Elemental diets

From the standpoint of the theory of adequate nutrition, elemental diets are defective for many reasons and, in particular, because they disrupt the properties and the ratio of nutrient (trophic) and toxic fluxes due to loss of protective functions of membrane digestion and changes in endoecology. Indeed, in monogastric organisms (including humans), the nutrition of bacteria is built on the use of predominantly unutilized or slowly utilized macroorganisms food components. Membrane digestion, realized by enzymes localized in the brush border that is inaccessible to bacteria, prevents them from absorbing nutrients and ensures sterility of the process. Such sterility can be considered as an adaptation of the macroorganism to co-existence with the intestinal bacterial flora and as a factor ensuring the preferential absorption of nutrients by the macroorganism. If the food is introduced into the body in the form of monomers, then the membrane digestion as a protective mechanism does not function. In this case, the bacteria find themselves in extremely favorable conditions for their multiplication as a result of excess of easily assimilated elements in the cavity of the small intestine, which leads to a violation of endoecology, an increase in the flow of toxic substances and the loss of a number of substances, including necessary, by the macroorganism. 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 prolonged use of monomeric diets. Such consequences include, inter alia, growth retardation and a decrease in body weight of animals, an increase in ammonia excretion, a decrease in the excretion of electrolytes, the development of hemolytic anemia, etc. Recently it has also been shown that with the prolonged use of elemental diets, some drugs introduced into the body in 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 violation of the synthesis of a number of enzymes that are necessary for normal activity of the organism. Further, because of the high osmotic activity of elemental diets, the distribution of fluid between the blood and the enteral medium is disrupted as a result of fluid transfer from the blood to the intestine.

However, with certain forms of disease and under certain conditions, elemental and ballast-free diets can be very useful. In particular, with congenital and acquired defects of the enzyme systems of the small intestine, it is most expedient to exclude from the food those substances (for example, lactose, sucrose, etc.), the hydrolysis of which is disturbed. Elemental diets can be used for various extreme effects that cause disturbances in the activity of the gastrointestinal tract. In this case, inadequacy, for example, imitation of a protein by a set of certain amino acids, manifests itself not immediately, but through a certain time interval during which these amino acids can serve as a complete replacement of the 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 repression of the synthesis and incorporation of enzymes in the membrane of intestinal cells that perform the final stages of digestion is observed. In this case, the absorption of amino acids and hexoses that make up 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 for stress, which is characterized by a loss of proteins. Such a negative nitrogen balance arises from gluconeogenesis. We have obtained results that broaden the classical notions of the origin of the negative nitrogen balance, which were published in 1972. Scientists have found that under stress, the level of disaccharidic and especially peptidase activity of the small intestine decreases due to inhibition of the inclusion of enzymes in the composition of the apical membrane of intestinal cells, which leads to a decrease in the assimilation of carbohydrates and mainly proteins. Thus, under stress, the negative nitrogen balance is caused not only by the destruction, but also by the insufficient intake of amino acids into the internal environment of the organism. Consequently, under different types of stress there is an effective way to correct protein metabolism by introducing into the diet instead of proteins that are not digested, imitating these proteins of amino acid mixtures.

[1], [2], [3]