Fish oil has become a popular dietary supplement – one endorsed by cardiologists, Consumer Reports and this column. It contains marine omega-3 fatty acids, known to biochemists as docosahexanoic acid (DHA) and eicosapentaenoic acid (EPA) that are thought to have beneficial anti-inflammatory and anti-clotting properties. But over the last six months, the safety and effectiveness of fish oil has been questioned, leading some to wonder… has the era of fishy burps come to an end? Could it be that the purported benefits of mackerel are actually baloney?
This past March, a group of plaintiffs, including the Mateel Environmental Justice Foundation, filed suit against five manufacturers of fish oil supplements – contending that the products contain levels of polychlorinated biphenyl (PCB) that are above California’s “safe harbor” limit. PCBs (for those, like me, who have a hard time keeping their environmental toxins straight) are industrial chemicals that take an extremely long time to degrade in the environment. Although they used to be widely used, PCBs are now banned. They’ve been linked to cancer (in rats) and to a number of other health conditions. The plaintiffs based their complaint on tests they’d performed themselves – by puncturing fish oil capsules and studying their contents. Their suit alleges wide ranges in PCB concentrations – with some products being well above the reportable level (90 nanograms a day). "The people buying these fish oil supplements,” attorney (and plaintiff) David Roe said “are not being told the PCBs are there." This legal announcement, and the accompanying press coverage, scared the fish oil right on out of some folks.
Then, just last month, The New England Journal of Medicine published the results of a Dutch study (the Alpha Omega Trial) that followed patients who’d previously had heart attacks and who were taking omega-3s (in the form of margarine fortified with marine and/or plant fatty acids). The study subjects (all on standard heart medications such as aspirin) were given small tubs of margarine – with or without different formulations of omega-3 fatty acids – and their intake was tracked by measuring the amount of unused margarine at 12-week intervals. The study followed nearly 5,000 patients for forty months and found no difference in “major cardiovascular events” (such as repeat heart attack or stroke) or in death rates between those who were and those who were not taking omega-3s of any type.
For fish oil advocates, this seems discouraging. And, if you factor in environmental concerns about over-fishing, perhaps it is time to re-consider fish oil. But wait, before you toss out those omega-3 soft gels and discontinue fresh fish Friday dinners, consider some additional perspective.
First, regarding PCBs, there are several reasons not to get too freaked out.
1) No one really knows how dangerous PCBs truly are. Numerous studies have failed to link PCBs to cancer in humans (rats are a different story). And while there is no good data on what a safe level of PCB exposure is, the California reporting limit is far below federal levels.
2) Previous, more comprehensive, studies of fish oil supplements have found limited contamination with heavy metals or PCBs. This is not to say that there aren’t outliers, but the vast majority of fish oil supplements likely contain less PCB than fresh fish or meat.
3) The brands with high PCB levels named in the recent lawsuit are predominantly cod and shark liver oil products. The liver, as you probably know, processes chemicals, meaning that oil from the liver is more likely to contain detectable levels of PCB. Perhaps, and I stress perhaps, it is better to avoid fish liver products.
In my opinion, recall the maxim “the dose makes the poison” and don’t be majorly concerned about PCB toxicity in your fish oil. But, what if, as the Alpha Omega Trial suggests, marine omega-3s offer no beneficial health effects? Well, that would be a different story. There are several reasons, however, to doubt this conclusion;
1) The Alpha Omega Trial, despite being a well-designed prospective study, has some weaknesses. These include the forty-month follow-up time – which does not give us a good sense of long-term events. Second, this study focused on a group of patients already on state-of-the-art cardiac treatment. Third, there is the choice of omega-3 delivery. Dr. Alan S. Go, a senior cardiovascular researcher at Kaiser-Permanente, told me “The choice of putting these agents into margarine was rather curious, especially given that the trans fatty acids in margarine are cardiotoxic and perhaps could have blocked any potential beneficial effects.”
2) Multiple previous studies have suggested an array of protective effects from omega-3s – particularly marine omega-3s. These benefits are not restricted to those people who have already had a heart attack – and it may be those at risk are more likely to benefit.
Where then, does this leave us? Well, as is often said in science, further study is necessary. But, Dr. Go and others are still on board the omega-3 boat; “the overall preponderance of evidence supports the efficacy of marine omega-3 fatty acids for reducing cardiovascular events and arrhythmic events - in selected populations - and the benefits of eating more fish with higher omega-3 levels likely outweigh the risks from contaminants (at least currently)."
This doesn’t mean I recommend fishy omega-3s for everyone, but those at risk should consider them (either via diet or supplements). If in doubt, talk to your doctor. I, for one, am not giving up Kirkland Signature soft gels just yet. Given my family history of heart problems and hypertension, I am willing to risk a few nanograms of PCB for a potentially healthier heart; I just hope my wife is willing to risk the olfactory offense of an occasional fishy burp.
