Exploring the impact of fermented foods on irritable bowel syndrome symptoms

A systematic review claiming to be the first to analyze the effects of fermented foods on irritable bowel syndrome (IBS) suggests fermented milk with probiotics may help people suffering from the gastrointestinal disorder. 

Fermented foods are made by microbial growth and enzymatic conversions of food components and are popular worldwide.

The paper in the journal Frontiers in Nutrition, which looked at randomized controlled trials, finds that these foods appear to benefit IBS symptoms. However, the finding should be taken with “caution” as there is a lack of current evidence.

The authors explain that the symptoms of recurrent abdominal pain associated with disordered bowel habits are hallmarks of IBS. It has also been associated with mental disorders, besides reduced quality of life and social functioning.

The condition has a global prevalence of 3.8–10.1% and is noted to have a substantial social healthcare burden. 

Role of diet 

IBS is not fully understood, however, scientists know diet plays a major role, with over 80% of patients reporting food sensitivities. 

Guidelines and dietetic associations have touted dietary therapy as effective in managing symptoms compared to randomized control trials, which say probiotics are beneficial in terms of cost, effect and safety.

Fermented foods are made by microbial growth and enzymatic conversions of food components and are popular worldwide.Backed by omics-based technologies, fermentation can enhance probiotic or prebiotic content and decrease undesirable compounds like FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols). Researchers say removing these compounds is believed to be beneficial for IBS in theory. 

Probiotics and milk

The review outlines that patients who received fermented foods experienced slightly better improvements in global symptoms of IBS than those treated with a placebo. Only fermented milk helped reduce symptoms. 

The gut microbiota change in humans and animals after consuming probiotic fermented milk showed that the probiotic effect is the primary source of the health benefits of fermented foods.

Based on studies, the authors suggest that fermentation can also enhance the nutritional value of oats, as it can “liberate bioactive compounds” from and reduce antinutritional compounds by altering the microstructure.

The authors detail: “With respect to the potential mechanisms, experimental studies have shown that probiotics can influence intestinal permeability, motility, sensitivity, immune system activity, etc., to modify gastrointestinal physiology. For example, Bifidobacterium alleviates IBS symptoms by normalizing the ratio of anti-inflammatory and proinflammatory cytokine, suggesting an immune-modulating role for the gut.” 

“Besides the probiotic effect, the compounds during the fermentation of milk also can be regarded as potentially conferring influence on gut health. For example, the fermentation of milk could improve the digestibility of milk proteins and remove lactose, reducing gastrointestinal symptoms.” 

The review outlines that patients who received fermented foods experienced slightly better improvements in global symptoms of IBS than those treated with a placebo.“Moreover, the fermentation of milk can lead to biosynthesis and increase the concentrations of various cofactors, such as cobalamin, which can improve intestinal barrier function and villus-to-crypt ratio.” 

Other fermented foods

The study spotlights sauerkraut, a nutritious fermented cabbage that is rich in microbial composition and contains certain Leuconostoc and Lactobacillus species. Sauerkraut is noted to show probiotic potential and antimicrobial activity. 

Although it can produce radical scavenging activity to protect from oxidative damage, the authors note a previous study showed no difference in those consuming pasteurized and unpasteurized sauerkraut. However, the review notes an absence of the raw cabbage group.

Another fermented food is kombucha, made from tea. The phenolic compounds have been found to improve symptoms of incomplete bowel emptying in female patients with IBS, but the review authors recommend further validation through larger-scale randomized control trials.

According to the paper, sourdough starter, which is created when lactic acid bacteria and yeasts ferment wheat, may have health benefits by reducing FODMAP and changing the nutritional value of bread during the fermentation process. The reviewers highlight one study finding improvement of IBS symptoms with sourdough rye bread, while another found no statistical difference between those who consumed sourdough bread and modern bread.