Balancing Risks and Rewards of a Seafood Diet

By March 10, 2015April 11th, 2021No Comments

We hear that eating fish is important for a healthy diet. But we also hear that we should be cautious of fish that pick up contaminants from polluted waters.

So should we be eating more seafood? And if the answer is yes, then what should we think about when selecting fish to eat?

These are issues that continue to challenge nutritionists and toxicologists, along with state and federal health officials. It turns out that eating fish is important, but some fish are more nutrient-rich than others.

Related: “Feds watch closely as state updates water-quality standards”

At the same time, if you want to protect yourself against dangerous chemicals, you must examine other lists — ones that indicate mercury, polychlorinated biphenyls (PCBs) and other chemicals pose health concerns when eating certain types of fish.

According to David McBride, a toxicologist with the Washington State Department of Health, dietary advice generally balances the benefits of eating fish against the risks, steering people toward the types of fish high in nutrients but low in toxics.

“Balancing the risks is not easy,” McBride said. “But we definitely don’t want people to take fish off the table.”

Meanwhile, in a new initiative before the Legislature, Gov. Jay Inslee has proposed a law that focuses not only on the effects of specific chemicals of concern but also how such chemicals work their way into state waters, into fish and eventually into humans.

Under his proposal, “chemical action plans” would address ongoing sources of persistent chemicals — such as PCBs, which are still getting into waterways despite a U.S. ban on their manufacture in 1977. The action plans also would tackle “emerging chemicals of concern,” a large category of chemicals found in consumer products, many of which require more study and a search for alternatives when harmful effects are found.

While the Legislature has been contemplating Inslee’s proposal this year, Washington Department of Ecology is going down a separate path in reviewing the state’s water-quality standards. These are specified limits for 96 chemicals found in water and aquatic animals — including those we eat. When a body of water meets the standards, those waters are deemed clean enough to comply with the federal Clean Water Act.

One factor driving the water-quality standards is an assumption about how much fish people eat. That question has become controversial, because everyone is different. Native Americans, for example, typically eat far more fish than the average state resident. Assuming a high fish-consumption rate results in more stringent water-quality standards to protect people’s health, other things being equal.

Eating Fish for Health

“We all want to eat a healthy diet, which can include fish and other sources of animal protein,” said Aimee Hayes-Herb, a certified nutritionist on Bainbridge Island. “Fish protein is somewhat different from other animal protein.

“When people come to me concerned about heart disease or with high blood pressure, I recommend eating fish as an animal-protein substitute (for beef, chicken or pork),” she said.

Fish not only contain less saturated fat, they are one of the best available sources of omega-3 fatty acids. Omega-3s are considered essential to the proper growth and function of the human body, including:

  • Development of the brain and neurological system, including memory and performance,
  • Regulation of the heart and circulatory system, including possible reduction in the risk of heart disease, and
  • Control of inflammation, which may include reduced pain from some types of arthritis.

“In fact, infants who do not get enough omega-3 fatty acids from their mothers during pregnancy are at risk for developing vision and nerve problems,” according to a summary of research by the University of Maryland Medical Center. “Symptoms of omega-3 fatty acid deficiency include fatigue, poor memory, dry skin, heart problems, mood swings or depression, and poor circulation.”

The U.S. Food and Drug Administration now considers omega-3s to be so critical to the health and development of children that the agency is updating its dietary guidelines. Proposed recommendations call for more fish to be eaten by pregnant and breast-feeding women, women who might become pregnant as well as young children.

Previous recommendations, last updated in 2010, only warned those groups about the dangers of mercury, suggesting they limit consumption of albacore tuna to 6 ounces per week and to avoid eating tilefish, shark, swordfish and king mackerel altogether. Such recommendations against eating fish high in mercury would remain in place under proposed guidelines, to be finalized later this year.

“For years many women have limited or avoided eating fish during pregnancy or feeding fish to their young children,” said Dr. Stephen Ostroff, the FDA’s chief scientist, in a news release. “But emerging science now tells us that limiting or avoiding fish during pregnancy and early childhood can mean missing out on important nutrients that can have a positive impact on growth and development as well as on general health.”

On a recent trip to Central Market in Poulsbo, nutritionist Hayes-Herb pointed out which fish are high in omega-3 fats.

“I would say good choices are salmon, prawns, shrimp, trout and black cod,” she said, scanning the seafood counter. “I would say the fish highest in omega-3s are the sockeye, king salmon and steelhead.

“In terms of contaminants,” she continued, “as a general rule, the larger the fish, the higher the level of contaminants.”

That’s largely due to bioaccumulation, or the tendency of certain chemicals to accumulate in tissues. The longer a fish is exposed to a contaminant, the higher the concentration. Larger fish tend to be older and more likely to have higher levels of toxic chemicals.

That’s why many nutritionists steer people away from the larger yellowfin and canned albacore tuna and toward the smaller “canned light” or skipjack tuna to reduce mercury exposure.

Tony D’Onofrio, sustainability manager for Central Market and other stores in the Town & Country chain, said many factors go into decisions about which seafood his company purchases from wholesalers to sell to store customers.

Freshness is a big factor, he said, along with issues of contamination. Sustainability — or protecting at-risk populations of fish and other sealife — is another concern.

Central Market sells only a few farmed seafood products, such as steelhead. Before buying from a fish farm, corporate officials visit the operation to ensure that it meets standards for water quality, freshness and sustainability, D’Onofrio said.

When buying fish or shellfish, consumers should not hesitate to ask about the origins of various seafood products, said Hayes-Herb. Under federal regulations, consumers must be able to learn the scientific name of any unprocessed seafood along with where it was caught. Some wholesalers are better than others at passing along additional information to retailers.

The essential omega-3 fatty acids are produced in the chloroplasts of algae and green plants. In water, small marine creatures eat the algae, and the omega-3s work their way up the food web to the fish that we eat. Cold-water fish high in oil — such as salmon, herring and mackerel — are especially rich in omega-3s.

Omega-3s also are found in grass-fed livestock and poultry, but levels decline once the animals are shifted onto a grain diet, such as in a feedlot, experts say. Another reason fish are recommended is because they have a much greater level of omega-3 in comparison to omega-6 fatty acids. That helps to balance typical American diets that are high in omega-6, associated with tissue inflammation and other problems.

For vegetarians and people who don’t like fish, good sources of omega-3 fats include flaxseed, hempseed, chiaseed and walnuts, plus oils from those seeds along with algae oil.

It may help if people avoid or reduce oils high in omega-6, including corn, soy, safflower, sunflower, sesame and most oil blends, often labeled “vegetable oil.”

“The way I think about things, variety is everything,” Hayes-Herb said. “Think about ways to balance your meats, dairy, fruits and vegetables. I don’t even purchase the same brand of peanut butter all the time.”

Puget Sound Toxic Study

Following an extensive study of chemicals in fish from Puget Sound, the Washington State Department of Health in 2006 recommended that people limit their consumption of chinook and coho salmon from Puget Sound along with rockfish and English sole, especially those caught in urban bays.

The analysis began with more than 100 chemicals and chemical groups listed as “priority pollutants” by the EPA. They ranged from chlorinated pesticides to hydrocarbons to various metals.

Most of the chemicals were not found in detectable levels in fish samples collected by the Washington Department of Fish and Wildlife. State health experts focused on eight chemicals detected in at least 10 percent of the fish samples. They were alpha chlordane, arsenic, benzyl alcohol, copper, DDT, DEHP, mercury and PCBs.

In the end, mercury and PCBs were found in concentrations high enough to be a concern. The health advisory issued in 2006 was based mainly on the amounts of those chemicals that people would consume if they ate significant amounts of fish from Puget Sound.

Rockfish, particularly from urban areas, were found to be high in both PCBs and mercury. Mercury, the key contaminant of concern, was generally related to the age of the fish, with higher levels in urban bays. PCB concentrations were strongly related to where the rockfish were caught, with the highest levels in Bremerton’s Sinclair Inlet and Seattle’s Elliott Bay. The resulting health advisory was to eat no rockfish from either bay and to limit consumption elsewhere in Puget Sound, especially urban areas.

Somewhat different recommendations were issued for flatfish, based on mercury and PCBs found in English sole, the only flatfish sampled. Mercury was found to be significantly lower in English sole than in rockfish. People were advised not to eat any flatfish from Seattle’s Duwamish Waterway, but no limits were proposed for most of Puget Sound except urban bays.

Chinook (also known as king salmon) from Puget Sound had higher levels of PCBs and mercury than coho (also known as silver salmon), although both species posed some health concerns. Blackmouth, which are immature chinook that stay in Puget Sound and don’t migrate to the ocean, had the highest levels of contamination among the salmon tested. Based on those findings, people were advised to eat no more than four meals a month of chinook and two meals a month of blackmouth from Puget Sound.

The agency concluded that even though mercury and PCBs were elevated in coho, the levels were not high enough to deviate from the standard advice of eating two to three meals of fish per week. Even though no sockeye, pink or chum salmon were tested in Puget Sound, other data suggest that they are no worse than most fish on the market.

“DOH encourages all Washingtonians to eat at least two fish meals per week as part of a heart-healthy diet …,” the agency states. “Most foods, regardless of source, contain some contaminants. Switching from fish to other types of food may not eliminate contaminant exposure.

“One can safely continue to eat the American Heart Association’s recommended two fish meals per week by avoiding fish that are high in contaminants.”

To help consumers understand their options, the 2006 study looked at PCBs and mercury in other foods that people may eat. Mercury concentrations in rockfish from urban areas of Puget Sound were comparable to what people might get by eating albacore tuna, based on FDA information. Rockfish from nonurban areas had mercury levels similar to halibut one can buy in a store.

About half of the fish on FDA’s list of commercially available fish contain higher levels of mercury than English sole or salmon from Puget Sound, according to the health assessment. The lowest mercury levels were found in commercial sardines, oysters, tilapia and hake.

Somewhat similar results were found when state health officials tested for mercury in fish from grocery stores in Washington state. Levels in commercially purchased salmon were lower than those in salmon from Puget Sound. The lowest levels were found in pollock and catfish from the stores.

A separate study of fish found in Washington grocery stores reported higher levels of PCBs in rockfish and English sole from urban areas of Puget Sound than any fish found on the market. Puget Sound chinook also were higher than store-bought fish. Rockfish and English sole from nonurban areas of the sound had PCB levels similar to commercial flounder, cod, pollock and tuna.

It’s important to recognize that PCBs and other toxic chemicals can be found in many foods, especially meats and other products high in fat, McBride said. Unfortunately, only limited analyses of PCBs are available for most food sources.

McBride also pointed out that testing for toxic chemicals in fish — which is very expensive — declined in recent years during the state budget crunch. He said he would like more species sampled to better evaluate health risks.

The ban on toxic PCBs is gradually causing a decline in PCB levels found in the environment, including fish, McBride said. At the same time, experts have seen a rise in toxic flame retardants — called polybrominated diphenyl ethers, or PBDEs — the worst of which were banned in recent years.

“Hopefully action is being taken soon enough to stay ahead of the curve,” McBride said, noting that experts must remain vigilant to risks posed by new chemicals or those used in new ways.

Meanwhile, a revised health advisory on the risk of eating crab and shrimp from Puget Sound is due to be released in a few months. Although the findings are not complete, McBride said, it appears crab and shrimp will get a fairly clean bill of health — except for those found in urban bays.

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