Recently by Mark Sisson: The Scattered Mind: Finding Focus in a World of Distractions
Learning about the various types of aquaculture setups is interesting and useful, but we’re ultimately interested in whether they can produce safe, nutritious, affordable seafood. Wild seafood can be pricey, unavailable, and of questionable merit or sustainability. Certain wild species are definitely worth pursuing — Alaskan salmon, sardines, herring, mackerel, to name a few — but there are environmental (overfishing, collateral damage to other important species, structural damage to the marine environment) and health (accumulation of heavy metals like lead and mercury, polychlorinated biphenyl/PCB, dioxin) issues that the conscious fish eater must stay abreast of. Healthy and safe farmed seafood, then, would be a welcome alternative, if it’s out there.
Okay. Let’s get down to it.
Which farmed seafood is safe to eat? Is there anything like grass-fed beef or pastured chicken available in scales or shells?
As a whole, farmed shellfish, when compared to wild shellfish, are very good bets for the simple fact that both lead very similar lives. Every marine shellfish, whether farmed or wild, spends its life in the ocean attached to something — rocks, a rope, a pillar, coral, the ocean floor. The only difference is that farmed shellfish are deliberately placed there by farmers, while wild shellfish are distributed by the hand of Poseidon (actually, the Nereids do all the work while he gets the credit, but such is the life of a sea nymph). Most importantly, they all use the same sea water. They all obtain their food by sifting through that same sea water. Farmers don’t have to provide food. They’re not scattering corn and soy across the water, because it would be a waste. Shellfish, you see, are filter feeders.
That brings me to the primary concern people have with shellfish, or mollusks. “Filter feeder” just sounds bad. When we hear the phrase, we think of physical filters, the type we use in everyday life, like an air filter in a car engine or a coffee filter. Physical filters accumulate the undesirable stuff and are either cleaned, tossed, or recycled. They certainly aren’t eaten. Well, shellfish aren’t physical filters. They process toxins. They render harmful compounds inert and expel them. It’s true that if they reside in waters rich in heavy metals and industrial contaminants (like PCB or dioxins), some of those metals and contaminants will show up in the meat, but that’s true for any sea creature. In fact, shellfish are some of the safest, least contaminated farmed seafood whenever they’re tested.
They’re also extremely nutritious. Shellfish are extremely rich in vitamins and minerals. Three measly ounces of raw Pacific oyster (the bulk of which are farmed) gets you over 100% of the RDA for zinc, copper, selenium, B12, and half of the RDA for iron. For every 1.5 g of omega-3 they provide, just 0.1 g of omega-6 comes along for the ride. Bay scallops are high in magnesium and selenium, clams are good for iron, copper, and selenium, abalone for selenium and magnesium, while the lowly sea snail gives massive amounts of magnesium (200 g of snail gives over 500 mg of magnesium; maybe they’re counting the shell?) and good amounts of selenium.
Lately, a favorite of mine has been the green-lipped mussel, shipped frozen from New Zealand. I initially got interested in this particular variety because of the research into green-lipped mussel extract as a canine arthritis treatment. Buddha isn’t arthritic, but I find this stuff fascinating. I’ve had some arthritis in the past, and it never hurts to cover all your bases ahead of time. Besides, mussels are delicious and nutritious. The NZ green-lipped mussel gets good marks from the Monterey Bay Aquarium Seafood Watch, owing to its farmers’ sustainable practices: attach young mussels to ropes, lower the ropes into the ocean, and let nature take its course. I was also surprised to see the amount of omega-3s in these things. According to one study, 100 g of them (flesh only, no shells, frozen) comes with 1.5 g of DHA, 1.26 g of EPA, and not even half a gram of omega-6 fats.
Farmed shellfish are safe and just as nutritious as wild. If you’re worried about contamination, check the source and do some research. Always buy still living shellfish (dedicated seafood markets or Asian grocers are great places to buy live shellfish) where you can. If frozen is available, check the label and avoid imports from China, where waters are more likely to be heavily polluted.
The channel catfish is a bottom feeder, which sounds bad but doesn’t have to be. They’re just rapacious eaters, or foodies, even — a bit like hogs. If you feed them garbage and raise them in polluted waters (like occurs in Chinese catfish farms — check your labels!), you can’t really blame the species.
Farmed catfish is far fattier than wild catfish while being lower in omega-3s, but catfish has never been prized for its omega-3 content. While farmed catfish does have more omega-6 than wild — about 1.5g for every 100 g fillet, compared to around 0.22 g — most of the “added” fat in farmed is monounsaturated (5.7 g/100 g) and saturated (2.5 g/100 g) (PDF). Not too bad, especially if you compare it to something like conventional skin-on chicken thigh, which gives you 4 g saturated fat, 6 g monounsaturated fat, and 3 g omega-6s for a 100 g serving. US catfish farmers may not be feeding their fish pristine, natural diets of bottom-dwelling crustaceans, insects, and small fish, instead opting for combinations of meat and bonemeal, bloodmeal, fishmeal, various seedmeals, corn, soy, wheat byproducts, and vitamin/mineral supplements, but catfish seem to turn out decent fatty-acid profiles despite the departure from ancestral tradition (PDF).