April 2013 Issue
By Aglaée Jacob, MS, RD
Vol. 15 No. 4 P. 38
Dietary intake of just the right amount of omega-6 and omega-3 fatty acids is crucial for optimal health. Learn more about these fats and strategies to better counsel patients.
Of all the different types of fatty acids, only two have been declared essential to human health: linoleic acid (LA), an omega-6 fat, and alpha-linolenic acid (ALA), an omega-3 fat. The balance between these two essential fatty acids is delicate, however, and too much of one and too little of the other can result in deleterious health consequences.
The standard American diet tends to skew the ratio of omega-6 to omega-3 in favor of omega-6 fats, which can contribute to a systemic inflammatory process and the increased prevalence of obesity, cardiovascular and nonalcoholic fatty liver diseases, rheumatoid arthritis, inflammatory bowel diseases (IBD), and cancer.
To ensure clients and patients get the right balance of omega-3 and omega-6 fats in their diet, it’s important to review the facts about omegas, learn what the right balance should be, and understand how to best achieve it.
As you probably know, fatty acids are classified according to the length of their carbon chain and the double bonds present on the molecule. Both omega-6 and omega-3 fats are considered polyunsaturated fatty acids (PUFAs) because they contain two or more double bonds. LA and ALA can’t be synthesized in the human body and therefore must be obtained from food.1
The theory is that elongation of LA and ALA, if consumed in sufficient amounts, can produce longer-chain fats as required. The body can more readily use such fats, which include arachidonic acid (AA) in the omega-6 family as well as EPA and DHA in the omega-3 family.
It’s still unclear whether LA and ALA’s own activity or the benefits from their elongation into AA, EPA, and DHA cause their essentiality. It can be argued that LA and ALA aren’t essential fats, provided that adequate longer-chain omega-6 and omega-3 fats are consumed. Some researchers claim it’s better to obtain more readily usable forms of omega fats, especially as EPA and DHA, considering humans’ poor ALA conversion rate. However, this topic is still up for debate.
Omega-6 fats are necessary for normal growth and development. They help maintain the reproductive system and contribute to the synthesis of hair, skin, and bones. Main food sources of omega-6 fats include most vegetable oils (eg, corn, soybean, and cottonseed), nuts, and animal products.
Omega-3 fats play an important role in cognition, behavioral function, mood, circulation, and skin and heart health. Although the ALA found in vegetable sources such as walnuts, flaxseeds, and chia seeds can, in theory, be converted into easier-to-use longer-chain omega-3 fats, it’s preferable to obtain EPA and DHA directly from marine sources, such as cold-water fatty fish (eg, salmon, sardines, herring, albacore tuna, lake trout, mackerel, sardines) and algae.
Omega-6 to Omega-3 Ratio
Despite the importance of consuming both omega-6 and omega-3 fatty acids, too much of either essential fatty acid (EFA) can impair how the other functions. Before the industrialization of food in the last century, scientists estimate that the ratio of omega-6 to omega-3 fats in the human diet averaged between 1:1 and 4:1.2
Substituting animal fats in the standard US diet with vegetable oils in margarines, salad dressings, and other processed foods has resulted in a drastic increase in omega-6 consumption. PUFA consumption rose from 13 to 37 g/day within the last 100 years and now accounts for 21% of total fat intake, mostly in the form of omega-6 fats.3
As a consequence of these dietary changes, the current omega-6 to omega-3 ratio has reached an all-time high, estimated at between 10:1 and 20:1.2 The excess of omega-6 fats and the deficiency in omega-3s in the US diet is thought to be associated with today’s increased prevalence of chronic and inflammatory diseases.
Health Risks of Unbalanced Omegas
Omega-6 and omega-3 fats carry out essential tasks. Through their involvement with the synthesis of different eicosanoids, such as prostaglandins, thromboxanes, and leukotrienes, omega-6 fats tend to have a mostly proinflammatory effect, whereas omega-3 fats seem to elicit anti-inflammatory actions.
The excessive intake of PUFAs in the standard US diet, which almost tripled compared with 100 years ago, before the common use of vegetable oils, also can cause damage because of their high peroxidability index. The double carbon bonds of PUFAs increase their susceptibility of reacting with oxygen, resulting in harmful compounds responsible for oxidation and inflammation involved in the aging process and the development of the following chronic conditions4:
A well-controlled study in which institutionalized men were randomly assigned to a diet providing 40% of calories from fat, either mostly in the form of saturated fatty acids or PUFAs was published in the Journal of Lipid Research in 1966. The main difference between the two diets was the replacement of animal fats with vegetable oils in the PUFA group. After five years, subjects with the diet high in PUFAs had three times as much omega-6 fats stored in their adipose tissue (32% vs. 11% at baseline) and weighed an average of 8 lbs more compared with the saturated fatty acid group.5
Since then, many studies have shown that obesity is associated with an inflammatory state resulting from the increased production of proinflammatory eicosanoids that can come from an unbalanced omega-6 to omega-3 ratio.2
Fatty Liver Disease
Although excess omega-6 fats are associated with obesity, metabolic syndrome, and diabetes, they also can contribute to nonalcoholic fatty liver disease, which has been rising steadily in the past several years.
Omega-3 fats appear to protect against fatty liver disease because they encourage adequate insulin sensitivity and direct fatty acids away from liver storage. Unfortunately, disproportionate levels of omega-6 fats inhibit these potential omega-3 benefits. Patients presenting with nonalcoholic fatty liver disease have been found to have higher levels of omega-6s and lower levels of omega-3s in their adipose tissues, indicating an imbalance in the dietary ratio of these fats.2
Low-grade systemic inflammation is now considered a significant risk factor in the development of cardiovascular diseases. Eicosanoids derived from omega-6 fats are associated with many factors involved in atherosclerosis, such as inflammation, vasoconstriction, endothelial dysfunction, and platelet aggregation.
Increased oxidative stress resulting from a high intake of oxidation-prone omega-6 PUFAs also can result in the formation of oxidized LDL particles, which are more susceptible to becoming incorporated into arterial plaques, eventually leading to cardiovascular problems.
A recent Japanese study showed that the complexity of coronary lesions in more than 200 patients diagnosed with stable angina was significantly correlated with a higher plasma AA to EPA ratio (too much omega-6 and too little omega-3).6 Another recent study found that high intakes of vegetable oils containing a high omega-6 to omega-3 ratio were associated with increased low-grade systemic inflammation, as measured by C-reactive protein levels, among a cohort of 2,031 individuals followed for 12 years.7
Many of the cardioprotective benefits of the Mediterranean diet can be derived from its more balanced omega-6 to omega-3 ratio, resulting from a higher omega-3 intake from cold-water fish and the liberal use of low omega-6 fats such as olive oil.
Other Inflammatory Conditions
The development of rheumatoid arthritis, IBD, cancer, and Alzheimer’s disease, and the severity of their associated symptoms, also may be affected by the proportions of omega-6 and omega-3 fats in the diet.2
The prevalence of IBD has been shown to increase with omega-6 intake, while omega-3 fats have been found to offer promising benefits to protect against its development. A low omega-6 and anti-inflammatory diet also has been shown to reduce symptoms in patients with rheumatoid arthritis. An excessive omega-6 and inadequate omega-3 intake also has been proposed to contribute to beta-amyloid deposition, an important factor in the pathogenesis of Alzheimer’s disease. Finally, inflammation associated with excessive dietary omega-6 has been linked with progression of various cancers.2
Balancing the Ratio
It’s not always clear whether excessive amounts of omega-6s, inadequate levels of omega-3s, or both worsen these conditions. More studies are needed to determine the mechanism of action and confirm the beneficial effects in various conditions in which inflammation appears to be a key player.
Despite the need for more evidence, RDs still can begin helping clients and patients make dietary changes to balance their overall omega-6 to omega-3 ratio, considering the safety and lack of side effects associated with such recommendations. Dietitians can suggest clients eat omega-3–rich, cold-water fatty fish two to four times per week. They should encourage marine sources of omega-3s over vegetable sources, such as flaxseeds, hemp, and chia seeds, considering the limited conversion rate of ALA into EPA and DHA. Conversion of ALA to EPA is estimated to be at most 8% in healthy adults, while conversion to DHA is significantly inefficient, varying between 4% to less than 0.1%, depending on the study.8 Research findings consistently show that increased ALA consumption can result in slightly higher EPA concentrations but doesn’t affect DHA levels.
In addition to improving the omega-6 to omega-3 ratio through the consumption of cold-water fatty fish, RDs can recommend patients use oils rich in polyunsaturated and monounsaturated fats, such as olive, avocado, and macadamia, to better absorb fat-soluble nutrients, some of which have the potential to reduce inflammation because of their antioxidant properties. Indeed, a study published in 2000 showed that 6% of the fat-soluble antioxidant lycopene was absorbed when using olive oil compared with only 2.5% with the use of omega-6–rich corn oil. Similar results were observed with fat-soluble antioxidants within the carotenoid family.9
While it’s important to encourage clients to include more food sources of omega-3, fats to glean anti-inflammatory benefits, reducing omega-6 fats in the diet is the most effective strategy to balance the ratio.
The risk of developing omega-6 deficiencies isn’t significant. The only cases of omega-6 deficiency were observed in individuals consuming a 100% fat-free diet, as was previously the case in infants and children who consumed some infant formulas as well as in adults who received IV feeding preparations.1 Including healthful sources of fat from olive oil, avocados, nuts, and nut butters provides enough of the small amounts of omega-6 fats required for optimal health.
There are several options for RDs trying to determine whether clients have the correct balance of omega-3 and omega-6 fats in their diet. They can suggest clients keep a food journal so dietitians can make an accurate assessment of the type of fats clients are consuming and the necessary adjustments.
RDs can request certain lab values from their clients’ physicians to assess the impact of modifying their dietary omega-6 to omega-3 ratio. Knowing a client’s complete blood lipid profile, blood pressure and glycemic measures, and inflammatory markers (C-reactive protein level) at baseline can be a motivating factor for patients if significant improvements are made three to six months later.
Dietitians can suggest clients avoid vegetable oils, such as corn, soybean, peanut, grapeseed, and sunflower as well as foods containing them. Salad dressings, mayonnaise, margarines, and other condiments are likely to be made with vegetable oils, so teach clients how to read labels and find suitable replacements.
Educate clients on the important anti-inflammatory properties of omega-3 fats and provide tasty fish-based recipes for their weekly consumption. Restaurant food can be a significant source of omega-6 fats, so recommend clients suffering from chronic inflammatory conditions request the chef use olive oil when preparing their food to reduce exposure to omega-6s. If restaurants aren’t cooperative, clients can ask that their meals be prepared without any fat and bring their own extra-virgin olive oil to drizzle over their food to maintain an anti-inflammatory diet.
Furthermore, encourage meat eaters to buy grass-fed varieties because of their higher concentrations of long-chain omega-3 fats (EPA and DHA).10 Their overall omega-6 to omega-3 ratio is more balanced and less inflammatory.
Vegetarians should buy an algae-based DHA supplement to meet their omega-3 requirements, considering the poor conversion of ALA into long-chain omega-3 fatty acids.
Fish Oil Supplements
Without a doubt, fish oil supplements can play an important role in increasing intake of omega-3 fats. But as tempting as it may be for clients to take large doses of fish oil supplements to balance their dietary omega-6 to omega-3 ratio, it’s best they stick to the recommended dosages to provide the right amount of omega-3 fats and then correct their omega ratio by directly addressing their omega-6 fat consumption—preferably through whole foods. Patients suffering from a clotting disorder or those taking antihypertensive, anticoagulant, or antiplatelet agents should consult their physician before taking fish oil supplements.
— Aglaée Jacob, MS, RD, is a freelance writer who specializes in diabetes education and digestive health, and is currently studying naturopathic medicine in Toronto, Canada.
1. Institute of Medicine Food and Nutrition Board. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, D.C.: National Academies Press;2005: 438.
2. Patterson E, Wall R, Fitzgerald GF, Ross RP, Stanton C. Health implications of high dietary omega-6 polyunsaturated fatty acids. J Nutr Metab. 2012;2012:539426.
3. Hiza HAB, Bente L. Nutrient Content of the US Food Supply, 1909-2004: a Summary Report. Washington, DC: US Department of Agriculture Center for Nutrition Policy and Promotion; 2007.
4. Hulbet AJ. On the importance of fatty acid composition of membranes for aging. J Theor Biol. 2005;234(2):277-288.
5. Dayton S, Hashimoto S, Dixon W, Pearce ML. Composition of lipids in human serum and adipose tissue during prolonged feeding of a diet high in unsaturated fat. J Lipid Res. 1966;7(1):103-111.
6. Hayakawa S, Yoshikawa D, Ishii H, et al. Association of plasma omega-3 to omega-6 polyunsaturated fatty acid ratio with complexity of coronary artery lesion. Intern Med. 2012;51(9):1009-1014.
7. Julia C, Meunier N, Touvier M, et al. Dietary patterns and risk of elevated C-reactive protein concentrations 12 years later. Br J Nutr. 2013:1-8.
8. Burdge GC, Calder PC. Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reprod Nutr Dev. 2005;45(5):581-597.
9. Clark RM, Yao L, She L, Furr HC. A comparison of lycopene and astaxanthin absorption from corn oil and olive oil emulsions. Lipids. 2000;35(7):803-806.
10. Wood JD, Enser M, Fisher AV, et al. Fat deposition, fatty acid composition and meat quality: a review. Meat Sci. 2008;78(4):343-358.
Food Sources of Omega Fats
Types of Fat
Vegetable oils (eg, peanut, soybean, sunflower, safflower, corn, cottonseed, grapeseed), salad dressings, mayonnaise, margarines, most nuts and their butters
Meat, egg yolks
Flaxseeds, hemp, chia seeds, walnuts
EPA and DHA
Fish (especially cold-water fatty fish), algae, grass-fed meat