The human body needs throughout the life, a steady and appropriate supply of minerals through the diet. The minerals form an integral part of a large number of vitamins, proteins, transport chains and enzymes. A good number of minerals are essential to that effect-some in higher amount (macro-elements) while others in relatively lesser quantities (micro-elements). Irrespective of the quantity, their significance cannot be weighed down. In the United States, the RDA (Recommended Dietary Allowances) forms the guidelines for the proper intake of minerals. Some of the important minerals required in our diet include iron, calcium, magnesium, phosphorous, zinc, copper, cobalt, iodine, fluoride. Although the mineral intake is important for the proper maintenance of our physiological activities, in a good percentage of the human population the threshold value for the intake and metabolism of the minerals is not met. Therefore, efforts are on to facilitate better utilization of the minerals in our body.
Factors affecting mineral absorption:
Mineral absorption and utilization by the human body depends on its physiological, hormonal and biochemical status. The mineral sources being divergent in nature their possible bioavailability needs to be checked before use. There are factors acting both in favor and against optimum mineral absorption. Stability maintenance, state of ingested mineral, if a potential transporter is present for the mineral, small sized particles, reduced intestinal motility and solubility are some of the factors facilitating absorption. While there are factors like high transit time, fats, fiber, some acids, precipitation of minerals in presence of alkalis which inhibit mineral absorption.
Problems faced during mineral deficiency:
Although the minerals are required in very trace amounts, their deficiency or depletion from the human body may give rise to a lot of diseased conditions. The two of the classic examples are formation of anemia due to iron deficiency and osteoporosis as a result of lack of calcium and phosphorous. In due course of time lack of minerals results into various forms of degenerative diseases some of which may be chronic in nature. In our daily lives we ourselves experience these mineral deficiencies when we feel fatigued and problems with memory or slower rate of metabolism. Some of the symptoms might be too subtle to experience but in the long run causes greater problems. Supplementation with mineral nutrients has helped ease some of these problems but could not eradicate the problem fully. Since, the excess minerals administered to the body were not being absorbed properly.
There are also conditions in the body when the minerals are required in higher amounts. One such state is the metabolic acidity wherein a greater supply for the minerals is wanted to balance out the acidic condition and restore back the alkalinity of the body. The minerals like potassium, magnesium and calcium provides the buffering activity that is needed to keep the food entering the body buffered and maintain the normal physiological pH at ~7.3. If the diet doesn’t supply the adequate buffering agents in terms of these minerals, the bones and teeth will be at risk of getting depleted of the minerals.
Role of probiotics in facilitating mineral absorption:
The indigestible carbohydrates like oligofructose, galactooligosaccharides and inulin have been found to cause enhanced mineral retention and absorption by the human body. Significant improvement in mineral absorption was also observed for sugar alcohols and starches. These carbohydrate compounds are able to bind and sequester the minerals and these carbohydrate-mineral complexes pass unabsorbed through the small intestine onto the colon when the minerals are released from the complex and absorbed. The probiotics can act on the nondigestible carbohydrates and gives rise to short chain fatty acids. The SCFAs so formed can affect an increased absorption of minerals like Mg2+ and Ca2+. As also the acidic condition that results from the formation of lactic acid, butyric acid or propionic acid can enhance the ionization of minerals that in turn results in passive diffusion according to the work of Cummings et al. Researchers like Resta, Feng and Christakos have demonstrated that the SCFAs can stimulate Vitamin D receptor expression on the eukaryotic cells. Now there were previous reports to suggest that in mammals Vitamin D can regulate the metabolism of calcium and hence ensures its proper absorption from the diet. The research also showed that the parts in probiotics can cause increased vitamin D receptor expression both independent and dependent of SCFAs. The signaling pathways involved in the regulation of transport of calcium are PKC and MAPK. In addition, the probiotics can cause increased transport of SCFA within the intestinal epithelia through the induction of their major transporters like monocarboxylate transporter 1 (MCT1) according to Lee et al. which promotes increase in cellular energy and VDR expression and proteins involved in calcium binding like calreticulin, Sp100. The calcium transporter, TRPV6 is also markedly induced by probiotic bacteria. In cereal foods, phytate binds and complexes the minerals. According to reports, trace mineral elements like iron, copper, zinc are highly reduced in diet with rich phytate content. The endogenous phytase is generally lacking in humans. Therefore, supply of probiotics to provide the required phytase could alleviate the problem.
What lies ahead?
The idea is to create a balance between the prebiotics and probiotics to overcome the problem of lack of mineral absorption. The future research should focus on the finding and characterization of more inulin like carbohydrates that can chelate and sequester the essential minerals. However, the prebiotics can bring along with them the problem of non-availability of minerals in certain regions of the body. The probiotics that can work on these otherwise nondigestible carbohydrates can bring relief in such situation. Therefore, the right combination of prebiotic-probiotic has to found out. But there are existing reports that suggest that the probiotic bacteria can cause sufficient improvement in mineral absorption even in the absence of the prebiotics. Efforts should be made to identify from the pool of probiotic bacterial strains the ones suitable for the purpose of mineral absorption. Strains could be so designed as to induce the increased production of mineral transporter genes. Nevertheless, the probiotics can definitely be used in improved absorption of minerals from the diet.
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