Published on June 4, 2025
Is it enough to take L. reuteri in capsule form for just a few days – or is yogurt more sensible in the long term?
The question of whether one can simply take Limosilactobacillus reuteri in capsule form for a few days and thereby permanently change something in the gut is frequently asked. Here are the most important scientifically proven facts about this:
1. Temporary colonization, no permanent colonization
Contrary to what many assume, L. reuteri does not permanently colonize the gut when taken orally. Several studies show that even probiotic strains with high tolerance and effect usually only pass through the gut temporarily as long as they are regularly supplied. If intake is stopped, the detectable amount of these bacteria disappears within a few days to weeks (Walter et al., 2018; Derrien & van Hylckama Vlieg, 2015).
This is partly because, in people in Western societies, the original ecological niches for these bacteria have been lost due to modern diet, medications (especially antibiotics), and hygiene standards (Blaser, 2014). Permanent settlement is rarely successful under these conditions.
Taking capsules for just a few days is usually not enough. It depends on the continuous supply, similar to a plant that must be watered regularly to thrive.
2. Capsule vs. yogurt – differences in effect and cost
While L. reuteri capsules are a convenient option, homemade yogurt offers several advantages:
- Cost: From a single capsule, up to 20 servings of yogurt can be produced through fermentation. This makes the yogurt significantly cheaper – especially with daily use.
- Dosage: The yogurt contains a much higher number of germs than a single capsule. Studies show that probiotic effects are often dose-dependent (Ouwehand et al., 2002).
- Additional metabolites: During fermentation, postbiotic substances such as short-chain fatty acids, B vitamins, or bioactive peptides are produced, which can additionally promote health (Wegh et al., 2019).
Survival rate of probiotics in the stomach: capsules vs. yogurt
Challenges for probiotics in the stomach
The human stomach, with its acidic pH (about 1.5 to 3.5), presents a significant hurdle for orally taken probiotics. Many probiotic strains are sensitive to this acid and can be inactivated during stomach passage.
Survival rate in probiotic capsules
A study examined the resistance of various commercial probiotics to simulated stomach conditions. The results showed that many of these products, especially those without acid-resistant coating, had a low survival rate. Some products showed a reduction of viable bacteria by up to 3 log levels after 90 minutes in an acidic environment (pH 2), corresponding to a 1,000-fold reduction.
Another investigation confirmed that many probiotic capsules without special protective mechanisms are not sufficiently resistant to stomach and bile acids, which calls their effectiveness into question.
Survival rate in fermented dairy products like yogurt
In contrast, fermented dairy products like yogurt provide a protective matrix for probiotic bacteria. A study showed that probiotic strains in yogurt had a higher survival rate during stomach passage. This is attributed to the buffering capacity of milk proteins and other components of yogurt, which raise the pH in the stomach and thus reduce the acid effect.
Additionally, it was found that the combination of probiotics with dairy products significantly improves the survival rate of bacteria compared to water. In one study, certain Lactobacillus strains survived in milk up to 197% better than in water.
The survival rate of probiotic bacteria during stomach passage is crucial for their effectiveness in the gut. Studies show that fermented dairy products like yogurt provide a protective environment that weakens the acid effect of the stomach and thus increases the survival rate of probiotics. In contrast, many probiotic capsules, especially those without acid-resistant coating, may have a lower survival rate.
Therefore, regular consumption of probiotic yogurt can be a more effective method to harness the benefits of probiotic bacteria.
3. Long-term effect requires long-term use
Many of the documented positive effects of L. reuteri, such as on oxytocin production, muscle mass, sleep, or mood, appeared in studies only after several weeks of daily intake. The effect is not only based on short-term colonization but on the constant interaction of the bacteria with the immune system, the gut nervous system, and hormonal axes (Varian et al., 2016; Poutahidis et al., 2013).
Summary:
- Taking L. reuteri capsules for several days is not enough, as the strain usually does not permanently settle in the gut.
- For a sustainable effect, regular intake is necessary.
- Homemade yogurt is more effective, cheaper, and contains additional health-promoting substances.
- The positive effects usually arise only after continuous use over several weeks.
Sources:
- Blaser MJ (2014). Missing Microbes. Henry Holt.
- Derrien M & van Hylckama Vlieg JET (2015). Fate, activity, and impact of ingested bacteria within the human gut microbiota. Trends in Microbiology, 23(6), 354–366.
- Ouwehand AC et al. (2002). Probiotic and other functional microbes: from markets to mechanisms. Current Opinion in Biotechnology, 13(5), 483–487.
- Poutahidis T et al. (2013). Microbial symbionts accelerate wound healing via the neuropeptide hormone oxytocin. PLoS One, 8(10):e78898.
- Varian BJ et al. (2016). Beneficial bacteria inhibit cachexia. Oncotarget, 7(9), 11803–11816.
- Walter J et al. (2018). Establishing or Exaggerating Causality for the Gut Microbiome: Lessons from Human Microbiota-Associated Rodents. Cell, 174(4), 800–804.e6.
- Wegh CA et al. (2019). Postbiotics and Their Potential Applications in Early Life Nutrition and Beyond. International Journal of Molecular Sciences, 20(19), 4673.
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