New fish oil studies offer mixed results for preventing heart attack, cancer. Here’s what you need to know.

The debate about the pros and cons of fish oil goes on and on.  Two studies just released at an American Heart Association meeting and published in the New England Journal of Medicine have added to the confusion.

Until now, no one has been certain that treating elevated levels of triglycerides – such as with fish oil — can lower cardiac risk.  Although both triglycerides and cholesterol are part of a routine lipid panel, elevated blood triglyceride levels are caused by the sugar and carbohydrates in our diet, and are the end product of our bodies digesting and breaking down food.  This is very different from elevated cholesterol levels, which come from ingesting saturated fats.  Statins lower cholesterol. Many medications can lower triglycerides, such as niacin and medications called fibrates (such as Tricor), but studies have not shown they actually prevent heart attacks.

One of the new studies shows that fish oil — in people with triglyceride levels at more than 200 milligrams per deciliter – is associated with preventing heart attacks and decreasing heart-related deaths by an average of 20 percent.

But, of course, it isn't as simple as it sounds.

First, this has only been proved to be true in people who already are taking a statin and have either heart disease or multiple risk factors, and if they take a very particular kind of fish oil.  The new study, called Reduce-It, gave people a brand of fish oil called Vascepa. It is pure eicosapentaenoic acid (EPA), while most fish oil contains a mix of both components of omega-3 fatty acids, EPA and docosahexaenoic acid (DHA).  DHA can actually raise your so-called bad cholesterol (LDL), and studies looking at fish oil have not shown that mixed DHA/EPA oils prevent heart attacks.

Amarin, the company that makes Vascepa, funded this trial to see if EPA alone is the most effective oil for the heart.  It is always wise to view industry-funded research with skepticism.

Still, the cardiology world is greeting this study with excitement, as it does show significant declines in cardiac mortality in specific kinds of patients.

Another caveat: The cost for a one-month supply at local pharmacies is over $220 without insurance, and even if covered by insurance, co-pays can be very high.

The second trial announced at the heart association meeting was funded by the National Institutes of Health. It looked at both Vitamin D (at 2,000 international units per day) and mixed EPA/DHA fish oil (one gram per day) to see if these medications prevented heart disease or cancer in nearly 26,000 healthy people.  Verdict: Neither Vitamin D nor omega-3 fatty acids lowered the incidence of major cardiovascular events or cancer, compared with a placebo.  The fish oil portion of the trial raised an interesting possibility: There may be a lower incidence of nonfatal heart attacks in the participants – especially Hispanics and African Americans — who did not eat much fish.  But that point, the authors said, needs to be studied more.

New health information, even when generated by well-designed studies, can often conflict with the results of other studies, and may make it seem as if doctors keep changing their minds. This perception is amplified by pharma companies and medical-device makers eager to show that their product works.  When you add the misinformation generated from bad science on top of this already-confusing situation, clarity is hard to come by.

How can you know what to do?  In the case of fish oil, here are some take-home points based on the best science available to us now:

David Becker, M.D., is a frequent Inquirer contributor and a board-certified cardiologist with Chestnut Hill Temple Cardiology in Flourtown. He has been in practice for 25 years.