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Not all Fish are Created Equal – And Then There’s Tilapia

Posted on | July 28, 2008 | 1 Comment

Fastest growing seafood choice has doubtful benefits

Eat fish, it’s brain food…Don’t it fish, it might have mercury and PCBs…Do eat fish, it’s high in protein and low in saturated fat…Don’t eat fish, it may be imported from China, laden with parasites and pesticides.  The news on fish is as confusing as any public health message today.  The dual discovery that methyl mercury in fish is unhealthy but that fish oils  (omega-3 fatty acids) are very healthy has led to arguments among normally very reasonable scientists about how much fish to eat.  The discussion needs to shift from "whether" to "which" – it’s not whether to eat fish, but which fish are safest and healthiest to eat.

It turns out that some species like swordfish are a bad deal for your body because they are low in omega-3 FAs but are high in mercury.  Salmon is just the opposite and so is generally a good choice, especially if you can find it in your budget to eat wild salmon . They are lower in dioxins than farmed salmon.  In between, the extremes of swordfish and salmon there are lots of common fish like sushi and shrimp and canned tuna and fish sticks – these all have their own ratio of omega-3 FA to methyl mercury.  Fish advisories issued by state agencies are starting to pay attention to this and offer species-specific consumption advice (e.g., eat more canned light tuna than canned white tuna because the white tuna is 3 times higher in mercury).  The Connecticut Dept of Public Health has a very helpful flyer showing which species to eat how often. 

Of course we know that fish are more than just good oils and bad contaminants.  There are other beneficial nutrients such as protein, iodide, selenium and iron.  But recent evidence on tilapia raises questions about another ingredient in fish, the polyunsaturated omega-6 FAs. Researchers at Wake Forest University have called tilapia worse for your health than hamburger because of its high omega-6 content.  There is evidence that omega-6 FAs can block the beneficial effects of omega-3 FAs and lead to greater stress and inflammation and higher risks of diabetes and heart disease.  Remember, we are not talking about saturated fat in meat here, the longstanding villian of our blood vessels.  Now we are splitting hairs within the category of supposedly good lipids, the polyunsaturateds.

So, why have the Wake Forest researchers targeted tilapia?  They found that farmed tilapia are raised on a corn-meal based diet, which leads to them be high in omega-6  and low in omega-3 FAs.  Their cheap diet also makes them inexpensive to buy.  In contrast, salmon are raised on fish meal and so are high in omega-3 FAs, low in omega-6, but are a more expensive purchase.

So, should America give up farmed tilapia?  Hardly.  That would also mean giving up salad dressing and cooking oils, both rich in omega-6 and low in omega-3 FAs.  However, we should be concerned if tilapia becomes so popular because of its cost that it becomes a staple food.  People need to get omega-3 FAs and fish are pretty much the only option.  We don’t want to waste all our fish-eating on a species that contains so little omega-3 and such a bad fish oil ratio – it’s something like filling up your diet with empty calories.  Farmed tilapia is low in contaminants and does have other fish nutrients, so an occasional tilapia meal makes sense.  But mix in some salmon, herring, trout, shellfish, and light tuna. And taking an omega-3 FA supplement every day is a good way to make sure you are getting enough of this critical nutrient, regardless of how much tilapia you may choose to eat.

Comments

One Response to “Not all Fish are Created Equal – And Then There’s Tilapia”

  1. Joseph White
    May 18th, 2010 @ 12:32 pm

    I am just concerned about the main source of Omega 3 which is the liver of fish. as you can see, fishes can accumulate mercury and pcb. ‘,”

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