The American Heart Association has issued a science advisory1 on the effects of omega-3 polyunsaturated fatty acid (fish oil) supplementation and its possible role in prevention of cardiovascular disease. They reviewed many randomized controlled trials and focused on the common indications for these supplements related to whether or not fish oil can prevent any diseases. Prior recommendations for patients with existent coronary heart disease were updated and new recommendations made for patients with other problems that included patients with diabetes and prediabetes and those with high risk for heart disease, stroke, heart failure, and atrial fibrillation (heart rhythm disorder). Their recommendations are presented below:

  • Treatment with fish oil supplementation is reasonable for retarding advancement of disease in patients who have already suffered from problems such as a prior heart attack (myocardial infarction) or from established reduced heart function.
  • Treatment with these supplements is, however, not recommended to prevent strokes in those suffering from atrial fibrillation, or in patients with diabetes, unless their risk of developing heart disease is excessively high.
  • Finally, the available evidence does not support the use of fish oil supplements in the general population who are not at high cardiovascular disease risk, including those with diabetes.


As I have stated previously, prior data have demonstrated a prevention of cardiovascular problems in individuals who consume fish (which contain omega–3 fatty acids), at least twice a week. This has led to randomized trials that evaluate the effect of fish oil supplements alone on cardiovascular outcomes. A potential mechanism by which they may decrease serious outcomes is through their ability to decrease the likelihood of serious or fatal heart rhythm disorders (ventricular fibrillation), in those who are already afflicted with such disorders. I also emphasize that this AHA statement refers to evidence-based recommendations about supplementing diet with fish oil, and this does not apply to eating fish or replacing meat with fish as a part of a healthy lifestyle.

The bottom line in the AHA statement is that fish oil may be beneficial for those already afflicted with heart disease. However, there is no evidence to support its use for prevention of cardiovascular disease in either low or medium-risk individuals from the general population. Furthermore, most of the evidence suggested no effect even in high-risk individuals such as those with a strong family tendency to develop these maladies, though there was a lack of consensus for these particular individuals. Therefore, use of these products is not helpful in most people who have shown no tendency to develop such problems. But, for all of us, the lifestyle dietary patterns that should be followed are still clearly in force!

1 Siscovick DS, Barringer TA, Fretts AM, et al. Omega-3 polyunsaturated fatty acid (fish oil) supplementation and the prevention of clinical cardiovascular disease: A science advisory from the American Heart Association. [Published online ahead of print March 13, 2017]. Circulation. doi:10.1161



As I have noted before, fish consumption is heart-healthy and provides an excellent source of protein. But there are risks associated. One of these is the fact that fish may contain mercury, which is a well-known toxin. When consumed in excess, mercury can cause damage to brain and nervous system causing prickly sensations with various additional problems with fine muscular coordination, speech, sleep, and walking. At highest risk are pregnant women and young children.

Many fish species do contain mercury, which is consumed from plants and tiny animals. When smaller fish are then eaten by larger fish, the latter’s tissue accumulates increasing amounts of mercury. Thus larger, predatory fish such as sharks and swordfish generally contain more mercury than smaller fish such as sardines, sole, and trout. Compounding this problem, mercury levels in the northern Pacific Ocean have risen about 30% over the past 20 years and are expected to rise further because of industrial input.

If you want to consume fish (and you should), here are my suggestions:

Lowest mercury fish are the following: Wild and Alaska salmon, sardines, tilapia, and shellfish such as shrimp, scallops oysters and squid.

Still low, but slightly higher, are haddock, flounder, sole, catfish, trout, and Atlantic mackerel.

The highest ones, to be generally limited or avoided, are swordfish, shark, king mackerel, orange roughy, marlin, grouper, Chilean sea bass, bluefish, halibut, Spanish mackerel (Gulf), and fresh or canned tuna.

The FDA and EPA warn most women (especially if pregnant) and children, against consumption of those fish in the highest mercury group noted above. Moreover, if you are a frequent consumer of more than 24 ounces of any type of fish each week, you are advised to avoid this latter category as much as possible.

Guidelines for limits on fish consumption are undergoing continued scrutiny. My conclusions at present are that women who are of childbearing age should limit themselves to no more than 12 ounces per week, primarily consuming those fish groups having the lowest mercury content. Similar limitations should be applied to children. As noted above, adults should limit their intake of high-mercury types of fish.

A useful tool to provide safer and more specific seafood choices can be found at Consumer Reports website: You can enter the types and amounts of fish you plan to consume, along with your body weight, and you will know whether you’ll be within acceptable limits.