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Written on September 17, 2012 at 5:12 am, by Eric Cressey
Today, I have a fantastic guest post from Dr. Hector Lopez, an expert in the world of nutritional supplements. This post comes in response to a mainstream media report (you can read it here) that called into question the benefits of fish oil. Hector and I had emailed privately about the concerns he had with this study, and I asked if he’d be willing to share his feelings with a larger audience. Enjoy! -EC
I have been asked for my professional opinion on the recent attention drawn to the September 2012 systematic review and meta-analysis published in the prestigious Journal of the American Medical Association by Rizos EC et al .
As you can imagine, the few days have been very busy answering emails/calls from various stakeholders in the dietary supplement and omega-3 fish oil industries. The stakeholders range from friends and family to fellow scientists and colleagues, to high-level executives and principals of client companies. I have a few things to say about the manner (at times disingenuous) in which the meta-analysis has been misrepresented.
Multiple video segments from major media outlets have even quoted some of their experts as saying, “they would rather the public spend their money elsewhere as the proof is in with this study.” Perhaps they would feel more at ease suggesting the consumption of another box of “whole-grain” yet low fiber, highly processed cereal, “natural fruit juice,” or better yet, “linoleate-rich vegetable oils full of omega-6 fatty acids” (hey, they are polyunsaturated too, right)? ☺
I don’t mind the media sharing their opinion, but at the very least, they should attempt to educate the very audience that they are obviously trying to persuade. I find it hard to believe that the public would not be interested in some other material facts to allow consumers to make an informed decision:
1. Out of over 3600 clinical studies and citations retrieved, ONLY 20 were used in this “analysis.”
2. The absence of statistically significant association in these 20 studies between omega-3 and cardiovascular disease (CVD) endpoints does not prove that a significant reduction of CVD with omega-3 does not occur.
3. These 20 studies were on a diseased population that were already using multiple cardiovascular drugs such as beta-blockers, statins, niacin, fibrates, resins, and anti-thrombotics – all of which clearly confound outcomes/ endpoints of interest to dilute and wash-out effects of long-chain omega-3 polyunsaturated fatty acids (PUFA). Fish oil at this low dose was likely “too little, too late” to show any statistically significant benefit.
4. A similar meta-analysis on secondary prevention was published earlier this year . And, clearly, the older studies showed benefit as these patients were likely not on as many cardio-protective medications. Hence, their was less of a “washout” in effect size.
5. A mean dose of less than 1.4g of EPA + DHA (the fish oils) was used in all 20 studies. This dose is typically far too low to compensate for the overabundance of omega-6 PUFA and imbalance in omega-6:omega-3 consumption in standard western diets. It’s no surprise that previous studies showing benefit of omega-3 fish oil in heart disease have utilized at least 2g of EPA + DHA. Future studies should also take this into consideration. In addition, future studies should attempt to carry out prospective data collection beyond two years.
6. There was no mention, consideration or control for background dietary intake of EPA/DHA or tissue fatty acids profiles. The researchers did not control for this important variable within each individual study included in this meta-analysis, and as a result, there is no way to determine if placebo groups already had sufficient levels of omega-3 in their diet or tissue, which would make it harder to demonstrate treatment effects of fish oil.
7. Clearly, these 20 studies were not adequately powered to detect changes in the CVD endpoints with omega-3 long-chain-PUFA, even if they were in fact present.
8. Interesting, despite all these flaws, based on the Confidence Interval data, there was still a “trend” toward cardioprotection! This was observed in terms of sudden death, myocardial infarction, cardiac and all-cause mortality. In other words, the data in this article still trended toward decreased risk of various cardiovascular disease outcomes. However, the headlines wouldn’t be juicy enough, though, so that was clearly glazed over. Hmm…
9. Sure, most Americans should eat more fish (in their whole food diet), but honestly, how many actually do? Where is the press coverage or meta-analyses looking at PCB/ Dioxin/ Persistent Organic Pollutants/Heavy Metal exposure? I suppose that when this omega-3 story dies down, the environmental toxin exposure story can quickly fill that void.
10. The findings of this selective meta-analysis are in direct conflict with the totality of the scientific evidence that demonstrates a cardiovascular benefit from fish oil in healthy populations, as well as in many of the populations with pre-existing CVD [3-10]. Consumers and health care providers alike continue to feel confident in the use of high-quality omega-3 fish oil for not only cardiovascular benefit, but also for supporting the health of just about every organ system in the body. The long chain omega-3 essential fatty acids found in fish oil are critical for everything from the cardiovascular system to the brain and nervous system, immune system, skin, joint and musculoskeletal tissues, to carbohydrate and lipid metabolism and beyond [11-19].
Finally, there is the issue of the potential mega-misrepresentation created by meta-analyses. It is evident that study selection criteria – as well as data extraction/synthesis – may allow researchers to make assumptions of consistency in the design individual studies included in the meta-analysis. As such, these assumptions may lead the authors – or worse, the less discerning media– to drawing erroneous conclusions. These erroneous conclusions then get virally disseminated throughout the general public. Doesn’t this string of events sound eerily familiar?
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Note: You can find references for this entire article in the first post in the comments section below.
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