Fluke or Trend? Fish Oil vs Heart Disease

In theory, science should be clear cut, but in reality, it isn't.  There's much debate regarding how to interpret data, somewhat akin to reading tea leaves at times.  Yes, we'd like to have randomized controlled trials of adequate size & duration involving all ethnicities, but more often we're left with conflicting observational & epidemiologic studies.  And so it is w/fish oil.  As much as you hear the hype over omega-3 fatty acids found in fish oils and even as we debate EPA vs DHA as well as EPA:DHA ratios and the role of krill oil vs fish oil, the evidence behind these omega-3's isn't as crystal clear as we'd like.  There's even more debate over the utility of plant-based omega-3s vs fish-based fatty acids.

In times like these, we often turn to meta-analyses to make sense of the tea leaves by collating many studies and analyzing the data looking for trends.  Of course, in doing so, we need to separate out the black tea leaves from the green tea leaves from the rest, right?  In a meta-analysis just published today in JAMA, the authors weeded through 3,635 citations to cull out just 20 studies for analysis.  The good news is that 68,680 participants were involved.  The bad news is that no benefit was found by taking fish oil supplements over placebo with regards to heart disease (death), stroke (death) & all-cause mortality.  

Of course, the true believers will claim some impropriety.  After all, average dose was just 1.51g/d of omega-3s of which 0.77g/d was EPA and 0.60g/d was DHA.  Others will claim that the trials were not of adequate duration w/average 2yrs w/maximum of 6+yrs.  Still others will claim that omega-3s were not meant to be used in 2o prevention (disease already manifest) but rather 1o prevention (prior to disease making itself known).

On the other hand, the authors noted that of the 20 trials meta-analyzed, 16 were intention-to-treat and (not necessarily the exact same) 16 were double-blinded.  But that won't dissuade a true believer.  So where does that leave us?  Rather than look for salvation in a pill, it's time we take another look at what's on our plate.  While we wait for a randomized controlled trial of adequate size & duration involving all ethnicities . . . By the way, in case you're curious, a review published in August 2008 in the International Journal of Clinical Practice couldn't find any benefit from omega-3 supplementation although it did conclude that there was benefit to eating fish.

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