
Fish Oil Claims Not Supported by Research - pk2200
http://well.blogs.nytimes.com//2015/03/30/fish-oil-claims-not-supported-by-research/
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magic5227
Notable comment in the post:

Bill Harris Sioux Falls, SD 56 minutes ago As a long-time researcher in
omega-3s, I've watched the fish oil rollercoaster since the mid 1980s. This
most recent posting by O'Connor continues the trend. The best meta-analysis
(grand summary of many studies) published to date was from Rizos et al. in
JAMA 2012;308:1024-1033). They concluded that fish oil capsules offer “no
benefit” for heart patients. Unfortunately, Rizos used a highly controversial
statistical maneuver. In their actual data (Fig 2) there was a highly
statistically significant reduction in cardiac death associated with fish oil
use (p<0.01 for the stat-saavy). So fish oils DID reduce risk for cardiac
death. Why the "no effect" conclusion? Rizos et al. decided to set the
statistical bar higher than I’ve ever seen it in meta-analyses. They defined a
significant p-value as <0.006, instead of the universally accepted p<0.05.
This trick changed a positive finding into a negative one and generated a
media storm of "fish oils don't work." More recent meta-analyses (Chowdhury et
al. Ann Intern Med 2014;160:398-406) reported that higher dietary intakes AND
higher blood levels of omega-3 fatty acids were both significantly linked to
reduced risk for heart disease. The problems with the recent fish oil studies
are legion, and include using a low dose for a short period of time in older,
already-ill patients who are also being treated with up to 5 heart medicines.
In this setting it’s nearly impossible to show a benefit. With 0 risk, I still
recommend fish oil.

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jimrandomh
I checked the Rizos et al study
([http://jama.jamanetwork.com/article.aspx?articleid=1357266](http://jama.jamanetwork.com/article.aspx?articleid=1357266))
and the statistical issue is a bit subtle. They applied a multiple-hypothesis
correction, to account for the fact that they were looking at multiple
subgroups and endpoints. The problem is that in their data, _most_ of the
subgroups and endpoints show an effect, and these aren't being combined
together. So in that paper, no one subgroup alone contains enough evidence to
show an effect, but the groups put together, do.

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tjradcliffe
The effects seen in the various sub-groups and endpoints are all non-
significant at the p = 0.05 level. The lowest I can see is p = 0.07 (cardiac
death prevention, as reported in their Table 3).

The multiple-hypothesis correction they apply is reasonably appropriate in the
case of simply looking at all results, which is what they do.

Furthermore, because the outcomes are disjoint (cardiac survival vs stroke vs
sudden death vs all-cause mortality, etc) there is no simple way to combine
the results.

To take a silly example, studying the effect of seatbelts on cancer and
cardiac death might well show a bit of an effect on both (because people who
wear seatbelts are generally healthier, say) but it would be illegitimate to
combine those two studies because the endpoints are (so far as we know)
unrelated to each other. Without some kind of causal account the issues become
very deep and difficult to say anything very definitive about.

So I'd say their statistical treatment is fair and appropriate. If fish-oil is
supposed to have such a large effect as to be worth taking the risk that it
increases the risk of prostate cancer, its effect should be unequivocally
measureable in population studies. That is not the case.

For what it's worth, I think the prostate cancer studies are at least as
flawed, at least the one I've seen, which is a case-control study that shows
an extremely modest increase in relative risk of the kind it is very easy to
produce from statistically identical populations:
[http://www.tjradcliffe.com/?p=1745](http://www.tjradcliffe.com/?p=1745)

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aresant
Short term, ranged, and non-clinical studies always remind me of the story of
the "Shoe-fitting fluoroscopes" (1)

AKA - x-ray machines placed in shoe stores so you could stick your foot in,
dial up the radiation, and see your wiggling toes in the shoe.

Invented in the 1920s. Debates raged for decades. Outlawed finally in most
states in the 1970s.

So for 50 years people thought taking your kid to the shoe store and blasting
their feet with radiation was a good idea.

Largely because they had limited data and ability to measure the outcome, as
the data became available it became crystal clear that these had the potential
to be dramatically harmful.

Even with this lesson in mind I took fish oil for years, despite a lack of
clear data.

The study a couple of years ago that linked fish-oil (natural and
supplemental) to a 41% increase in prostate cancer / 71% increase in
aggressive prostate cancer, reminded me of the flouroscope story. (2)

This Harvard health article, a couple of years old, puts it best:

"How food, and its component molecules, affect the body is largely a mystery.
That makes the use of supplements for anything other than treating a
deficiency questionable." (3)

(1) [http://en.wikipedia.org/wiki/Shoe-
fitting_fluoroscope](http://en.wikipedia.org/wiki/Shoe-fitting_fluoroscope)

(2)
[http://jnci.oxfordjournals.org/content/early/2013/07/09/jnci...](http://jnci.oxfordjournals.org/content/early/2013/07/09/jnci.djt174.abstract)

(3) [http://www.health.harvard.edu/blog/fish-oil-friend-or-
foe-20...](http://www.health.harvard.edu/blog/fish-oil-friend-or-
foe-201307126467)

~~~
magic5227
Not sure that comparing x-rays to fish oil is a good comparison of
risk/reward.

People (like myself) take fish oil for a variety of reasons, in my case to
lower the risks of serious heart disease over the risks it might contribute to
prostate cancer.

There are even studies that show fish oil could reduce the chances of prostate
cancer:
[http://www.ncbi.nlm.nih.gov/pubmed/12540506](http://www.ncbi.nlm.nih.gov/pubmed/12540506)

Ultimately each person has to judge the benefits/risks for themselves until
better data is available. It's also worth noting that prostate cancer is
increasingly a risk for all men as they age, fish oil or not.

~~~
jsprogrammer
Why not supplement with hemp seed?

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raverbashing
Vegetable sources of Omega-3 are usually ALA, not EPA or DHA like in Fish Oil
(they get converted into those by the body though)

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therealdrag0
An independent overview of the research:
[http://examine.com/supplements/Fish%20Oil](http://examine.com/supplements/Fish%20Oil)

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palidanx
What I'm really curious about is the research for fish oil and dry eyes. After
I had lasik, I was told to take fish oil 4 times a day for a long time. My dry
eyes seem to have gotten better, but I don't know whether that is due to the
fish oil or from just a general recovery.

~~~
wellpast
I use fish oil for dry and red eyes and I also notice a big difference. _Seem_
to notice, I suppose...

~~~
palidanx
I'm kind of curious, which brand do you use?

~~~
wellpast
Nordic Naturals Ultimate Omega. My eye doctor was specific on this brand--
emphasizing the EPA and DHA levels.

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mqsoh
I take it because it might benefit my myelin sheath. That association is
probably bunk, too.

[https://en.wikipedia.org/wiki/Myelin](https://en.wikipedia.org/wiki/Myelin)

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moveroovee
One^H^H^H Fish Oil Claim Not Supported by Research

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tghw
The title is a little misleading. Claims about fish oil and its potential
decrease of cardiovascular events in high-risk populations is not supported by
research. The article does not address other potentially beneficial effects,
such as decreased inflammation.

~~~
evo_9
Or it's more profound, positive effects on mood.

My wife takes fish-oil daily as a mood stabilizer. When she skips a day or two
all hell breaks lose in our house. Hell I take a smaller dose myself and it's
amazing how much better I am at keeping my mood in check; I've never had much
trouble but I have always gotten little edgy when hungry. That doesn't happen
anymore.

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cjensen
It is nearly impossible to be objective about your own brain. If you suspect X
makes you happier, then it probably will. After it works once, you will
probably believe X makes you happier, and if definitely will.

In other words, even if fish-oil does work as a mood stabilizer, there would
be no way for you, as a consumer of fish oil, to be even slightly certain it
works.

~~~
narrator
>It is nearly impossible to be objective about your own brain.

People can't trust their own perceptions? Isn't that what gaslighting is
about? Why do we accept eye-witness testimony in court cases if people should
not trust their own perceptions?

If a person saw another person strike another person, should we trust their
testimony? No! We should have a double-blind placebo controlled experiment
where we go back in time and have a large sample size of identical people
watching the same person getting struck and not struck in alternate universes
and ask them if the person was struck to determine if their perceptions can be
trusted.

~~~
jsprogrammer
Eye-witness testimony is mostly bunk and is often not trusted in court. It's
been shown over and over that eye-witnesses can be manipulated (even without
their knowledge) and are not reliable.

No, you can't trust your own perceptions. You can only really trust that you
are having a perception at this moment in time.

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jheriko
interesting, not entirely surprising given how we love to jump to conclusions
over these things, and the history of fish oil as a 'common knowledge' 'good
thing'.

slightly disappointed that the headline was not fish oil is actually snake
oil? or something suitably witty... :)

~~~
pbreit
It looks like you've just jumped to a conclusion. That may be wrong.

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cbd1984
This is still an April Fool's joke.

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cbd1984
April Fool!

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seattlegal
My Colon disagrees.

