A cardiologist's top 10 things to know about fish oil supplements

Despite many studies done over the last few years, there is no absolute proof that taking omega-3 fatty acids will decrease your risk of having a heart attack. Studies are in progress to determine whether adding omega-3 fatty acids to a medical regimen including statins will lower your risk of a heart attack if you already have coronary artery disease.

DHA (docosahexaenoic acid ethyl ester) and EPA (ethyl eicosapentaenoic acid) are the active ingredients in omega-3 fatty acids and have been shown in multiple studies to lower triglyceride levels. Triglycerides are a kind of fat, very different from cholesterol, that can cause irritation of the lining of blood vessels, especially when accompanied by low HDL (good) cholesterol.

Although there are popular myths that taking fish oil lowers your cholesterol, it does not. It will lower your triglycerides, may modestly raise your HDL (which is a benefit), but can actually raise your LDL (bad) cholesterol, which is not a benefit.  Only the pure EPA type of fish oil has been shown to not raise LDL cholesterol.

Omega-3 supplements may have health benefits other than for the heart. Some people experience relief from arthritis pain and depression, and it may have a role in decreasing inflammation.

One study that got a lot of attention in 2013 suggested that taking fish oil might increase a man's risk of having prostate cancer. This caused much consternation, and led to many men stopping their supplements.  The trial had many flaws in its design, and there is no good evidence that omega-3 fatty acids cause prostate cancer.

There are many different products on the market, and not all fish oil is the same. Many are available over the counter, and they are not held to unified standards.  Some may be very unpleasant to take.  I will always remember when my brother bought an inexpensive salmon oil after I suggested he take a fish oil supplement.  He immediately began burping up a fishy taste and of course blamed me!  Look for a product rich in DHA and EPA, but even this is not a guarantee of quality.

There are 3 prescription brands of omega-3 fatty acids, and they are all high quality. One, called Lovaza, is a mixture of DHA and EPA.  The second product is called Vascepa, which contains only EPA.  The third, Epanova, is purified in a different way, said to be more easily absorbed by the body.  All the prescription brands are pricey, and all work in similar ways.

Several generic versions of Lovaza have been available since 2014, yet many insurance companies will not cover any prescription-brand fish oil, or will charge a large co-pay, often making them prohibitively expensive.

The usual dose for heart-disease prevention is 1 gram once or twice per day. If your triglyceride level is more than 200 mg/dl, you might benefit from higher doses, as much as 6 grams per day.  Keep in mind that fish oil has 9 calories per gram.

Side effects from omega-3 fatty acids, other than burping up a fishy taste, may include stomach distress, diarrhea, and heartburn. Keeping it refrigerated can help with heartburn. There may be a slight risk of increased bleeding, which is why someone who needs elective surgery is asked to not take fish oil for at least a week before the operation.  In rare cases, allergic reactions are possible.  Remember to store your supplement in a cool, dry place, as fish oil can become rancid in the heat, making it ineffective as well as unpleasant.