Acacia Fiber and Probiotic BLa80 in Irritable Bowel Syndrome with Constipation


The Impact of Acacia Fiber and Probiotic BLa80 on Irritable Bowel Syndrome with Constipation: Insights from the NUTRIC Study

Irritable Bowel Syndrome with predominant constipation (IBS-C) affects a significant portion of the global population, impairing quality of life and increasing the risk for various health complications. Despite numerous studies, effective and safe long-term treatments remain elusive. The NUTRIC study aims to explore the potential benefits of Acacia fiber (AF) and Bifidobacterium animalis subsp. Lactis (BLa80) on IBS-C symptoms.

Study Design

The randomized, double-blinded, placebo-controlled trial included 180 participants, conforming to the Rome IV criteria for IBS-C. Over 8 weeks, participants received either a probiotic supplement, a fiber supplement, or a placebo, following an initial 4-week observation period to establish baseline measurements. The primary outcomes measured were stool frequency, consistency, and mass, alongside secondary outcomes focusing on IBS severity, constipation symptoms, anxiety, depression, and quality of life.


The intervention revealed significant improvements in stool frequency for both the AF and BLa80 groups compared to placebo. The AF group experienced a clinically meaningful increase in weekly stool frequency, exceeding the threshold set by the US FDA for clinical relevance. Conversely, while BLa80 significantly decreased IBS symptom severity scores, the change in stool frequency was less pronounced compared to AF.

Interestingly, no significant improvements were observed in stool mass or overall stool consistency across the groups. The study also noted high compliance rates with study supplements and protocols, and only mild to moderate gastrointestinal symptoms were reported as adverse events, which were mostly unrelated to the study treatments.

Efficacy of Treatments

The NUTRIC study provides compelling evidence that both Acacia fiber (AF) and Bifidobacterium animalis subsp. Lactis (BLa80) can enhance stool frequency significantly in patients suffering from Irritable Bowel Syndrome with constipation (IBS-C). Notably, the AF treatment surpassed the clinical significance threshold for stool frequency improvement, which aligns with the U.S. FDA guidelines suggesting that an increase of more than one stool per week is meaningful for patients with IBS-C. This result points to the potential of AF as a reliable supplement to improve bowel regularity.

In contrast, while the probiotic BLa80 demonstrated a significant reduction in the severity of IBS symptoms compared to placebo, its impact on stool frequency was modest. This finding is crucial as it suggests that while BLa80 may alleviate some symptoms related to IBS, its efficacy in modifying stool patterns is less robust than AF. However, the substantial decrease in symptom severity scores suggests that BLa80 could play a vital role in improving the overall quality of life and managing the discomfort associated with IBS-C.

Mechanistic Insights

The study did not explicitly investigate the mechanistic pathways through which AF and BLa80 exert their effects. Previous literature suggests that probiotics like BLa80 may enhance gut motility and modulate the gut microbiome, thereby improving stool frequency and reducing symptom severity. The mechanism is likely linked to alterations in the microbial composition, particularly increases in beneficial bacteria such as Bifidobacteria, which can influence gut motility and immune function.

On the other hand, AF’s effectiveness might be attributed to its high fermentability and the resultant production of short-chain fatty acids (SCFAs) which are known to stimulate colonic transit. Additionally, AF’s prebiotic effects include increasing the biomass of beneficial microbial populations, which could further assist in normalizing bowel movements.

Limitations and Placebo Response

A significant aspect of the NUTRIC study is the high placebo response, which is a common occurrence in dietary intervention studies, especially those involving gastrointestinal symptoms. This placebo effect complicates the interpretation of treatment efficacy, particularly for subjective outcomes like pain and discomfort. It highlights the necessity of employing robust clinical trial designs that can distinguish between true treatment effects and placebo responses more effectively.

The study’s reliance on self-reported outcomes introduces potential biases, where subjective interpretations can affect the reporting of symptom severity and stool characteristics. While the use of validated questionnaires attempts to mitigate this issue, future studies could benefit from incorporating more objective measures, such as biomarkers or direct motility assessments, to provide a clearer picture of the physiological impacts of treatment.

Future Research Directions

Given the promising results of AF and BLa80, further research should explore their potential synergistic effects when used in combination (synbiotics), which might enhance therapeutic outcomes. Additionally, studies should aim to elucidate the specific mechanisms by which these treatments affect gut physiology and microbiome composition. Understanding these pathways will be crucial for optimizing treatment strategies and tailoring interventions based on individual patient profiles, potentially improving treatment efficacy and patient compliance.

Moreover, extending the duration of the intervention and including larger sample sizes could help to confirm the findings and establish long-term safety and effectiveness, providing more definitive guidance for the management of IBS-C.


The NUTRIC study’s findings underscore the potential of specific dietary supplements in managing IBS-C effectively. By further exploring and understanding the complex interactions between diet, microbiome, and gut motility, healthcare providers can better tailor interventions to meet the unique needs of IBS-C patients, potentially improving outcomes and enhancing the quality of life.


  1. JanssenDuijghuijsen L, van den Belt M, Rijnaarts I, et al. Acacia fiber or probiotic supplements to relieve gastrointestinal complaints in patients with constipation-predominant IBS: a 4-week randomized double-blinded placebo-controlled intervention trial. Eur J Nutr 2024 Apr 23.
Last update: 28 April 2024, 09:12


Gastroenterologist - Hepatologist, Thessaloniki

PhD at Medical School, Aristotle University of Thessaloniki, Greece

PGDip at Universitair Medisch Centrum Utrecht, The Netherlands

Ex President, Hellenic H. pylori & Microbiota Study Group