Essential Fatty Acids There are mainly two groups of essential fatty acids -  omega 3 fatty acid and  omega 6 fatty acid. Examples of omega 3 fatty acids include alpha-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), while arachidonic acid is an example of omega 6 acid.
Sources Omega 3 Fatty Acids can be found in oily fish, linseed or flax oil, hemp oil, soybean oil, pumpkin seeds, walnuts, dark green vegetables. While, omega 6 Fatty Acids can be found in unrefined safflower, corn, meat, sesame and sunflower oils. They both are essential for optimal health!
Omega 3 fatty acids EFAs like Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) are derived from different sources, and are a part of several chains of metabolic events in the body that prevents disease, assist the transport and uptake of oxygen, maintain brain function, maintain the immune system, cardiovascular health and keep hormone levels where they should be as we age. EFA deficiencies in today's society are directly associated with cardiovascular disease, cancer, diabetes, multiple sclerosis and other degenerative conditions.
Omega 6 fatty acids Omega-6 fatty acids are a family of unsaturated fatty acids that have in common a final carbon–carbon double bond in the n−6 position. There are two important omega-6 fatty acids, and they are linoleic acid and arachidonic acid. Linoleic acid is an essential fatty acid, while arachidonic acid is the precursor for prostaglandins and other important physiologically molecules. [Wikipedia, 2013]
The Importance of The Ratio of Omega-6 Fatty Acids to Omega-3 Fatty Acids It has been noticed that a high ratio of certain omega-6 fatty acids to certain omega-3 fatty acids may put a subject at risk of multiple conditions, such as increased water retention, raised blood pressure etc, especially in presence of air pollution, smoke and other exogenous toxins. According to Wikipedia.com, 2013, a ratio of 2–3/1 omega 6 to omega 3 helped reduce inflammation in patients suffered from rheumatoid arthritis. A ratio of 5/1 benefited patients with asthma but a 10/1 ratio had a negative effect. A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 was not effective. Prolonged excessive production of omega-6 eicosanoids is linked to arthritis, inflammation and cancer, and many drugs for treating these conditions work by blocking the effects of arachidonic acid. Some drugs used to treat bipolar disorder also work by targeting the arachidonic acid cascade in the brain. [Wikipedia. 2013]
Prostate Cancer Consumption of polyunsaturated fatty acids (PUFA) modulates the development and progression of prostate cancer. High amounts of omega-6 fatty acids have been linked with increased prostate cancer risk, whereas omega-3 fatty acids have been shown to inhibit prostate cancer growth. Researchers at The University of Texas at Austin treated LNCaP prostate cancer cells with dietary-based ratios of omega-6 to omega-3 fatty acids. They found that a low omega-6 to omega-3 PUFA ratio can delay the progression of cells toward castration-resistance by suppressing pathways involved in prostate cancer progression. [Apte SA et al, Nutr Cancer. 2013;65(4):556-62]
Colitis In a study of mice, researchers found that the colonic inflammatory severity and the level of mucosal PGE2 in the experimental colitis mice were affected by the changed ratio of PUFA ω-3/ω-6 in the feed. Increased ratio of PUFA ω- 3/ω-6 (i.e. a low omega 6 to omega 3 ratio) in the feed had a protective effect on the intestinal mucosa in the experimental colitis mice, otherwise had hazards. [Tian Y et al, Beijing Da Xue Xue Bao. 2013 Apr 18;45(2):227-32.]
Reproduction Eighty male Sprague Dawley (SD) rats were supplemented with diets containing different n-3/n-6 PUFA ratios (0.13, 0.40, 0.85, 1.52 and 2.85) for 60 days. Sperm density and sperm motility of the 1.52 group were higher than other groups (P < .05), and the development of testis and the morphological structure of sperm in the 1.52 group were better than other groups. [Lipids Health Dis. 2013 Mar 13;12:33]
Dementia Loef M and Walach H European University Viadrina Germany reviewed 14 reports and concluded an association between the omega-6/omega-3 ratio, cognitive decline, and incidence of dementia and a positive association between the dietary omega-6/omega-3 ratio and the risk of Alzheimer's disease. [J Nutr Gerontol Geriatr. 2013;32(1): 1-23]
Triglyceride Wang et al investigated the levels of PUFAs, and their correlation with triglycerides and other factors in blood of 156 healthy individuals. They found that the level of ω-3 fatty acids was low in the subjects and the omega-3 (ω-3) index was 4.25%, while the omega-6:omega-3 (ω-6:ω-3) ratio was at a satisfactory level. There was a strong inverse correlation between ω-3 fatty acids and triglycerides, and a strong positive correlation between ω-3 fatty acids and high density lipoprotein (HDL). Eicosapentaenoic acid and docosahexaenoic acid were inversely correlated with triglycerides, and positively correlated with HDL. [Exp Ther Med. 2012 Dec;4(6):1107-1111.]
Osteoporosis Casado-Diaz A and co-workers Hospital Universitario Reina Sofía, Spain, concluded from their study that an increase in the intake of omega-3 respect to omega-6 may provide protection against the loss of bone mass. They explains, "Arachidonic acid induces adipogenesis in human mesenchymal stem cells cultures, and high concentrations inhibit osteoblastogenesis. In mesenchymal stem cells, arachidonic acid promotes the differentiation of adipocytes and inhibits the osteoblast differentiation. While omega-3 fatty acids do not affect the adipogenic differentiation." [Osteoporos Int. 2013 May;24(5):1647-61]
Coronary Artery Disease Nozue T and colleagues from Yokohama Sakae Kyosai Hospital, concluded that decreases in serum n-3 to n-6 polyunsaturated fatty acid ratios are associated with progression in coronary atherosclerosis from a study of statin- treated patients with coronary artery disease. [Am J Cardiol. 2013 Jan 1;111(1):6-11.]
Hip Fracture Risk Orchard TS and co-workers, The Ohio State University, claimed that "omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFA) in red blood cells (RBCs) are an objective indicator of PUFA status and may be related to hip fracture risk." in their research article. They found that higher RBC α-linolenic acid, as well as eicosapentaenoic acid and total n-3 PUFAs, may predict lower hip fracture risk. Contrastingly, a higher RBC n-6/n-3 ratio may predict higher hip fracture risk in postmenopausal women. [J Bone Miner Res. 2013 Mar;28(3):505-15]