Part 5: Fish and Seafood Based on the book “What to Eat” by Marion Nestle
To make an intelligent choice of fish at the supermarket, you have to know more than you could possibly imagine about nutrition, fish toxicology, and the life cycle and ecology of fish–what kind of fish is it, what it eats, where it was caught, and whether it was farmed or wild. If you are at all concerned about environmental issues, you will also want to know how it was caught and raised and whether its stocks are sustainable. As a group, fish are excellent sources of protein, vitamins, and minerals. Their fats are largely unsaturated and are especially rich in omega 3s, particularly EPA and DHA. These omega 3s show up in the brain and are believed critical to the normal development of the nervous system. Fish are the best source of omega 3s and practically all health authorities advise pregnant women to eat fish 1-2x per week. More than that, some research suggests that EPA and DHA might prevent the blood clots and irregular heartbeats that often lead to heart attacks or strokes. The fish committee does not say how you are supposed to know which fish are rich in EPA and DHA nor does it offer much help with figuring out which fish are high or moderate in mercury. Another question is whether fish oil supplements are as effective as fish. Supplements are often problematic because they are basically unregulated, but tests of omega 3 supplements indicate most are fine and contain what they say they do. Fish are good to eat for their nutritional value and especially for their content of omega 3s. However, all seafood is contaminated with methylmercury, a toxic substance that is dangerous for developing fetuses especially during the early months of pregnancy. The amounts of methylmercury in fish vary widely and it is a good idea to avoid eating the most contaminated kinds. Unfortunately, figuring out how to follow advice about methylmercury is your problem to solve. You have to remember which fish are high in methylmercury so you can avoid them. Methylmercury, unlike lead, does not stay in the body for long. Its half-life is just 2-3 months meaning that if you start now to reduce the amount of methylmercury you eat half will be gone in a few months and then half of what's left in another few months and most will be gone in a year or so along with any risks it might pose. You have to keep track of the amount of fish you eat in a week or a month, and you have to decide whose information is more believable, the FDA, EPA, the Tuna Foundation, or the EWG. How important is it to eat omega 3s from fish? Fish are the best sources of omega 3s, but the amounts of EPA and DHA in 3 oz of fish vary from .1g in cod to a gram or more in fish like anchovies, herring, mackerel, tuna, and salmon. The richest source being caviar. Most american fish are relatively low in omega 3s, but fortunately it only takes a small amount of EPA and DHA to produce benefits. Fish are not the only sources of omega 3s. Chicken and eggs naturally have small amounts of EPA and DHA. Plants contain omega 3s in the form of ALA which converts to EPA and DHA. The better plant sources are flax and flax oil. You can also get omega 3s by taking fish oil supplements or DHA from algae. It helps to keep omega 3s and fish in perspective. Omega 3s may be good for the heart, but so are other nutrients, vitamins, minerals, phytochemicals, and fiber in veggies, nuts and seeds. Fish are excellent sources of many nutrients, but you can also get these from other foods. Fish are not essential requirements of a healthful diet and there is no compelling reason to eat it if you don't want to. If you are going to follow heart healthy advice to eat two servings of fish per week, you will need to know more than you ever wanted to know about the diets of fish as well as your own. Did the fish eat the other fish? If so, they might have methylmercury, but also more than their share of other dilemma inducing pollutants, PCBs, and other related toxic chemicals. The PCBs in fish cause the same type of dilemma as the one involving omega 3s and methylmercury, but with one unpleasant addition: all fish have PCBs, but farmed fish, those fed fish feed and fish oil, have more. This is because farmed fish need proteins and fats to grow and they grow better when those nutrients come from fish feed and fish oils, but these feeds contain high concentrations of PCBs. All fish are contaminated with PCBs and similar chemicals that are best avoided. These chemicals are organic hydrocarbons usually with chlorine or bromine attached. They include especially nasty agricultural pesticides and dioxins from industrial wastes and emissions. Although most of these chemicals have been discontinued or banned for years they persist in the environment and thoroughly pollute streams, lakes, and oceans. At high levels of exposure, such as those experienced by victims of industrial accidents, they cause severe problems with skin, reproduction, development, and behavior. A safe level of intake is not really known. The amount of PCBs in fish seem harmless but the word most often used to describe their effects is uncertain. When you eat fatty fish like albacore tuna, herring, or mackerel, precisely the ones highest in omega 3s, you also get a relatively high dose of PCBs. Fish oil supplements would have even higher amounts but luckily these are cleaned up (refined) to eliminate most of these toxins. According to the Coastal alliance for Aquaculture Reform: farmed salmon are raised like cattle in feedlots. They are confined in pools of antibiotics, pesticides, chemicals, and wastes which then spill the equivalent of raw sewage into local waters. If the fish escape, which they do on occasion, they can end up in the wrong ocean, compete for resources, and spread diseases like sea lice to wild fish and when they mate with wild fish change the genetic basis of the population and reduce biodiversity. This group insists that you are much better off eating wild salmon for reasons of safety, health, and environmental protection. Farmed fish are less active fish, they have 2x the fat and more than 2x the amount of saturated fat of their wild counterparts. Their omega 3 content depends entirely on what they are fed and varies by species and by farm. In captivity on fish farms salmon eat the equivalent of dog food: first small and then larger pellets of fish meal and fish oil, soy protein, wheat, and vitamins and minerals. The pellets also contain meat and bone meal made from the rendered leftover meat, blood, and bones of cows, pigs, and other animals. Wild salmon are a gorgeous pink because the fish eat marine krill. Farmed salmon are not, they are fed pellets and in turn are a grayish brown color. Research in the industry tells us two things about salmon: the darker the color of pink the more likely you are to buy it and if the salmon is gray you won't buy it at all. So salmon farmers resort to cosmetics. They add dyes to the feed pellets knowing that the farmed salmon can easily absorb the color and their flesh will turn just as pink as wild salmon. Farmed fish are not the only fish that get cosmetic treatment. Wild tuna steaks which are naturally red tend to turn brown when exposed to air or when frozen, so seafood companies spray them with carbon monoxide to keep this from happening. These observations caused the researchers to draw three conclusions: 1. consumption of farmed atlantic salmon may pose risks that detract from the beneficial effects of fish consumption, 2. The importance of labeling salmon as farmed is important, as is 3. identifying the country of origin. The vast majority of farm raised atlantic salmon should be consumed at one meal or less per month. Knowing what fish to eat then means knowing: where the fish comes from, whether it's farmed or wild, where it is on the food chain, whether it is listed in a state advisory, and how much fat it contains. Once you have this information you can avoid the fish likely to be most heavily contaminated with PCBs. On this basis you will want to avoid farm raised fish from Europe, farmed fish fed lots of fish meal and fish oils, the ones listed on state advisories, and the larger and fattier species such as those highest in methylmercury. Organic on seafood means the same as natural on meat, however the seller chooses to define it. The three fish guide producers belong to the alliance and so do a long list of other environmental and food advocacy and professional associations. These are listed at www.seafoodchoices.com. Under the auspices of the alliance the three groups got together and now produce a single guide that addresses health as well as environmental concerns. They call the unified guide the fish list. This guide simplifies seafood choices into green (enjoy) and red (avoid).