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 , 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.