Yeast-fermented bread shows promise in preventing asthma symptoms

A recent study published in Current Developments in Nutrition investigated the effects of a functional bread fermented with yeast (Saccharomyces cerevisiae) in asthma prevention.

​​​​​​​Study: A Functional Bread Fermented with Saccharomyces cerevisiae UFMG A-905 Prevents Allergic Asthma in Mice. Image Credit: Sunshine Seeds/Shutterstock.com

Background

Asthma is a complex, heterogeneous disease characterized by airway inflammation, remodeling, and hyper-responsiveness.

Asthma prevalence has been increasing, particularly in more urbanized and high-income countries. Various factors, such as lifestyle changes, obesity, gut microbiota, diet, and environmental exposures, are associated with this surge in prevalence.

Preclinical studies have demonstrated that fungi, bacteria, and other microbes could prevent the development of asthma. While the potential role of probiotics has been highlighted, the best microbe, dose, preparation, and regime are yet to be defined. Probiotics are bacteria from Bifidobacterium and Lactobacillus genera.

Other bacteria and yeasts are also used as probiotics. S. cerevisiae UFMG A-905, isolated from a Brazilian alcoholic beverage, exhibits probiotic characteristics and can prevent bacterial infection, food allergy, colitis, and mucositis.

Previously, the study’s authors reported that the isolation prevented asthma-like characteristics in an animal model.

About the study

In the present study, researchers examined the effects of S. cerevisiae UFMG A-905-fermented bread (UFMG-A905 bread) in asthma prevention. They developed microcapsules containing the yeast isolate by the ionotropic gelation method.

The number of viable cells in the microcapsules was determined. Further, they prepared three bread formulations: 1) commercial yeast-fermented bread (COM bread), UFMG-A905 bread, and UFMG-A905 bread with microcapsules (UFMG-A905-C bread).

Breads were lyophilized and reconstituted into biscuits for better acceptance by animals. Samples of preparations (acid masses, loaves, and bread) were collected to enumerate total bacteria, lactic acid bacteria, and yeasts.

BALB/c mice aged six to eight weeks were sensitized twice with ovalbumin (OVA) or saline a week apart and intranasally challenged with OVA for three days a week later.

Mice were stratified into five groups – 1) saline-treated and -challenged (SAL), 2) saline-treated, OVA-challenged (OVA group), 3) COM bread-fed, OVA-challenged (COM group), 4) UFMG A-905 bread-fed, OVA challenged (UFMG-A905 group), and 5) UFMG-A905-C bread-fed, OVA-challenged (UFMG-A905-C group). Bread feeding was initiated 10 days before sensitization and continued until the challenge protocol.

Animal weight was measured weekly, and fecal yeast counts were determined. Respiratory function was measured 24 hours after the last challenge.

Bronchoalveolar lavage (BAL) was analyzed for cytokine production; total cell count was estimated.

The right lung was homogenized with a protease inhibitor cocktail. Interleukins (ILs) were measured in the BAL and lung homogenate.

Findings

The COM bread comprised 1.2 x 10⁹ colony-forming units (CFU) of total bacteria/g, 4.6 x 10¹¹ CFU of lactic acid bacteria/g, and 6.85 x 10⁴ CFU of yeast/g. The UFMG-A905 bread had increased yeast but reduced total and lactic acid bacteria.

Microbial growth did not occur after baking. Variations in the body weight of mice during treatment, sensitization, and challenge protocols were not significantly different between groups.

On treatment day 1, no significant yeast growth occurred (in feces) in any group. However, on the day of sensitization and challenge, only the UFMG-A905-C group exhibited a significant yeast recovery.

The OVA group showed significantly higher airway hyper-responsiveness than the SAL group. Notably, the UFMG-A905-C group had significantly reduced airway hyper-responsiveness relative to the OVA group.

Besides, some hyper-responsiveness parameters were significantly reduced for the COM group compared to the OVA group. There were no significant changes in hyper-responsiveness for the UFMG-A905 group.

Total cells and eosinophils in the BAL were significantly higher in the OVA group than in the SAL group. While total cell counts were unaffected in bread-fed groups, the eosinophil percentage was significantly reduced in these groups compared to the OVA group.

The levels of IL-4, IL-5, and IL-13 in the lung were significantly elevated in the OVA group. IL-5 levels in the BAL were significantly reduced in bread-fed groups.

The UFMG-A905-C group showed significantly lower IL-5 and IL-13 but higher IL-17A levels in the lungs. The COM group showed no significant changes in ILs in the lung.

Conclusions

The study examined the effects of bread fermented with S. cerevisiae UFMG A-905 on asthma prevention in mice. The UFMG A-905 group exhibited partially decreased airway inflammation.

In contrast, adding microcapsules reduced airway hyper-responsiveness and elevated IL-17A levels. Notably, the team did not examine the survival of yeast in microcapsules after baking. Besides, they did not test COM bread with microcapsules.