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Fish: Landing the Healthiest Choices

By Dr. Marisa Weiss on April 1st, 2011 Categories: Uncategorized

Are you hearing mixed messages about fish? One article says that fish is good for you and another talks about the risks of eating fish. It’s enough to confuse anyone. On one hand, eating fish can help reduce the risk of heart disease and promote brain development, and there’s some research that suggests certain types of fish may even help reduce the risk of breast cancer. On the other hand, some types of fish contain high levels of mercury and other contaminants such as dioxins and PCBs (polychlorinated biphenyls).

Despite this conflicting information, no experts call for you to completely avoid eating fish. By carefully choosing which types you eat, fish can remain or become an important part of your diet. Research shows that just the protective heart  benefits of eating fish make it well worth eating. But whether or not eating fish helps protect breast health is harder to determine.

Fish benefits: EPA, DHA, and other nutrients. Two omega-3 fatty acids, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), are a big part of what makes fish healthy food. Besides reducing the risk of heart disease and stroke, some studies done in animals suggest that EPA and DHA may stop the growth of breast cancer cells. But it’s not clear if these protective effects happen in people. And it’s also not clear how much or what kind of fish has to be eaten for these potential effects to happen. Levels of EPA and DHA vary quite a bit in different types of fish. Fatty, coldwater fish, such as salmon, mackerel, sardines, and herring have the highest levels. Warmer-water fish such as catfish, red snapper, trout, and pike have lower levels.

Certain fish also can be a great source of vitamin D; fish are the only strong dietary source of this nutrient and some research suggests that vitamin D may help protect against breast cancer. Excellent fish sources of vitamin D are salmon, sardines, herring, catfish, oysters, and halibut. Fish also is a great source of the mineral selenium. Selenium helps your body make antioxidants, which help prevent cell damage.

Fish risks: Contamination. Mercury is the most well known fish contaminant. It can impair neurological development. So far there’s been no proven tie between mercury and breast cancer risk. Mercury in the air from industrial sources dissolves in rain and falls into bodies of water. Mercury and other contaminants in water can be absorbed and retained by living creatures. The fat in fish tends to store the most contaminants. As larger fish eat smaller fish, the mercury builds up. That’s why predator fish, such as shark, swordfish, and marlin, that live for a long time, are the most contaminated. So people — especially children and pregnant women — should avoid these types of fish. Smaller fish with shorter life spans have lower mercury levels.

PCBs and dioxins can be found in fish, too. PCBs, which were banned in the United States in 1979, are man-made chemicals used in flame retardants, dyes, and plastics. PCBs can cause cancer in animals and affect the immune system. Much like mercury, PCBs don’t break down easily in the environment and so can build up in larger predator fish. Dioxins are formed when things burn and during some manufacturing processes, such as paper pulp bleaching. Dioxins accumulate in the fatty tissues, so again larger predator fish usually have the highest levels. Dioxins can cause development and reproductive problems and have been linked to higher cancer risk.

Select the healthiest fish. By carefully choosing the types of fish you eat, you can make sure the benefits of eating fish outweigh the risks. Based on analyses of contaminants by the Environmental Defense Fund (EDF), these fish are safe for everyone to eat 4 or more times per month:

·         anchovies
·         clams
·         cod (Atlantic)
·         crab (Dungeness, U.S. king, and snow)
·         crawfish (U.S.)
·         haddock (trawl)
·         herring (Atlantic)
·         lobster (U.S./Maine)
·         mackerel (Atlantic)
·         mussels (blue)
·         oysters (farmed)
·         red porgy (U.S.)
·         salmon (canned)
·         sardines
·         scallops (bay, farmed)
·         shrimp (pink, Oregon)
·         shrimp/prawns (imported)
·         squid
·         tilapia

No one should eat bluefin tuna because of concerns about mercury and PCBs (sorry, sushi fans). As far as shark, men can eat one serving a month, but women and kids should avoid this large fish because of elevated mercury levels.

To look up the number of safe meals of other fish for women, men, older children, and younger children, see the EDF website.

Dr. Marisa Weiss

Marisa Weiss, M.D. is the founder, president and guiding force behind Breastcancer.org, the world's most trafficked online resource for medically reviewed breast health and breast cancer information, reaching over 8 million visitors per year. A breast cancer oncologist with over twenty years of active practice in the Philadelphia region, Dr. Weiss is regarded as a visionary advocate for her innovative and steadfast approach to informing, empowering, and treating patients with breast cancer.

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