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NON-MEDICATED LIFE - Benefits of Consuming Fish and Fish Oil

By Paul E. Lemanski, MD

This is the 57th in a series on optimal diet and lifestyle to help prevent and treat disease. Any planned change in diet, exercise or treatment should be discussed with and approved by your personal physician before implementation. The help of a registered dietitian in the implementation of dietary changes is strongly recommended.

Medicines are a mainstay of American life and the healthcare system not only because they are perceived to work by the individual taking them, but also because their benefit may be shown by the objective assessment of scientific study. Clinical research trials have shown that some of the medicines of Western science may reduce the risk of heart attacks, strokes and cardiovascular death while others may reduce certain types of cancer.

In the first 56 installments of the Non-Medicated Life, informed diet and lifestyle have been shown to accomplish naturally for the majority of individuals, many, if not most of the benefits of medications in the treatment of chronic medical conditions. Moreover, informed diet and lifestyle as a medical intervention may accomplish such benefits at lower risk for side effects and at a lower cost. With the advent of new studies on the effects of omega-3 fish oil, it is appropriate to reexamine the evidence for a recommendation to eat fish or consume fish oil supplements as one way to help lead a non-medicated life.

Fish is a heart healthy food. It is a good source of protein, is naturally low in saturated fat, and is high in a special type of polyunsaturated fats called n-3 PUFA or more simply omega-3 fat. The omega-3 fats in fish include EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), and have effects on both blood fats and cardiovascular risk.

Consuming foods high in saturated fat results in an increase in LDL or “bad” cholesterol in the blood, which increases the risk for cholesterol plaque formation; such plaque is a necessary prerequisite for nearly all heart attacks or strokes. Consuming fish in place of meat will therefore usually decrease LDL cholesterol in the blood, and modestly lower triglycerides, as well as modestly raise HDL. Omega-3 fats in higher dose achieved with supplementation may also decrease triglycerides 30% to 45%, will increase the HDL or “good” cholesterol by about three to nine percent, and will decrease a measure of all “bad” blood fats, called non-HDL cholesterol, by about 15%. For those with very high triglycerides (greater than 500), in whom triglyceride levels actually suppress LDL formation, correction of the triglycerides with high dose fish oil supplementation can be shown to paradoxically raise LDL back to non-suppressed levels. This paradoxical raising of LDL is accepted because the risk of pancreatitis – that may be life-threatening – increases markedly for those with triglycerides great than 500.

The effects of omega-3 fats on cardiovascular risk are complex. Omega-3 fats have been shown to modestly decrease blood pressure in those under 45 years old by three to four millimeters of mercury (mmHg) systolic, or “upper number” blood pressure, and two to three mmHg diastolic, or “lower number” blood pressure. Omega-3 fats decrease blood clotting tendency and may decrease heart arrhythmias. The evidence for benefit from clinical trials is mixed, with most studies suggesting that the consumption of fish or fish oil reduces coronary heart disease mortality, the risk for fatal heart attack, and the risk for sudden cardiac death in those with established heart disease – and also to a lesser extent in those without established heart disease.

In the Gizzi-Prevenzione Trial individuals were randomized to placebo or 1,000 milligrams (mg) of fish oils within three months of a heart attack. Compared to placebo, there was a 20% reduction in the risk of subsequent death, a 30% reduction in the risk of cardiovascular death, and a 45% reduction in sudden death, presumptively from arrhythmia. In the Lyon Diet Heart Study consumption of a high omega-3 Mediterranean diet reduced fatal heart attack and cardiovascular death by 70%. In 2012, a large meta-analysis – which is a study comparing multiple randomized trials of similar although not identical design – showed significant reductions in fatal heart attack, sudden death, and total mortality with benefit obtained whether the omega-3 fats were obtained from supplements. By contrast, the Risk and Prevention Study with 13,513 patients having multiple cardiovascular risk factors, or known cardiovascular disease, found no reduction in coronary heart disease death when omega-3 supplements were compared to placebo.

If the mixed results of clinical trials raise the concern of possibly smaller benefit than previously believed, the safety of consuming fish and fish oil supplements would still lead you to recommend them. Recently, however, the publication of a follow up case controlled cohort study based on the results of the SELenium and vitamin E Cancer prevention Trial (SELECT), has raised concern of a possible causal relationship between blood levels of omega-3 fats and prostate cancer. In this study the higher blood levels of EPA and DHA were associated with the higher risk for prostate cancer. An association, however, does not prove causality and further studies are needed with randomized, prospective, placebo controlled design.

Until such studies are completed an individualized assessment of risk and benefit is in order and should be discussed with your physician or cardiologist. For those with known coronary artery disease, the American Heart Association recommends daily consumption of 1,000 mg of EPA and DHA, which can be obtained from four ounces of a fatty fish such as sardines, mackerel, salmon or herring. Alternatively, fish oil supplements containing 1,000 mg per day of EPA and DHA may be used on days when fish is not consumed. For those without evidence of cardiovascular disease, AHA recommends the consumption of two fatty fish meals per week.

In summary, fish and fish oil contain omega-3 fats which alter blood cholesterol levels in a beneficial way and reduce the risk of total death, heart attack death and sudden death especially in those with established cardiovascular disease. There is evidence of benefit as well in those without established cardiovascular disease, but this evidence is less robust, and the benefit of treatment should be weighed against potential risk. If such an approach is used, omega-3 fats may allow one to avoid a strict reliance on the proverbial bottle of pills to address one of most significant health problems of Western society.

Paul E. Lemanski, MD, MS, FACP is a board certified internist with a master’s degree in human nutrition. He is director of the Center for Preventive Medicine of Paul E Lemanski MD PLLC. Paul is an assistant clinical professor of medicine at Albany Medical College and a fellow of the American College of Physicians.

**Originally published in Adirondack life magazine

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