A proper and balanced nutrition can be the answer to many human diseases. However, during the acute phase of the manifestations of a disease e.g., Inflammatory Bowel Disease (IBD), the host body cannot accommodate the synthesis of the desired nutritional requirements. The microbial action when used to prepare cultured foods has a proven and profound effect on the overall availability and quantity of dietary nutrients. It can also effectuate a positive impact in the digestion of food. Therefore, the ensuing question was whether the probiotics can have an effect on nutrient synthesis.
Release of vitamins and enzymes:
There have been numerous reports of enhanced vitamin levels in probiotic products or foods supplemented with them. This can be accounted from the fact that probiotic bacteria take part in food fermentation. The food fermented with lactic acid bacteria causes increased levels of folic acid in bifidus milk, yogurt and kefir. In addition, Niacin and riboflavin contents were also found to be enhanced in yogurt. These results were reported by various groups including Deeth, Alm and Rajalakshmi. While others have demonstrated the presence of vitamin B6 and Vitamin B12 in Cheddar cheese and Cottage cheese respectively. The probiotic bacteria are useful source of different kinds of enzymes needed by the host body. Some of the enzyme types include proteases and peptidases, malolactic enzymes, polysaccharidases and glycosidases, ureases, esterases and lipases. If different strains of probiotics can be properly characterized for their vitamin and enzyme producing abilities, they are obviously a rich and cheap source for vitamins.
Synthesis and role of Short Chain Fatty Acids:
The probiotic bacteria release lactic acid that lowers the pH of the intestine which can consequently alleviate malabsorption in the intestine by inhibiting the growth and development of the pathogenic microflora (Mallett et al.). The enzymatic activity of the probiotics on the utilizable substrates (which may otherwise remain unutilized) results in the increased production of short chain fatty acids (SCFA). Some of those synthesized SCFAs are butyric acid, propionic acid and the all important lactic acid. Lactic acid may act as an inducer for the production and synthesis of other significant factors. According to the report of Cook and Selin SCFA has also a role to play as nutrients for the colonic epithelium. They can also act as modulators of cell volume. Besides, the study suggests that they can regulate gene expression, proliferation and differentiation. Some of these genes may express critical bacterial enzymes which are required in the metabolism of carcinogens and other foreign compounds in the gut according to Mallett. The other roles of SCFAs are reduction in bile acid solubility, decrease in the absorption of ammonia and an increase in indirect mineral absorption. Above all according to a study by Rombeau et al., the SCFAs may act as conserved source of energy and result in the available energy pool for the host.
Production of other essential nutrients:
At various stages of fermentation the probiotic bacteria can produce many essential nutrients depending upon the substrates that they use. The products reported are non-protein nitrogen, free sugar from the metabolized carbohydrates. Radhakrishna Rao and group established the presence of amino acids like methionine and choline in Idli. Some other groups have reported that the probiotics may even cause an increase in the production of limiting essential amino acids like lysine (Sands and Hankin). The supply of essential amino acids through the probiotics can have greater implications from the point of view of growth and development of the host. As the present sources of amino acid supplements are quite expensive and transient in nature, the probiotics can be used as a potential replacement. But before using them as a source of a specific amino acid thorough investigation is needed about the strains that may produce it. Besides, some strains of probiotics might cause the breakdown of phytate in bread dough according to the work of Davidson et al. While others report their association with the breakdown of trypsin inhibitors in some fermented legume preparations. Another important aspect of probiotics is that they are able to enhance the release of important cytokines. Now, many of these cytokines are involved in the catabolism of essential nutrients and serve the immune system with micronutrients, amino acids as also energy that might be required during acute period response.
The action of the probiotics can provide the host with vital nutrients that are usually missing from the diet of an individual. However, it is also noteworthy to keep in mind that these bacteria can make the food more bio-available thereby increasing the digestibility of the subject concerned. e.g., many researchers have shown that appropriate lactobacilli strains, in specific amounts can provide relief in cases of lactose intolerance. While others have proven that L. bulgaricus, S. thermophilus when used in fermented dairy products can provide enough bacterial lactase to the body. According to a study by Fernandes et al., the probiotics can even enhance the bioavailability of fats, carbohydrates and proteins with the help of their different hydrolytic enzymes.
For the purpose of fruitful nutrition, the changes that the probiotics can bring about would be highly useful if they represent what may be called the general pattern of fermentation. There are many groups of microorganisms that can participate in fermentation and bring about the desired changes in our nutrient availability to the body. Also, it should be kept in mind that in some instances the energy cost of synthesis of these vital nutrients by the probiotics is very high. The exact mechanism of action of the degradation of nutrients by the probiotics or the process of nutrient synthesis is still not well defined for the majority of the cases. A broader knowledge in this aspect is yet needed. With the advancement in the fields of genetic engineering and DNA recombinant technology, it is now possible to increase the essential nutrients in the food during fermentation. As also specific details of the mechanism of nutrient synthesis can be known to put them into use in practical lives.
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