probiotics (Lactobacillus spp., Bifidobacterium spp., Saccharomyces boulardii)

Cochrane 2019 and AGA 2020 rated the evidence base for probiotics in IBS as moderate with high strain-dependence. Some meta-analyses showed reduced pain and bloating. AGA 2020 does not recommend probiotics for IBS in adults outside clinical trials due to result heterogeneity and study quality. In some IBS-D patients, Bifidobacterium infantis 35624 or combination preparations provide clinical improvement.

Cochrane 2017 showed a reduction in CDI on antibiotic therapy with probiotic use. However, ACG 2021 and AGA 2020 do not give an unambiguous recommendation – results are inconsistent across strains, and probiotic-associated bacteraemia risk exists in immunocompromised patients. Standard recurrent CDI therapy: fidaxomicin, faecal microbiota therapy, bezlotoxumab.

WAO 2015 gives a conditional recommendation in favour of probiotics in pregnant women with allergic history and their newborn infants for atopic dermatitis prevention. The effect is modest – about 10% absolute risk reduction. Most international allergy societies (AAAAI, EAACI) do not include probiotics in atopy prevention standards. Effects on food allergy or asthma prevention are not proven.

«Gut dysbiosis» as a standalone diagnosis is absent from the international classification of diseases. AGA, ACG, BSG, and WGO do not recognise it as a clinical entity and do not recommend «treating dysbiosis» with probiotics. In Russian practice the diagnosis is made by two methods, both problematic. First is stool culture, which does not reflect actual gut microbiota because 99 % of intestinal bacteria are strict anaerobes that do not grow on culture media. Second is the Osipov test (chromatography-mass spectrometry of microbial markers). The Russian Academy of Sciences in Memorandum No. 22 (2020) explicitly called this method pseudoscientific. Prescribing probiotics for a diagnosis that is not in the ICD, based on a test that the Academy considers pseudoscientific, has no evidence base.

Probiotics do not work in acne. AAD Acne Guidelines 2024 and EDF 2024 do not include probiotics. Systematic reviews show a few low-quality RCTs with small samples; the effect on acne severity and inflammatory lesion count is clinically insignificant. The «gut-skin axis» concept is heavily promoted in supplement marketing, but clinical evidence for acne treatment is absent. Standard acne therapy: topical retinoids, benzoyl peroxide, azelaic acid; topical or systemic antibiotics for moderate disease; isotretinoin for severe disease.

Probiotics for autism spectrum disorder have no evidence base. The 2018 Cochrane review (Parracho HM et al.) and 2021–2023 updates showed no convincing effect on core ASD symptoms. The American Academy of Pediatrics and AACAP do not include probiotics in their recommendations. Core ASD interventions: behavioural therapy, communication programs, early intervention. Positioning probiotics as «autism treatment» in post-Soviet marketing is particularly dangerous because it distracts families from evidence-based interventions and financially exploits parents in difficult circumstances.

«Psychobiotics» is a marketing term for probiotics positioned as treatment for depression and anxiety. APA, NICE Mental Health, and WFSBP do not include probiotics in depression or anxiety recommendations. Small RCTs showed weak reductions in subjective anxiety scores in healthy students – this is not clinical depression treatment. Large RCTs in patients with established major depressive disorder did not show an effect. Standard depression therapy: CBT, SSRIs, SNRIs – not probiotics.

Probiotics for boosting “general immunity” and preventing acute respiratory infections are not mentioned in international guidelines. Systematic reviews show a weak effect on respiratory infection incidence in children in daycare – clinically minor. In adults the effect is not confirmed. This positioning is marketing rather than scientific.

International guidelines do not include probiotics for weight loss. Systematic reviews (John GK et al. Genes 2018) showed an absolute weight reduction of 0.6 kg over 12 weeks, clinically insignificant. Endocrine Society, ACP, and AACE do not mention probiotics in obesity management. The «microbiome and weight» marketing relies on observational associations between bacterial profiles and obesity, but causality has not been established.