Over 45 years ago Dr. Sinclair proposed that heart disease might be partly due to a deficiency of fatty acids. It was observed the Coronary heart disease (CHD) deaths were reduced among Greenland Eskimos who eat large amounts of omega-3 fatty acids as part of their diet. A recent mega-analysis with over 200,000 people showed that fish consumption was related to a reduced death risk from CHD. Many other studies provide evidence to support the positive association between omega-3 fatty acids and a healthy heart.
A recent report in the Journal of Cardiovascular Nursing, discusses the important role omega-3 fatty acids play in maintaining a healthy heart and cardiovascular system.
There are 2 major polyunsaturated fatty acids. Linolenic acid, an omega-6 fatty acid, is found in vegetable oils such as corn and safflower. Alpha-linolenic acid, an omega-3 fatty acids if found in green leafy vegetables, walnuts, canola, and flaxseed oils. These fatty acids are considered essential because the human body cannot make these so they must be consumed in the diet.
The human body can through a series of enzymatic steps convert these shorter polyunsaturated fatty acids into longer ones. Arachidonic acid (AA) is a longer omega-6 fatty acid, whereas eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are longer omega-3 fatty acids. These longer fatty acids can be obtained directly from the diet. AA is found in meat, and EPA and DHA are found in fish and fish oil supplements. DHA can also be found in algae. Increased dietary consumption of omega-3 fatty acids replaces AA in cell membranes of blood cells, artery cells, and in the various organs such as the heart, brain, and liver.
Omega-6s, which are high in the average Western diet are proinflammatory, whereas omega-3s are anti-inflammatory. “The typical Western diet is rich in omega-6 fatty acids with a ration of 10-20:1 (omega-6 fatty acids to omega-3 fatty acids). It has been proposed that a ratio of 1-2:1 in the diet would shift the balance from a prothrombotic, proinflammatory, vasoconstrictory state to a favorable antithrombotic, anti-inflammatory, and vasodialtory state.”
The largest clinical trial to test omega-3 fatty acid supplements was the GISSI-Prevention Trial, which examined over 11,000 patients. The trial examined patients with recent heart attacks. The patients were randomized to omega-3 fatty acid supplements, vitamin E, both omega-3 fatty acids and vitamin E, or none for 3.5 years in conjunction with a Mediterranean diet. “Omega-3 fatty acid supplementation significantly reduced all-cause death by 20% and nonfatal myocardial infarction and stroke by 15%.”
The Diet and Reinfarction Trial, also know as DART, study included 2,033 men who had recently suffered a heart attack. They were randomized to 2 servings of fish per week or an equivalent amount of omega-3 supplements. “A significant 29% reduction in cardiovascular and total mortality over 2 years was reported in patients who consumed fish regularly compared to those without fish in their diet.”
Another study included 360 patients after suspected heart attack. They were randomized to either fish oil supplements, mustard seed oil – rich in alpha-linolenic acid – or placebo. “After 1 year, total cardiac events were significantly decreased by 25% in the fish oil group and 28% in the mustard seed oil group.”
The current guidelines of the American Heart Association (AHA) underscore the importance of dietary omega-3 fatty acids for a healthy heart. People without any signs of heart disease are recommended to have fish twice a week. For secondary prevention of CHD, patients should consume EPA and DHA (1 gram per day) from fish or supplements.
“Environmental toxins such a mercury, dioxins, and polychlorinated byphenyls may be found in fish and fish oil supplements. The content may be higher in farm-raised fish compared to wild types. The toxins may also be increased in larger fish and the risk may be reduced by consuming a variety of fish. Caution is recommended for specific fish consumption (eg, shark, swordfish, king mackerel) in pregnant and lactating women and young children to limit mercury exposure.”
“Initially, patients consuming fish oil supplements may experience an occasional fishy aftertaste. The supplements may be consumed after freezing the capsules to limit this effect. Gastrointestinal upset may also be a potential side effect of omega-3 fatty acid supplementation. Although fish oil reportedly increases bleeding time, low (0.85-1.5 grams per day) and moderate doses (2-5 grams per day) of EPA and DHA appear to be safe.”
The authors conclude, “Substantial clinical evidence support dietary omega-3 fatty acids as a practical, therapeutic strategy for cardiovascular health and disease. Omega-3 fatty acids modulate a number of important physiological responses which contribute to their cardioprotective effects.”
Source: Journal of Cardiovascular Nursing, January/February 2006