Elemental diets

From the standpoint of the theory of adequate nutrition, elemental diets are defective for many reasons, in particular because they disrupt the properties and ratio of nutritive (trophic) and toxic flows due to the loss of protective functions of membrane digestion and changes in endoecology. Indeed, in monogastric organisms (including humans), bacterial nutrition is based on the use of predominantly non-utilizable or slowly utilized by macroorganisms food components. Membrane digestion, implemented by enzymes localized in the brush border inaccessible to bacteria, prevents them from absorbing nutrients and ensures the sterility of the process. Such sterility can be considered as an adaptation of the macroorganism to coexistence with intestinal bacterial flora and as a factor ensuring the preferential absorption of nutrients by the macroorganism. If food is introduced into the body in the form of monomers, then membrane digestion does not function as a protective mechanism. In this case, bacteria find themselves in extremely favorable conditions for their reproduction as a result of the excess of easily digestible elements in the small intestine, which leads to a disruption of endoecology, to an increase in the flow of toxic substances and to the loss of a number of substances by the macroorganism, including essential ones. When studying the effects of monomeric nutrition, we, and then many other researchers, registered dysbacteriosis and additional deamination of amino acids.

There are negative consequences of long-term use of monomeric diets. These consequences include, in particular, slower growth and reduced body weight of animals, increased excretion of ammonia, decreased excretion of electrolytes, development of hemolytic anemia, etc. It has also been recently shown that with long-term use of elemental diets, some drugs introduced into the body are transformed into toxic forms. In addition, monomeric diets lead to a decrease in the functional load on the enzyme systems of the gastrointestinal tract, which is accompanied by a disruption in the synthesis of a number of enzymes that are necessary for the normal functioning of the body. Furthermore, due to the high osmotic activity of elemental diets, the distribution of fluid between the blood and the enteral environment is disrupted as a result of the transition of fluid from the blood to the intestine.

However, in some forms of diseases and under certain conditions, elemental and ballast-free diets can be very useful. In particular, in case of congenital and acquired defects of the enzyme systems of the small intestine, it is most advisable to exclude from the diet those substances (for example, lactose, sucrose, etc.), the hydrolysis of which is impaired. Elemental diets can be used in case of various extreme effects that cause disorders of the gastrointestinal tract. In this case, inadequacy, for example, imitation of protein by a set of certain amino acids, does not manifest itself immediately, but after a certain time interval, during which these amino acids can serve as a full-fledged replacement for protein. Probably, the negative consequences of elemental diets are associated with a change in the bacterial composition or at least with a change in the properties of the bacterial population of the intestine.

Elemental or monomeric diets are important in pathological conditions in which there is repression of the synthesis and inclusion of enzymes into the intestinal cell membrane that perform the final stages of digestion. In this case, the absorption of amino acids and hexoses that are part of the oligomers does not occur. Such phenomena can be observed, in particular, under the influence of stress factors. Then amino acids can be used to maintain a satisfactory nitrogen balance, negative under stress, which is characterized by protein loss. Such a negative nitrogen balance occurs due to gluconeogenesis. We have obtained results that expand on the classical ideas about the origin of negative nitrogen balance, which were published in 1972. Scientists have discovered that under stress, there is a decrease in the level of disaccharidase and especially peptidase activities of the small intestine due to the inhibition of the inclusion of enzymes into the apical membrane of intestinal cells, which leads to a weakening of the assimilation of carbohydrates and mainly proteins. Thus, under stress, the negative nitrogen balance is caused not only by destruction, but also by insufficient supply of amino acids into the internal environment of the body. Consequently, under various types of stress, there is an effective way to correct protein metabolism by introducing into the diet, instead of proteins that are not absorbed, amino acid mixtures that imitate these proteins.

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