effects."

But Steenbergen warns that there are many different brands and species of probiotic bacteria, some of which act differently than others in the body. These bacteria may also act differently when used alone or in combination with other probiotic strains or species. Furthermore, some probiotic bacteria may actually compete with others and become less effective in the process. Any mix of probiotics, as well as doses, would have to be tested before researchers know if different strains produce similar or different effects.

Probiotics and Prebiotics

In order to survive and thrive, probiotics need their own forms of food, known as prebiotics. Prebiotics are fiber-like, non-digestible carbohydrates found in foods including whole grains, bananas, onions, and honey, as well as supplements. Some foods, such as yogurt, contain both prebiotics and probiotics. One small recent British study found that participants who took prebiotic supplements for three weeks were less inclined to dwell on negative thoughts than those who took a placebo. Overall, however, early research on prebiotics’ effect on emotional reactions have had mixed results.

How Probiotics May Improve Moods

Research has yet to determine specifically how pre- or probiotics help reduce symptoms of depression and anxiety, but some scientists also think there is a link to the vagus nerve, which runs from the brain to the intestinal tract. The vagus nerve sends important signals about hunger, fullness, and feelings of comfort and discomfort from the gut to the brain and back again. Some researchers speculate that probiotic stimulation of the vagus nerve could account for the positive effect on mental health. (Since the nerve runs through several organs, it also plays other roles in health and wellbeing, such as controlling heartbeat.)

"In animal studies, Lactobacillus strains have also been shown to produce neurotransmitters (chemicals that send signals from one brain cell to another), like GABA (gamma-aminobutyric acid), which can help reduce levels of the stress-induced hormone cortisol in the body," explains Tania Tyles Dempsey, MD, ABIHM, founder of Armonk Integrative Medicine in New York. "Controlling cortisol levels is important for overall health, but can also decrease anxiety and depression."

Although generally considered safe, probiotics in supplement form can act like medication and potentially interfere with other therapies. If you have any medical condition or are considering giving probiotics to children or elderly adults, speak with your physician first.

How You Can Benefit

"Eating fermented foods that contain some of the same strains of bacteria used in the study might be beneficial to one's mental health," says Dempsey. "But there are many fermented foods on the market that contain added sugars and other ingredients that can cancel out these good effects, so it is important to check ingredients on labels to assure that you are getting the highest quality product." Look for plain (unflavored) yogurt and kefir with "live & active cultures" on the label; every brand is likely to contain at least one or two strains of probiotic bacteria used in the study.

Tania Tyles Dempsey, MD, reviewed this article.


Dempsey, Tania Tyles, MD. E-mail to author, May 16, 2015.

Steenbergen, Laura. E-mail to author. May 15, 2015.

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