Fish or foul: How healthy is seafood?

It appears that consumption of fried fish and fish burgers did not raise their Omega-3 fatty acid levels.  The researchers were not sure, however, if the fatty acids were destroyed by frying or if the lower Omega-3 levels were due to the fried fish and fish burgers being cod and pollock, which are lean fish and have fewer Omega-3 fatty acids to begin with. 

Now for the downside.  What should we worry about when it comes to fish consumption? 
The chief concern is that fish may be contaminated with a number of toxins, and when ingested in large quantities, these can adversely affect our health.  And even small amounts may cause developmental injury to a fetus or child. 

Methyl mercury gets into our system through the consumption of fish and sea mammals.  Some of this mercury toxin arises naturally from gas that evaporates from the earth’s soil and water, as well as from the emissions of active volcanoes. But it’s not all nature’s fault; our atmosphere has now been inundated with increasing amounts of mercury gas, produced from coal burning sources and other industrial processes. This mercury vapor then gets into the rain and soil and continues to circulate for years. It enters both nearby and distant bodies of water, attaches to aquatic sediment and microorganisms such as algae, and is converted to methyl mercury.  Now it’s in the food chain.  It’s eaten by little fish; the little fish are eaten by bigger fish, and so on.  The more predatory, the older and the bigger the fish, the higher its concentration of methyl mercury.  Once we eat the fish, we metabolize its methyl mercury content slowly and poorly.  It’s stored in our fat, and it can take months, even a year, to clear. 

How dangerous is methyl mercury to us or to our offspring?
If adults consume high amounts of very “mercuried” fish, they can develop neurological symptoms such as numbness, pain, vision and balance problems.  Elevated blood pressure and an increased risk of heart attack have also been correlated with mercury toxicity. 

The chief concern, however, is that the fetal, infant and childhood nervous systems, as well as that of the elderly, may be especially sensitive to methyl mercury.  A recent article published in the Journal of the American Medical Association seemed, however, to give some reassurance for older adults who want to eat fish for their heart health.  Researchers examined 475 Baltimore residents, aged 50 to 70, and found that the mercury levels in their blood were not associated with the outcomes of neural behavioral test scores.  They then theorized that the growing population of aging baby boomers were not at risk for cognitive impairment if they consumed fish for its “well known benefits.” 

Our chief concern remains, however, that harm can accrue to the fetus and/or a young child as its nervous system develops.  Methyl mercury, in levels that normally would not harm an adult, can pass freely through the placenta and breast milk and destroy developing brain cells. The FDA has recommended that women who may become pregnant (remember, it can take a year to clear existing mercury levels) as well as those who are pregnant or nursing, avoid eating fish with high mercury content.  And since all children’s brains are developing and hence more vulnerable, they too should abstain.  The safety of canned tuna (the most consumed fish) and its mercury content has also caused concern.  It turns out that albacore tuna has more mercury than other forms of tuna. 

The current FDA advisory for pregnant or nursing women states the following: 

Do not eat:
Shark
Swordfish
King mackerel
Tile fish

No more than six ounces (one portion) per week:
Albacore tuna

Up to twelve ounces (two portions) a week:
A variety of fish and shellfish
Shrimp
Canned light tuna
Salmon
Pollock
Catfish

Meanwhile, you should also check local advisories about fish. If in doubt, do not eat more than six ounces (one portion) per week.

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