With many people turning from meats to fish in an effort to cut down on heart disease, lose weight and reduce the risk for obesity and type 2 diabetes there is now increased worry about heavy metal poisoning.

Most of the worry about fish and heavy metal poisoning dates as far back as 1970, when a chemistry professor in upstate New York reached into his food pantry, grabbed a can of tuna and, on a hunch, tested it for mercury. The professor found values of mercury far above U.S. food safety limits.

Tainted tuna soon captured national headlines and from this point on, the concern about toxic metal contamination in canned tuna and other fish became quite real. Back in 1970 the finding led to a recall of 12 million cans of tuna. Although the US Food and Drug Administration (FDA) deemed canned tuna safe, canned tuna still contains mercury, and sometime contains mercury in levels far above what the FDA considers safe. The FDA is responsible for the safety of commercial seafood.

In 2004 the FDA updated its mercury warning, classifying canned light tuna as low in mercury to "keep market share at a reasonable level," one agency official told an FDA advisory panel, according to transcripts of the meeting.

Tuna and Mecrcury Poisoning Risk Difficult to Access 

Making choices about canned tuna based on mercury risk is complicated because not all tuna species contain the same amount of the toxic metal, which can harm children's developing brains, effect pregnant women's fetus and cause neurological problems in adults.

Mercury Poisoning  - Albacore vs. Light Tuna

Because albacore tuna is a large fish albacore tuna tends to have higher mercury levels than smaller species of tuna, like skipjack.  While the government does caution at risk groups, like small children, pregnant women and women wishing to become pregnant who consume albacore tuna, the FDA has not issued the same warning for those who consume light tuna. This is said to be because light tuna is made mostly with skipjack, which the FDA believes has safe levels of mercury because it is a a relatively small species. The problem with this approach however is that approximately 15% of all canned light tuna actually comes from another species: yellowfin. This equates to roughly 200 million cans of yellow fin light tuna in the united States alone. While the mercury content of yellowfin varies, industry testing found the average to be equal to that of albacore.

Buyer Beware

The government has recommended that children and pregnant women eat canned light tuna because it generally contains less mercury than canned albacore does. Yet industry officials acknowledged in interviews that tens of millions of cans of light tuna sold each year are made with a species that on average contains just as much mercury as albacore.

The problem today is that many cans of light tuna are not labeled "yellow tail" light tuna, so the consumer has little chance of knowing whether the can of light tuna that they are buying is more likely to be made from tuna that has less mercury, or from yellow tail tuna which is most likely to contain mercury levels as high as the more contaminated albacore tuna. These cans can contain up to 300% more mercury than the light tuna made from skipjack tuna.

FDA Clueless on Tuna Safety?

According to a report on tuna safety published back on December 13, 2005 by Chicago Tribune reporters Sam Roe and Michael Hawthorne a high ranking official with the FDA said in an interview that the the FDA did not know the tuna industry is putting high-mercury yellowfin tuna into a product the government has explicitly recommended to groups at risk for mercury exposure.

"We do not have information on what is put in canned light tuna," added David Acheson, the FDA's chief medical officer.
When the FDA tests light tuna for mercury, Acheson said, the FDA treats each can as if it were the same. "If there are some of those tuna that have higher levels, then that will come out through the testing by means of an average," according to Acheson.

Tuna is Not All Bad

It is important to recognize that tuna, and many other species of fish contain essential macronutrients and micronutrients that the body needs for good health. For example, tuna is an excellent low fat high protein source. Tuna is also a good low-fat source of omega-3 fatty acids, which are thought to help prevent heart disease,reducing the risk for coronary artery disease, hypertension, stroke and heart attacks. Omega-3 fatty acids are also thought to reduce the risk to several types of cancers, and have also shown to help improve cognitive thinking and reduce depression, and mental decline with age. The tuna industry points to these qualities in touting tuna as a healthy meal.

Eating Tuna Safely

While it is important to recognize the mercury levels can vary widely in each can of tuna, because mercury levels can vary between species and between fish themselves the following table can provide a guideline on how much canned tuna it is safe to eat. The levels are levels established by the Environmental Protection Agency (EPA).

Tuna Industry Weighs In

At-risk consumers do not need to steer clear of gourmet canned tuna or canned light tuna in general, according to John Stiker, a former executive vice president of tuna producer Bumble Bee Seafoods and a leading tuna industry spokesman. Stiker stated that while he thought the government's consumer warnings on mercury in fish were too strict, he said the industry believes at-risk consumers should heed the advice and eat no more than 12 ounces of fish in a week.

David Burney, executive director of the U.S. Tuna Foundation, an industry lobbying group, said he feared consumers will overreact to the mercury issue.

"That would be the greatest calamity to public health in this country," Burney stated, "if we literally reached a point where everybody said, `My God. I'm so worried about eating fish. I'm just not going to eat it anymore.'"Medical experts say fish is a good low-fat source of proteins and omega-3 fatty acids, which are thought to help prevent heart disease. The industry points to these qualities in touting tuna as a healthy meal.

Bottom Line on Tuna Safety

Tuna does provide many health benefits. If eaten in moderation tuna can be a safe part of your diet. It is important to recognize however that certain  at risk groups such as  young children, women who are pregnant and women who are planning to become pregnant should be vcery conswervative when including tuna as part of their diet since they are at much graeter risk to mercury poisoning from potentially contaminated tuna. 

About the Author Jeff Behar

Jeff Behar, MS, MBA