Recently by Mark Sisson: Farmed Seafood: What's Safe andNutritious
In the comment section of last week’s post on farmed seafood, readers asked about the safety of regular, everyday seafood that you can find in any supermarket in the country — the popular, easily obtainable species that conventional supermarkets proudly display on ice, in frozen sections, and in cans and packets. Not crayfish, New Zealand green lipped mussels, and boutique tank raised Coho salmon, but tilapia, cod, and crab. They may not be ideal or as sexy as some of the species from last week, but they are common.
So — what’s common? To make this as objective and universal as possible, I’ll examine the ten most common seafoods consumed by Americans. As of 2009, they were, from most eaten to least eaten: shrimp, canned tuna, salmon, pollock, tilapia, catfish, crab, cod, clams, and pangasius. Shrimp I’ll cover in depth next week, catfish and clams were handled last week, and I covered farmed versus wild salmon a couple years ago, but what about the others? Which are worth eating? Which should be avoided?
Let’s take a look.
The tuna is a big predatory fish, rather high up on the food chain. As such, it tends to accumulate heavy metals present in the food chain, with mercury being the most egregious of the bunch. Mercury in tuna gets a ton of bad press, not because it’s the worst offender — that honor is shared by shark, marlin, king mackerel, and a few other niche fish — but because it’s the second-most consumed fish in the nation, and small children and unborn fetuses are particularly vulnerable to it. You don’t see toddlers clamoring for king mackerel casserole, do you? It’s also affordable, comes in convenient cans, mixes well with mayo, tastes relatively mild (as opposed to canned sardines or mackerel), and is a staple for bodybuilders everywhere. It’s essentially really easy to eat a lot of canned tuna on a regular basis, so the relatively elevated levels of mercury in tuna are problematic.
There are many species of tuna with varying mercury contents. Canned white, or albacore, tuna has more mercury on average than canned light tuna, which is skipjack, tongol, or smaller yellowfin; pregnant women and small children are advised to eat no more than six ounces of the former or twelve ounces of the latter each week. To be on the safe side, I’d suggest those groups avoid the stuff altogether and maybe eat sardines, mackerel, or wild salmon for the omega-3s instead. Both canned varieties tend to have less mercury than tuna steaks or fillets, probably because larger (and thus, more mercury-rich) fish produce better steaks, while smaller fish work better in cans. Other types of fresh or frozen tuna you might run into include ahi, also known as yellowfin (longline caught yellowfin are larger and contain higher levels of mercury, while troll/pole-caught yellowfin are smaller and contain lower levels), and albacore, which is more expensive than ahi and milder.
Bottom line: Tuna is tasty, especially the steaks, and it’s a decent source of omega-3s, but the mercury content can’t be ignored. Avoid if you are pregnant, nursing, or a small child, and don’t make tuna of any kind a daily staple. Look for troll and pole-caught tuna over longline-caught tuna, as the former tend to run smaller and accumulate fewer contaminants than the latter. Also, Atlantic tuna seems to run with higher mercury content than Pacific tuna, regardless of species, with ahi/yellowfin running lower than albacore.
Regular grocery store salmon is almost always of the farmed Atlantic variety, which happens to be the variety I already lambasted. Avoid it and stick with wild Alaskan salmon, the fisheries of which are extremely well managed and sustainable. There’s also wild Pacific salmon caught off the coasts of California, Washington, and Oregon, which I sometimes get at local farmers’ markets. I still like Alaskan sockeye salmon best, even the frozen stuff, but they’re all worth eating.
Bottom line: Eat wild salmon, which is a great source of protein, omega-3s, and selenium. Avoid farmed salmon (unless it’s that fancy tank-raised Coho salmon I mentioned last week).
Tilapia is fast-becoming a consumer favorite, for a few reasons. It’s cheap to raise. It isn’t carnivorous, meaning farmers can use corn and soy pellets without springing for comparatively pricey fishmeal. The fish’s vegetarianism also endears tilapia to those who worry about the state of wild fish stocks (a concern that, though I also share it, must be meted out against concerns about corn and soy subsidies). Parents and schools love it because it’s bland enough to feed to picky kids with dysfunctional industrial taste buds (just add ketchup). Plus, it’s technically fish and therefore “healthy,” meaning heart disease patients and hospitals can satisfy the AHA’s recommendations that folks eat at least two servings of fish a week by eating a few inexpensive, inoffensive tilapia fillets.
Don’t tell them that they aren’t getting much omega-3 out of it, though. According to the USDA nutrient database, tilapia contains very few omega-3 fatty acids at just 200 milligrams per 100 gram serving. In fact, that same 100 gram portion contains very few fatty acids in general — 800 mg saturated fat, 700 mg monounsaturated fat, and 200 mg omega-6 polyunsaturated fat. According to a recent study, however, tilapia has far more omega-6 than the database would suggest, with most of it coming as arachidonic acid (which admittedly isn’t as problematic as excessive dietary linoleic acid). Overall, it’s a lean fish, akin to chicken breast. I find it pretty inoffensive if uninteresting. It’s low in contaminants, inexpensive, and melds into any dish without asserting itself. Good as a cheap source of protein, but not as a source of unique marine nutrition.
Tilapia comes frozen, whole, live, or in fresh fillets. Most frozen tilapia comes from China or Taiwan, while fresh comes either from US or South/Central American farms. Live tilapia are US farmed, and pretty rare (go to Asian supermarkets for these). Asian tilapia is inexpensive, but the Monterey Bay Seafood Watch recommends against eating it very often due to poor farming conditions. Stick to US farmed tilapia if possible. South/Central American also gets good marks. Tilapia farming is fairly intensive, and caged tilapia raised in freshwater ponds can pollute surrounding waters, but standards seem to be changing for the better.
Bottom line: American and S/C. American tilapia is a safe source of protein, but it’s not a good source of omega-3s. If environmental impact matters, buy American. Avoid Asian imports (at least until the aforementioned farming standards are adopted worldwide).