Researchers tested whether a specific type of beneficial bacteria called Limosilactobacillus reuteri could help improve health in people aged 50-69. Ten volunteers took capsules containing these bacteria daily for 12 weeks. While the bacteria didn’t significantly change sex hormone levels as hoped, the study found encouraging results: participants experienced decreases in body fat percentage, blood pressure, and inflammation markers. The bacteria also changed the gut microbiome in ways that previous research suggests could help fight obesity. Though this is an early-stage study with a small group, it suggests this particular bacterial strain might have real health benefits worth studying further.

The Quick Take

  • What they studied: Whether taking a specific probiotic (beneficial bacteria) supplement could improve body composition, blood pressure, and hormone levels in middle-aged and older adults
  • Who participated: 10 healthy adults between ages 50-69 who participated in a 12-week study at a university in Japan
  • Key finding: After 12 weeks, participants showed meaningful reductions in body fat percentage, blood pressure, and inflammation markers, though sex hormone levels didn’t change as expected
  • What it means for you: This suggests the bacteria may support weight management and cardiovascular health in older adults, but much larger studies with control groups are needed before making recommendations. Don’t expect this as a standalone treatment, but it may be a helpful addition to healthy lifestyle choices

The Research Details

This was a pilot study, which means it’s a small, early-stage test to see if an idea is worth studying more carefully. All 10 participants received the same treatment—capsules containing 10 billion living bacterial cells daily for 12 weeks. Researchers measured body composition, blood pressure, blood sugar, inflammation markers, and analyzed stool samples to see how the bacteria changed the gut microbiome. A pilot study doesn’t have a comparison group (placebo group), so researchers can’t definitively say the bacteria caused the improvements versus other factors.

Pilot studies are important because they help researchers decide whether to invest time and money in larger, more rigorous studies. This approach allowed researchers to gather preliminary evidence about safety and potential benefits before conducting expensive, large-scale trials. Understanding how specific bacteria affect the gut microbiome helps scientists identify which strains might be genuinely helpful versus just marketing hype.

This study has both strengths and limitations. Strengths include careful measurement of multiple health markers and analysis of gut bacteria changes. Limitations include the very small sample size (10 people), lack of a control group for comparison, and the open-label design where participants knew they were receiving treatment (which can create placebo effects). The short 12-week duration means we don’t know about long-term effects. These factors mean the results are preliminary and need confirmation in larger studies.

What the Results Show

The main goal was to see if the bacteria would increase testosterone levels in older adults, similar to what happened in mouse studies. This didn’t happen—sex hormone levels remained relatively stable. However, the study revealed several unexpected positive findings. Body fat percentage decreased significantly in the group, and blood pressure measurements improved. Additionally, markers of inflammation in the blood decreased, which is important because chronic inflammation is linked to many age-related diseases. These improvements occurred despite participants not making major lifestyle changes, suggesting the bacteria itself contributed to the benefits.

Analysis of stool samples showed that taking the bacterial supplement increased three specific types of beneficial bacteria: Butyricimonas, Holdemania, and Odoribacter. Previous research has linked these bacteria to better metabolic health and reduced obesity risk. This finding is important because it shows the supplement actually colonized the gut and created measurable changes in the bacterial community, not just passed through the system unused.

Earlier studies in mice showed this bacterial strain could prevent weight gain and boost testosterone. This human study confirms some benefits (body fat reduction) but contradicts others (testosterone increase). This difference between animal and human results is common in nutrition research and highlights why animal studies must be confirmed in people. The findings align with growing evidence that specific probiotic strains can modestly improve metabolic health markers, though effects are usually smaller in humans than in controlled laboratory settings.

The biggest limitation is sample size—10 people is very small, making it hard to know if results would hold in larger groups. Without a placebo control group, we can’t rule out that improvements came from participants’ expectations or other lifestyle factors. The study lasted only 12 weeks, so long-term effects remain unknown. The study was open-label, meaning participants knew they were receiving treatment, which can influence results through placebo effects. Additionally, all participants were relatively healthy, so results may not apply to people with obesity or metabolic diseases.

The Bottom Line

Based on this pilot study alone, we cannot recommend this specific probiotic as a treatment. However, the results are promising enough to warrant larger, well-controlled studies. If you’re interested in probiotics for metabolic health, discuss options with your doctor. General recommendations remain: maintain a balanced diet, exercise regularly, manage stress, and get adequate sleep—these have strong evidence for improving body composition and blood pressure. Confidence level: Low to Moderate (this is preliminary research).

This research is most relevant to adults aged 50 and older interested in natural approaches to metabolic health. People with high blood pressure, elevated body fat, or chronic inflammation might find this interesting. However, people with compromised immune systems, severe metabolic diseases, or those taking certain medications should consult doctors before trying new probiotics. This study doesn’t provide enough evidence for anyone to make treatment decisions yet.

In this 12-week study, improvements in body fat and blood pressure appeared within three months. However, individual results vary greatly, and longer studies are needed to understand sustained effects. Realistic expectations: if this bacteria proves beneficial in larger studies, noticeable changes would likely take 4-12 weeks, with continued improvement over months. Don’t expect dramatic overnight changes.

Want to Apply This Research?

  • Track weekly body weight and waist circumference measurements, plus monthly blood pressure readings if you have a home monitor. Note energy levels and digestive comfort daily. This creates a personal data set to compare against any future larger studies or if you try this supplement under medical supervision.
  • If this supplement becomes available and recommended by your doctor, set a daily reminder to take it at the same time each day (consistency matters for probiotics). Pair this with tracking one lifestyle behavior: daily steps, water intake, or vegetable servings. This helps isolate whether improvements come from the supplement or lifestyle changes.
  • Establish baseline measurements before starting any new supplement: body weight, waist circumference, blood pressure, and how you feel. Measure these same metrics every 4 weeks. Keep a simple log of any digestive changes, energy levels, or other health observations. Share this data with your healthcare provider to help inform future treatment decisions as research evolves.

This research is a small pilot study and should not be used to make medical decisions. The findings are preliminary and require confirmation in larger, controlled studies before clinical recommendations can be made. Probiotics affect individuals differently, and some people may experience digestive side effects. People with weakened immune systems, serious illnesses, or those taking medications should consult their healthcare provider before starting any probiotic supplement. This article is for educational purposes only and does not replace professional medical advice. Always discuss new supplements with your doctor, especially if you have existing health conditions or take medications.