What are the benefits of taking probiotics?
WHO define Probiotics as live microorganisms which, when administered in adequate amounts, confer a health benefit on the host .
The benefit of probiotics is described in figure below 
Anti-pathogenic activity is regarded as one of the most beneficial effects of probiotics because they do not disturb or change the composition of the complex population of the gut microbiota, unlike classic antibiotics.
The mechanism includes: (1) production of short-chain fatty acids, which help to maintain an appropriate pH in the colonic lumen ; (2) production variety of anti-pathogenic compounds,which are mostly involved in increasing the membrane permeability, thus,cell death  ; (3) lowering pH by organic acids like lactic and acetic acids ; (4) stimulation host anti-pathogenic defense pathways ; (5) competing for pathogen binding and receptor sites, as well as for available nutrients and growth.
Angiogenesis has been an important phenomenon and is necessary for wound healing process through delineated cellular responses to regenerate damaged tissues . The molecular mechanisms by which probiotics mediate these beneficial effects however remain unclear. It may include alteration of inflammatory cytokine profiles, down-regulation of pro-inflammatory cascades or induction of regulatory mechanisms in a strain-specific manner, epithelial barrier function enhancement, visceral hypersensitivity reduction, spinal afferent traffic, and stress response.
Urogenital health care
Imbalance in the microbial composition greatly influences the health of the vaginal microenvironment, potentially leading to compromised state of bacterial vaginosis (BV) and UTI. These compromised states can be reassured by balancing the number of Lactobacillus sp. via the supplementation of probiotics .
Effect on brain and CNS
Gut microbiota influence human brain development function . In children with autism spectrum disorder, a daily dose of L. plantarum WCFS1 led to an improvement in their school records and attitude towards food . Messaoudi et al.  discussed reduced psychological distress in a randomized trial involving healthy volunteers treated with oral administration of Lactobacillus helveticus R0052 and B. longum R0175. Rao et al.  showed a decrease in anxiety symptoms by administration of L. casei strain Shirota to patients suffering from chronic fatigue syndrome. However, probiotic trials involving patients suffering from anxiety and clinical depression are lacking and therefore require more studies to validate this effect.
Probiotics possess physiological functions that contribute to the health of host environment regulating microbes. In most instances, weight loss is facilitated by thermogenic and lipolytic responses through stimulating the sympathetic nervous system . Probiotic strains, Lactobacillus gasseri BNR17 have shown properties of inhibiting the increase in adipocyte tissue that are the main source of leptin and adiponectin and thereby, limiting leptin secretion . Other probiotic microbes such as L. casei, Lactobacillus acidophilus and Bifidobacterium longum have also been reported to have hypocholesterolemic effects .
Crohn's disease (CD) and ulcerative colitis (UC) are among the most chronic inflammatory diseases of the GIT and are collectively called IBD. The imbalance in the gut microbiota plays an important pathophysiological role in the positive regulation of IBD and the disorder could possibly be altered by supplementation with probiotics, prebiotics, and synbiotics , , . IBD is being associated with impaired production of SCFAs. Lactobacillus, Bifidobacterium, Enterobacter and E. coli are the most widely used probiotics in these cases.
In vitro studies have demonstrated that probiotic strains, Lactobacillus fermentum NCIMB-5221 and -8829, have highly potent in suppressing colorectal cancer cells and promoting normal epithelial colon cell growth through the production of SCFAs . Two different probiotic strains L. acidophilus LA102 and L. casei LC232 have also been found to show pronounced cytotoxic activities, with in vitro anti-proliferative activity against two colorectal cancer cell lines (Caco-2 and HRT-18) . However, research is limited only to in vitro tests.
In vitro studies of certain probiotics, such as Lactobacillus plantarum L67, have shown the potential to prevent allergy-associated disorders with the production of interleukin-12 and interferon-γ in their host . In another study, L. plantarum 06CC2 significantly alleviated allergic symptoms and reduced the levels of total immunoglobulin E, ovalbumin-specific immunoglobulin E, and histamine in the sera of ovalbumin-sensitized mice . Further work may be helpful in evaluating the anti-allergic activity of probiotics and their mode of action.
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