Another guest post from Susan Macfarlane, a Registered Dietitian Nutritionist running a busy private practice in Canada’s capital of Ottawa, Ontario:
Omega 6/Omega 3
Omega 6 and 3 are two essential fats that are categorized as polyunsaturated fatty acids, or PUFAs for short. These fats are essential since we lack the ability to make them in our bodies and must obtain them from food or supplements. Once ingested, our body uses these fats to create other types of fats with important biological and health-promoting roles.
Below is a diagram demonstrating the relationship between these different types of fats, along with a brief definition of each.
PUFAs: a type of unsaturated fat that is liquid at room temperature and susceptible to oxidation from heat or light.
ALA: The parent omega 3 fat. Once ingested, you body converts small amounts of ALA to the longer-chain fats, EPA and DHA, but this is limited (1).
LA: The parent omega 6 fat.
AA: A derivative of omega 6, AA creates cell signaling messengers that play a role in inflammation
EPA & DHA: long-chain omega 3 fatty acids derived from ALA or certain types of fish/algae. These fats have an anti-inflammatory role in the body.
Role of Omega 6 and 3 in Body Processes and Disease
Omega 6 and 3 have many biological roles, including cell structure as well as eye and brain development, but are probably best known for their role in inflammation. In general, omega 6 fats are considered pro-inflammatory, while omega 3 fats are considered anti-inflammatory. However, both omega 6 and omega 3 fats can promote and inhibit the body’s inflammatory response, although omega 6 appears to produce a greater inflammatory response compared to omega 3 (1). On the other hand, DHA and EPA can turn off the body’s inflammatory response and even influence certain genes to halt the production of inflammatory molecules (1).
Omega 3’s anti-inflammatory capabilities have motivated researchers to explore its role in the prevention and treatment of various diseases. A summary of these findings is presented below. Note that the omega 3 fats of study in such research trials are EPA and DHA.
The role of omega 3 fats in the prevention and treatment of cardiovascular disease has been well-studied and includes the following:
Improved lipid profile (2,3)
Reduced inflammation (2) and platelet aggregation (4)
Improved blood pressure (2)
Prevention of arrhythmias (5,6)
Despite these benefits, several well-designed studies (7,8) have failed to demonstrate a reduction in cardiac events or mortality with the supplementation of omega 3 fats. This finding suggests that DHA/EPA only helps to lower cardiac risk, but does not compensate for other risk factors, such as diet, activity, disease, and genetics.
Autoimmune diseases occur when the body initiates an inflammatory response against its own tissues. Given its role in inflammation, it is believed that omega 3 fats have the potential to be used as an adjunct therapy in autoimmune diseases. A 2012, systematic review (9) found that high-dose EPA/DHA supplementation reduced joint pain and swelling in patients with rheumatoid arthritis, although it’s role in other inflammatory conditions remains unknown (1).
Alzheimer’s is a progressive disease in which inflammation is found in the brain tissue (2). Studies suggest that supplementation with EPA/DHA may slow the development of more severe dementia symptoms (10).
Epidemiological studies suggest that a low intake of omega 3 fats may contribute to the development of mental illnesses, including schizophrenia, ADHD, personality disorder, and bipolar disorder (2). Supplementation with omega 3 fats may have a beneficial impact on clinical symptoms, as was shown in a study of elderly men where each 50 mg increase in omega 3 fats resulted in a 7% reduction in depressive symptoms (11).
Does Omega 6 Contribute to Disease?
It’s well-reasoned that because omega 6 is a precursor for inflammatory mediators, that reducing one’s intake of omega 6 will result in decreased inflammation and a potential reduction in the risk of chronic diseases where inflammation plays a contributing role. However, the research to date does not support this hypothesis, at least when it comes to heart disease. The conversion of LA to AA (see diagram above), from which inflammatory mediators are produced, is tightly regulated (12). Furthermore, a scientific advisory released from the American Heart Association (12) found that omega 6 PUFAs either lowered or had no impact on inflammatory markers and that when LA replaced either saturated fat or refined carbohydrates, there was a reduction in LDL cholesterol and the risk for heart disease.
The role of omega 6 fats in other inflammatory diseases, such as Alzheimer’s disease, fatty liver disease, and irritable bowel disease is unclear and may be more related to the ratio of omega 6 to omega 3, as discussed below.
The Ideal Ratio of Omega 6: Omega 3
Ancestral studies suggest that humans evolved consuming an equivalent amount of omega 6 relative to omega 3, or a ratio of 1 (13). In today’s world, where a significant proportion of calories are derived from processed foods rich in vegetable oils and animal-derived fats, the ratio of omega 6 to omega 3 is approximately 15:1. At this higher intake, metabolism of omega 6, and consequently, inflammation, may be favoured (13).
The exact ratio of omega 6 to omega 3 needed for disease prevention/treatment is unknown. Most health organizations recommend a ratio of 4:1, however, a ratio of 2-3:1 may be beneficial for those with certain diseases, such as cancer and rheumatoid arthritis (13)
In addition to achieving an ideal ratio of omega 6 to omega 3, it’s also important to ensure that minimum amounts of omega 6 (remember, it’s still essential) and omega 3 are consumed. The American Academy of Nutrition and Dietetics/Dietitians of Canada advise for 3-10% of calories to come from LA(14), while the Institute of Medicine recommends a minimum daily intake of 17 g and 12 g for adult male and females respectively (15). Regarding ALA, the Institute of Medicine encourages a daily intake of 1.6 g and 1.1 g per day for adult male and females, respectively (15). No consensus has been reached on the amount of DHA/EPA to aim for per day, although most health organizations suggest an intake of 500 mg (16).
Practical Tips for Perfecting your Omega 6/3 Ratio
1. Meet your omega 6 needs through plant-based, whole-food sources.
To achieve the ideal ratio of omega 6 to omega 3, you need to simultaneously reduce your intake of omega 6, while increasing how much omega 3 you consume each day. The most concentrated sources of LA are found in plant-based oils like safflower, sunflower, grapeseed, and corn. As such, it’s better to use an oil that is low in omega 6, such as olive oil, and meet your LA needs from less concentrated sources, including almonds, pumpkin seeds, and cashews.
2. Include a daily source of ALA
You can meet your daily ALA requirement by including 1 tbsp of ground flax/whole chia seeds or 2 tbsp of hemp seeds. These seeds are great added to a smoothie, sprinkled on toast, mixed into a salad dressing, or stirred into yogurt.
3. Get enough DHA/EPA
The only food source rich in DHA/EPA is fatty fish. However, ocean pollution has raised concerns about the safety of fish consumption, since fat-soluble pollutants (such as dioxins) are stored in the fish’s fat cells and are incorporated into our own body’s cells through a process called bioaccumulation. If you do consume fish, avoid larger species such as tile fish and king mackerel and limit the frequency you eat fish to twice a week. If you avoid fish, it is recommended that you take a microalgae supplement providing at least 500 mg of DHA/EPA per serving.
Reidiger ND, Rgia, AO, Miyoung S, Moghadasian MH. A systemic review of the roles of n-3 fatty acids in health and disease. J Am Diet Assoc. 2009;109:668-679. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/19328262
Kelley DS, Siegel D, Vemuri M, Mackey BE. Docosahexaenoic acid supplementation improves fasting and postprandial lipid profiles in hypertriglyceridemic men. Am J Clin Nutr. 2007;86:324-333. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/17684201
Din JN, Harding SA, Valerio CJ, Sarma J, Lyall K, Riemersma RA, Newby DE, Flapan AD. Dietary intervention with oil rich fish reduces platelet-monocyte aggregation in man. Atherosclerosis. 2008;197:290-296. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/17575985
Hooper L, Thompson RL, Harrison RA, et al. Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ. 2006;332(7544):752-760. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/16565093
Rizos EC, Ntzani EE, Bika E, Kostapanos MS, Elisaf MS. Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events: a systematic review and meta-analysis. JAMA. 2012;308(10):1024-1033. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/22968891
Miles EA, Calder PC. Influence of marine n-3 polyunsaturated fatty acids on immune function and a systematic review of their effects on clinical outcomes in rheumatoid arthritis. Br J Nutr. 2012;107 Suppl 2:S171-184. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/22591891
Freund-Levi Y, Eriksdotter-Jönhagen M, Cederholm T, Basun H,Faxén-Irving G, Garlind A, Vedin I, Vessby B, Wahlund L-O, Palmblad J. Omega-3 fatty acid treatment in 174 patients with mild to moderate Alzheimer disease: OmegAD Study. Arch Neurol. 2006;63:1402-1408. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/17030655
Kamphuis MH, Geerlings MI, Tijhuis MAR, Kalmijn S, Grobbee DE, Kromhout D. Depression and cardiovascular mortality: A role for n-3 fatty acids? Am J Clin Nutr. 2006;84:1513-1517. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/17030655
Harris WS, Mozaffarian D, Rimm E, Kris-Etherton P, Rudel LL, Appel LJ, et al. Omega-6 fatty acids and risk for cardiovascular disease: a science advisory from the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation. 2009;119:902-907. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/19171857
Kris-Etherton PM, Innis S, for the American Dietetic Association, Dietitians of Canada. Position of the American Dietetic Association and Dietitians of Canada: dietary fatty acids. J Am Diet Assoc. 2007;107:1599–1611. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/17936958
Institute of Medicine. Dietary Fat: Total Fat and Fatty Acids. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. 2006. Washington, DC: The National Academies Press.