Could the relationship between probiotics and sleep be more important than we once thought?

A small new clinical trial has reported improvements in digestive symptoms, stool consistency, sleep quality and happiness after healthy adults took one particular probiotic strain for eight weeks.

That is genuinely interesting. The gut and brain do communicate, and researchers are increasingly investigating whether gut microorganisms may influence sleep and emotional well-being.

But before your pillow starts ordering probiotic capsules online, we need to read the small print.

This study tested one strain, at one dose, in one small group, for eight weeks. It did not prove that probiotics generally treat insomnia, depression, anxiety or age-related decline. It also did not test Noster ProBiotics.

The responsible message about probiotics and sleep is therefore encouraging, but cautious: one strain produced promising early findings that now need larger, longer and independent studies.

What did the probiotic and sleep study test?

The randomised, double-blind, placebo-controlled trial was published in The Journal of Nutrition in 2026.

Researchers enrolled 75 healthy adults aged 55 to 70. Participants were randomly assigned to receive either:

• a placebo containing maltodextrin; or
• maltodextrin containing 30 billion colony-forming units of Pediococcus acidilactici PA53 each day.

The intervention lasted eight weeks, and 69 people completed the study.

Researchers assessed digestive symptoms, stool consistency, sleep quality, happiness and perceived stress. They also examined blood markers associated with inflammation and analysed faecal bacteria using 16S ribosomal RNA sequencing.

What did the researchers find?

After eight weeks, the PA53 group showed statistically significant improvements in several measures.

Why digestive comfort matters when studying probiotics and sleep

The Gastrointestinal Symptom Rating Scale score decreased from 17.50 to 15.83, a reported improvement of approximately 9.5%.

The Bristol Stool Scale score moved from 2.50 to 3.20. That shift suggests stool consistency moved closer to the range usually considered easier to pass.

This digestive finding matters when discussing probiotics and sleep. Abdominal discomfort, constipation, reflux and bloating can all make a peaceful night feel like an unreasonable request. If someone feels physically more comfortable, sleep may improve too.

However, this study does not establish whether better gut comfort caused better sleep. It simply found that both changed during the same intervention.

Sleep quality

The average Pittsburgh Sleep Quality Index score in the PA53 group decreased from 5.62 to 4.33, which the researchers described as a 23% improvement.

A lower score on this questionnaire generally indicates better perceived sleep quality.

The word perceived is doing useful work here. Participants reported how they slept; the study was not described as measuring sleep in a laboratory with polysomnography or continuously with an objective sleep device.

Self-reported sleep matters because the person lying awake at 2 am is rather involved in the experience. But questionnaires can also be influenced by expectations, day-to-day variation and other changes in health or routine.

Happiness and perceived stress

Happiness scores increased from 33.75 to 38.05, a reported improvement of 12.7%.

Perceived stress scores fell by 3.3% in the PA53 group, but that within-group change was not statistically significant. The paper reported a significant advantage compared with placebo, yet the lack of a clear within-group improvement is another reason not to turn this into a sweeping mental-health claim.

The trial assessed healthy adults. It did not show that PA53 treats depression, anxiety or another diagnosed psychological condition. Happiness on a study scale is not the same thing as recovery from clinical depression, however enthusiastically a supplement advertisement may try to introduce the two at a party.

Inflammatory markers

The researchers reported reductions in the blood markers IL-6 and TNF-alpha, while IL-25 increased.

These changes may be relevant because immune signalling is one of the proposed communication routes within the microbiota–gut–brain axis.

Still, a laboratory marker is not a diagnosis, and changing a biomarker does not automatically prove that a person will sleep better, feel happier or remain healthier over the long term. Biomarkers can provide clues. They are not tiny medical fortune-tellers wearing lab coats.

Gut microbiome changes

PA53 supplementation was associated with changes in the relative abundance of certain gut bacteria. The researchers reported increases in genera including Ruminococcus, Blautia and Faecalibacterium.

These organisms are often discussed in relation to fermentation, short-chain fatty acid production and intestinal health. But microbiome interpretation is complicated. More of a named genus is not automatically beneficial in every person, and 16S sequencing usually cannot tell us everything about what the microorganisms were actually doing.

A changed microbiome is interesting biological evidence. It is not proof that the microbiome caused every reported improvement.

What is the gut–brain axis?

The gut–brain axis is the two-way communication network connecting the digestive system, gut microorganisms and nervous system.

Possible communication routes include:

• the vagus nerve and other nerve pathways;
• immune and inflammatory signalling;
• hormonal and stress-response pathways;
• microbial metabolites, including short-chain fatty acids; and
• signals connected with the intestinal barrier.

The relationship also travels in both directions. Stress and poor sleep may affect digestion and microbial patterns, while digestive discomfort can disturb sleep and mood.

In other words, your gut and brain are not separate tenants who politely ignore one another. They exchange messages all day—and occasionally send noisy voice notes at 3 am.

This biological connection makes research into probiotics and sleep plausible. It does not make every probiotic a treatment for every brain-related symptom.

Why the exact probiotic strain matters

The most important phrase in this article may be strain-specific.

The study did not test “probiotics” as one interchangeable family. It tested Pediococcus acidilactici PA53 at 30 billion CFU per day.

Probiotic effects can depend on:

• the genus, species and exact strain;
• the daily viable count;
• the formulation and delivery method;
• storage conditions;
• the length of use;
• the population studied; and
• the particular outcome being measured.

A positive result for PA53 cannot be pasted onto every Lactobacillus, Bifidobacterium, multi-strain product or fermented food.

One strain cannot win a small race and drag every probiotic onto the podium by the capsule.

What does the wider evidence say about probiotics and sleep?

This is not the first study to explore probiotics and sleep. Researchers have already tested several probiotic strains in people with different sleep patterns, stress levels and health backgrounds.

A 2024 systematic review and meta-analysis included 15 randomised controlled trials. It found that probiotic groups showed improvements in certain questionnaire-based sleep measures, including the Pittsburgh Sleep Quality Index. However, the authors also highlighted risk of bias in some studies and called for more research into specific sleep outcomes.

A growing pattern of encouraging findings is worth investigating. Yet the studies use different strains, doses, populations, durations and sleep measurements. That variation makes it difficult to prescribe a universal “sleep probiotic”.

The fairest conclusion about probiotics and sleep is that selected probiotics may influence subjective sleep quality in some settings, but evidence is not yet strong or consistent enough to treat probiotics as established insomnia therapy.

Why this PA53 trial needs replication

The study had worthwhile strengths. Randomisation, blinding and a placebo group help reduce several common sources of bias. Researchers also collected microbiome and blood-marker data rather than relying only on one questionnaire.

Even so, research into probiotics and sleep needs results that can be repeated by different teams in larger and more varied groups.

Important limitations include:

• It was small: only 75 participants were randomised and 69 completed the trial.
• It was short: eight weeks cannot tell us whether any benefit lasts for months or years.
• It studied healthy adults: the findings cannot be assumed to apply to people with diagnosed insomnia, depression, anxiety, dementia or significant digestive disease.
• Sleep and happiness were self-reported: these were meaningful but subjective questionnaire outcomes.
• Not every psychological measure improved: perceived stress did not significantly improve within the PA53 group.
• Many outcomes were examined: isolated findings, particularly those near the usual statistical threshold, need confirmation.
• It was one strain and dose: the results cannot be generalised to all probiotics.
• The study product came from its manufacturer: published coverage reports that Wecare Probiotics supplied PA53 and the matching placebo. The paper states that the authors reported no conflicts of interest, and the corresponding author said the company did not fund the research or control the data or publication decision. Independent replication would still strengthen confidence.

None of these points means the study should be dismissed. It means the findings should be treated as a promising beginning rather than the final bedtime story.

Does this mean probiotics treat insomnia?

No.

The trial did not recruit people with diagnosed insomnia, and it did not compare PA53 with cognitive behavioural therapy for insomnia, appropriate medicine or another recognised intervention.

Probiotics should not replace assessment when poor sleep is persistent, severe or affecting everyday function.

A conversation about probiotics and sleep should never delay a proper search for the actual cause of ongoing insomnia.

Sleep problems can be related to stress, anxiety, depression, pain, reflux, medicines, caffeine, alcohol, menopause, restless legs, thyroid problems, sleep apnoea and many other factors.

A probiotic capsule cannot apologise on behalf of four late-afternoon coffees, a snoring airway or a phone screen glowing six centimetres from your nose at midnight.

Practical ways to support your gut and your sleep

If you are interested in probiotics and sleep, keep the supplement in its proper place: one possible part of a much broader routine.

Useful habits may include:

• keeping a reasonably consistent bedtime and waking time;
• getting daylight and physical activity during the day;
• reducing caffeine later in the day;
• limiting alcohol and nicotine, particularly near bedtime;
• creating a quiet wind-down routine;
• making the bedroom dark, cool and comfortable;
• reducing stimulating screen use before bed;
• avoiding very large meals shortly before lying down;
• addressing reflux, pain, constipation or other symptoms that disturb sleep; and
• supporting gut health with varied fibre-rich foods, adequate fluids and regular movement.

Please aim for consistency, not perfection. If you have ever lain awake worrying that you are failing at sleep, you will know that turning bedtime into a performance appraisal is not especially relaxing.

Where do Noster ProBiotics fit?

Noster ProBiotics are refrigerated live culture probiotics intended to support everyday gut balance.

Noster ProBiotics were not used in the PA53 trial. We therefore do not claim that Noster will reproduce the study’s changes in sleep, happiness, inflammatory markers or gut bacteria.

That distinction matters whenever we discuss probiotics and sleep: evidence belonging to one named strain and formulation must stay attached to that strain and formulation.

Noster is also not promoted as a treatment for insomnia, depression, anxiety or age-related decline.

A carefully selected live culture probiotic may complement a routine built around nourishing food, movement, stress management and healthy sleep habits. It should not be asked to perform the jobs of your doctor, psychologist, sleep clinic, mattress and bedtime routine while everyone else takes the evening off.

If your goal is everyday digestive and microbial support, you can learn more about Noster Live Culture Probiotic Capsules.

Pop it in the fridge. Take it daily. Keep the claims wide awake.

When poor sleep needs professional attention

Speak to a doctor or qualified healthcare professional if:

• sleep problems have continued for months;
• poor sleep is making daily life difficult to manage;
• you snore loudly, gasp or appear to stop breathing during sleep;
• you have severe daytime sleepiness;
• pain, reflux, urinary symptoms or restless legs repeatedly wake you;
• your mood has remained low or anxiety is becoming difficult to manage; or
• you suspect a medicine or health condition is disrupting your sleep.

If you feel unable to cope or keep yourself safe, seek urgent help. In South Africa, the South African Depression and Anxiety Group lists its 24-hour Suicide Crisis Helpline as 0800 567 567.

Frequently asked questions

Can probiotics improve sleep?

Some randomised trials and meta-analyses have reported improvements in subjective sleep measures with selected probiotics. Results vary by strain, dose, study population and outcome. Probiotics are not established treatments for insomnia.

What probiotic was used in the new study?

The trial used Pediococcus acidilactici PA53 at a daily dose of 30 billion CFU for eight weeks.

Did PA53 treat insomnia?

No. The participants were healthy adults rather than patients recruited for diagnosed insomnia. The study found an improvement in a self-reported sleep-quality score, which is encouraging but is not proof of insomnia treatment.

Did the probiotic treat depression or anxiety?

No. Happiness improved on one scale, while perceived stress did not significantly improve within the probiotic group. The study was not a treatment trial for depression or anxiety, and probiotics should not replace counselling, prescribed medicine or other professional care.

Can the PA53 findings be applied to every probiotic?

No. Probiotic effects are strain-specific, dose-specific and outcome-specific. A result for PA53 cannot be assumed for a different strain or formulation.

Was Noster ProBiotics tested in this trial?

No. Noster ProBiotics were not tested, so this study cannot be used as evidence that Noster improves sleep, mood or happiness.

Is it safe for everyone to take a probiotic?

Probiotics have a history of apparently safe use in generally healthy people, but safety data are not equally strong for every product and population. People who are seriously ill, severely weakened or immunocompromised should seek professional advice before using a live microorganism supplement.

The friendly pharmacist’s final word

The PA53 study gives researchers another encouraging reason to investigate probiotics and sleep.

After eight weeks, healthy adults taking one specific strain reported better digestive comfort, stool consistency, sleep quality and happiness. Their inflammatory markers and gut microbial composition also changed.

That is worthwhile early evidence. It is not proof that probiotics generally treat insomnia, depression or the complications of ageing.

The trial was small, short and strain-specific. Several important outcomes were subjective, not every psychological measure improved, and the study product was supplied by its manufacturer. Larger, longer and independently replicated research is needed.

For now, look after the gut, respect the science and keep miracle claims out of the bedroom.

Your gut and brain may talk to each other, but neither has appointed a probiotic as the new Sandman just yet.

Resources

• The Journal of Nutrition: Randomised PA53 trial in healthy adults aged 55–70
• Study coverage and corresponding-author comments on product supply and independence
• Systematic review and meta-analysis: Effects of probiotics on sleep parameters
• NCCIH: Probiotics—usefulness and safety
• NHS: Insomnia guidance and when to seek help
• South African Depression and Anxiety Group: Mental-health support and helplines

This article provides general educational information and does not replace individual advice from your doctor, pharmacist, psychologist or sleep-care professional.