Many Americans have been passing up the steak at dinner in favor of what has been deemed a healthier choice-fish. What they don't know is that there is growing concern among health organizations that consuming large amounts of fish may be detrimental to your health.
Fish has long been promoted as a health food because it is low in calories and full of vitamins and omega-3 fatty acids. However, because pollutants are so widespread, most fish contains at least some toxic methylmercury.
A recent study found that among patients at a California medical practice, those who ate a lot of fish had high levels of toxic mercury, or methylmercury, in their systems. They were also suffering from symptoms of low-level mercury poisoning, including hair loss, depression, difficulty concentrating, headaches and fatigue.
The Food and Drug Administration (FDA) permits 480 micrograms of methylmercury per one pound of fish. However, commercial fish is not regulated and there is no way to know just how much mercury is in any given fish. Moreover, people tolerate mercury very differently. Much like a bee sting can make one person extremely ill while hardly affecting another, varying amounts of mercury can cause reactions ranging from severe to mild.
Mercury is especially dangerous to children and can cause birth defects during pregnancy. For this reason, the FDA recommends that women who are pregnant or may become pregnant limit their intake of fish to 12 ounces per week, and 10 states warn pregnant women to limit their consumption of seafood.
Methylmercury is a potent neurotoxin, causing axonal demyeliniation. Adults can experience symptoms months after an acute exposure consisting of ataxia, blurred vision, hearing deficits and paraesthesias.
Fetuses are particularly sensitive to methylmercury, as shown by the more than 1,400 infants from the Minimata area of Japan who were acutely exposed to the toxin in utero when their mothers ate fish contaminated by a factory discharge. The children, while often normal at birth, developed abnormal reflexes, problems with suckling, swallowing, gait, and speech, and mental retardation.
Stop Eating Fish BEFORE Becoming Pregnant
It is critical that women of childbearing age stop eating all fish for six months to one year before becoming pregnant. Currently, it is estimated that about eight percent of women of childbearing age have enough mercury in their systems to cause potential learning disabilities in their unborn babies.
Elemental mercury from rocks and soil exists naturally in background levels in lakes and streams but is concentrated in the environment by emissions from hydroelectric projects, smokestacks, the burning of garbage and fossil fuels, municipal waste facilities, other hazardous waste combustors and industrial pulp and paper and mining processes.
Microorganisms in lake and stream sediments convert elemental mercury to organic methylmercury, which binds tightly to the proteins in fish tissue and is concentrated in fish higher up the food chain.
Mercury is converted into methylmercury, an organic form, by bacteria in water. The substance is about 95 percent absorbed when consumed and is toxic to humans because it is very hard for the body to eliminate. This allows it to build up in the system where it can eventually affect the central nervous system.
Humans are exposed to methylmercury largely through fish consumption. The toxin accumulates in fish, as it does in humans, therefore big fish that eat other fish typically contain high levels of mercury. This includes meatier fish such as swordfish, shark, mackerel, and tuna. Swordfish had the highest correlation with mercury levels out of the 30 fish used in the study. Fish that generally have low levels of mercury include salmon, flounder, cod, catfish and trout.
When ingested by humans, methylmercury is easily absorbed and retained by the body; it has a half-life in blood of about 44 days, which makes blood tests useful measures of acute exposure. It concentrates in new hair, and consecutive hair segments indicate a person's exposure history. Methylmercury is eliminated fecally as inorganic mercury.
Although practices such as trimming off fat can reduce the intake of organic pollutants such as polychlorinated biphenyls, pesticides, insecticides and dioxins, mercury intake is unaffected by this because it is deposited uniformly throughout fish tissue.
Environmental Health Perspectives November 1, 2002
Canadian Medical Association Journal October 15, 2002;167(8):897
Further compelling evidence to heed the mercury warnings I have posted for some time now.
Although omega-3 fat with DHA and EPA fatty acids, naturally found in fish, is one of the most important elements of high-quality nutrition -- and sorely lacking in the American diet -- our culture has long since passed the point where it is healthy to obtain omega-3 from most commercially available fish. I now highly recommend routinely consuming fish oil/cod liver oil, instead, as they are purified of mercury and other toxins.
Mercury is rampant in the waterways of the world, and, as the article expresses, mercury is not just in the fat of the fish -- it is in all of the tissues.
Clinically, I use hair analysis on most of my patients as a way to determine mercury levels. While many view this as a controversial test, very few would deny its utility as a sensitive screen for heavy metal exposure. A person's mercury level in their hair is almost always related to their consumption of fish.
There are exceptions, of course, as there are other environmental exposures to mercury. I recently tested a dentist who was not eating fish but was still actively removing mercury amalgams, and he had very high mercury levels in his system. This is not typical, though, as the mercury measured in the hair analysis is usually related to mercury exposure in the last three months, and most mercury from a person's amalgams is low level and will not exceed that consumed in fish.
Nonetheless, the mercury from amalgams is still a problem as it accumulates over time, but it rarely shows up in the hair unless you have had amalgams removed in the three months prior to the hair analysis and a large mercury exposure resulted from the removal.
It is a tragedy that we have virtually devastated fish, previously one of the healthiest foods on the planet, with mercury toxicity. We have polluted the environment with hundreds of millions of tons of mercury by burning coal for electricity. The mercury eventually finds its way into the waterways where it is bio-accumulated to very high levels in most fish. Generally the larger the fish, the more mercury it contains. In fact, some mercury levels in fish have been unbelievably high.
Tragedy is an understatement.
Some fish have less mercury than others, but nearly all fish are contaminated with mercury. I have done thousands of hair mineral analyses on patients and can confidently state this as truth. Patients who don't eat any fish are the only ones who have immeasurable levels of mercury in their hair. In my experience, anyone eating fish has mercury in their system, and it is nearly always in direct proportion to the frequency of their fish consumption.
So here is my recommendation:
Avoid eating all fish, unless you know the fish has been tested and shown not to contai harmful levels of mercury and other toxins.
Almost all fish has mercury that will absolutely compromise your health. The one apparent exception are very small fish like sardines or anchovies that haven't been in the ocean long enough to accumulate much mercury. Presently, I am also searching the market for safe sources of other fish, perhaps those caught from more pristine water sources that may still exist.
We all need the omega-3 fats found in fish -- in the case of most Americans, in fact, omega-3 is desperately needed -- but you should get them from a clean source. Most fish oil supplements, like the Carlson brand of fish oil/cod liver oil that I highly recommend and offer on this site, go through a molecular distillation process to clean out the mercury. The Carlson brand is also routinely tested using standard international protocols in an independent, FDA registered laboratory; this testing not only ensures freedom from detectable levels of mercury, but also cadmium, lead, PCBs and 28 other contaminants. If you are using a brand besides Carlson, you should definitely contact the manufacturer to confirm they go through this process and testing.
Another reason I specifically recommend Carlson fish oil/cod liver oil is that I have seen clear and often substantial improvements in my patients who use it. For instance, the Carlson brand has helped them get high cholesterol back to appropriate levels, and it has also shown particularly positive benefits in those with rheumatoid arthritis, Raynaud's and Scleroderma. Meanwhile, the Costco brand of fish oil I now advise against, but at one time recommended for its low cost, did not show these same results; indeed, many patients who switched from Carlson to Costco fish oil showed a relapse in their original improvements. I do not yet know what to attribute this to in the Costco brand, but I now strongly suggest you use caution when choosing your brand of fish oil/cod liver oil.
You can find the Carlson fish oil/cod liver oil in my "Recommended Products" section; your local health food store may also carry Carlson, and usually they are very helpful in recommending any other trustworthy brands.
Finally, if you are concerned about potential mercury toxicity, numerous research projects in the United States and Europe indicate that chlorella, a type of green algae, can aid the body in the breakdown of metallic toxins such as mercury. This detoxification of heavy metals and other chemical toxins in the blood will take three to six months to build up enough to begin this process.
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