SEAFOOD.COM NEWS by John Sackton - Recently there has been some discussion on the seafood list (for seafood technologists and professionals) about mercury in seafood. We are reprinting this story from December, which discusses the issue in light of Consumers Union's December article on mercury in seafood.
Consumers Union has its facts wrong. In a new report, they again warn Americans not to eat canned tuna because it contains low levels of methyl mercury. Unlike hurting a particular manufacturer, in this case their widely disseminated report on canned tuna threatens to harm Americans' health.
How could they get things so wrong? First, they ignored the science and regulatory information available to them. Second, the accepted a discredited narrative about mercury in diets that has begun to be challenged by a number of scientists.
Third, they confused EPA and FDA threshold targets on mercury, and in the process, failed to give warnings where such warnings may in fact be important.
Consumers Union tested 42 samples from cans and pouches of tuna bought in the metro New York area.
They found that 100% of their samples were below the limit of mercury that the FDA considers acceptable in American diets, i.e. 1 part per million.
Mercury is a naturally occurring element, that has been present since the formation of life on Earth, and is primarily released into the atmosphere today through volcanic eruptions and coal burning powerplants.
Some of this mercury accumulates as methyl mercury in fish. The FDA has recommended that women and young children may eat up to 6 ounces of light tuna per week. Scientific panels advising the FDA are now suggesting that the FDA advice on mercury, particularly for pregnant women, must be updated because it is contributing to sub-optimal outcomes for children.
Here is what Consumers Union says:
Consumers Union's fish-safety experts continue to suggest a more cautious approach. Because of its potential effects on fetal development, Consumers Union advises pregnant women, as a precaution, to avoid eating tuna. Consumers Union further advises that children who weigh more than 45 pounds limit their intake to 12.5 ounces of light tuna or 4 ounces of white tuna per week; and children who weigh less than 45 pounds limit their intake to no more than 4 ounces of light tuna or 1.5 ounces of white tuna.
'Canned tuna, especially white, tends to be high in mercury, and younger women and children should limit how much they eat. As a precaution, pregnant women should avoid tuna entirely,' said Dr. Urvashi Rangan, director of technical policy, at Consumers Union, nonprofit publisher of Consumer Reports.
This is simply regurgitation of old arguments that have become scientifically discredited.
The key to newer scientific understandings is that the way methyl mercury is harmful in the body is that it can replace the metabolic activity of selenium in cells, with deleterious effects. In order for this to happen, a diet must have an imbalance where selenium is restricted or absent, and methyl mercury is high. In the scientific literature, this condition was met in the mercury poisoning event in Minamta Japan, and in a contamination of wheat flour with Mercury in Iran, and in the Faroe Island population that consumed significant amounts of whale meat along with their fish diet.
But in other studies, such as the long term study in the Seychelles where women eat a hugely concentrated fish diet and have no negative outcomes at all, and in the UK, where longitudinal studies have shown that eating fish leads to higher IQ development in Children, the key factor has been that the intake of selenium from seafood was much higher than the intake of methyl mercury.
The chart below shows that yellowfin and skipjack tuna have some of the highest positive ratio's of selenium to mercury of any fish. Albacore tuna also scores high.
Data presented by Nick Ralston, Univ. of N. Dakota, at the Seafood and Health Conference, Melbourne, Australia 2010
Nick Ralston is one of the leading researchers in the world on the biological effects of selenium, and the interaction of selenium and mercury.
Chemically selenium is a million times more potent binding with mercury molecules than anything in the human body. When a diet is higher in selenium intake than in methyl mercury, the selenium appears to bind and neutralize the mercury. The only time when mercury is able to act as a toxin is when there is not enough selenium in the diet, and in this case, says Ralston, the metabolic pathway changes and the body attempts to use mercury molecules to compensate for its lack of selenium.
The fact is that Consumers Union has rehashed a study they did in 2006, and has not updated their approach with any of the current science.
Why does this matter?
The problem, from a public health perspective, is that American diets are woefully short of DHA and Omega-3 fatty acids, essential to brain and eye development. The reason is that over the past 50 or 60 years, the American diet has changed from a ratio of approximately 3 to 1 for Omega 6 vs. Omega 3 to about 25 to 1 Omega 6 vs. Omega 3. The Omega 6 in the diet comes from vegetable oils. Omega 6's also compete with Omega-3's in the body, and a imbalance in the diet has been clearly linked to increased heart disease and inflammation. Increasing the ratio of Omega 3 and DHA both leads to less heart disease, and better brain and eye development.
Because fish and seafood is one of the principal dietary sources of omega-3 and DHA, when women, especially pregnant women, are given false advice about mercury, the impact is to scare them away from eating fish. In most cases, this makes their diet worse, and according to some studies, leads to worse outcomes for their children who lack the eye development and brain development that children have from mothers with adequate intakes of Omega 3 and DHA.
Consumers Union is perpetuating a public health fraud on Americans, by focusing so narrowly on a toxicology that they do not understand.
There is no excuse to accept this report or allow it to stand unchallenged.
Consumer Reports' tests, conducted at an outside lab, found:
*Every sample contained measurable levels of mercury, ranging from 0.018 to 0.774 parts per million.
This means that every sample tested was below the FDA approved actionable limit.
*Samples of white tuna had 0.217 to 0.774 ppm of mercury and averaged 0.427 ppm. By eating 2.5 ounces (about half a can) of any of the tested samples, a woman of childbearing age would exceed the daily mercury intake that EPA considers safe.
The EPA estimate is based on different parameters than the FDA. The EPA is primarily concerned about intake from personally harvested fresh water fish. Because many fresh water fish do not have nearly the levels of selenium found in salt water fish, there is some concern among scientists that the exposure from low-selenium, high methyl mercury lake fish could be harmful. Consumers Union does not make nor understand this distinction.
Consumers Union makes some acknowledgment of the health benefits of seafood.
They say fish are rich in protein, vitamin D, and omega-3 fatty acids. Omega-3s reduce the risk of heart attack and stroke and might also elevate mood and help prevent certain cancers, cognitive decline, and certain eye diseases. During pregnancy, omega-3s might help in developing the fetus's brain and visual system.
'Fortunately, it's easy to choose lower-mercury fish that are also rich in healthful omega-3 fatty acids,' Dr. Rangan said. 'That's especially important for women who are pregnant or might become pregnant, nursing mothers, and young children, because fetuses and youngsters are still developing their nervous systems and are therefore at particular risk from methylmercury's neurotoxic effects.'
Some popular seafood, including clams, Alaskan salmon, shrimp, and tilapia, contain relatively little mercury and are better choices. Other lower-mercury choices include: oysters, pollock, sardines, Pacific flounder and sole, herring, mullet, and scallops.
This advice would actually be more complete if it was changed to say that consumers should strive to choose fish where the ratio of selenium to mercury is high; and avoid fish where the ratio is lower than 1. Under this scenario, there is reason for caution about levels of consumption of certain sharks, but other than that, all women should be encouraged to be eating more seafood.
Research has shown that mercury warnings, and particularly discussions by doctors advising women to not eat seafood due to concerns about mercury, are actually harmful to public health.
Our history is replete with ideas about diet and health that at one time were widely accepted, but have subsequently been proven to be damaging, and in fact were having the opposite effect of what was intended.
The scientific community is beginning to understand that the warnings about mercury and seafood are in this category, and the sooner better understandings are communicated, public health will improve. Consumers Union, by ignoring this new science, has done a serious disservice to America.
John Sackton, Editor And Publisher Seafood.com News 1-781-861-1441 Email comments to jsackton@seafood.com
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