Millions of people make fish, a low-fat, vitamin-rich source of protein, part of their diet for nutritional reasons, or simply because they enjoy the taste. ut eating a diet high in fish is becoming increasingly controversial, as some studies tout the benefits of eating fish while others argue that the mercury in fish outweighs any of the potential benefits.
Last week, there was good news for aging fish lovers: according to a study by Rush University Medical Center in Chicago, eating fish once a week was associated with slower rate of 10 percent per year cognitive decline in adults over 65. But in 2002, Research Institute of Public Health at the University of Kuopio in Finland found that Finnish men with the highest concentrations of mercury also had the highest death rates from cardiovascular disease.
Larger fish, such as tuna and swordfish, that have lived longer tend to have the highest levels of mercury because they had more time to accumulate it, absorbing from the polluted water and from eating algae and other fish. People with elevated mercury levels can experience what's called mercury poisoning or mercury toxicity, which can cause physical and neurological problems. No government agencies track cases of mercury poisoning, so it's difficult to determine the breadth of the problem.
A woman's high level of mercury is thought to affect the neurological development of her unborn child, who would be at risk for learning disabilities, poor motor function and seizures. Mount Sinai Center for Environmental Health warned in an article published in "Environmental Health Perspectives" this past February warned that the projected 300,000 and 600,000 American children born each year with a reduced IQ due to mercury poisoning will end up costing the U.S. $8.7 billion in lost earnings.
The Food and Drug Administration and Environmental Protection Agency advises women and young children not to eat shark, swordfish, king mackerel or tilefish -- fish all high in mercury. Federal guidelines further advise that women and young children can eat up to 12 ounces a week of fish and shellfish that are lower in mercury, such as canned light tuna (which is lower than canned white albacore or tuna steaks), salmon and shrimp. These guidelines were developed based on a few studies, but especially what is referred to as the Faroe Islands study. A study by the Harvard School of Public Health published in February 2004 studied 1,022 mothers and their children there and found that the electrical signals in the brains of children exposed to mercury aren't transmited as quickly as in unexposed children. It also appeared that mercury weakened the children's heartbeats.
But a study in the Seychelles conducted by the University of Rochester, which also looks at children whose mothers ate a lot of fish, just recieved funding to monitor their subjects twice more. So far, the researchers have not yet witnessed any adverse effects in these children.
Mercury Poisoning from Fish
Dr. David Perlmutter, a neurologist in Naples, Fla., said he thinks women of childbearing age should not eat any fish.
"We discover three or four people each week with mercury toxicity -- everything from kids with hyperactivity to elderly people with cognitive difficulties," he said.
Perlmutter, medical director of the Perlmutter Health Center in Naples, Fla., and author of "The Better Brain Book," said most people don't even think of mercury when they see health problems.
"Most of the people we end up treating are those in whom the idea of mercury hasn't been explored," he said. He diagnoses his patients by first blood test, and then confirms it by giving them a chelating agent and testing their urine.
"Usually if people had issues relating to mercury, they improve right away," he said. "Generally, people in their 20s and 30s have wonderful recovery and we see it every day."
Even though mercury-based tooth fillngs and vapors from industrial pollution can be culprits for mercury toxicity, Perlmutter said most of his patients get it from fish.
"I think more and more it's from fish, because the levels are getting higher and higher, and dentists are using less and less mercury, not because they're concerned about the mercury, although they should be, but because aesthetically people prefer white fillings," Perlmutter said.
He said he still thinks people should eat fish "but much less than they do." He recommended people eat fish that are low in mercury, such as tilapia and wild salmon, about twice a month.
Then there is the fear that a woman's high level of mercury can affect the neurological development of her unborn child, who would be at risk for learning disabilities, poor motor function, seizure disorders and cerebral palsy. Women in their child-bearing years, he added, shouldn't eat any fish.
But Philip W. Davidson, who has spent the 15 years studying children in the Seychelles born to mothers who consume high amounts of fish and hasn't seen any adverse effects, thinks people shouldn't be so quick to cut fish from their diet.
Davidson, a professor of pediatrics at the University of Rochester, said he thinks there is not enough evidence for Americans to be cutting fish entirely out of their diet based on mercury fears.
"Our own feeling is that warning people not to eat fish has adverse effects of its own because fish is very nutritious," he said.
Davidson has been working on a study conducted by the University of Rochester Medical Center that suggests that eating fish -- and therefore consuming mercury -- during child-bearing years and pregnancy may not be problematic after all. In 1990, Davidson along with other researchers began studying children in the Seychelles, an archipelago nation off Africa's eastern coast, where women typically eat 12 meals of fish per week -- even when they're pregnant.
"The hypotheisis has always been that there adverse effects from consuming fish during pregnancy," Davidson said.
The mothers -- who predominantly eat karang or jack but also regularly consume tuna, red snapper, parrotfish, mackerel, kordonye and grouper -- have mercury levels far higher than the average American. The Seychelles women in the study averaged six parts per million, while the average American has one part per million.
"Up to now, six times we've seen these kids, and we've been unable to confirm adverse effects," Davidson added.
The researchers have measured the functioning of 700 children based on 64 different "endpoints" including cognitive abilities, perception, social skills and memory. The oldest children in the study are 15, as they were born when the study began.
The study recently recieved funding to visit the Seychelles and measure the children twice more.
Mercury Affects People Differently
Perlmutter cautions against people thinking they are safe to eat all the fish they want based on this study.
"To make a global statement that high levels of mercurty are safe based upon this study would be unfair," he said. "Some people are affected at lower levels."
"Lots of people are walking around with high levels of mercury," he added. "People tolerate different levels."
But even those who tolerate higher levels, would be better off without it, Perlmutter contends.
"Where could they be in terms of functioning if they didn't have the mercury?" he says.
But so far, the children of the Seychelles appear to be functioning just fine. And Davidson said that he didn't believe the entire group he studied could be immune to effects of mercury because they are a diverse population.
"It's not likely," he said. "People have immigrated from all over -- it's a fairly young country."
"At this time, EPA and FDA have no current plans to revise the advisory," said Jim Pendergast of the EPA's Office of Water. "However, as science continues to advance, there is always a possibility to revisit the advisory."
Daphne Zuniga's Story
Fish had become large part of Dapne Zuniga's diet, who was eating "your average Hollywood stay in shape diet, a ton of fish and low carbs."
"I was eating tuna four times a week," said Zuniga, who stars in the ABC Family series "Beautiful People." "I would go out for sushi and think 'oh great, at least we're not going for Italian, with all the oil and carbs.' "
She was also experiencing an array of mysterious health problems. In addition to severe headaches, she had cramping in her fingers and feet. She also frequently felt "a sort of tingling, as if someone was ticking you, all up and down my body and on my legs, and it got more and more pronounced," she said.
Mercury poisoning can also affect your cognitive functioning, and Zuniga, 43, found that she was unable to remember her lines -- even if she had learned them the night before.
"I had crying spells, lowgrade depression, loss of memory, and brain fog, which is where I would be talking to you and I would get disoriented," she said.
Then, in February 2004, after eating sushi four times in one week, Zuniga broke out into an itchy rash all over her body that landed her in the emergency room. She saw all sorts of doctors, but no one mentioned mercury poisoning.
In October, Zuniga asked her doctor about whether she could have mercury poisoning after she read that an oft-quoted statistic from an EPA study that one in six women of childbearing age has elevated mercury levels. Sure enough, the level of mercury that showed up in a blood test revealed that she was significantly over the safe level.
Road to Recovery
Zuniga immediately stopped eating seafood, and has no plans to start again.
She also embarked on treatment to rid her body of the mercury. Her doctor gave her regular chelation injections, which helps the body excrete heavy metals through urine. She also took supplements she found at the health food store that contain natural chelating ingredients. It's important to note, however, that taking chelating supplements on your own and not under a doctor's care can be dangerous.
Six months later, her symptoms of cramping and tingling were gone. Her mind was much clearer and her mood had improved.
Zuniga still drinks shakes with protein powder that contains glutathione, a protein that binds to toxins like mercury and helps the body get rid of them.
Despite her ordeal, Zuniga still encounters her share of skeptics.
"People don't want to acknowledge the effects of mercury will say things like 'oh that's our society, we're so overstimulated,' " she said.
"I have experienced the difference between the disconnected brain fog and the clarity," added Zuniga, who is working with the Turtle Island Restoration Network, a California environmental group, on their campaign to inform the public about mercury. Right now, this group is trying to get the national supermarket chain Safeway to post a signs in all of its supermarkets warning about the dangers of mercury in fish.