Methylmercury, a poisonous substance, is in the fish we eat. Thousand of tons of mercury are released into the air each year through pollution and waste. In the environment the mercury can transform into organic mercury, which is known as methylmercury, and accumulate in steams, oceans, water and soil.

Methylmercury also accumulates in the food chain, so each fish absorbs the mercury in other fish and organisms it eats. For this reason, larger and older fish such as shark and swordfish contain the highest levels of methylmercury.

People who regularly eat fish have higher levels of methylmercury than those who don’t. Pregnant or breastfeeding women who eat a lot of fish put their newborns at risk, as methylmercury can harm a developing baby’s brain and nervous system. Other particularly groups that are particularly sensitive to mercury exposure include children under the age of 6 years, people with impaired kidney function and people with sensitive immune responses to metals.

Both the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) have issued health advisories about consuming fish due to methylmercury contamination. The FDA recommends that pregnant women, nursing mothers and children limit their consumption of fish to 12 ounces per week and completely avoid shark, swordfish, king mackerel and tilefish (also known as golden bass and golden snapper). The EPA issued even stricter guidelines.

Particular concern has been raised about tuna since Americans consume so much of this fish. Canned tuna typically has lower levels of methylmercury than fresh tuna because canned tuna usually comes from smaller fish. However, since Americans eat canned tuna in high quantities, it could still pose a risk. It is therefore recommended that pregnant women, nursing mothers and children limit their consumption of tuna to no more than one 6-ounce can per week, as it is possible that more could result in neurological damages to babies and young children.

Methylmercury toxicity can result in paraesthesia (a tingling sensation on the skin), depression, and blurred vision. In fetuses and developing infants it can also have negative effects on attention span, language, visual-spatial skills, memory and coordination. It is estimated that nearly 60,000 children each year are born at risk for neurological problems due to methylmercury exposure in the womb.

For information about the mercury risk posed by specific fish, please see below.

National Center for Policy Research for Women & Families May 2003

Dr. Mercola's Comments:

As I have been saying for many years now, you really need to be careful with regard to fish. It is a tragedy that we have contaminated the waters and infected nearly all fish with methylmercury and other toxins. Avoid the spin that the seafood industry is putting on this issue. Fish is potentially dangerous and methylmercury is toxic. Fortunately, you do have viable options for obtaining the nutritious benefits of fish, such as regularly consuming high-quality purified fish oil like the Carlson's brand of fish oil I offer, and enjoying the absolutely delicious Alaskan wild red salmon I now offer from the one source I discovered, through independent lab-testing my team coordinated, to be mercury-free and safe. The diets of most Americans are dangerously low in omega-3, a fat essential to good health but only found in fish oil and a few other foods. I recommend, above almost any other addition to everyone's diet, fish oil and cod liver oil. I have researched and tried many fish oil brands but only carry Carlson's brand fish oil and cod liver oil as I have found it to be the most superior available. It is purified to the highest standards to be free from mercury and other toxins and is made without chemical modification and processing. Additionally, early last year we did extensive testing on fish from a company that takes the salmon from the interior of Alaska and were surprised and delighted to find that the mercury levels were virtually undetectable. If you enjoy the delicious taste and immense health benefits of some of the world's finest salmon--Alaskan wild red--but you are concerned about the mercury now found in dangerous amounts in almost all fish, then please consider trying the Alaskan wild red salmon from Vital Choice that tested safe and that I now carry. Related Articles: Finally, FDA Radically Lowers Safe Mercury Level Toxicology: How Mercury Harms Humans Diet, Not Fillings, is Your Major Source of Mercury Risk Mercury In Your Fish Learn How Mercury Is Affecting You and the Ones You Love