Ocean Fish is Health Food

Concerned about Mercury in Fish? Health messages seem to conflict—encouraging us to eat more seafood for a healthy heart but at the same time to avoid seafood that contains mercury. Let’s consider the evidence.

Mercury in Fish advisories. The US Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA) issued a joint advisory in 2004 specifically for pregnant women and young children to limit their exposure to methylmercury from eating certain types of fish. There are no advisories for the rest of the population. It’s important to know that a 10-fold safety factor is built into this advisory. The advice is to eat no more than 1 meal of tuna steak per week. What this means is that there is no scientific evidence of harm from eating 10 meals per week. The EPA/FDA advisory recommends that all fish consumption be limited to no more than 2 meals per week regardless of mercury content. But, this recommendation is contradicted by many other studies and health guides.

Fish is part of a healthy diet and lifestyle. Numerous studies have demonstrated the health benefits of eating seafood. A long-term and very large study in England evaluated about 8,000 children born to mothers that ate fish during pregnancy. This study showed for the first time that children of women that limited fish consumption to 2 meals of fish per week or less fell into the lowest 25% in verbal IQ and other standard testing scores. This study raises serious questions about the EPA/FDA recommendation and the possibility that the advisory is causing women to avoid the health benefits of seafood and may actually be harming their children. The average seafood consumer in the US eats less than 1 fish meal per week. This study indicates that we should be eating more, not less seafood.

What evidence is the EPA/FDA advisory based on? The Faroe Islands Study detected a statistical correlation between lower developmental testing scores of children and their mothers’ exposure to dietary mercury during pregnancy. However, 90% of the mercury in the diet was from pilot whale meat. We do not eat whale meat in the US, and pilot whales are not fish. The Faroe Islands Ministry of Health immediately warned women to avoid eating pilot whale meat during pregnancy but to continue to eat fish, because of the need for essential long-chained omega-3 fatty acids for the developing brain. However, the EPA/FDA chose to make the fish consumption advisory for pregnant women based on the pilot whale diet study because they had no evidence of mercury harm from actually eating fish.

What about real fish eaters? Seychelles Islanders are heavy fish eaters. In the Seychelles Islands Study, women ate 12 meals of ocean fish per week during pregnancy. No evidence of harm could be found after regular testing of their children up to the age of 9. EPA and FDA could not use this study to develop the advisory because no harmful effects were found that are needed to assign risk. Some of the children with the highest mercury exposure had higher testing scores. Does mercury make you smart? No, but something else in fish does. In this study (as for most people) mercury accumulation is merely an indicator of ocean fish consumption. Finding elevated hair mercury levels is not the same thing as mercury poisoning.

So what might explain the outcomes of Seychelles Islands Study? Ocean fish contain health promoting nutrients. We know that long-chained omega 3 fatty acids are essential for brain development in children, and brain function and heart health later in life. But ocean fish are also known to be rich sources of selenium, an essential mineral nutrient that has critical anti-oxidant functions in the brain. USDA reports that 17 of the top 25 food sources of selenium in the American diet are ocean fish.

Selenium-mercury interactions. As early as the 1960’s researchers first reported that selenium and mercury bind together strongly and form an inert complex, mercury selenide. When selenium is in excess of mercury in foods, the symptoms of mercury poisoning are not present. In 1972, a study published in Science reported that yellowfin tuna protected against mercury toxicity when added to the diet of animals fed artificially high levels of mercury. Further studies into the early 1980’s concluded that the rich levels of selenium and selenium’s mercury neutralizing effects explained why we still have not seen an outbreak of mercury poisoning from eating open ocean fish. Ever. Anywhere. The Center for Disease Control and Prevention does not have reports of confirmed cases of mercury poisoning on record from eating ocean fish.

The importance of Selenium and Mercury ratios in fish. The protective effects of selenium on mercury toxicity have been demonstrated in every animal model tested to date. For this reason, the selenium to mercury ratio in foods is the most important factor to consider, not just the mercury content alone. Hawaii’s open ocean fish are the first to have been evaluated for selenium to mercury ratios. A 2007 study in Hawaii documented that the 14 most common open ocean fish contained an excess of selenium over mercury. Only the mako shark, rarely caught or eaten in Hawaii, contained more mercury than selenium. Most of Hawaii’s fish including tuna and billfish are a good source of health-promoting selenium and more likely to help prevent mercury toxicity than contribute to it.

What is the difference between pilot whale meat and ocean fish? It turns out that Faroe Islands’ pilot whale meat contains not only much higher mercury levels than our ocean fish, but also contains much more mercury than selenium. While Hawaii’s ocean fish are more likely to prevent mercury toxicity, pilot whale meat is more likely to cause it.

So is mercury in fish dangerous or not? The only record of outbreaks of mercury poisoning from eating seafood occurred in Minamata Bay and later in Niigata Japan in the 1950’s and 1960’s. But these outbreaks were caused by extremely high levels of mercury accumulated in fish and shellfish and very high seafood consumption rates. The source of the mercury in both cases was uncontrolled mercury pollution from chemical manufacturing plants and NOT natural levels of mercury like those found in open ocean fish. We now know that in these tragic cases, mercury levels in the seafood far exceeded the selenium levels. Consumers should be concerned about any fish that may contain mercury from industrial pollution because levels may exceed selenium levels and present a potential health risk. Our focus of concern should shift from open ocean fish that contain natural environmental background levels of mercury to freshwater fish in the vicinity of mercury pollution such as coal fired power plants, and gold and mercury mining, that may contain very high levels of mercury exceeding selenium.

Ocean fish is health food. The overwhelming evidence continues to confirm that the known health benefits of fish consumption far outweigh the adverse effects of the levels of mercury found in open ocean fish. At this time, the real concern is that women are being scared away from eating fish during pregnancy by the EPA/FDA advisory and that they may be depriving their children of essential and health promoting nutrients. The question should be…

“Are you getting enough selenium and omega 3’s?”