Nutrient absorption rate

The lower rates of nutrient absorption associated with diets high in nonstarch polysaccharides are probably due to the increased viscosity of digesta (Vaugelade et al., 2000), which increases the thickness of the unstirred layer overlying the enterocytes and causes anon-specific decline in solute absorption. This explains why diets high in 3-glucans, which are structural carbohydrates and which increase viscosity of digesta, reduce absorption of nutrients and... 

A high rate of ethanol consumption can lead to inhibition of gastric secretion and irritation of the gastric mucosa. Ethanol irritates the entire gastrointestinal tract, which may lead to constipation and diminished absorption of nutrients. Other pathological effects include pancreatitis and peripheral neuropathy. Severe gonadal failure is often found in both men and women, accompanied by low blood levels of sex hormones. 

Various modifications are reported with respect to the experimental setup (single pass or recirculated intestinal perfusion) as well as the site of blood collection, e.g. mesenteric vessels for estimation of the intestinal absorption rate (DeGraw RT, Anderson BD 2004). vs. peripheral veins for estimation of systemic availability of the candidate compound. This method is widely used for investigation of intestinal absorption of nutrients by using radioactive tracers (e.g. cholesterol, glucose) and their interference with the candidate compound (Arts et al. 2004). In addition the secretion of the candidate compound into the intestine can be studied by peripheral administration of the compound into a peripheral vein and subsequent determination of the appearance of the candidate compound in the intestinal perfusate (Merino et al. 2003 Berggren et al. 2004). Also variations are reported using chronically isolated intestinal loops in rats (Poelma et al. 1992). 

Tannic acid is not consistently absorbed from intestinal mucosa or from the skin. Enhanced absorption rates can be seen in denuded skin and mucus membranes. Tannic acid can cause hardening of the gastrointestinal mucosa. This hardening can result in reduced gastrointestinal absorption of nutrients as well as of xenobiotics. Tannic acid has been experimentally shown to be able to reduce the carcinogenic potency of some amine derivatives and polycyclic aromatic hydrocarbons in laboratory animals. Tannic acid s anticarcinogenic properties appear to be mediated through the modulation of enzymes involved in xenobiotic metabolism. 

Figure 4. Nutrient absorption rate as a function of nutrient concentration comparison of Michaelis Menton theoretical curve with data from Ketchum (37)...

As an example, the data from Ketchum (37) for the rate of phosphate absorption as a function of both phosphate and nitrate concentration can be satisfactorily fit with a product of two Michaelis-Menton expressions. The resulting fit, obtained by a multiple nonlinear regression analysis, is shown in Figure 5. The Michaelis constants that result are 28.4 p.g NOa-N/liter and 30.3 pg P04-P/liter, with a saturated absorption rate of 15.1 X 10 8 pg P04-P/cell-hr. This approximation to the growth rate behavior as a function of more than one nutrient must be regarded as only a first approximation, however, since the complex interaction reported between the nutrients is neglected. 

The parasympathetic system, organized mainly for discrete and locahzed discharge, slows the heart rate, lowers the blood pressure, stimulates GI movements and secretions, aids absorption of nutrients, protects the retina from excessive light, and empties the urinary bladder and rectum. Many parasympathetic responses are rapid and reflexive. Although the parasympathetic branch of the ANS is concerned primarily with conservation of energy and maintenance of organ function during periods of satiety and minimal activity, its elimination is incompatible with hfe. 

By approximately 8 weeks after birth, the mminant has developed a fully functional mmen capable of extensive fermentation of feed nutrients (4). The rate of development of the mminal environment depends on the amount of milk consumed by the neonate in relation to its growth requirements, the avadabihty and consumption of readily digestible feedstuffs, and the physical form of the feedstuffs (4). The mmen develops much faster with hay than with milk (36). Concentrates, ie, high cereal grain diets, increase the absorptive surface of the mmen but mminal size and musculature develops much more slowly with a concentrate diet than with a forage diet (4). 

Proteinaceous phytochemicals can contain toxic epitopes that elicit defense responses for example gliaden and glutein peptides which cause celiac disease and other mucosal disorders (Tighe and Ciclitira, 1995 Van de Wal et al, 1999). The mucosal inflammation caused by feeding carnivorous Atlantic salmon diets with soybean meal decreases rates of nutrient absorption (Nordrum et al, 2000), whereas the detrimental influence of such diets is much less pronounced when fed to omnivorous fish, such as catfish and tilapia. 

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