Omega-3s for Heart Health

December 20, 2006

11 Min Read
Omega-3s for Heart Health

Photo: Alaska Seafood Marketing Institute

These days, everyone from consumers to health experts is pumped up about omega-3 fatty acids’ role in fighting heart disease. A body of evidence has been building that suggests omega-3 fatty acids have heart-healthy benefits not only for those with cardiovascular disease (CVD), but even for healthy individuals.

Oceans of support 

“Over the past few years, there has been some compelling nutrition science research showing the links between omega-3 fatty acids providing heart health benefits,” says Jeannie Moloo, Ph.D., R.D., nutrition consultant specializing in cardiovascular disease, and nutrition and national spokesperson for the American Dietetic Association, Chicago. “They may help lower triglyceride levels, lower the risk of arrhythmias, slow the growth rate of fatty plaque buildup, reduce inflammation and slightly lower blood pressure.”

According to primary and secondary prevention studies, consumption of omega-3 fatty acids, fish and fish oil reduces all-cause mortality and CVD outcomes like sudden death, cardiac death and myocardial infarction (MI). Two omega-3 fatty-acid superstars have emerged: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They specifically show promise in counteracting the development of atherosclerosis and thrombosis, reducing levels of plasma triglycerides, improving blood flow, decreasing blood pressure and changing cholesterol profile, thus reducing the risk of coronary heart disease (CHD).

Health organizations are enthusiastically extolling the benefits of omega-3 fatty acids. The American Heart Association (AHA) recommends healthy people, those at high risk of CHD and those with CHD consume fish (particularly fatty fish that are high in EPA and DHA, including mackerel, lake trout, herring, sardines, albacore tuna and salmon) at least two times per week.

The AHA also recommends tofu, as well as soybeans, canola, walnut, flaxseed and their respective oils as sources of alpha-linolenic acid (ALA), which may be modestly converted into longer-chain omega-3 fatty acids by the body. The Dietary Guidelines for Americans 2005 states that limited evidence supports an association between the consumption of fatty acids in fish and reduced risk of mortality from CVD for the general population, and that sources of EPA and DHA may provide similar benefits. Even the popular heart-health guru, Dr. Dean Ornish, recommends in his Lifestyle Program omega-3 fatty acids at the levels of 3 grams per day for both men and women, from a source free of mercury, PCB or dioxin.

Omega-3 101 

Two families of essential polyunsaturated fatty acids exist: omega-6 and omega-3. They are essential because humans cannot make them, thus they must be obtained through the diet. Sources of omega-6 are liquid vegetable oils, including soybean, corn and safflower. Omega-3s are found in oily fish and certain vegetable sources, including the seeds of chia, perilla, flax, walnuts, purslane, lingonberry, sea buckthorn and hemp, and the fruit of the açaí palm. Important omega-3 fatty acids include EPA and DHA, both of which are considered long-chain polyunsaturated fatty acids (lcPUFAs) and ALA.

Cold water, oily fish, like salmon, herring, mackerel, anchovies and sardines, are the most widely available source of EPA and DHA, and have a profile of about seven times as much omega-3 fatty acids as omega-6. Other oily fish, such as tuna, contain omega-3 fatty acids in lower amounts. The amount of EPA and DHA in fish varies among species and within variables, such as whether they are wild or farm-raised. For instance, farm-raised catfish tend to have less omega-3 fatty acids than wild catfish, yet salmon and trout are similar in amount.

In the science spotlight 

Since 1996, when the AHA first released a Science Advisory on fish consumption, fish oils, lipids and CHD, important new findings have sprung forth on the benefits of omega-3 fatty acids in preventing heart disease. In three epidemiological studies within populations, men who ate at least some fish weekly had a lower CHD mortality rate than men who ate none. In the GISSIPrevention Study, published in Lancet (1999, 354:447-455), the largest prospective, randomized, controlled study testing the efficacy of omega-3 fatty acids for secondary prevention of CHD, 11,324 patients with CHD were randomized to either 300 mg of vitamin E, 850 mg of omega-3 fatty acids (EPA and DHA), both or neither. After 3.5 years of follow-up, the group given the omega-3 fatty acids alone experienced a 15% reduction in number of deaths, nonfatal MI and nonfatal stroke. The study also found a 20% reduction in all-cause mortality and a 45% reduction in sudden death, compared with the control group. Triglycerides decreased by 4% and low-density lipoprotein (LDL) cholesterol levels increased by 2.5% after six months in the omega-3 fatty-acids treatment groups, compared with controls.

Research indicates that omega-3 fatty acids wage war against CHD in a number of ways. Omega-3 fatty acids from fish oil at levels of 4 grams per day decreased serum triglyceride concentrations by 25% to 30%, increased LDL cholesterol by 5% to 10%, and decreased high-density lipoprotein (HDL) cholesterol by 1% to 3%. Omega-3 fatty acids appear to have a small ability to decrease blood pressure, which depends on dose and the degree of hypertension. Based on a meta-analysis looking at omega-3 fatty acids from fish oils, significant reduction in blood pressure in hypertensive subjects may be found with levels of 5.6 grams/day of omega-3 fatty acids, but experts caution that omega-3 fatty acids have a limited role in the management of hypertension, considering the high dose required to lower blood pressure. Omega-3 fatty acids may also reduce the risk of sudden cardiac death, perhaps due to their stabilizing effect on the myocardium itself and their potential antiarrhythmic effect.

Their net effects are a reduction of the inflammatory processes, vasoconstriction and platelet aggregation. In addition, more evidence is pointing to ALA and its role in lowering the risk of MI and fatal ischemic heart disease, which may be due to a reduction in fatal ventricular arrhythmias and sudden cardiac death.

Even though the majority of studies seem to show a beneficial effect of omega-3 fatty acids on CHD, a noticeable number have reported less then positive results. For example, in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, published in the American Journal of Epidemiology (1997, 145:876-887, researchers found that omega-3 fatty acid intake from fish was linked with a trend toward increased relative risk of coronary death. While scientists have debated whether study populations might have resulted in conflicting data in such studies, a newer worry has arisen over the potential adverse effects of methylmercury, an environmental contaminant found in certain fish that might ambush the health benefits of omega-3 fatty acids. No clearcut results have yet come from studies looking at the effects of methylmercury on CHD risk, but consumers of oily fish are advised to be on the lookout for the potential presence of heavy metals and fat-soluble pollutants that may accumulate in the food chain.

A healthy dose of omega-3s 

Today’s intake of total omega-3 fatty acids is estimated at 1.6 grams per day in the United States. Of this amount, ALA accounts for about 1.4 grams per day, with only 0.1 to 0.2 grams per day coming from EPA and DHA combined. Many countries, as well as the World Health Organization, have made population- based dietary recommendations for omega-3 fatty acids at levels of approximately 0.3 to 0.5 grams per day of EPA plus DHA, and 0.8 to 1.1 grams per day of ALA. The Dietary Reference Intakes set an Adequate Intake level of ALA at 1.6 grams per day for men, and 1.1 grams per day for women. The AHA recommends 1 gram per day of EPA plus DHA (preferably from fatty fish) for patients with CHD. For patients who need to lower triglycerides, AHA suggests 2 to 4 grams per day of EPA plus DHA, through capsules, under a physician’s care. Studies demonstrate that effective doses of EPA and DHA omega-3 fatty acids range from 3 to 5 grams per day, but intake of 3 grams or more of EPA and DHA should be done only under a physician’s care, as intake at that level is associated with a potential risk of excessive bleeding in some individuals. FDA recommends that consumers not exceed more than a total of 3 grams per day of EPA and DHA, with no more than 2 grams per day from a dietary supplement.

The ratio of omega-6 to omega-3 fatty acids in the diet of early humans is thought to be 1:1, but these days, the typical western diet provides ratios of between 10:1 and 30:1, a ratio that dramatically leans toward omega-6. This draws concern because of the competition between omega-6 linoleate and the omega-3 alpha-linolenate for metabolic conversion to longer chain, physiologically active metabolites. The higher the ratio of omega-6 to omega-3 fatty acids in platelet phospholipids, the higher the death rate from CVD.

Fish vs. the pill?

Some experts maintain that food is still the best source of omega-3 fatty acids, for several reasons: a variety of other nutrients are provided; an emphasis on fish reduces saturated fat intake from animal protein sources in the diet; and it is difficult to over-consume omega-3 fatty acids through dietary sources alone. But research has also supported the heart-healthy benefits of omega-3 fatty acids in supplemental form, and experts point out that it may not be possible to get adequate amounts of DHA and EPA to affect health change in those with CHD through diet alone. In addition, most suppliers of omega-3 ingredients remove heavy metals and other contaminants from the fish oil, which increases purity, potency and safety of the product, compared with dietary sources of DHA and EPA.

Omega-3 fatty acid dietary supplements may cause complaints of a fishy aftertaste, gastrointestinal disturbances and nausea. “Omega-3 fatty acids from food are preferable. However, people with existing coronary artery disease may not be able to get enough omega-3 from food alone and may need to talk to a physician about taking supplements,” advises Moloo.

The sea of functional foods 

Omega-3s have great potential as a functional ingredient. FDA’s 2004 qualified health claim for the reduced risk of CHD on conventional foods that contain EPA and DHA helps to establish omega-3’s place in the functional food kingdom. Omega-3 supplements have been a staple on shelves for some time, and now food processors have begun fortifying foods with DHA and EPA, including spreads, milk and yogurt. Oil-containing foods may be enriched with omega-3 fatty acids in oil form. Microencapsulated powders are also available for enriching food products with low water activity, stressed production conditions or extended shelf life. Ocean Nutrition Canada, Dartmouth, Nova Scotia, produces highly concentrated omega-3 powders that have been successfully incorporated, through the use of the company’s micro-encapsulation technology, into a wide range of food products, including bread, milk, yogurt, nutrition bars and confectionary products.

Martek Biosciences Corporation, Columbia, MD, produces DHA from natural vegetarian sources: two strains of algae that are naturally high producers of DHA. The company sells it primarily for use in infant formulas, but it is also used in beverages, nutrition bars, milk alternatives and supplements.

Some omega-rich food supplementation has occurred lower down in the food chain. Eggs enriched with Martek DHA™ are available in many countries, including the United States and the United Kingdom. Chickens that wander freely in the countryside, eating rich sources of omega-3 fatty acids, produce eggs with 20 times more omega-3 fatty acids than grain-fed chickens.

Improving the ALA content of feed provided to hens also increases the DHA concentration of the resulting eggs. Increased-DHA eggs offer a healthier ratio of omega-6 to omega- 3. The Omega Egg, patented by University of Nebraska-Lincoln, is produced by hens fed a patented diet containing flaxseed. The Omega Egg has 350 mg of omega-3 fatty acids, nearly six times that of conventional eggs, as well as one-third less saturated fat and less cholesterol.

Meat from grass-fed animals is also typically higher in omega-3 fatty acids than that of grain-fed animals. Milk and cheese from grass-fed cows may be good sources of omega-3 fatty acids, as well.

The Université de Sherbrooke, Quebec, developed a process to extract krill oil, and the exclusive rights were acquired by Neptune Technologies & Bioressources, Laval, Quebec, to produce Neptune Krill Oil, a product that naturally contains EPA and DHA. Since krill is at the bottom of the food chain, heavy metal levels are low.

Maloo believes there is much more to learn about the role of omega-3 fatty acid in heart health, and that further studies are needed to clearly define the health benefits from foods and supplements. In the meantime, omega-3 fatty acids seem to be riding high on the sea of functional foods with heart-health promise.

Sharon Palmer is a registered dietitian with 16 years of experience in health-care and foodservice management. She writes on food and nutrition for newspapers, magazines, websites and books. Palmer makes her home in southern California.

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