Caution: Not all omega-3 fish oils are equal

March 15, 2012

Experts caution that many unregulated over-the-counter fish oil products have little benefit, with some having no benefit at all.

In 2003, the American Heart Association advocated Americans eat more fish and recommended supplemental omega-3 fatty acids for people with known heart disease. While this sparked a flood of consumer fish oil products making heart-healthy claims, experts caution that many of these unregulated over-the-counter products have little benefit, with some having no benefit at all.

In the last 5 years researchers studying the connection between fish oils and heart disease have reported impressive clinical value of marine-based, long-chain polyunsaturated fatty acids, also called omega-3s.

Omega-3 fatty acids are pharmacologically active fats found in wild-caught fish such as albacore, salmon, trout, herring, sardines, and anchovies, as well as algae and shellfish. Their 2 key components, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), provide cardioprotective and anti-inflammatory benefits, reducing risk for people with heart disease, and provide benefits for immune disorders, Alzheimer's disease, and other conditions such as arthritis.

Cardiovascular specialist and omega-3 investigator, Mandeep R. Mehra, MD, MBBS, professor of medicine at Harvard Medical School, and executive director for the Center for Advanced Heart Disease at Brigham Women's Hospital in Boston, said, "The one place where there is almost universal benefit is in the state of heart failure."

Mehra said research in people with coronary heart disease has documented omega-3 fatty acids' capacity to "restore and improve cardiac metabolism, decrease systemic inflammation, and reduce oxidative stress." He cites omega-3 clinically significant action in preventing secondary heart attacks, lowering blood pressure and heart rate, decreasing triglyceride levels, and lowering cholesterol. They also have "powerful anti-inflammatory capabilities," in reducing interleukin-6 and cytokine levels found in advanced heart disease, he said.

However, Mehra advised caution when choosing supplements because there is "dramatic variability in omega-3 fish oils."

Ultra-refined is best

One prescription fish oil supplement (Lovaza) has a cost-per-day of about $10, and several pharmaceutical-grade, ultra-refined, non-prescription fish oil products range from $1-$2 per day. Numerous other retail fish oil products cost just pennies per day, but these are not equivalent to the ultra-refined product.

The inexpensive oils are derived from the fish carcasses used in commercial food processing such as tuna and swordfish, usually harvested off the coast of Southeast Asia. While these fish have high concentrations of EPA and DHA, large fish may also have higher concentrations of polychlorinated biphenyls (or PCBs), mercury, and other contaminants.

Without voluntary regulation, the oils may contain harmful impurities. The products made from these fish are technically "100% fish oil" as many claim, but may also contain high levels of saturated fats, and have no or very low levels of EPA and DHA. Therapeutic benefit could require consuming 10 or more capsules each day.

Pharmaceutical-grade, ultra-refined products use only small, wild-caught fish, such as anchovies, mackerel, and sardines. The crude oils are separated from the meats in a vacuum environment and are further treated in sophisticated refinery manufacturing plants to remove impurities and contaminants. Next, a sequential distillation process concentrates the oils to provide high levels of EPA and DHA, 325 mg to 450 mg of each component. These oils have almost no "fishy" odor and a daily dosage of 1 to 4 capsules can achieve a health benefit.

Be aware of interactions

Mehra suggested pharmacists also should be aware of possible supplement interactions.

"I think the pharmacist should recognize that just taking a micronutrient is not necessarily benign in the construct of other medicines. For example, in patients taking blood thinners – aspirin, warfarin, clopidogrel – omega-3s can increase their bleeding potential," Mehra said. "Another concern is in patients with gastrointestinal reflux who are taking fish oil. Fish oils can sometimes worsen that disorder, so pharmacists should be mindful of competing diagnoses."

Barbara Hesselgrave is a freelance medical author from Baltimore, Md.