Arachidonic acid dietary sources

Arachidonic acid (5,8,11,14-eicosatetraenoic acid), a polyunsaturated fatty acid derived from dietary sources or by desaturation and chain elongation of the essential fatty acid linoleic acid, is found widely in the body. It is transported in a protein-bound state and stored in the phospholipids of cell membranes in all tissues of the body [108] from where it can be changed into biologically... 

Fig. 3. Effects of dietary supplementation with arachidonic acid (AA 0.5%) and docosahexaenoic acid (DHA 1%) on performance in Trial 2 of spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) groups at 60-s and 60-min intertrial intervals (ITI). Data are presented as means + SEM. Both strains performed significantly worse on the 60-min ITI and with the novel stimulus than on the 60-s ITI. There were no significant effects of diet. Source adapted from Reference 37.

Except for eicosanoic acid, the proportions of all fatty acids in egg yolk lipids were significantly (P < 0.01) influenced by the dietary CLA (59). The proportions of myristic, palmitic, and stearic acids, and CLA cis-9,trans- CLA and transit),cis-f2 CLA) in egg yolk lipids were increased by dietary CLA, but those of palmitoleic, oleic, linoleic, and linolenic, arachidonic acids, and DHA were decreased. These changes in fatty acid composition of yolk lipids are similar to those reported by Chamruspollert and Sell (60), although the total CLA concentration observed in the current research when a 5% CLA diet was fed (8.5-8.6%) was less than the 11.2% reported by those authors. The decrease in the concentrations of linoleic and linolenic acids in yolk lipids of hens fed CLA likely reflects the relatively low concentration of these fatty acids in the CLA source compared with soybean oil. Decreases in arachidonic acid and DHA in yolk lipids from hens fed CLA also could be related to the low concentration of dietary linoleic and linolenic acids, which serve as precursors to the formation of arachidonic acid and DHA. Another possibility is that CLA may compete with Unoleic and/or linolenic add for A6-desaturase, the rate-limiting step for the conversion of these fatty acids into arachidonic acid and/or DHA in liver microsomes (48). Feeding CLA increased the concentration of stearic acid in yolk lipids. 

Arachidonic (all ds 5,8,11,14-eicosatetraenoic) acid has been shown to have equivalent or even greater activity than linoleic add, and linolenic (all d59,12,15-octadecadienoic) acid is about 1.5 times as effective as linoleic acid. Mammals cannot synthesise fatty acids with double bonds closer than carbon atom 9 from the terminal methyl group. Such acids have to be supplied in the diet. Linoleic add (18 2n-6) and a-linolenic acid (18 3 n-3) are thus dietary essentials. Arachidonic acid is synthesised in the body from linoleic acid. However, one of the steps in the synthesis, a A-6 desaturation, is rate-limiting and production may be slow and an exogenous supply advantageous (see Box 3.1). Linoleic and a-linolenic acids are referred to as the essential fatty acids (ERA). Like other polyunsaturated acids, they form part of various membranes and play a part in hpid transport and certain lipoprotein enzymes. In addition, they are the source materials for the synthesis of the eicosanoids. These include the prostaglandins, thromboxanes and leukotrienes, hormone-like substances that regulate... 

Earlier sections of this chapter have emphasized that, in addition to their use as energy sources, fatty acids have a number of roles that are essential to cell and tissue function (Figure 5). A range of fatty acids is required for membrane composition, integrity and function to be retained. This means that a supply of the correct balance of fatty acids to cells and tissues is essential for the optimal functioning of those cells and tissues. Furthermore, different cells and tissues may require a different balance of fatty acids (i.e. they may have different demands for fatty acids). Although many fatty acids can be synthesized in the human body, some caimot (linoleic and a-linolenic acids) and so these fatty acids must be consumed in the diet. In the absence of significant dietary intakes, synthesis of some other fatty acids (e.g. arachidonic acid) requires the provision of a preformed precursor fatty acid (e.g. linoleic acid). This means that dietary supply of some fatty acids is very important to meet the demands imposed by optimal ceU and tissue function. Thus, an inadequate or unbalanced supply of fatty acids may impair cell and tissue function and lead to ill health and disease. Therefore, dietary fatty acids can influence human health. 

Examples of dietary omega-6 FAs are linoleic add (C,g2) and arachidonic acid (C20 4)- The major dietary sources of linoleic acid are vegetable oils, and linoleic acid may be converted to arachidonic add in diverse cells prior to its conversion to prostaglandins of the 2 series. 

Oil from marine and freshwater fishes varies in the contents of arachidonic acid, EPA, and DHA. The most widely available dietary source of EPA and DHA is cold-water oily fish, such as salmon, herring, mackerel, anchovies, and sardines. Peru, Chile, and Denmark are the leading producers of fish oil and collectively accoxmt for over 50% of the global production (Transparency market research, 2013). Liver oils are produced from the livers of cod, coalfish, haddock, and several species of shark. Cod liver oil has been replaced by liver oils obtained from other fish species, such as Alaska pollock, other gadoid species, and hake liver oils. 

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