TABLE OF CONTENTS

Title page    –         –         –         –         –         –         –         –         –         –          i

Certification           –         –         –         –         –         –         –         –         –          ii

Dedication   –         –         –         –         –         –         –         –         –         –          iii

Acknowledgment  –         –         –         –         –         –         –         –         –          iv

Table of contents   –         –         –         –         –         –         –         –         v-vi

INTRODUCTION         –         –         –         –         –         –         –         –          1-5

THE POLYUNSATURATED FATTY ACID     –         –         –         –          6-7

Types of polyunsaturated fatty acid     –         –         –         –         –         –          7

Omega-3 fatty acid          –         –         –         –         –         –         –         –          7

Omega-6 fatty acid          –         –         –         –         –         –         –         –          8

Omega-9 fatty acid          –         –         –         –         –         –         –         –          9

Nutritional Needs/Dietary References Intake           –         –         –         9-13

Natural and Industrial Sources of Omega-3 Fatty acid       –         –         13-15

Effect of Polyunsaturated Fatty Acids in the Body  –         –         –         –          15

Immunological System and Inflammation     –         –         –         –         15-17

Cancer         –         –         –         –         –         –         –         –         –         18-20

MECHANISM OF THE EFFECT OF N-3 PUFAS ON CARDIOVASCULAR DISEASE    

Anti-aggregatory Effect of n-3 PUFAs          –         —       –         –         21-22

Effect of n-3 PUFAs on circulating Lipid Profile    –         –         –         22-23

Effects of n-3 PUFAs on Cell Membranes     –         –         –         —       24-25

Antiaggregatory Effects of n-3 PUFAs          –         –         —       –         25-27

Antiarrhythmic Effect of n-3 PUFAs   –         –         –         –         –         27-28

Roles of Polyunsaturated Fatty Acids in Heart        –         –         –         28

Cardiovascular Benefits of Alpha-Linolenic Acid   –         –         –         29-30

n-6 PUFAs and Blood Lipid      –         –         –         –         —       –         30-31

n-6 PUFA and Blood Pressure ( BP)    –         –         —       –         –         31

Biochemical Roles of Omega-3 and Omega-6 Fatty Acids          –         31-34

SUMMARY AND CONCLUSION

Summary     –         –         –         –         –         –         –         –         –         –          35

Conclusion  –         –         –         –         –         –         –         –         –         –          35

References

INTRODUCTION

Polyunsaturated fatty acids (PUFAs) contain more than one unsaturation in their molecules and due to this feature they have the potential to be beneficial to health Fats are essential for living organisms. Fatty acid (FA) molecules have a variable length carbon chain with a methyl terminus and a carboxylic acid head group (Salem, 1999); they can be categorized based on the degree of saturation of their carbon chains. Saturated FAs possess the maximal number of hydrogen atoms, while monounsaturated FAs and polyunsaturated FAs (PUFAs) have one, or two or more, double bonds, respectively. PUFAs can be further subdivided on the basis of the location of the first double bond relative to the methyl terminus of the chain. For example, n-3 and n-6 FAs are two of the most biologically significant PUFA classes, and have their first double bond on either the third or sixth carbon from the chain terminus, respectively. The final carbon in the FA chain is also known as the omega carbon, hence the common reference to these FAs as omega-3 or omega-6 PUFAs.

Long-chain n-3 and n-6 PUFAs are synthesized from the essential FAs (EFAs) alpha-linolenic acid (ALA) and linoleic acid, respectively. An EFA cannot be made by the body and must be obtained through dietary sources. Animals and humans have the capacity to metabolize EFAs to long-chain derivatives.

Because the n-6 and n-3 pathways compete with one another for enzyme activity, the ratio of n-6 to n-3 PUFAs is very important to human health. An overabundance of FAs from one family will limit the metabolic production of the longer chain products of the other. The typical Western diet provides n-6 and n-3 PUFAs in a ratio ranging from 8:1 to 25:1 (1), values in severe contrast with the recommendations from national health agencies of approximately 4:1 (Holub, 2002). Lowering the n-6: n-3 ratio would reduce competition for the enzymes and facilitate the metabolism of more downstream products of ALA.

Because most diets are already very rich in n-6 PUFAs, greater focus needs to be placed on incorporating n-3 PUFAs into the diet. Dietary sources of n-3 PUFAs are readily available but in limited quantities. Many foods contain ALA, including certain vegetable oils, dairy products, flaxseed, walnuts and vegetables (Lazmann, 2001). Fishes, such as mackerel, herring and salmon, provide an excellent source of the long-chain derivatives of ALA, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (Holub, 2002).

Fatty acids participate in various processes in the body, such as the characterization of lipids and plasma levels. They have action on inflammatory processes, the hepatic lipid metabolism, and adipose tissue.

PUFAs have their importance related to their melting point and chemical structure (carbon chain folding, location of methylene carbon, and number of double bonds), and may exert different functions in the body.

In the 1900s (industrial revolution), there was increase in the consumption of fat and oils, which are essentially composed of saturated fatty acids (SFA) and PUFAs of the omega-6 series. On the other hand, there was a decrease in the consumption of PUFAs of the omega-3 series. This imbalance has been associated with circulatory problems (Simopoulos, 1991).

Omega-3 and omega-6 PUFAs are essential for the body and compete for desaturase and elongase enzymes originating differentiated series of eicosanoids (prostacyclin, thromboxane, and leukotrienes), which will have specific functions in each tissue type, namely: production and inhibition of platelet aggregation; anti-inflammatory, chemotactic, and vasodilator effect; and uptake of cholesterol from the tissues. It is worth mentioning that polyunsaturated and trans fatty acids may interfere in the mechanism of these enzymes and inactivate the eicosanoids. The vast majority of the eicosanoids derived from omega-6 fatty acids have proinflammatory and proarrhythmic effects and induce fever, pain, bronchoconstriction, proaggregating effect, and vasoconstriction. Eicosanoids derived from omega-3 fatty acids have anti-inflammatory, antiarrhythmic and anti-aggregation effects, and are associated with decreased oxidative stress (Kinsellar et al., 1981; Rose and Connolly, 1999).

The main polyunsaturated fatty acids (PUFAs) representative of the omega-3 fatty acids are: apha-linolenic acid (ALA); eicosapentaenoic acid EPA; and docosahexaenoic acid (DHA), and of the omega-6 fatty acids are: linoleic acid (LA) and arachidonic acid (AA) (Youdim et al., 2000). Omega-3 PUFAs have proven to be beneficial for health. In cardiovascular cases, they inhibit platelet aggregation (anti-thrombotic effect), stimulate vessel dilation, have anti-inflammatory effect, reduce chemotaxis of leukocytes, inhibit the synthesis of triacylglycerides in the liver by inhibiting the secretion of smaller VLDL particles which become larger LDL particles (atherogenic), stimulate the reverse transport of this cholesterol favouring its capture to the liver and its elimination through the bile duct (Micha and Mozaffarian, 2010).

These fatty acids have great significance in brain development, especially during pregnancy and early life, and they are incorporated into the retina. Docosahexaenoic acid (DHA) has active participation in the following brain processes: synaptogenesis; neuronal migration; and neurogenesis. Its importance is related to fluidity in the cell membranes of the central nervous tissue and rods and cones in the retina. It increases light sensitivity of photoreceptors; facilitates the movement of neurons from the ventricular to the peripheral zone (neurogenesis), stimulates pre and post-natal development of glia cells, and stimulates synaptogenesis in preformed neurons (Patterson et al., 2012).