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.
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.