Curriculum in CardiologyUnderstanding omega-3's
Section snippets
What are omega-3's?
There are 3 types of naturally occurring fats classified by the number of double bonds present in their fatty acid side chains: saturated, monounsaturated, and polyunsaturated (Figure 1). The food industry created a fourth class, trans fats, by adding hydrogen ions to polyunsaturated fats through a process called hydrogenation (Figure 1). Polyunsaturated fats can be further classified into 2 groups based on the position of the first double bond site: omega-3 fatty acids and omega-6 fatty acids (
Where are omega-3's?
Dietary intake of omega-3 and omega-6 fatty acids varies within and between different populations. NHANES III, the largest database of nutrient consumption of Americans, reports a median intake of EPA + DHA of 0 and <1 g/d of ALA.5 The ratio of omega-6 to omega-3 intake is estimated to be 20 to 1 in a modern Western diet, compared with that of our Paleolithic ancestors who ate a diet much richer in omega-3's (estimated omega-3/omega-6 ratio of 1-2:1) (Figure 3).6, 7 This dramatic dietary shift
The metabolism of omega-3's
A dietary shift toward less omega-3's and more omega-6's may significantly impact one's health because of their different metabolic pathways. Eicosanoids are a class of bioactive molecules derived from omega-3's and omega-6's that include leukotrienes, prostaglandins, and thromboxanes (Figure 2). Eicosanoids derived from omega-6's are generally proinflammatory and proaggretory, whereas those derived from omega-3's are predominantly anti-inflammatory and inhibit platelet aggregation.6 This
Epidemiologic data
Several important observational studies have concluded that omega-3 consumption is inversely related to CVD, especially cardiac death.18, 19, 20, 21, 22 In a study of 22 071 male American physicians, those who consumed fish once a week had a 52% reduction of sudden cardiac death compared with those who ate fish less than once a month (P = .04).20 There was no additional protective effect for men eating fish in amounts greater than once a week. Although a reduction in sudden cardiac death and
Prospective randomized trials
The impact of omega-3's on cardiovascular end points has been evaluated in 4 well-designed secondary prevention trials. These trials evaluated omega-3's either as part of a comprehensive diet plan or as a capsule supplement, and although these trials differed in many respects, their findings were consistent and compelling—omega-3's are effective for secondary prevention of cardiovascular events.
The DART26 randomized 2033 post–myocardial infarction Welsh men to one of the following groups: (1)
Clinical use
In addition to being useful in the secondary prevention of CVD events, a prescription formulation of omega-3 fatty acids, Omacor, has gained Food and Drug Administration (FDA) approval as an adjunct to diet to reduce very high (>500 mg/dL) triglycerides in adults. Two studies of 4 g/d of Omacor demonstrated a 50% reduction in triglycerides and a 44.5% increase in low-density lipoprotein (LDL) cholesterol in 84 adults with primary hypertriglyceridemia.32 A review of 10 trials in 606 subjects
Safety
The US Department of Health and Human Services Agency for Healthcare Research and Quality identified 148 omega-3 fatty acid studies that reported on adverse events in >20 000 subjects.5 In summary, gastrointestinal complaints were reported in 6.6% of the subjects taking omega-3's versus 4.3% in the placebo groups. An increased incidence of bleeding was not observed, and only 1 of the 148 studies reviewed reported such an association in patients randomized to 6 g/d of omega-3. There are no
Conclusion
Omega-3's are a unique group of polyunsaturated fats that can be found most abundantly in fatty fish, flaxseed, walnuts, soy, and canola oil (Table II). The metabolism of omega-3's from fish (EPA + DHA) and vegetables (ALA) results in the production of the same eicosanoids (thromboxane, leukotrienes, prostaglandins); however, it is unclear as to what extent ALA is metabolized into these eicosanoids and if this metabolism is directly related to its effect on CVD. It does seem clear from the 4
References (46)
- et al.
Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis?
Lancet
(1978) Essential fatty acids in health and chronic disease
Am J Clin Nutr
(1999)Fatty-acid ratios in free-living and domestic animals. Possible implications for atheroma
Lancet
(1968)- et al.
Lower ratio of n-3 to n-6 fatty acids in cultured than in wild fish
Am J Clin Nutr
(1990) - et al.
Consumption of (n-3) fatty acids is related to plasma biomarkers of inflammation and endothelial activation in women
J Nutr
(2004) - et al.
Effects of changes in fat, fish, and fibre intakes on death and myocardial reinfarction: diet and reinfarction trial (DART)
Lancet
(1989) - et al.
Mediterranean alpha-linolenic acid–rich diet in secondary prevention of coronary heart disease
Lancet
(1994) Management of dyslipidemias in the age of statins
Prim Care Clin Off Pract
(2003)- et al.
Prenatal methylmercury exposure from ocean fish consumption in the Seychelles child development study
Lancet
(2003) - et al.
Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis
J Nutr
(2004)
Long-chain (n-3) fatty acid intake and risk of cancers of the breast and the prostate: recent epidemiological studies, biological mechanisms, and directions for future research
J Nutr
Nutrition C. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease
Circulation
Alpha-linolenic acid metabolism in men and women: nutritional and biological implications
Curr Opin Clin Nutr Metab Care
Interplay between different polyunsaturated fatty acids and risk of coronary heart disease in men
Circulation
Effects of omega-3 fatty acids on cardiovascular disease
Evid Rep Technol Assess (Summ)
Paleolithic nutrition. A consideration of its nature and current implications
N Engl J Med
Purslane: a terrestrial source of omega-3 fatty acids
N Engl J Med
Atherosclerosis—an inflammatory disease
N Engl J Med
C-reactive protein and other markers of inflammation in the prediction of cardiovascular disease in women
N Engl J Med
Habitual dietary intake of n-3 and n-6 fatty acids in relation to inflammatory markers among US men and women
Circulation
Cardiovascular effects of omega 3 fatty acids. Atherosclerosis risk factor modification by omega 3 fatty acids
World Rev Nutr Diet
Clinical studies on the effects of n-3 fatty acids on cells and eicosanoids in the cardiovascular system
J Intern Med Suppl
The fats of life: the role of omega-3 fatty acids in the prevention of coronary heart disease
Arch Intern Med
Cited by (122)
Health claims and nutrition marketing
2023, Functional Dietary Lipids: Food Formulation, Consumer Issues, and Innovation for Health, Second EditionNutritional adjuvants with antioxidant properties in the treatment of canine leishmaniasis
2021, Veterinary ParasitologyCitation Excerpt :Given the metabolic impact of inflammatory and parasitic factors of CanL, the therapeutic potential of nutraceutical molecules, such as those in fish oil, krill oil, and dried mushrooms has been evaluated (Cortese et al., 2015; Lombardi et al., 2019; Mastellone et al., 2020). Among commonly used nutritional adjuvants with antioxidant properties, omega-3 polyunsaturated fatty acids (PUFA), defined as long-chain polyunsaturated fatty acids (PUFA) mostly isolated from cold-water fish are extensively cited in the literature due to their anti-inflammatory and antioxidant properties (DeFilippis and Sperling, 2006; Backes at al., 2016; Braz-De-Melo et al., 2019). Omega-3 therapeutic effects have been demonstrated in studies of human and animal diseases (Brown et al., 1998; Thomas et al., 2015; Backes et al., 2016; Barrouin-Melo et al., 2016; Rahimi-Niyyat et al., 2018; Freitas and Campos, 2019).
The effects of Canola oil on cardiovascular risk factors: A systematic review and meta-analysis with dose-response analysis of controlled clinical trials
2020, Nutrition, Metabolism and Cardiovascular DiseasesCytochrome P450-derived eicosanoids and inflammation in liver diseases
2020, Prostaglandins and Other Lipid MediatorsIntensified synthesis of structured triacylglycerols from fish, flaxseed and rice bran oil using supercritical CO<inf>2</inf> or ultrasound
2019, Chemical Engineering and Processing - Process Intensification