Dietary influences polyunsaturated fatty acids

Thies, F., Miles, E.A., Nebe-von-Caron, G. et al., Influence of dietary supplementation with long-chain n-3 or n-6 polyunsaturated fatty acids on blood inflammatory cell populations and functions and on plasma soluble adhesion molecules in healthy adults, Lipids, 36, 1183, 2001. 

Opposing effects of certain individual fatty acids could have influenced the lack of a relationship between dietary fat and fat type with the risk of breast cancer. Well-conducted animal studies suggest that linoleic acid promotes development of mammary tumors, whereas saturated, monounsatu-rated, and trans fatty acids have little or no effect. In many cases, w-3 polyunsaturated fatty acids suppress tumor development. Conjugated linoleic acid (CLA) is the most potent anti-cancer fatty acid in that amounts of 1% or less of dietary fat can substantially inhibit the development of mammary tumors (Ip, 1997). 

As mentioned earlier that sesame lignans, especially sesamin and epi-sesamin, could influence the metabolism of polyunsaturated fatty acid and the production of prostaglandins. As prostaglandin is one of the most influential factors for mammary carcinogenesis, Hirose et al. (99) studied the effect of sesamin on dimethylbenz-anthracene (DMBA)-induced mammary cancer. Their results showed that sesamin at a dietary level of 0.2% considerably reduced the cumulative number and mean number of mammary cancer the effectiveness of sesamin was similar to a-tocopherol. 

Enrichment of the dietary fat with PLs or TAGs may or may not affect fecal excretion of fat and minerals and may increase or decrease saturated fat absorption depending on the PL and TAG source (83). Long-chain polyunsaturated fatty acids were better absorbed in preterm infants when fed as PLs than as TAGs (84). Feeding long-chain polyunsaturates as PLs or TAGs influences the distribution of these fatty acids in plasma lipoprotein fractions, affects their content in different plasma... 

By feeding nutritionally adequate diets, dietary intake of 18 2n-6, 18 3n-3, or the proportion of 18 2n-6 to 18 3n-3, particularly during development, has been shown to influence the content of long-chain polyunsaturated fatty acids in membrane lipids by changing the composition of the whole brain, oligodendrocytes, myelin, astrocytes mitochondrial, microsomal, and synaptosomal membrane (Bourre et al., 1984 Foot et al., 1982 Lamptey Walker, 1976 Tahin et al., 1981). Feeding diets with a 18 2n-6 to 18 3n-3 fatty acid ratio between 4 1 and 7 1 to rats from birth to 1, 2, 3, and 6 wk of... 

It is largely accepted that a high dietary intake of poly-unsaturated fatty adds (PUFA) in the a>-3 series has beneficial effects. Recently, cellular lipid metabolism has been suggested as a target for cancer therapy. Cancer cells, compared with normal cells, seem to be vulnerable to exposure of certain polyunsaturated fatty acids (PUFAs), especially those in the o -3 series. Characteristic for these compounds are their poor abihty to be oxidized in the cell due to multiple double bonds. They are however likely to be ester-rfied to oflier Upids, and their incorporation into membrane phosphohpids will influence membrane properties such as fluidity, protein interactions and susceptibility to lipid peroxidation. The hypohpidemic properties of some (0-3 fatty acids, such as EPA, are probably e lained by an induction of mitochondrial P -oxidation that is not found after adrninistration of the non-hypolipidemic (o-3 PUFA docosahexaenoic acid (DHA)." However, both eicosapentaenoic acid (EPA) and DHA cause increased peroxisomal... 

Dietary fatty acids will influence the cardiac phospholipid composition of the rat but to a lesser extent than the cardiac neutral lipids (Carroll, 1965). Dietary fatty acids may be incorporated as saturated and monounsaturated fatty acids, or they may be incorporated and converted to more polyunsaturated fatty acids (PUFA), i.e., linoleic acid to 20 4 n-6, 22 4 n-6, and 22 5 n-6 and linolenic acid to 20 5 r/-3, 22 5 n-3, and 22 6 n-3 (see Chapter 16). Dietary saturated and monounsaturated fatty acids are incorporated to a small extent into cardiac phospholipids (Carroll, 1965). On the other hand, dietary 18 2 n-6 and 18 3 n-3 cause a significant increase in the pentaenoic and hexaenoic acids which is greater in the heart than in any other organ of the rat (Rieckehoff et aL, 1949 Widmer and Holman, 1950). With this background it may be useful to discuss changes in the composition of the different cardiac phospholipids with diet. 

Recently, there have been two extensive reviews of the role of polyunsaturated fatty acids in the diet. Hoffman and Forster (1981) discussed the influence of dietary linoleic acid on blood pressure regulation-particularly in relation to salt-loaded individuals. In addition, the mechanism of the hypochol-esterolaemic effects of polyunsaturated fatty acids was discussed by Paul et aL (1980). These authors classified the hypocholesterolaemic effect as being due to reduced absorption of cholesterol, redistribution of cholesterol from blood to tissues, reduced cholesterol synthesis and increased excretion of cholesterol or its catabolites. These various factors have all been involved in the hypocholesterolaemic effect but the evidence is equivocal in each case. Other sources of information on dietary polyunsaturated fatty acids are Vergroesen (1975) and Kunau and Holman (1977). 

Prebiotics, polyunsaturated fatty acids (PUFAs) and phytochemicals are the most well characterized dietary bioactive compounds. The beneficial effects of prebiotics mainly relay on their influence on the gut microbiota composition and their ability to generate fermentation products (short-chain fatty acids) with diverse biological roles (Laparra and Sanz 2010). PUFAs include the co3 and co6 fatty acids, whose balance may influence diverse aspects of immunity and metabolism. 

A typical American diet contains about 40% of its total energy content as fat. About half this energy is in the form of saturated fatty acids, one-fourth as monounsatu-rated fatty adds, and one-fourth as polyunsaturated fatty adds (PUFAs) (Ginsberg et dl., 1990). The quantity and nature of dietary fats carx influence the lex. d of plasma cholesterol. A reduction in total fat from the typical 40% of energy intake to 30% can result in a decrease in plasma cholesterol. 

German, J.B., Lokesh, B., and Kinsella, J.E. (1988) The Effect of Dietary Pish Oils on Eicosanoid Biosynthesis in Peritoneal Macrophages Is Influenced by Both Dietary n-6 Polyunsaturated Pats and Total Dietary Pat, Prostaglandins Leukot. Essent. Fatty Acids 34, 37-45. 

In one study, Tomassi and Olson (1983) examined the effects of dietary fatty acid composition on hepatic retinyl ester composition and on yitamin A utilization in the rat. The fatty acid composition of retinyl esters in the liver was not perturbed by the presence of a large amount of polyunsaturated fat in the diet over a 10-day feeding period. The predominant retinyl ester in the liver was retinyl palmitate, regardless of whether rats were fed 10% com oil, coconut oil, or linseed oil. In addition, the ingestion of polyunsaturated fat did not significantly influence the mobilization rate of vitamin A from the liver. 

The distribution of cholesterol between the luminal oil phase (provided largely by dietary fat) and the micellar phase, is therefore a major influence in the efficient absorption of cholesterol, and can be influenced by both the content and composition of the dietary fat. As the products of fat digestion (monoglycerides, fatty acids) are produced, micelles are expanded, increasing the solubility potential for cholesterol[17,18], and improving overall absorp-tion[19,20]. Thus, it has been clearly demonstrated that cholesterol absorption is most efficient in the presence of unesterified fatty acids[19,21] and particularly those which are mono or polyunsaturated [2 1,22] ... 

The fatty acid composition of the structural lipids of the animal tissues used as food is remarkably uniform irrespective of the animal s diet or whether it is simple stomached or a ruminant (Table 5.2), although there are clearly some species differences and diet can influence membrane composition in subtle ways (sections 5.2.2 and 8.9). A predominant fatty acid is arachidonic acid, a member of the n-6 family, and meat provides most of our dietary supply of this fatty acid. Plant structural fats are similarly dominated by polyunsaturated acids and supply mainly a-linolenic acid, a member of the n-3 family. 

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