Psoriasis is a chronic immune-mediated inflammatory skin disease that affects approximately 2% of the global population, or an estimated 40-160 million individuals, with about 4 million new cases diagnosed annually. Although the precise cause remains unclear, researchers believe that genetic susceptibility, systemic inflammation, and gut microbiota dysbiosis all contribute to disease development.

A review published in Nutrition Reviews suggested that biotics, including probiotics, prebiotics, synbiotics, and postbiotics, may offer a promising adjunctive approach to psoriasis management by modulating the gut microbiota and immune response.

Although topical therapies, systemic agents, biologics, and phototherapy can effectively control disease activity, these treatments may be associated with adverse effects. Therefore, researchers evaluated whether nutritional interventions based on biotics, which are generally considered safe and have immunomodulatory and microbiota-modulating properties, could improve clinical outcomes without adding a substantial treatment burden.

The review included randomized controlled trials published between 2013 and 2024 that evaluated the effects of biotics in individuals with psoriasis.

Microbiota Changes

Most studies evaluated lactic acid bacteria, particularly Lactobacillus and Bifidobacterium species, combined with prebiotic oligosaccharides. Overall, researchers found evidence of favorable changes in gut microbiota composition, reductions in inflammatory biomarkers, and improvements in psoriasis severity after several weeks of treatment.

The reported benefits were as follows.

• Specific biotic formulations increased the abundance of beneficial gut bacteria, including Lactobacillus species and Parabacteroides species. 
• Researchers also reported reductions in systemic inflammatory biomarkers. Several trials found decreases in C-reactive protein, TNF, interleukin (IL)-6, lipopolysaccharide, and IL-1-beta. In another study, Lactiplantibacillus plantarum IS-10506 reduced IL-17 while increasing IL-10 and FOXP3, findings consistent with the modulation of the immune response. 
• These biologic changes were accompanied by clinical improvement. Most studies have reported reductions in disease severity, with improvements measured using the Psoriasis Area and Severity Index. 

Speaking with Univadis Spain, part of the Medscape Professional Network, Fiorella Palmas, MD, member of the Nutrition Division of the Spanish Society of Endocrinology and Nutrition, said, “Traditionally, we believed that probiotics had to remain alive to colonize the gut and exert beneficial effects.”

“However, this review included a trial using heat-inactivated Prevotella histicola, or nonviable bacteria, which produced a surprising result. Although it did not permanently alter the gut microbiota, half of the participants experienced at least a 25% improvement in the severity of their skin lesions.”

Gut-Skin Axis

“The study shows that combining lactic acid bacteria with prebiotic fibers, such as inulin or oligosaccharides, significantly increases the abundance of protective bacteria in the gut,” Palmas said.

According to the review, the findings further support the existence of the gut-skin axis and reinforce the concept that psoriasis is a multifactorial disease involving genetic susceptibility, systemic inflammation, impaired intestinal barrier function, and gut microbiota dysbiosis.

However, the authors emphasized the important limitations of the available evidence. Only 10 randomized controlled trials met the inclusion criteria, each enrolling fewer than 30 participants and using heterogeneous treatment protocols and outcome measures. In addition, assessments of gut microbiota composition, cytokine concentrations, and clinical severity have varied across studies.

As a result, the authors concluded that although probiotics appear promising for improving the quality of life and modulating inflammation in psoriasis, current evidence remains insufficient to support firm clinical recommendations.

Palmas noted that psoriasis shares important inflammatory and metabolic pathways with obesity, metabolic syndrome, and type 2 diabetes mellitus.

“Recent research on the inflammasome has shown how chronic inflammation develops,” she said. “Experimental studies indicate that diets high in saturated fat and animal protein activate specific intestinal macrophages that promote inflammation and worsen psoriasis.”

For this reason, she said that psoriasis management should extend beyond conventional drug therapy to include strategies that support gut health.

“Probiotics and fiber supplements will not cure psoriasis on their own,” Palmas concluded. “However, they may serve as valuable adjuncts that enhance the effectiveness of conventional therapies, reduce the severity of flare-ups, and help patients live with fewer symptoms.”

The authors and Palmas reported having no relevant conflicts of interest.

This story was translated from Univadis Spain.