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Omega-3 Fatty Acids

An overview of health benefits

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The inclusion of omega-3 fats in the diet can provide a variety of health benefits. Omega-3 and omega-6 fats are essential fatty acids; the body cannot synthesize them on its own and instead must obtain them from exogenous sources such as cold water fish and specific plant foods.

Omega-6 Fats

Omega-6 fats occur in foods such as polyunsaturated margarines and vegetable, corn and soybean oils. Omega-6 fatty acids lead to oxidation of low-density lipoprotein, affect platelet aggregation and interfere with the incorporation of essential fatty acids in cell membrane phospholipids. Omega-6 fats help stimulate skin and hair growth, maintain bone health, regulate metabolism and maintain the reproductive system. These essential fatty acids can, however, promote inflammation. Experts have concluded that a balance of omega-6 and omega-3 acids is needed. This article focuses on the benefits of omega-3 fats.

Omega-3 Fats

Three omega-3 fats exist: docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and alpha linolenic acid (ALA). Cold-water fish such as salmon, tuna, sardines and anchovies contain EPA and DHA, which provide numerous health benefits. Most plant sources of omega-3 fats provide ALA; these include walnuts and almonds, chia and hemp seeds, flax seed and flax oil, and to a lesser extent, beans, tofu and green leafy vegetables.

Although all omega-3 fats are beneficial for the body, the EPA and DHA provided by fish and fish oil are particularly so. More than 8,000 clinical studies have examined the effects of EPA and/or DHA in the body. With an abundance of data to support their inclusion in the diet, it's important for healthcare providers and consumers to understand the benefits of omega-3 fatty acids.

Another important point: Although plant sources of omega-3 ALA are converted to the beneficial fatty acids EPA and DHA, research shows that the conversion rate is as low as 1%.2 So to obtain the amount of EPA and DHA contained in half a can of sardines, a person would have to eat a 10-ounce bag of flaxseeds.

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Although the primary source of omega-3 fats is fish, seafood consumption in the United States is well under 1 ounce a day, meaning that most Americans do not consume the recommended level for prevention and treatment of disease.2 One study estimated that 96,000 premature deaths per year occur as a result of insufficient omega-3 intake.1

Cardiovascular Health

The American Heart Association (AHA) and other health organizations include fish in their dietary guidelines for the prevention and treatment of disease. For example, the AHA recommends eating fish (particularly fatty fish such as salmon, lake trout, sardines, tuna, etc.) at least two times a week (Table 1).2 The AHA's guidelines for heart disease prevention in women provide further guidance on omega-3 fatty acid intake and supplementation, recommending oily fish intake at least twice a week.3 These guidelines acknowledge that omega-3 fatty acid supplements are also an option for obtaining higher levels of these acids, but they note that their usefulness/efficacy is less well established by evidence.

In addition to reducing traditional heart disease risk predictors, consuming fish oil from dietary sources (Table 2) seems to reduce the risk of cardiovascular and all-cause mortality for people with existing coronary heart disease (CHD). Consuming as little as 1 gram of fish oil daily can provide benefits.

A 2013 evidence review found that in general, treatment with omega-3 supplements may lower triglycerides, but in patients with very high triglyceride levels, supplementation also raised low-density lipoprotein; EPA alone did not.4 The literature review concluded that "given the favorable risk-to-benefit ratio for these essentially nutritional agents, use is expected to continue to expand."4

A meta-analysis published in 2004 examined the effects of dietary and supplemental intake of omega-3 fats on CHD.5 It assessed nearly 16,000 patients (8,000 each in the intervention and control groups). The intervention group consisted of patients who consumed dietary or nondietary sources of omega-3s. They were compared with patients who followed a control diet or received placebo. Dietary and nondietary sources of omega-3 fats reduced overall mortality, mortality due to myocardial infarction and sudden death in patients with CHD.5

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A 2006 review assessed dietary omega-3 content and cardiovascular risk. The authors determined that as little as 1 to 2 ounces of cold-water fish daily provides benefit because fish are major sources of the longer-chain omega-3 fatty acids.6 The authors suggested that due to the cardioprotective effects of omega-3 fatty acids, consumption of food sources that provide them should be increased.6 While eating cold-water fish is certainly encouraged, adherence to this recommendation can be a challenge, making supplemental omega-3 fish oil useful.

Brain Health, Cognition and Mood

A 2003 study assessed dietary factors that might modify cognitive decline that results from aging. 8 Fatty acids are important components of brain development and were considered in this trial. The study assessed the relation between erythrocyte membrane fatty acid composition and cognitive decline in volunteers. It enrolled 246 men and women ages 63 to 74. Each underwent a cognitive assessment in which moderate cognitive decline was defined as a 2-point decrease over the 4-year study. A higher proportion of total omega-3 fatty acid intake was associated with a lower risk of cognitive decline when compared with omega-6 fats.8 Omega-3 fats may therefore be one part of the puzzle of cognitive decline associated with aging.

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A 2004 study examined whether community-dwelling older adults with depression have a fatty acid composition that is different from that of people who are not depressed.9 Adults 60 and older were screened for depression symptoms. The researchers compared percentages of omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) and their ratios in patients with depression symptoms. They found that patients with depressive disorders had a higher ratio of omega-6 to omega-3 PUFAs. Importantly, depressed patients had a substantially altered fatty acid composition, with lower percentages of omega-3 PUFAs and higher ratios of omega-6 to omega-3 PUFAs compared to controls. The authors concluded that in community-dwelling people, fatty acid composition is related to depression. Because this relation was not secondary to inflammation, atherosclerosis or possible confounders, it suggests a direct effect of fatty acid composition on mood.9

A 2006 study10 produced similar results. This study, an 8.5-year follow-up to a longitudinal Italian study that rollowed 65- to 84-year-olds, found that polyunsaturated and monounsaturated fatty acid intake was significantly correlated by better cognitive performance.

Inflammation

An additional noteworthy component of omega-3 fats is their effect on chronic inflammation, an underlying issue for many of the previously discussed diseases.11 Omega-3 fatty acids from fish have anti-inflammatory and antithrombotic effects because they compete with arachidonic acid in the cyclooxygenase and lipoxygenase pathways. A review from the Center for Genetics, Nutrition and Health discussed placebo-controlled trials that examined the benefits of fish oil in chronic inflammatory and autoimmune disorders.12 Many of the trials identified benefits to omega-3 fats, including reduction in disease activity and decreased use of anti-inflammatories.12

Important But Overlooked

Omega-3 fats play an important role in the American diet, yet they are often overlooked as a topic for discussion during a healthcare visit. Given the abundance of research proving beneficial effects, NPs should make more efforts to educate patients about the benefits of omega-3 fats and to encourage their consumption in foods and supplements.

References

1. Danaei G, et al. The preventable causes of death in the U.S.: comparative risk assessment of dietary, lifestyle, and metabolic risk factors. PLoS Med. 2009;6(4):e1000058.

2. Kris-Etherton PM, et al. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation. 2002;106(21):2747-2757.

3. Mosca L, et al. Evidence-based guidelines for cardiovascular disease prevention in women: 2011 Update. Circulation. 2011;123:1243-1262.

4. Harris WS, et al. Omega-3 fatty acids and cardiovascular disease: new developments and applications. Postgrad Med. 2013;125(6):100-113.

5. Yzebe D, Lievre M. Fish oils in the care of coronary heart disease patients: a meta-analysis of randomized controlled trials. Fundam Clin Pharmacol. 2004;18(5):581-592.

6. Psota TL, et al. Dietary omega-3 fatty acid intake and CVD risk. Am J Cardiol. 2006;98(4A):3i-18i.

7. Heude B, et al. Cognitive decline and fatty acid composition of erythrocyte membranes. The EVA Study. Am J Clin Nutr. 2003;77(4):803-808.

8. Tiemeier H, et al. Plasma fatty acid composition and depression are associated in the elderly: the Rotterdam Study. Am J Clin Nutr. 2003;78(1):40-46.

9. Whalley LJ, et al. Cognitive aging, childhood intelligence, and the use of food supplements: possible involvement of n-3 fatty acids. Am J Clin Nutr. 2004;80(6):1650-1657.

10. Solfrizzi V, et al. Dietary intake of unsaturated fatty acids and age-related cognitive decline: an 8.5-year follow-up of the Italian Longitudinal Study on Aging. Neurobiol Aging. 2006;27(11):1694-1704.

11. Flock MR, et al. Immunometabolic role of long-chain omega-3 fatty acids in obesity-induced inflammation.

12. Simopoulos AP. Omega-3 fatty acids in inflammation and autoimmune diseases.

Christopher Mohr is a registered dietitian who is a sports nutritionist for Under Armour and an advisory board member for Nordic Naturals.




     

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