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Fish Alert: Red light or Green light?
Susan M. Kleiner, PhD, RD, FACN, CNS
Whenever there is news about fish, my nutrition antennae tune in. Fish is a food close to my heart. First of all, I love to eat it. Fish is such an incredibly healthful food that I recommend that my clients eat 5 servings of fish each week. But the recent news about the potential for harmful pollutants in fish has put a note of caution into the praises being sung for fish.
"Tuna is one of the most frequently consumed fish in the United States. Mercury levels in tuna vary. Tuna steaks and canned albacore tuna generally contain higher levels of mercury than canned light tuna. You can safely include tuna as part of your weekly fish consumption." Cancer-causing pollutants The lead story in the news of the week column published in the January 9, 2004 edition of the journal Science was about the dangers of eating farm-raised salmon. The concern is over the levels of cancer-causing pollutants found in the flesh of farm-raised salmon. These levels are significantly lower in wild salmon. Wild salmon are born in the cold rivers that run from Alaska to California. After hatching they struggle their way to the ocean where they grow into a mature fish, returning to their natal rivers to spawn. Most of the wild salmon is caught in a short period in the late spring through the summer when the fish migrate back from the oceans to the rivers. This natural life process produces a lean, high-quality protein fish that is high in vitamins D and E and omega-3 fatty acids. Contrary to the lives of wild salmon, farm-raised salmon are raised in an industrialized and contained habitat that allows for mass production. They are fed an artificial diet made up of small fish that are ground up into fishmeal. An artificial dye is added to the fishmeal to give the fish the pinkish hue that they will not naturally develop since it comes only from consuming the same diet as wild salmon. Pollutants get into farmed salmon through the small fish used in the fishmeal. Pollutants, such as factory runoff, enter the habitat of small fish. The small fish absorb the pollutants and then are highly concentrated in the fishmeal. When the fishmeal is fed to the farmed salmon the pollutants are stored in the salmon's fat. A study examining 700 salmon from around the world analyzed them for more than 50 contaminants. The greatest difference between farmed and wild salmon was in the organochlorine compounds, and particularly the cancer-causing polychlorinated biphenyls (PCBs), dieldrin and toxaphene. Farmed salmon in Europe had the highest levels, followed by those from North America. Farm-raised Chilean salmon were the cleanest. The authors stated the concern that eating more than one meal of farmed salmon per month may hike the risk of cancer. Then they got down to specifics. You can safely eat:
These recommendations are based on how much salmon is safe to eat for the average person. Advice for pregnant women is still under debate. These pollutants can damage the developing endocrine system, immune system and brain. The compounds build up in body fat and linger there for decades-where they can be passed to a woman's fetus during pregnancy or fed to the baby through breast milk. Farmed salmon in the diets of women of child-bearing age are a definite concern. PROCEED WITH CAUTION Although the negative data look bleak, you should not eliminate fish from your diet. Based on studies examining the risk of developing heart disease, The American Heart Association recommends that people with cardiovascular consume 6 to 12 ounces of fatty fish each week to raise their dietary intake of omega-3 fats. Because of the overwhelming health benefits of fish, I recommend 5 fish meals a week to my clients. Good seafood choices that are generally low in contaminants include anchovies, sardines, oysters, crab, mussels, halibut, sole, turbot and pollock. When you eat salmon, your best choice will be wild salmon. If you choose farmed salmon, ask where it was farmed; Washington State and Chile have the cleanest fish. When it comes to tuna, there really are some important points. While generally speaking tuna steaks and canned albacore tuna have higher levels of methylmercury, the size of the fish and where it is caught makes an enormous difference. Because fish become contaminated with mercury by eating other, smaller fish contaminated with mercury, the issue becomes a factor of where the fish falls on the food chain. Large fish eat more fish. The fish that they eat are more highly contaminated due to the volume of other fish that they consume, so the concentration of mercury rises with the weight of the fish. Conversely, the smaller the fish the lower the concentration of mercury in its body. Ocean waters vary in the level of mercury contamination. Tuna caught in cleaner waters have lower levels of mercury contamination. Fishing vessels that catch tuna for the large national canners most commonly found on supermarket shelves catch very large fish: at least 40 to 50 pounds in weight or higher. They need to catch fish in the most cost-effective manner, using nets, which often takes them to ocean waters with higher levels of mercury content, since these are more accessible to them. Canned tuna from these large tuna canneries are generally high in mercury. Privately owned boutique canneries in the Pacific Northwest catch smaller fish, one-at-time by trolling, rather than in a net. The fish weigh an average of 10-15 pounds. They fish in cleaner waters because their smaller fishing vessels and different style of fishing allows them to be more flexible and maneuverable, leading to cleaner areas of ocean waters. These canned tuna are virtually mercury-free. The canning process used by these boutique canneries is also different, and results in a far superior product both in taste and nutritional content. Commercial canners cook the fish twice, resulting in a substantial loss of natural oils and juices. Vegetable broth is then added along with additives such as pyrophosphate or hydrolyzed casein. This is the commercial canners' "water-pack". The smaller canneries use a "raw pack" method of canning, which cooks the fish one time only, in the can, and all the natural juices and beneficial oils remain in the finished product. One cannery which has tested the levels of omega-3 fats in their tuna found 1.7 grams per serving, compared to 0.5 grams found in Starkist brand tuna. That is 4 times higher than the commercial brand. (See sidebar for contact and ordering information.) EAT SMART Not unlike many other issues with food, fish safety comes down to becoming an informed consumer. Fish is way too healthy and delicious to eliminate from your diet. But you have to eat smart. Follow the guidelines and avoid unsafe fish while you are pregnant or nursing, and when you feed young children. Choose the safe and clean varieties of salmon and tuna, so that you can continue to enjoy them in your diet with confidence. References:
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