Nutrition Nutrients Organic substances

Fresh organic matter plays a fundamental role in plant nutrition by supplying nutrients released through degradation processes however, humified organic substances also become a source of nutrients when subjected to mineralization processes. The main aspects of the cycle of organic matter at the rhizosphere soil are reported in Chap. 6. 

INOSITOL. A constituent of body tissue. In purified form it is used as a nutrient and dietary supplement in some foods and feed-stuffs. The chemical name of inositol is hexahydroxycyclohexane, CAS 87-89-8. CfiHalOHls- ZHjO. There are nine isomeric forms of inositol. Myoinositol or meso-inositnl (err 1.2,3.5-fram-4.6-liexatiydroxycyclohexanc) is the isomer that possesses essential nutrient activity. The substance, often identified as a vitamin, is found in small amounts in many vegetables, citrus fruits, cereal grains, liver, kidney, heart and other meat. The commercial source is com (maize) steep liquor. In addition to its use in nutrition, it finds use in medicine and as an intermediate for organic syntheses. 

Animal experiments have shown that faulty nutrition, i.e. > 90% fat, < 10% protein and < 2 mg choline per day, leads to pronounced fatty fiver and even fatty cirrhosis within a few weeks. The same changes could be observed when the protein intake remained more or less normal, while extremely little methionine and choline was offered. With a partial surplus of certain foodstuffs, the special nature of the excessive nutritional components is also of considerable importance. The term partial malnutrition may, for example, be associated with a pronounced protein deficiency (and thus possibly inadequate production of lipoproteins) or a lack of lipotropic substances (such as methionine, choline, cystine, glycocoUbetaine, pyridoxine, casein and various N- or S-methylated substances). Protein deficiency has particularly severe consequences when toxic substances are absorbed at the same time or when the organism has to fight bacterial or parasitic infections. A diseased liver reacts to both a serious deficiency in and an excessive supply of different nutrients (e.g. proteins, certain kinds of amino acids, various lipids, trace elements) with unfavourable or even complicative developments during the course of disease. 

According to conventional definition (Potischman, 2003), a nutritional biomarker can be any biological specimen that is an indicator of nutritional status with respect to intake or metabolism of dietary constituents. It can be a biochemical, functional, or clinical index of status of an essential nutrient or other dietary constituents. Nutritional biomarkers usually are external components, such as food components or other external substances metabolized by the organism (metabolites), analyzed in the participants biological samples and used to determine their exposure to the intake of a specific food or component. 

Organic nutrients also include vitamins. Inorganic chemical compounds, such as dietary minerals, water (and oxygen), may also be considered nutrients. Vitamins and dietary minerals are collectively known as accessory (additive) nutrients and are often referred to as essential nutritional factors. With the exception of some vitamins that humans cannot synthesise, these accessory nutrients must be obtained from foods. They are therefore known as exogenous factors. Another essential nutrient is water, which is obtained in small amounts by oxidation of primary nutrients, but in much larger quantities from foods, and especially from beverages. Most foods contain a mixture of some or aU of the nutrient classes, together with many other substances. Some nutrients can be stored internally (such as the fat soluble vitamins), while others are required more or less continuously. Poor health maybe caused by a lack of required nutrients or, in extreme cases, too much of a required nutrient. 

According to the Webster s New World Dictionary, nutrition is defined as, a series of processes by which an organism takes in and assimilates food for promoting growth and replacing worn or injured tissues. It follows that a nutrient is a substance in food that is essential for maintaining health. These include carbohydrates, proteins, lipids, vitamins, and minerals. Therefore, functional foods contain nutrients in the proper balance to not only help maintain health, but they also contain other compounds that promote and protect health. 

Various species and strains of Streptococcus (see Table IX) require pyridoxin as an essential nutrient. The nutrient requirements of these organisms are complex, and other essential metabolites besides pyridoxin must be given them. Here it is worth stressing that, just as the requirement for a given essential metabolite as a nutrient is conditional on the rate of synthesis of this substance by the cells, so too there may be considerable interdependence in requirements for different essential metabolites, because of the general interlinking of metabolic processes in the cells. Thus a nutritional requirement for a given essential metabolite may be conditional not only on its rate of synthesis but also on the rate of synthesis of another essential metabolite. 

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