How probiotics could help boost your daily mood

For this study, researchers recruited 88 participants who had not taken any probiotics or antibiotics in the previous 3 months, and did not have a past or current diagnosis of a mental disorder.

Study participants were randomly assigned to one of two groups: one group taking a probiotic and the other receiving a placebo for 4 weeks.

All participants also completed a series of commonly-used mental health questionnaires both at the start of the study and after 4 weeks.

These questionnaires included the Penn State Worry Questionnaire (PSWQ), the Perceived Stress Scale (PSS), the Centre for Epidemiological Studies Depression Scale (CES-D), and the Bermond–Vorst Alexithymia Questionnaire (BVAQ).

Additionally, all participants reported their mood each day to researchers.

“While lots of people have started to take probiotics, science still doesn’t have a good understanding of precisely how probiotics work and all the various effects they may have on our physiology,” Katerina Johnson, PhD, a postdoctoral researcher in the Clinical Psychology Unit at the Institute of Psychology at Leiden University in The Netherlands, and co-lead author of this study told Medical News Today.

“This field may though in the future be able to offer novel solutions when it comes to treating mental health,” Johnson added.

“The burgeoning field of the gut microbiome is revealing the numerous effects that bacteria in the gut may have on the brain and behavior,” she continued.

“We know that the gut–brain connection provides various routes through which bacteria in the gut can influence how we feel and behave, including via the vagus nerve, immune system, and hormones. So here we used a combination of methods to capture how probiotics might influence the ability to regulate our emotions and affect our mood,” the researcher explained.

At the study’s conclusion, researchers found that probiotics helped improve participants’ negative mood through their daily mood reporting.

However, the scientists reported not finding any evidence of a beneficial effect from probiotics when using the standard psychological questionnaires assessing emotion.

“It’s interesting that we saw this significant reduction in negative mood based on tracking how people felt each day,” Johnson said. “By monitoring people daily, rather than just assessing them before and after, it gives us [a] much better resolution of changes over time when taking probiotics.”

“One disadvantage with psychological questionnaires is that they attempt to dissect how people are feeling into discrete categories e.g. stress, anger, anxiety or depressive tendencies,” she continued.

“In contrast, asking how positive or negative someone is feeling can holistically capture a change in any emotional state. All in all, our results suggest that following people’s feelings on a daily basis can detect changes that may be missed by using the standard psychological questionnaires that are common practice in the field,” said Johnson.

Johnson and her team also found that the probiotics took about 2 weeks to help reduce a participant’s negative feelings, which is a similar time span for antidepressants to start working.

“The comparable timescales are an interesting aspect of our findings,” Johnson pointed out. According to her:

“It may be a sign that both antidepressants and probiotics can affect our mood through shared pathways. In fact, we know that both can signal to the brain via the vagus nerve — the main nerve connecting the gut and brain — and also that they both have anti-inflammatory effects.”

“Our research has promising implications in terms of the effect of probiotics on mood, but there still remain unknowns surrounding probiotics and their long-term effects,” she added.

“More studies would have to be conducted first, but it’s possible that in the future probiotics could be used in a targeted way to help prevent low mood progressing to mental health conditions like depression,” said Johnson.

MNT had the opportunity to speak with Nathan Caroll, DO, chief resident psychiatrist at Jersey Shore University Medical Center in New Jersey, about what he called an “exciting study.”

“While we have known about the gut-brain connection for a long time, new aspects of this connection are continuously being discovered,” Caroll, who was not involved in the recent research, commented.

“This study highlights additional ways in which gut health can be optimized to reduce negative feelings. Probiotics may offer a novel gut-brain pathway to help address depression or anxiety,” he suggested.

As for the context in which we should consider the study findings, Carroll proposed that:

“The research into probiotics can be viewed in the context of a larger discussion about a holistic, or whole-body, approach to mental health. Most people don’t know that the gut contains five times more neurons than the spinal cord! It’s called our enteric nervous system.”

“I was very impressed by the large reduction in negative mood symptoms the researchers saw with the addition of probiotics,” the psychiatrist told us.

“Given that probiotics are generally considered safe and well-tolerated, there may be an argument for using them as part of a lifestyle psychiatry approach to treating mental illness. Of course, people should speak with their physician before starting any new supplement,” he advised.

For those who may want to try boosting their mood through their diet and possibly try a probiotic, Monique Richard, MS, RDN, LDN, a registered dietitian nutritionist and owner of Nutrition-In-Sight, offered some tips.

First, Richard advised, it is important to assess product labelling carefully. “Refrain from blindly choosing the most convenient probiotic at your fingertips or brands touting the ‘highest count’ of strains,” she cautioned.

“More does not always necessarily equate to better. Consuming loads of new or different species into your current microbiota environment may not bode well, and could cause bloating, flatulence, diarrhea, and other side effects,” the nutritionist added.

Secondly, and as importantly, Richard emphasized that nothing can replace direct, individually tailored health and nutrition advice from a qualified profesional.

“Everyone’s individual microbiome is unique and each person will have a different response to taking a probiotic,” she explained. “Meet with a registered dietitian nutritionist (RDN) in order to understand what strain(s) of probiotics may be beneficial to your current goals, health status, dietary intake, and gut profile.”

Probiotics are abundant in fermented foods, so that may be one way to go, rather than opting for dietary supplements straight away.

Even in that case there are pros and cons to be aware of, Richard said:

“Overall, there are limited studies on specific recommendations [regarding] fermented foods‘ impact, and [this] can vary widely per product in ‘active live culture’ strain levels due to processing methods, shelf life, and more, but [fermented foods] also often go hand-in-hand [with] being naturally high in fiber and beneficial plant compounds, so try kimchi, kefir, sauerkraut, natto, miso, […] or kombucha.”

Finally, she said, we must not forget about the basics. “Adequate protein, carbohydrate, and fat intake also play a critical role in neurotransmitter production of serotonin, dopamine, gamma-aminobutyric acid (GABA), melatonin, and more that affect mood,” noted Richard.

“And make sure to get enough fiber from fruits and vegetables are an essential prebiotic — food for the probiotic to digest,” she added.

Reflecting on the results of the recent study, in which she was not involved, Richard mused:

“‘Don’t worry, be happy’ — if only it were as easy as those song lyrics suggest, right? Maybe it can be, with practice. We do know that nourishing our body with variety, balance, and goodness from nutritious foods and clean water regularly help naturally navigate how we respond and regulate emotions and our ability to be resilient.”