The mercury issue, or more directly, mercury poisoning caused by consuming seafood, really started to gain attention in the 50's and 60's. It was during this time that Minamata Bay was the source of many cases of mercury poisoning due to seafood in Japan. The toxic metal plagued the local community that was consuming fish that was caught in the Bay and children were especially affected. The Bay had been polluted by wastewater and the dumping of heavy metals, especially mercury by-products. The result, a community was nearly destroyed by consuming seafood from a specific area that was polluted by the surrounding businesses in the community. This event spawned studies, specifically two main studies that took place in the Faroe Islands and Seychelles. In the Faroe study it was found that the people were eating a large amount of large ocean species such as shark and whale and children were having adverse affects, such as lowered I.Q. The Seychelles study produced different results. The children who were consuming a large amount of smaller ocean species such as snapper and mackerel were gaining 3-5 points on average to their I.Q. Why the difference? It is important to note that families in the Faroe's were eating mostly pilot whale and large sharks, while children in the Seychelles were consuming mostly tunas, jacks, and other smaller fish. So why is this important? The answer and the key to the solution of the mercury riddle can be found in the secrets unlocked by one word: Selenium.
Selenium is essential for many of the body's functions and has powerful anti-oxidant and cancer preventing qualities. It fosters growth and development of the brain, especially in children, and is important in the daily function of the brain, heart, and immune system. Ocean fish are one of the richest sources of selenium and constitute 17 of the top 25 sources found in our diet. Put it this way: without enough selenium, you risk cancer, liver diseases, autism, Alzheimer's, diabetes, brain tumors, asthma, and much more. Our bodies need selenium. Here is where the mercury comes into play: Many of the fish that we consume in the U.S. are very rich in selenium but have trace amounts of mercury. If you go to page 3 here you will be able to take a glimpse of the ratios of mercury to selenium in a list of popular fish species. Mercury binds to selenium and inhibits its use to our bodies. However, in most of the fish we consume in this country, the selenium parts far outnumber the mercury. This translates in a net gain of selenium when consuming seafood, with the resulting mercury levels being a non-factor.
One way to look at it is you have an empty basket (your body) that you fill up with apples. Those apples (selenium) come with worms (mercury) unfortunately. Lets say that you purchased 40 apples. With those 40 apples came 10 worms. The worms attached to the apples and you lost 10 of the apples, this is like mercury attaching to beneficial selenium which is a negative for your body. However, that still leaves you with 30 apples (selenium) so your body still makes out in the positive and you have plenty enough apples to make that pie! When consuming fish with traces of mercury, the mercury will attach to the selenium and render it ineffective. However, there is more selenium than mercury in most of the fish we eat, so your body will still end up in the positive when it comes to the mercury/selenium consumption ratio. The actual process that is taking place in your body is much more complex than this simple example, but the truth of the matter is that many species of fish and shellfish contain much higher amounts of selenium than mercury. This is an important ratio, because when it comes to consuming seafood, as long as you are not eating whale or large sharks, your body is profiting from the experience.
One way to look at it is you have an empty basket (your body) that you fill up with apples. Those apples (selenium) come with worms (mercury) unfortunately. Lets say that you purchased 40 apples. With those 40 apples came 10 worms. The worms attached to the apples and you lost 10 of the apples, this is like mercury attaching to beneficial selenium which is a negative for your body. However, that still leaves you with 30 apples (selenium) so your body still makes out in the positive and you have plenty enough apples to make that pie! When consuming fish with traces of mercury, the mercury will attach to the selenium and render it ineffective. However, there is more selenium than mercury in most of the fish we eat, so your body will still end up in the positive when it comes to the mercury/selenium consumption ratio. The actual process that is taking place in your body is much more complex than this simple example, but the truth of the matter is that many species of fish and shellfish contain much higher amounts of selenium than mercury. This is an important ratio, because when it comes to consuming seafood, as long as you are not eating whale or large sharks, your body is profiting from the experience.
I recommend you taking a look at Professor Nick Ralston's work to learn more about the studies done in this area. It's important for us to look past the dogma of "seafood is bad for your children, seafood can give you mercury poisoning," and really understand where this ideology came from and why it might be at odds with real, contemporary science-based research. I agree with Professor Ralston that we need a paradigm shift in this country from 'you can't eat too much ocean fish because its bad for you' to 'you can't eat too much ocean fish because you just can't get enough'.