>> NARRATOR: The third most
widely used supplement in
America is fish oil.
The Omega-3s contained in the
oil are believed by many to be
essential for good health.
>> DHA Omega-3 in particular
is extremely important.
>> NARRATOR: It also helps
prevent disease, according to
the man who heads one of the
largest fish oil trade
associations.
>> There's certainly ample
evidence that it helps things
like reducing blood pressure,
reducing your risk of coronary
death.
>> NARRATOR: But the science
behind fish oil is a little more
complicated than that.
>> So these are two capsules.
This is a FDA-approved
product...
>> NARRATOR: Dr. Preston Mason
is a Harvard university
researcher.
Here, he's comparing
prescription-quality fish oil
to the oil found in
over-the-counter supplements.
>> And give it a smell.
>> It smells a little bit fishy,
but not bad.
>> Right.
You're gonna have always
some smell.
>> NARRATOR: One of the issues
with fish oil is it's delicate.
It's extracted as a byproduct
from oily fish like anchovies.
As the fish get crushed, the oil
is exposed to oxygen, and it
doesn't take much oxygen to turn
the oil rancid.
>> This is a common supplement
for fish oil.
See what that smells like.
>> Oh...
>> What?
>> That doesn't smell good.
That smells like it's going bad.
>> Yeah, right.
It's a very strong fishy smell.
>> NARRATOR: If it was simply
an odor issue, that would be one
thing, but oxidized oil contains
oxidized lipids, one of the
building blocks of cells.
We've long known that lipids,
when oxidized, can be harmful.
>> So an oxidized lipid triggers
inflammatory responses within
our body, particularly in our
cells, and if we ingest
oxidized lipid, we can trigger
these inflammatory changes
that can lead to things like
cardiovascular disease.
>> NARRATOR: Recently, Mason
published his own study
of fish oil supplements.
The results were consistent
with other studies, showing
high levels of oxidation.
One in New Zealand
found 83% of fish oils tested
failed to meet the industry's
own standard.
>> It was shocking to see such
a high proportion of products
that had high oxidation levels.
And so we went and actually
bought 47 products from the
New Zealand market and had them
tested at multiple labs, and we
did not see that same effect.
>> Well, what was the percentage
that you discovered that were
not in compliance?
>> It was around 20%.
>> Would you agree that 20%
is still problematic, from
the consumer's point of view?
>> Well, if it's truly 20%, then
yeah, we would like to see those
20% improved.
>> NARRATOR: But improving the
quality won't address the other
issue with fish oil: the growing
questions about whether it
prevents disease.
Two years ago, epidemiologist
Dr. Andrew Grey compiled all
the best studies on fish oil
as reported in the world's most
prestigious scientific journals.
>> I think for cardiovascular
disease, one has to say there
is no compelling evidence that
taking fish oils protects
against a first heart attack
or a second heart attack.
And so people who are advised
to do that or are doing it
are wasting their time
and their money.
>> NARRATOR: But the fish oil
industry continues to insist
there is a benefit, particularly
for preventing heart attacks.
We asked their spokesman
to send us his best evidence,
which included some of the same
studies Grey had cited, and
didn't seem to support his case.
>> This one says it doesn't
appear to reduce sudden cardiac
death.
The next one,
"Insufficient evidence."
JAMA 2012: "Overall, Omega-3
supplementation was not
associated with a lower-risk
of all-cause mortality."
Another journal, "The evidence
is not clear-cut, and any
benefits are almost certainly
not as great as previously
believed."
So, that doesn't seem to be
suggesting there's an
overwhelming amount of evidence.
>> Yeah, well, I think what
you're looking at are the
abstracts.
>> But the conclusions
are the conclusions.
>> But again, those papers are
looking at very large areas of
cardiovascular disease, and I
think it's hard to argue that
Omega-3s aren't important
for how your heart functions.
>> NARRATOR: Many researchers
agree-- if you get them
from eating actual fish.
The problem is, science still
hasn't proven it's true for
supplements.
>> We would think that
something that's natural,
that's essential to normal cell
function and body function,
would have clinical benefits,
it just has to be proven.
But in the meantime,
there's certainly been a lot of
promotion suggesting a benefit
in everything from Alzheimer's
disease to cardiovascular
disease.
But we still need the strong
clinical trial to validate those
hypotheses.
