Nutrients, lipids

Nutrients lipids, fibers, other carotenoids Bile salts pH... 

Of the three major categories of nutrients, lipids are the slowest to be digested and absorbed. Furthermore, these processes take place only in the... 

When used for a long time, mineral oil may come to interfere with the absorption of fat-soluble vitamins and other essential nutrients. Lipid pneumonitis may evolve if mineral oil is used as a vehicle for drugs that are taken nasally. 

The lipids of the diet include triglycerides, phospholipids, choJestcrol, cholesteryl esters, and fat-soiuble vitamins. Lipids are soluble in w ater, but only at extremely iow concentrations many thousands of times lower than those attainable by water-soluble nutrients. Lipids are called fat-soluble because they tend to adhere to, migrate into, or be easily dispersed into fats and oils. (The term oil-soluble also maybe used to describe lipids,) A lipid that is solid at room temperature generally i called a fat one that is liquid at room temperature is called an oil. 

Dietary fat depresses gastric secretion, slows gastric emptying and stimulates biliary and pancreatic flow, thereby facilitating the digestive process. Often, the acceptance of food and its palatability depends upon flavor and aroma. Although TAG in the pure state are relatively tasteless, they absorb and retain flavor of food. Furthermore, in combination with other nutrients, lipids provide a texture that enhances palatability and contributes to a feeling of satiety. Finally, dietary lipids serve as carriers for fat-soluble vitamins A, D, E, and K, and as an aid to then-absorption in the intestine. 

Cell membrane. This encloses the cell and regulates the passage of ions, nutrients, lipid-soluble ( fat-soluble ) substances, metabolic products, toxicants, and toxicant metabolites into and out of the cell interior because of its varying permeability for different substances. The cell membrane protects the contents of the cell from undesirable outside... 

The importance of the basal medium in culturing normal cells was demonstrated by Dr. Richard Ham (Ham and McKeehan, 1979). Dr. Ham s laboratory developed a number of different types of culture media, in which the concentrations of the individual nutritional components have been optimized to support the growth of specific types of normal, differentiated cells. The most widely used is nutrient mixture FI2, which contains nonessential, as well as essential, amino acids, a number of lipids, and trace elements (Table 5). 

With few exceptions, small particles of vegetable foods are generally stripped of their more accessible nutrients during digestion in the GI tract. In this way starch, protein, fat and water-soluble small components (sugars, minerals) are usually well absorbed. This is not always the case, however, for larger food particles or for molecules that cannot diffuse out of the celF tissue. Neither is it the case for the lipid-soluble components. These need to be dissolved in lipid before they can be physically removed from the cell to the absorptive surface, since the cell wall is unlikely to be permeable to lipid emulsions or micelles, and the presence of lipases will strip away the solvating lipid. 

Historically, the absorption of lipid-soluble nutrients has been considered to be carrier-independent, with solutes diffusing into enterocytes down concentration gradients. This is true for some lipid-soluble components of plants (e.g. the hydroxytyrosol in olive oil Manna et al., 2000). However, transporters have been reported for several lipid-soluble nutrients. For example, absorption of cholesterol is partly dependent on a carrier-mediated process that is inhibited by tea polyphenols (Dawson and Rudel, 1999) and other phytochemicals (Park et al., 2002). A portion of the decreased absorption caused by tea polyphenols may be due to precipitation of the cholesterol associated with micelles (Ikeda et al., 1992). Alternatively, plant stanols and other phytochemicals may compete with cholesterol for transporter sites (Plat and Mensink, 2002). It is likely that transporters for other lipid-soluble nutrients are also affected by phytochemicals, although this has not been adequately investigated. 

Natural antioxidants may be classified according to their nutritive value or according to their solubility. The hydrophobic vitamin E and the hydrophilic vitamin C are thus important both as nutrients and as antioxidants. The nonnutritive antioxidants may similarly be divided into lipid-soluble and water-soluble antioxidants, as shown in Fig. 16.3, which will also form the basis for a discussion of exploitation of combinations of anhoxidants in order to improve protective effects. 

The sinusoids transport both portal and arterial blood to the hepatocytes. The systemic blood delivered to the liver contains nutrients, drugs, and ingested toxins. The liver processes the nutrients (carbohydrates, proteins, lipids, vitamins, and minerals) for either immediate use or for storage, while the drugs and toxins are metabolized through a variety of processes known as first-pass metabolism. The liver also processes metabolic waste products for excretion. In cirrhosis, bilirubin (from the enzymatic breakdown of heme) can accumulate this causes jaundice (yellowing of the skin), scleral icterus (yellowing of the sclera), and tea-colored urine (urinary bilirubin excretion). 

PN admixtures can be prepared by mixing all components into one bag [3-in-l admixture or a total nutrient admixture (TNA)] or by mixing and infusing dextrose, amino acids, and all other components together and infusing intravenous lipid emulsion separately (2-and-l admixture). 

DF Driscoll, MN Bacon, BR Bistrian. Physicochemical stability of two types of intravenous lipid emulsion as total nutrient admixtures. J Parent Enteral Nutr 24(1) 15-22, 2000. 

Commonly administered LVPs include such products as Lactated Ringers Injection USP, Sodium Chloride Injection USP (0.9%), which replenish fluids and electrolytes, and Dextrose Injection USP (5%), which provides fluid plus nutrition (calories), or various combinations of dextrose and saline. In addition, numerous other nutrient and ionic solutions are available for clinical use, the most popular of which are solutions of essential amino acids or lipid emulsions. These solutions are modified to be hypertonic, isotonic, or hypotonic to aid in maintaining both fluid, nutritional, and electrolyte balance in a particular patient according to need. Indwelling needles or catheters are required in LVP administration. Care must be taken to avoid local or systemic infections or thrombophlebitis owing to faulty injection or administration technique. 

Parenteral hyperalimentation involves administration of large amounts of nutrients (e.g., carbohydrates, amino acids, lipids, and vitamins) to maintain a patient who is unable to take food orally for several weeks at caloric intake levels of 4000 kcal/day or more. Earlier methods of parenteral alimentation, which involved IV... 

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