And n-3 PUFA

Fat is a key component in the human diet. Research shows that excessive consumption of saturated fat negatively impacts several biomarkers of health while monounsaturated and n-3 PUFAs are beneficial to human health. Moreover, research shows that imbalanced dietary ratios of n-6 n-3 may lead to various health complications as well as disease progression while increased n-3 levels impart prevention and health promoting effects (Burghardt et al., 2010 Goodstine et al., 2003 Simopoulos, 2002 Wan et al., 2010). The American Heart Association recommends eating fatty fish meals at least twice a week due to their promising health and especially cardiovascular benefits. Here, we review some of the health benefits of n-3 PUFAs, due in part to their anti-inflammatory effects in cancer, cardiovascular diseases (CVDs), obesity, and other metabolic disorders. 

To advance understanding of the dynamic influence of dietary lipids, research efforts are focusing on the importance of the balance between n-6 and n-3 fatty acids in the human diet. What is emerging is recognition that these PUFAs modulate eicosanoid biosynthesis in numerous tissues and cell types, alter signal transduction, and influence gene expression (87, 118). The effect of n-6 and n-3 PUFA on CVD, cancer and bone/joint health is related to the newer discoveries of how dietary PUFA impact health. 

Watanabe S, Doshi M, Hamazaki T (2003) n-3 Polyunsaturated fatty acid (PUFA) deficiency elevates and n-3 PUFA enrichment reduces brain 2-arachidonoylglycerol level in mice. Prostaglandins Leukot Essent Fatty Acids 69 51-59... 

Vingrys AJ, Weisinger HS, Sinclair AJ. The effect of age and n-3 PUFA level on the ERG in the guinea pig. In Huang Y. Sinclair A eds.. Lipids and Infant Nutrition. AOCS, Champaign, IL, 1998. 

Ln recent years, interest increased in the ratio of omega-6 (n-6) to omega-3 (n-3) PUFA, or LA ALA, in part due to the link between inflammation and several lifestyle diseases, such as cardiovascular disease (CVD) and Type LL diabetes. However, whether this ratio is directly associated with an increased risk of inflammatory diseases is unclear. Furthermore, the low conversion of dietary ALA to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (Goyens et al., 2005 Hussein et al., 2005 Pawlosky et al., 2001) means that a lower n-6 n-3 PUFA ratio does not necessarily reflect physiologically important increases in EPA and DLiA (Harris, 2006). Consequently, evaluating absolute dietary intakes of specific n-6 and n-3 PUFAs may be most appropriate, particularly when few human experimental and clinical trial data exist to support the use of an n-6 n-3 PUFA ratio. Nevertheless, when considering the composition of SBO, notably, SBO has a lower n-6 n-3 PUFA ratio than other commonly used vegetable oils, such as corn oil. 

A substantial body of literature exists reporting the inflammatory (or anti-inflammatory) effects of n-6 and n-3 PUFA. LA and ALA undergo a series of desaturation and elongation steps that yield arachidonic acid (AA, 20 4n-6) and EPA (20 5n-3), respectively. Additional metabolism of EPA produces the n-3 PUFA DHA (22 6n-3). However, the conversion of ALA to EPA, and especially DHA, is limited in humans (Goyens et al., 2005 Hussein et al., 2005 Pawlosky et al., 2001). Based on a metabolic model, Goyens et al. (2005) estimated that 7% of dietary ALA is converted to long-chain PUFA 99% is converted to EPA and 1% to docosapentaenoic acid (DPA). DHA is subsequently produced via elongation and desaturation of DPA. Ilierefore,... 

Singer, P., Berger, L, Moritz, V., and Taube, C. (1990) N-6 and n-3 PUFA in Liver Lipids, Thromboxane Formation and Blood Pressure from SHR During Diets Supplemented with Evening Primrose, Sunflower Seed or Fish Oil, Prostag. Leukote. Ess. 39,207-211. 

The right balance of n-6 and n-3 polyunsaturated fatty acids (PUFA) is important for good health. The n-3 PUFA such as eicosapentaenoic acid PA) and docosahexaenoic acid (DHA) are mainly found in fish oils. Marine plants can convert a-linolenic acid (ALA) into EPA and DHA, which find their way through the food chain to fish tissues. Another source of n-3 PUFA is the ALA that is found mainly in flaxseed, canola, and soybean oils. Unlike plants, mammals cannot convert oleic acid into linoleic acid, linoleic acid into ALA, or convert n-6 PUFA to n-3 PUFA. Linoleic acid and n-3 PUFA are therefore known as essential fatty acids (1). 

Keys et al. [138] and Hegsted et al. [139] showed from mathematical equations that serum cholesterol concentration of a person would be predicted by the diet fat consumption. Furthermore, SFAs were two times more effective in raising cholesterol, and PUFA reducing them. In this context, SFA can not correspond with more than 1/3 of fat diet intake. Nevertheless, there are great reservations about those equations, due to they were made with middle-aged men who consumed high fats contents and, therefore, they re not necessarily valid to other populations in different diet conditions. In addition, in 1960, when the biochemical and dietary analyses were done, trans and n-3 PUFA could not be identified and hence only information on saturated monounsaturated and polyunsaturated fats were report. 

LDL. The corresponding fragmented alkyl phosphatidylcholines, butanoyl GPC and butenyl GPC products are inflammatory platelet-activating factor (PAF)-like phospholipids and also named butanoyl PAF and butenyl PAF. These C-4 core aldehydes are probably the most stable and are readily analysed directly by LC-MS. Several additional and perhaps more bioactive unsaturated core aldehydes are also expected by non-enzymatic oxidation and fragmentation of PC and CE containing arachidonic, linoleic and n-3 PUFA acids (see Chapter 4) in oxidized LDL. These unsaturated core aldehydes may not have been detected because they may form covalent PC-apoprotein adducts that are not readily identified and analysed directly by LC-MS. However, these unsaturated core aldehydes may be potentially more bioactive and important than the saturated core aldehydes reported in oxidized LDL. 

Ratnayake, W.M.N., Ackman, R.G. and Hulan, H.W. (1989) Effect of redfish meal enriched diets on the taste and n-3 PUFA of 42-day-old broiler chickens. J. Sci. Food Agric. 49, 59-74. 

Alterations in the level of palmitoleic acid have been found in tissues under certain physiological and disease conditions, including essential fatty acid deficiency (EFAD), cancer, cardiovascular disease, and diabetes mellitus. These changes are often associated with changes in the relative levels of n-6 and n-3 PUFA in the tissues. 

FFAD is a physiological, sometimes pathological, condition caused by abnormalities in dietary intake, absorption, and/or metabolism of n-6 and n-3 PUFA. A typical feature of FFAD is a decrease in the levels of linoleic acid and arachidonic acid (20 4n-6), an increase in the levels of palmitoleic, oleic, and eicosatrienoic (20 3n-9) acids, and increases in the eicosatrienoic arachidonic, palmitoleicilinoleic, and oleic linoleic acid ratios in plasma phospholipids (Chardon et al., 1985). In FFAD the relative proportion of palmitoleic acid is also increased in other tissues in both human and animal models (Berghaus et al., 1975 Alam et al., 1994 Gomez-Tubio et al., 1999). Pregnancy and high... 

Taonis et al. (2002) investigated the effects of dietary fatty acids on insulin signalling in mnscle tissne. For their study, 5-week-old male Wistar rats were fed one of three diets for 4 weeks control (high carbohydrate), n-6 PUFA (58% energy from safflower oil), or n-3 PUFA (39% energy from safflower oil and 19% energy from flsh oil). To determine effects of insulin stimulation, the rats were injected with insulin 7 min before termination. The results of this study showed that insulin-induced tyrosine phosphorylation of IR and IRS was similar in the muscle of the animals fed control and n-3 PUFA diets, but depressed in the animals fed the n-6 PUFA diet. 

PUFAs are categorized as n-6 PUFAs (mainly derived from linoleic acid) and n-3 PUFAs (mainly present in fatty fish and also derived from alpha-linoleic acid). Clinical trials, in which n-6 PUFAs (containing linoleic acid) were substituted for SFAs showed a greater impact on reduction of both plasma cholesterol and CHD risk, in contrast to trials where low-fat diets were employed. 

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