It’s a very valid question - not because this is an age of processed foods – because unless you have some amount of belief in what you are doing; chances are you won’t reap the fullest benefits. I guess that’s what people call faith healing. However, getting a grip on Lactobacilli’s general mechanism of action takes away the divine or eerie strains from its effectiveness.
At its simplest (and as evident from several molecular studies), there are three main mechanisms through which Lactobacillus acts. Lactobacilli as a probiotic, inhibit pathogens and restores microbial homeostasis (microbe-microbe interaction). Besides, it enhances the epithelial barrier function, thus modulating and stimulating the body’s immune responses. These three are complex functions and they vary with the strains.
It is L. acidophilus that is most profusely used as a probiotic that builds large numbers of amino acids and peptides transport systems other than encoding several other proteins that aid metabolism and transport of carbohydrates, especially raffinose and FOS (fructo-oligosaccharides or pre-biotics). However, short-chain FOS is best handled by the L. plantarum, so its presence is must in a probiotic supplement.
L. plantarum exhibits larger regulatory and transport functionalities by aiding glycolysis (glucose breakdown) and enhancing the phosphoketolase. On top of that, it also has a larger fermentative capacity due to its capacity for larger pyruvate dissipation.
As for L. salivarius, it metabolizes additionally sugars like rhamnose, ribose, and sorbitol and adapt to environments caused by frequent dietary fluctuations.
The L. reuteri strain is particularly helpful to synthesize glucans/fructans from sucrose and helps to keep up a carbohydrate reserve when conditions lead to carbohydrate depletion.
As for the adherence mechanism of lactobacillus in the host, it sticks either to the epithelial cell lines or in the collagen and fibronectin, forming micro-colonies, thus forming the host defense systems and competing with resident pathogens for nutrients as well as space, thus controlling mucosal shedding and the peristaltic flow for an effective washing of the epithelial cell lining of the gastro-intestinal tract.
This is just a brief idea on how lactobacilli brings all its benefits; however, bifido brings the benefits by altering microbial metabolism in the GIT. This they do chiefly in two ways. Firstly, by increasing the activities of useful enzymes like beta-galactosidase, which alleviates lactose indigestion problems and making some of the colonic enzymes like beta-glucuronidase, beta-glucosidase, nitroreductase, azoreductase and steroid-7alpha-dehydroxylase, which have been found to exhibit carcinogenic effects.