By Dr. Mercola
Fish has always been the best source for the animal-based
omega-3 fatty acids EPA and DHA.
However, as the understanding of mercury's toxic effects has
grown, it has become even more critical to ensure you are
choosing the right fish so you can receive the benefits of the
healthful fats that many low mercury fish provide, as explained
recently by a leading expert from Harvard Medical School.1
The question of which fish you should eat and avoid is
receiving renewed attention, as the US Food and Drug
Administration (FDA) and the Environmental Protection Agency
(EPA) stand poised to update the national advisory for fish
consumption for pregnant women, nursing mothers, women of
childbearing age, and young children.2
While the Agencies have yet to announce what the new advice
will say, or when the updated advisory might be made public, the
prospect of new recommendations have already unleashed a public
relations fight.
40 Tons of Mercury Are Released Into the Air in the US Every
Year
Let's first understand how mercury winds up in our fish and
seafood. It all circles back primarily to how most energy in the
world is generated. Sadly, even in the 21st century the majority
of U.S. man-made emissions are released from burning coal laced
with mercury.
Combustion in power plants of coal containing mercury is a
major source of environmental pollution.
Mercury pollution from coal-fired power plants and other
sources moves through the air and is deposited in water and
finds its way into fish, accumulating especially in fish that
are higher up the food chain.
The good news is that about 70 percent of tested wild caught
fish consumed in the US contain relatively low levels of
mercury.3
However, fish like tuna, marlin, shark, barracuda, and swordfish
have some of the highest levels of contamination.
This is due to the fact that the oceans and thousands of
water bodies have been seriously polluted. As a result, pregnant
women who should be especially careful to consume the right
types of fish. It is quite certain that consuming fish is a
crucial part of your diet, but you should be sure to optimize
with the right kinds of fish - to receive maximum benefits with
minimal mercury exposure.
That's because the toxic heavy metal can cross the placenta
to harm the rapidly developing nervous system, including the
brain. Studies have associated prenatal methylmercury exposure
with impaired development of sensory, motor, and cognitive
functions, resulting in learning difficulties, poor
coordination, and inability to concentrate.
About 10 percent of the US population—including many
children, pregnant women, and women of childbearing age, in
particular—have mercury levels above the levels currently
recommended for fetal and child health.
Seafood Industry Pressures FDA
The seafood industry is suggesting that the updated advisory
will relax warnings against consuming certain fish
containing high mercury levels. Industry executives, speaking
last month at a trade show in Boston, said they expected the FDA
to change the advisory in a way to get people to eat more tuna
and other seafood. For example, John Connelly, president of the
trade organization National Fisheries Institute has said:4
"Whether it be pregnant women, nursing moms, or guys
[in their 50s], you're better off eating seafood, your risk
is not eating enough seafood. I think the government is
understanding that now."
Christopher Lischewski, chief executive of Bumble Bee Foods
LLC, one of the largest canned tuna companies in North America,
recently made a similar statement:5
"Based on the accurate science they've looked at
since [2004], FDA recognizes they made an error in 2004 in
putting out a mercury advisory that had no scientific
merit."
No scientific merit? That may be a stretch, as the industry
appears to have overlooked more than a dozen epidemiology
studies over the past decade that have reported adverse effects
of mercury on brain development at levels as low as one-tenth of
what was thought to be harmful ten years ago when
the advisory was written.6
These studies found no threshold level below which prenatal
methylmercury exposure has no adverse effects
The new Minamata Convention on Mercury,7
named after the fishing village in Japan where a severe
poisoning incident occurred, has as its symbol a fish. That's
because the treaty's main objective is to reduce human exposure
to mercury through a range of provisions designed to reduce uses
and emissions of mercury from major sources, like coal-fired
power plants.
Time is of the essence when it comes to reducing mercury
emissions. That's because mercury can circulate in the global
environment for decades, making it "...likely to be several
years or decades before reductions in mercury emissions have a
demonstrable effect on mercury levels in nature and the food
chain," according to the United Nations Environment Program.
In the meantime, sufficiently health protective mercury
advisories are necessary to inform women of child bearing age
about fish consumption both before and during pregnancy. Such
advisories should try to balance two objectives:
- Promoting fish consumption for its nutritional benefits
(including important benefits to the developing fetus)
- Protecting the exquisitely sensitive fetal nervous
system from the toxic effects of methylmercury exposure
Caught Up in 'Wishful Thinking'
The 2004 EPA/FDA guidance instructs women of childbearing
age, pregnant women, young children, and nursing mothers to
limit their consumption of albacore tuna to a maximum of six
ounces per week and abstain completely from swordfish, tilefish,
shark, and king mackerel.
This is due to high mercury levels in these larger fish.
According to the EPA/FDA advisory, some fish and shellfish
"contain higher levels of mercury that may harm an unborn baby
or young child's developing nervous system."
Unfortunately, while most consumers understand that (a) fish
have significant health benefits, and (b) that fish contain
mercury, most do not know which fish are high and low
in mercury.
Rather than encouraging pregnant women to eat, say less tuna
and more salmon, the industry insists (against the weight of
scientific evidence) that all fish are beneficial, regardless of
the mercury content, even though only a relatively small
percentage of fish species have higher mercury levels.8
Which is why some of the fishing industry is now trying to
"psych out" the FDA by predicting that the agency's new fish
advisory will lean in their favor. This, however, may be little
more than wishful thinking, as suggested in the Wall Street
Journal:9,
10
"'It's 'wishful thinking' on the part of the seafood
industry to think the updated advisory will tell those in
the at-risk groups to eat more tuna,' said Carl Safina,
president and founder of the environmental group Blue Ocean
Institute. 'The FDA is considering changes to its advice,'
he said. 'No one apparently knows what they are considering…
so it's fantasy for fishermen to think the advice on tuna
will be relaxed.'"
I've previously addressed the issue of what fish to safely
eat during and before pregnancy, noting that while eating fish
certainly has important health benefits, it's really critical to
use discernment.
The challenge is to find and choose the 25 varieties of fish
and shellfish that qualify as low or very low in mercury.11
Several of them are quite high in omega-3s.
Wild-caught Alaskan salmon, for example, is one very low
mercury fish. Tuna is by far the largest source of mercury
exposure in our diet, and anyone who wants to reduce their
mercury intake needs to eat less tuna. The tuna population has
also been decimated due to over-fishing, I believe it is best to
avoid tuna and make better choices when consuming seafood.
Advocacy Groups Sue FDA for Failure to Warn About Mercury Levels
Last month, on behalf of the Mercury Policy Project (MPP) and
the Center for Science in the Public Interest (CSPI), Earth
Justice filed a lawsuit12,
13 against the FDA. The groups are suing FDA for
failing to respond to a July 2011 petition in which the groups
asked the Agency to give consumers clear, accurate and
accessible information about toxic mercury in the seafood they
eat.
According to Michael Bender, MPP's director, the FDA's
recommendations are both out-of-date, and do not reach the
people who need them most—pregnant women, parents of young
children, and heavy fish eaters. A package label would rectify
that problem. As reported by Bloomberg Business Week:14
"The Center for Science in the Public Interest and
the Mercury Policy Project filed a lawsuit... against the
Food and Drug Administration requesting regulations to label
fish containing high levels of mercury and include
information on what levels of consumption are safe. They
also want the government to require supermarkets to display
this information on signs at the fish counter...
According to the complaint, hundreds of thousands of
children in the US. are born every year with elevated blood
mercury levels caused by their mothers' consumption of fish
and shellfish contaminated with methylmercury, a neurotoxin
that has been linked to learning disabilities, lowered IQ,
and impaired cognitive and nervous system functioning."
Despite the fact that the FDA is charged with consumer safety
and protecting the public from harmful contaminants, it
repeatedly falls short of this task. Thirteen years ago, the
CSPI filed a petition with the FDA requesting warning labels on
high-mercury fish,15
but the agency never responded. It was legally required to do so
within 180 days. The current lawsuit seeks a court ordered
deadline for the FDA to make a final decision on the issue.
Mercury Levels in Fish
Your total mercury exposure depends on two factors: which
fish you eat and the amount of fish you eat. As noted
by Bender, "this critical fact is often obscured by industry
exhortations to 'eat more fish,' without regard to mercury
content."
Mercury content can vary 100-fold from one species to
another, so it certainly makes sense to pay close attention to
which fish are on the high side and which are on the low end.
For example, research16
published in 2010, which quantified the contributions to total
mercury in the US seafood supply by 51 different varieties of
fish and shellfish, found that tuna was responsible for more
than one-third of Americans' total exposure to
methylmercury.17
According to the author:
"The analysis performed here identifies the relative
importance of different fish and shellfish as sources of
mercury in the US seafood supply and proposes improved
consumer advice, so that the public can benefit from fish
consumption while minimizing mercury exposure. Except for
swordfish, most fish with the highest mercury levels are
relatively minor contributors to total inputs.
Tuna (canned light, canned albacore and fresh/frozen
varieties) accounts for 37.4 percent of total mercury
inputs, while two-thirds of the seafood supply and nine of
the 11 most heavily consumed fish and shellfish are low or
very low in mercury. Substantial improvement in risk
communication about mercury in fish and seafood is needed;
in particular, several population subsets need better
guidance to base their seafood choices more explicitly on
mercury content."
For a handy list that you can print out for reference, please
see the Mercury Policy Project's
guide to mercury levels in different varieties of fish and
shellfish.18
Among the safest are shrimp and salmon. Canned tuna, mackerel,
swordfish, grouper, marlin, and orange roughy have some of the
highest levels of mercury levels. For even more information
about mercury in fish, I recommend reviewing MPP's website,
Mercury and Fish: The
Facts.
Parents: Beware of Feeding Your Child Too Much Canned Tuna
A 2012 report19
by the Mercury Policy Project offers risk management advice for
schools and parents, and warns that canned tuna is a
major source of mercury exposure in children. Based on average
contamination levels in tested samples, small children should
eat light tuna no more than twice a month, and albacore tuna
should be avoided entirely. The report also recommends that if
your child eats tuna once per week or more, you should have
their blood tested for mercury. If the result is over 5
micrograms per liter (ug/L), his or her consumption should be
restricted.
Keep in mind that methylmercury harms a person's nervous
system to differing degrees, depending on how much mercury
you've accumulated. At above average doses, brain functions such
as reaction time, judgment, and language can be impaired. At
very high exposures, mercury can affect your ability to walk,
speak, think, and see clearly. Another 2012 study20
that evaluated the effects of mercury on cognition in otherwise
healthy adults found that those with blood mercury levels below
5 µg/L had the best cognitive functions. Mild impairment was
evident at blood mercury levels of 5 to 15 µg/L and above 15
µg/L, cognition was significantly impaired.
Tell the FDA Where You Stand on Mercury Warnings
Given the above facts, let the FDA know where you stand! To
make your voice heard, email or call FDA Commissioner Margaret
Hamburg, either via email or a telephone call.
To contact FDA Commissioner Margaret Hamburg directly, you
can call her at (301) 796-5000, or send her an email:
Margaret.Hamburg@fda.hhs.gov.
You can also contact your representatives by visiting the
US Congress Members
page.
Please Eat Fish, Just Make Sure It's Low in Mercury
Remember, you don't need to quit eating fish altogether. But
you DO need to be aware of which fish are safer to eat, and
which you'll want to eat only rarely, if at all. As stated by
Edward Groth,21
an independent food safety consultant and author of the report
titled: "An Overview of Epidemiological Evidence on the Effects
of Methylmercury on Brain Development, and a Rationale for a
Lower Definition of Tolerable Exposure:"22
"If women are eating less fish because they're
confused, and there's some evidence that's the case, then
we're not getting the result we want. The secret is to get
women to eat more low-mercury fish."
To take advantage of the health benefits of fish, avoid
eating large predatory fish that are high on the food chain. An
excellent choice is wild-caught Alaskan salmon. The reason for
this is that it contains some of the highest amounts of
beneficial omega-3 fats, in combination with being among the
least contaminated. Yet there are many other good choices as
well, that you can find on the FDA23
and MPP24
websites.
Copyright 1997- 2014 Dr. Joseph Mercola. All Rights Reserved.