Osteoporosis which once affected only the aged population is now expanding its grasp to a wider section of humans irrespective of their age. It has been called a progressive disease of the bone and involves characteristics such as the loss of density of bone minerals, reduction or loss of essential proteins in bone and an overall deterioration of bone architecture. As the probiotics are able to cause enhanced mineral absorption in humans, they might as well be useful in the improvement in bone mineral density (BMD).
Outline of Pre-Existing Knowledge:
Some of the probiotic strains like B. lactis lafti are able to effectively utilize a wide range of indigestible carbohydrates like inulin and other oligosaccharides. There are also reports that Bifidobacterium and S. thermophilus strains synthesize folic acid (Vitamin B9). The folic acid content of the erythrocytes is associated with enhanced BMD and overall content of the bone. Therefore, this folate synthesizing ability of the probiotics might indicate the potential of the beneficial bacteria in improving the health of the bones. However, there are concerns regarding the physiological relevance of the folate amount provided by the probiotics under given set of conditions. Synergic effects of prebiotic-probiotic combination intake are now postulated to provide better results in the improvement of bone.
Probiotics and Prebiotics in Alteration of Bone Composition:
There are reports that suggest that the probiotics could stimulate effective accretion of the bone even in the absence of the prebiotics. This might be as a result of the ability of the probiotic bacteria to produce enzymes and vitamins or the release of microbial metabolites. Now a number of these vitamins like Vitamin C, D or K are intricately associated with the formation of bone matrix and the right accretion of the bone. However, there are experimental data that provide enough evidence for the application of the right combination of prebiotic and probiotic to reduce bone related problems. According to the work of Gopal et al., synbiotics stimulated enhanced mineral absorption as compared to the administration of bifidobacteria and lactobacilli or the prebiotics alone. In yet another study, it was found that B. longum strains alongwith lactulose enhanced the breaking force in the subjects. It was also reported that the strains of L. casei, L. gasseri and L. reuteri administered through yoghurts could increase the absorption of calcium and the overall bone mineral content (BMC) within the recipients. Other similar studies have found a reduced level of excreted phosphorus when the host was fed with probiotic supplements.
Mode of Action:
A number of factors have been elucidated that might contribute to the underlying mechanism by which the probiotics improve absorption of minerals and subsequently alleviate problems related to reduced BMC. The production of higher amounts of short chain fatty acids due to better utilization of the available substrates by the probiotic strains increases the mineral solubility. The by-products of probiotic fermentation like butyrate and lactate enhances the overall surface area for absorption through the promotion of enterocytes proliferation. There are also evidences for the overexpression of proteins involved in calcium binding and uptake when subjects were provided with the right probiotic dosage. Besides, more recent developments have been taking place that precisely outline the role of probiotics in the BMD improvement. These mechanisms are well supported by the data generated from experiments and contribute greatly to our knowledge of how probiotics aid in maintenance of a good bone health.
Impact of Bone-Modifying Factors:
It was previously known that fructo-oligosaccharides could enhance the effect of phytoestrogens in bone preservation which was based primarily on the increase in bioavailable isoflavones. These isoflavones on the other hand are more rapidly absorbed when present in their aglycone forms. Many probiotic strains of Bifidobaterium or Lactobacillus origin have the β-glycosidase activity that can easily hydrolyze the glycosidic bonds to yield the absorbable aglycones. The polyamines are well known inducers of mucosal growth. These polyamines are in turn synthesized by some of the useful bacteria. Schrezenmeir and his team therefore evaluated the possibility whether the improved BMC in the prebiotic fed hosts were due to the result of polyamines produced by the beneficial microflora that benefited from the specific diet. They found exiting results to indicate that indeed that was the case and that an optimum level of polyamine supply could promote improvements in the bone structure.
Probiotics Degrade Mineral Complex Forming Phytate:
People all over the world take cereal based whole grain foods through their diet. Such diet is rich in phytic acid which results in the complexing and sequester of essential minerals. Earlier reports have demonstrated significant reduction in the availability of microelements like iron, zinc and copper in individuals dependent on diet rich in phytate. The work of Scholz-Ahrens and his group suggested that the calcium absorption ability in adolescents were not hampered by phytate but it was so in youths and adults. This result showed that the mineral complex formation by phytate can be counteracted by casein depending on the diet content and the age of the individuals. Humans lack the endogenous phytate degrading enzyme, phytase. Addition of phytase producing probiotic bacteria can alleviate the problem to a great extent. Infact, it has been found that a large number of probiotic strains possess the ability to break down phytate thereby releasing the minerals from the phytate-mineral complexes.
Stimulation of Calcium Uptake:
It was documented that L. helveticus containing fermented milk has beneficial effects on the metabolism of calcium in postmenopausal women. The bacteria were found to be involved in the reduction of parathyroid hormone thereby increasing the serum calcium. A change in calcium metabolism may be due to the induced higher calcium absorption by the enterocytes. The proper selection of the probiotic strain is very significant while considering the improvements in calcium absorption. As for example Gilman et al., found that strains of L. salivarius were useful in improving calcium uptake but not the B. infantis strains. According to a study published in the Journal of Cellular Physiology L. reuteri administration to the host enhanced osteoblast related serum markers and improvements in bone formation.
Probiotics have a definitive role to play in the improvement of bone mineral density and overall bone content. The right choice of the probiotics to be taken in this regard is the key to the intended success of probiotic mediated maintenance of bone health.