By Dr. Mercola
Omega-3 fat is important for proper energy storage, oxygen
transport, cell membrane function, and regulation of inflammation.
It's also critical for healthy development in utero, especially for
eye and brain development, and plays a role in the length of
gestation.
Recent research has again confirmed the importance of omega-3
fats during pregnancy, and the danger of too much omega-6.
The former you get primarily from fish, whereas processed vegetable
and seed oils — staples in the standard American diet — are the
primary sources of the latter.
The ideal ratio between these two essential fats ("essential"
meaning your body cannot produce them, so you have to get them from
your diet) is 1:1, but a processed food diet provides FAR more
omega-6 than omega-3.
Unless you avoid vegetable oils and either eat plenty of fish or
take a high quality omega-3 supplement, you may be getting around 16
times more omega-6 than omega-3 from your diet.
As one recent animal study1
shows, such a lopsided ratio during pregnancy can have severe health
consequences for your baby.
Another Major Concern With Your Oils
Another major factor that has contributed to a large percentage
of the amount of chronic disease present in Western nations is the
introduction of refined vegetable oils.
Prior to 1900, the average intake of vegetable oils was less than
a pound a year and in 2000, that had increased to 75 pounds per
year. We simply never had the ability to consume this much vegetable
oil prior to food processing.
Refined oil contributed to the massive distortions in the omega
3:6 ratios. There is nothing intrinsically wrong with omega-6 oils
if they are consumed in their native form, which is typically in
unrefined seeds and nuts.
The key take-home point is to avoid virtually all refined
vegetable oils. Not only do they allow you to overconsume them but
they are also highly susceptible to oxidation and are typically
damaged by the time you use them.
I personally consume about 10 to 15 grams of omega 6 oils a day
but not one microgram is refined. They are all in the form of seeds
and nuts that I eat raw, or freshly grind them immediately prior to
eating.
I also eat about 4 ounces of clean fish a day in the form of wild
Alaskan salmon, sardines, or anchovies. That and my seeds give me
nearly 10 grams of omega-3 fat a day so my omega 6:3 ratio is about
1.5:1.
Lopsided Omega-3 to Omega-6 Ratio Harms Brain Development
In the featured study,2
animals fed a diet in which the omega-6 to omega-3 ratio matched the
standard American diet produced offspring whose brains were much
smaller than those fed equal amounts of omega-3 and omega-6.
Once the offspring reached adulthood, they also developed
emotional problems, exhibiting greater levels of anxiety. This
despite eating a healthy diet from birth, onward. As reported by
Medical News Today:3
"The team performed the first comprehensive measurement
of lipid metabolites in the developing brain; they identified
that metabolites of omega oils are vital regulators of
neural stem cells — the cells that go on to develop into fully
fledged brain cells.
In the rats with diets heavier on the omega-6 than 3, the
neural stem cells developed more rapidly, to their detriment.
The results ... show that increased levels of omega-6 produce an
increase in omega-6 oxides. These omega offshoots cause
premature aging of fetal neural stem cells.
The study's authors conclude: 'These findings provide
compelling evidence that excess maternal consumption of omega-6
combined with insufficient intake of omega-3 causes abnormal
brain development that can have long-lasting effects on the
offspring's mental state.' [Emphasis mine]
Fish Consumption in Pregnancy Linked to Better Brain Health
A second study4,5,6
strengthens the argument by showing that the brain benefits of
omega-3 appear to outweigh many of the hazards associated with
mercury exposure.
Here, the researchers looked at 2,000 pregnant women, who
reported their seafood intake — including the specific species of
fish — via food questionnaires, starting in their first trimester.
On average, the women ate about three servings (500 grams) of fish
per week during pregnancy.
At birth, the umbilical blood was assessed for omega-3 DHA,
mercury, and PCBs. The children underwent cognitive tests and
autistic spectrum disorder evaluation at the age of 14 months and
again at age 5.
The results showed that:
- Higher fish consumption during pregnancy was associated with
increased cognitive scores, and decreased risk of autistic
symptoms in the children
- For every additional 10 grams of fish per week over 500
grams, there was a corresponding improvement in test scores
- Eating 600 grams (21 ounces, or about four servings) of fish
per week was linked to a 2.8 point increase in IQ score. This
link was particularly strong for large fatty fish, including
tuna, even though tuna also has some of the highest levels of
mercury
- Fish intake during the first trimester also had the
strongest associations, compared to higher fish intake during
the second through fourth trimester
- Above 600 grams of fish per week the cognitive benefits
tapered off, suggesting this may be an ideal level, above which
the risks of mercury exposure could begin to outweigh the
benefits
I was not aware of these intriguing results but find it
interesting in light of my transition to 4 ounces most days of
either anchovies, sardines or Vital Choice Alaskan salmon. This is
around 700 grams a week.
Additionally, many are concerned about Fukushima radiation
contaminating fish. While I don't doubt it is an issue for some
fish, I personally test the fish I consume from Vital Choice with a
$1,000 Inspector Geiger counter and it has never measured anything
higher than background radiation.
Recommendations for Pregnant Women
While fish have always been an ideal, rich source of omega-3 fat,
the presence of pollutants such as PCBs and mercury does make
caution advisable. It's not a reason to ditch ALL fish from your
diet though.
As detailed in a presentation by a leading expert from Harvard
Medical School,7
it's important to understand both the risks of consuming
high-mercury fish and the benefits that low-mercury fish provide.
Your total mercury exposure depends on two factors: which
fish you eat and the amount of fish you eat. The challenge
is to select fish that qualify as low or very low in mercury.
Fortunately, the U.S. government has finally seen the light and
is now specifying that pregnant women should be careful to select
low-mercury seafood.
The joint recommendation8
by the U.S Food and Drug Administration (FDA) and the Environmental
Protection Agency (EPA) regarding fish consumption for pregnant
women, those who may become pregnant, breastfeeding mothers, and
young children is 8 to 12 ounces of fish per week from choices
that are lower in mercury.
In their estimation, this maximizes the benefits of omega-3 while
minimizing the risk of mercury exposure. According to the study
above, this may even be a conservative estimate.
Resources for Identifying Fish Low in Mercury
So where can you find information about the mercury content of
any given fish species? Here are three resources:
- The FDA has a Webpage9
listing and ranking seafood based on their mercury content
- For a list that you can print out for reference, please see
the Mercury Policy Project's
guide to mercury levels in fish and shellfish10
- The National Resources Defense Council has a
mercury calculator you can use to give you an idea of how
much mercury you're getting from any given fish species
Best and Worst Fish Choices
On the up-side, several fish species that are low in mercury are
also high in omega-3s.
Wild-caught Alaskan salmon11
is one example. Just one 3.5-ounce serving provides around 2 grams
of omega-3s,12
which is more than most Americans ingest in a week. Only
walnuts and flaxseeds provide more.13
Another benefit is that it has a nicely balanced omega-3 to omega-6
ratio.
Other species with lower mercury content include pollock,
tilapia, catfish, and cod, along with smaller fish like sardines and
anchovies. There are some questions as to the sustainability of
anchovies though.
According to Wild Planet,14
anchovies are an abundant and prolific fish stock, and a fine
sustainable choice, but the Safina Center's Sustainable Seafood
Program15
and The Environmental Defense Fund16
give Mediterranean and Black Sea anchovies a poor eco rating.
Avoid tilefish, shark, swordfish, and king mackerel, as these
four have the highest mercury levels of any fish tested. The FDA/EPA
also wisely recommends limiting white albacore tuna to 6 ounces per
week due to its elevated mercury content. Tuna is by far the largest
source of mercury exposure in our diet —especially for children —
and anyone who wants to reduce their mercury intake should eat less
tuna.
According to a 2012 report17
by the Mercury Policy Project, young 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.
At What Level Does Mercury Become a Health Hazard?
Mercury is extremely toxic, so ideally, you don't want to be
exposed to any. However, given the level of mercury pollution in the
world today, this probably isn't feasible. You're bound to ingest or
be exposed to some here and there, be it via air, water, of fish.
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.
One 2012 study18
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.
When it comes to infants, 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.
But bear in mind that the benefits of the omega-3 you get from
fish can, and most likely does, outweigh the risk of methylmercury
provided you don't overdo it, and stay away from fish known to be
high in mercury. Again, the featured study found NO additional
cognitive benefits for eating more than 600 grams/21 ounces of fish
per week, which is about 4 servings.
A more cautious recommendation would be to limit your fish
consumption to a maximum of 12 ounces of high omega-3/low-mercury
varieties and take a high quality omega-3 supplement, such
as krill.
If you believe your health problems may be related to mercury
toxicity, get tested for heavy metals, and if need be, take
appropriate action to detoxify. For more information, see my
Revised Mercury Detox Protocol. That said, it's undoubtedly
easier to avoid mercury exposure than it is to detoxify once it has
built up. This is why it's so important to use discernment when
selecting seafood.
Beware of Farmed Fish
While the FDA/EPA recommends salmon, they do not specify the type
of salmon. I strongly discourage consumption of
farmed salmon due to their inferior nutritional profile, their
environmental drawbacks, and potential health hazards, detailed in
my previous article, "Norway
Issues Warnings About Health Dangers of Farmed Salmon."
Unfortunately, recent investigations19
have shown that as much as 80 percent of the fish marked as "wild"
may actually be farmed, and that includes salmon. In restaurants, 90
to 95 percent of salmon is farmed, yet often listed on the menu as
"wild."
Given these inaccuracies, how can you tell whether a salmon
really is wild or farmed? The flesh of the salmon will give you a
clue. Wild sockeye salmon is bright red, courtesy of its natural
astaxanthin content. Sockeye salmon actually has one of the highest
concentrations of natural astaxanthin of any food.
Wild salmon is also very lean, so the fat marks — those white
stripes you see in the meat — are quite thin. If a fish is pale pink
with wide fat marks, the salmon is likely farmed. Avoid Atlantic
salmon, as salmon bearing this label are almost always farmed.
The two designations you want to look for are: "Alaskan salmon"
(or
wild Alaskan salmon) and "sockeye salmon," as neither is allowed
to be farmed. Canned salmon labeled "Alaskan salmon" is a good bet,
and if you find sockeye, it too is assured to be wild (provided it's
not mislabeled; again be sure to visibly inspect the fish and look
for the telltale signs).
My favorite brand of wild Alaskan salmon is Vital Choice Wild
Seafood and Organics, which offers a nice variety of high-quality
salmon products that test high for omega-3 fats and low for
contaminants.
In addition to PCBs and mercury, radiation from the leaking
Fukushima power plant in Japan is another concern, and many have
simply given up on eating fish for fear of radioactive
contamination, or they opt for farmed fish, thinking it's a safer
option. I disagree on the latter point. Instead, I would suggest
contacting the distributor of whatever wild fish you may be
interested in, and ask them whether or not they test for radiation.
If You Choose Wisely, the Benefits of Fish May Still Outweigh Its
Risks
As you can see, the situation is complex. You absolutely need
omega-3 fats, as your body cannot make it, but it's not as easy as
saying "eat more fish." You also need to take pollutants into
account (including potentially radioactive contaminants).
This is particularly important for pregnant women and young
children. Sustainability is yet another factor that is worthy of
consideration. The good news is that even when all of these factors
are taken into account, you have still have a number of good, viable
options available.
To reiterate, wild-caught Alaskan (not Atlantic) salmon
is very high in omega-3 and among the lowest in mercury. It's also
still a sustainable choice, plus it's not allowed to be farmed —
another benefit — and it has not been genetically engineered, so the
likelihood of accidentally getting the now approved
GMO salmon when buying wild Alaskan is limited. For other good
options, see the three resources listed earlier.
Last but not least, even if you eat fish, you may benefit from
taking a high-quality omega-3 supplement such as
krill oil, which is a far more sustainable choice than fish oil.
The best certification for sustainability my team has found is The
Marine Stewardship Council.20
We spent quite a bit of time and expense working with them; it took
over 5 years of observation, but they have certified our krill
supply as one of the best managed resources in the world.21
If you avoid fish, an omega-3 supplement like krill oil becomes
an absolute necessity. If you’re pregnant, I would highly recommend
taking the “better safe than sorry” route, and limit fish to about
12 ounces per week, and supplement with krill oil, as there’s very
little risk of krill being contaminated with heavy metals and other
pollutants.
© Copyright 1997-2016 Dr. Joseph Mercola. All Rights Reserved.