Lipid intakes

It is clear from the above discussion that alterations in dietary lipid intake can profoundly affect cell membrane composition in human skin, and consequently influence many physiological and pathological processes. While deficiency of LA results in loss of barrier function and hyperproliferation, an altered n-3 and n-6 EFA balance may influence many processes including a wide range of inflammatory and immune responses, and skin carcinogenesis. There is evidence that alterations in eicosanoid production may contribute to many of the activities, while there is also an increasing understanding... 

The coefficient of fat absorption is defined as the amount of fat absorbed as a percentage of the ingested amount. This coefficient normally exceeds 93% and is used (rather than crude fecal fat excretion) to indicate efficacy of luminal fat digestion following different dietary lipid intakes. By contrast, fecal carbohydrate measurements do not fully reflect the extent of starch malabsorption because carbohydrates are metabolized by the intracolonic microbial flora. Since intracolonic metabolism of carbohydrates... 

In a prospective prevalence study of liver disease in 90 patients with permanent intestinal failure receiving parenteral nutrition hver biopsy was performed in 57 (95). Chronic cholestasis developed in 58 patients after a median of 6 (range 3-132) months, and 37 developed comphcated liver disease after a median of 17 (range 2-155) months. Chronic cholestasis was significantly associated with a risk of liver disease independent of parenteral nutrition, a bowel remnant shorter than 50 cm, and a lipid intake of 1 g/kg/day or more hver disease related to parenteral nutrition was significantly associated with chronic cholestasis and a parenteral hpid intake of 1 g/kg/day or more. The authors concluded that the prevalence of hver disease increased with the duration of parenteral nutrition and was one of the main causes of death in patients with permanent intestinal failure. Parenteral intake of long-chain hpid emulsion should be restricted to less than 1 g/kg/day. 

Venkatraman, J.T., Rowland, J.A., Denardin, E., Horvath, P.J., and Pendergast, D. 1997. Influence of the level of dietary lipid intake and maximal exercise on the immune status in runners. Med. Sci. Sports Exerc. 29, 333-344. 

An abundance of food has obvious consequences it promotes our specific appetites. Lipids account for about 40% of the calories ingested in Western countries, whereas nutritional recommendations are 5-10% lower. This excessive lipid intake, associated with a qualitative imbalance (excess of saturated fatty acids and cholesterol, too high to6/to3 ratio) strongly favours the development of obesity and associated diseases (atherosclerosis, non insulin-dependent diabetes, hypertension, cancer). This attraction to fatty foods is not specific to humans. Rats and mice spontaneously prefer lipid-rich foods if provided with a free choice (Tsuruta et al. 1999 Takeda et al. 2000). This attraction to lipids is so strong that mice given free access to an oil as an optional diet rapidly become obese (Takeda et al. 2001a). The origin of this preference for lipids remains unclear. 

Normally more than 95% of ingested lipid is absorbed. When a large fraction is excreted in the feces, it is called steatorrhea. Measurement of fecal lipid with adequate lipid intake is a sensitive indicator of lipid malabsorption. Malabsorption can result from impairment in lipolysis (Table 12-6), micelle formation (Table 12-7), absorption, chylomicron formation, or transport of chylomicrons via the lymph to blood. 

Ans. More than twice as much energy is generated per gram of lipid metabolized compared to protein or carbohydrate. A high lipid intake results in excess (unmetabolized) lipid which is then stored in fat adipose) tissue. Weight increase results in a higher load on the heart. 

There is no required intake of fats and other lipids, with exception of EFA. Thus, there is no established reconunended daily intake for lipids. Current dietary guidelines follow reconunendations of the FAOAVHO expert consultations on fat and oils in human nutrition published in 1994 as the FAO Food and Nutrition paper No. 57 (FAOAVHO, 1994). General conclusions and reconunendations of the consultations regarding lipids intake are as follows ... 

The rate of de novo synthesis is reduced when the dietary lipid intake is increased, and also the specific activities of both the ATP citrate lyase and the malate enzyme in liver decrease (Griminger, 1986). Together they catalyse the production of acetyl-CoA and reducing equivalents needed for the synthesis of fatty acids. 

Del Prado, M., Delgado, G., and ViUalpando, S. (1997) Maternal Lipid Intake During Pregnancy and Lactation Alters Milk Composition and Production and Litter Growth in Rats, J. Nutr. 127,458 62. 

Lipids After Lipid Intake Atti Conv. Intern. Lipid Aliment, Simp. Genuinita Oli Aliment., 3°, Rimini, Italy, 1962 (Pub. 1963) 595-598 CA 60 11136a... 

Based primarily on immunological studies in model systems, dietary recommendations, though tentative, should include moderation of caloric and lipid intake. The recommended dietary intakes of trace elements and antioxidants, for selected populations such as pregnant women, should be reexamined with reference... 

In addition to physical activity independendy affecting plasma lipid levels, a combination of interventions, including diet and exerdse regimens, has been shown to be effective at positively altering plasma lipid profiles. Decreased saturated fat intake and exercise incorporation induce complementary effects on plasma lipid levels, the combination of which shows a more optimal plasma hpid profile than either intervention alone."" The modification in dietary lipid intake complements the reduced levels of plasma HDL cholesterol and triglycerides often seen by an increase in physical activity. Therapies involving both a low-saturated-fat diet and exercise incorporation lowered plasma total cholesterol, LDL cholesterol, and triglyceride... 

Many claims for health benefits have been made for CLA in both animals and humans. These have been reviewed in detail elsewhere (Yurawecz et al, 1999a) and will only be discussed briefly here. The first indication that CLA might be biologically active was reported in 1979 when an extract from grilled beef was found to inhibit mutagenesis in a rat liver cell fraction (Pariza et al, 1979). Studies on the potentially anti-carcinogenic properties of CLA, both in vitro and in vivo (Pariza et al, 2001), have demonstrated that the isomer with an active effect on cancer cells is probably the 9-cis, ll-trans isomer. In vivo studies in rodents showed that dietary CLA supplementation decreased the number and size of mammary tumours, regardless of other lipid intake (Ip et al, 1996), and that topically applied CLA reduced the size and number of skin... 

The quantity of total fats in the diet seems to have a great influence on blood lipid levels. Populations with high fat diets, generally present high levels of serum cholesterol populations with poor lipid diets have low levels of cholesterolemia. Anyway it seems that, at similar lipid intake, considerable individual variations exist. 

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