Diabetes Forecast

Adding Fish to Your Diet

There's a lot to learn about choosing seafood for health

By Tracey Neithercott/Recipes by Robyn Webb, MS, LN , ,

The fish counter can be a confusing place. There's Alaskan salmon and Atlantic salmon. Striped bass and wild-caught striped bass. The main difference between two similar fish is where they were caught: the Atlantic Ocean, the Pacific Ocean, or somewhere else around the world. But other times, how the fish are caught—say, from the wild or from large tanks on land where they were raised—is crucial to know when you're choosing between one fish and the other. Whether you're more concerned with the nutritional content of fish, its potential contaminants, the environmental impact of getting it into your supermarket, or simply what it's going to cost to put a healthy dinner on the table, there's a lot to learn about choosing fish.

Farm to Table?

Because of the high demand for fish, some fish populations have been depleted, sending the prices of wild fish sky high. Large-scale fish farming took off in the 1970s and tripled in size between 1995 and 2007. The 20th-century surge began as a way to alleviate the problems of price and availability. Farmed fish are raised in controlled conditions—in pens with water and other fish—and fed pellets of food. Wild fish, on the other hand, live freely in the oceans, lakes, or rivers and feed on plants, insects, and other fish. Differences in habitat mean that farmed fish are available year-round while wild fish are seasonal.

One major difference between the two types is cost. In almost all situations, farmed fish will be cheaper than their wild counterparts. A pound of farmed (also known as Atlantic) salmon may be around $8 while the same amount of wild salmon can be $10 to $20—or more.

Then there are the personal aspects of picking one type over the other: "The flavor and the texture of the fish are noticeably different between wild and farmed fish," says Sheila Bowman, a senior outreach manager with the Monterey Bay Aquarium's Seafood Watch program. Wild fish are firmer, less fatty, and have a stronger flavor while farmed fish have a softer texture and milder taste.

The Bad Stuff

Which type of fish is the most contaminated? It's a toss-up. Wild ocean-dwelling fish aren't likely to contain antibiotics like farmed fish, and may contain fewer pesticides and environmental pollutants. But fish farming provides greater control of water quality, which may result in less pollution. "Organic pollutants are all over the map," says Joyce Nettleton, DSc, a nutrition scientist and consultant who studies fish. Some data show that wild fish have more contaminants—including mercury, pesticides, and chemicals—than farmed. Yet studies have also shown that farmed fish have 10 times the amount of PCBs (polychlorinated biphenyls, a toxic chemical) that wild fish do. Regardless of which you choose, contamination levels for both types of fish are generally low enough, experts say, that they won't cause harm.

The exception: mercury, a heavy metal that can wreak havoc on the body. Nearly all fish contain mercury, but it's the amount that counts. Certain large fish have higher levels of the contaminant than others (left). Children and pregnant women should limit the amount of high-mercury fish they eat, replacing those options with fish that have low mercury levels. Since farmed fish often aren't exposed to the ocean and the pollutants in it, wild-caught fish are more likely to contain higher levels of mercury.

Where the Mercury Is

Limit These Pick These
These fish have the highest mercury content
These fish have the lowest mercury content
Shark Anchovies
King Mackerel Catfish
Tilefish Flounder
Ahi Tuna
Swordfish Sardines
Source: Food and Drug Administration

The Good Stuff

Whether you pick wild or farmed, fish is a healthy source of protein and is lower in saturated fat than beef, lamb, pork, or poultry. "It's fair to say that both are very healthful foods," says Nettleton. "The farmed fish tend to be a little fattier than the fresh. The big difference is in the amount and type of omega-3 fatty acids they have."

Because wild fish swim freely through raging waters and must try to evade predators (sometimes traveling hundreds of miles before they're finally caught), they have less overall fat than farmed fish. While the wild fish thrash about in open water, farmed fish live in close quarters with hundreds of others. Farmed fish plump up from their feed and—with no need to fight off predators, battle wild waterways, or journey for food or reproduction—they end up fattier overall.

But while farmed fish have more fat, wild fish contain more essential omega-3 fatty acids, thanks to the sea plants and smaller fish they eat that are rich in omega-3s. Still it's difficult to say just how many more grams of omega-3s wild-caught fish have compared with farm-raised. Other factors, like the species of fish or the feed a farmer uses, help determine fatty acid content. In people with diabetes, omega-3s can lower the risk of heart disease, raise HDL ("good") cholesterol, and improve triglyceride levels. They also reduce inflammation and may play a role in lowering the risk of arthritis, cancer, and chronic diseases.

That said, if you're looking to add more omega-3s to your diet, it's important to consider the different fish varieties—no matter if you're eating wild or farmed. Salmon, sardines, anchovies, trout, and bluefin tuna are all high in omega-3s.

Another difference between the two types of fish is how much omega-6 fatty acids they have. Farmed fish are higher in omega-6s. The body works best when there's a balance between omega-3s and omega-6s, both essential fatty acids. But, notes Nettleton, "our diets are already awash in [omega-6] fatty acids." Omega-6s are abundant in the American diet, mostly coming from soybean, safflower, cottonseed, corn, and vegetable oils.

The Greater Environment

When fish farms were first developed, they were the answer to the growing problem of overfishing in rivers, streams, lakes, and oceans. Fish species were dwindling, and some teetered on the edge of extinction. In an effort to make more fish available (and drive down costs), the farms bred fish for Americans' plates.

It wasn't until years later that problems with the system were discovered. Scientists learned that farmed fish, which often lived in netted pens in open waters, were affecting life in the wild. Waste from the pens was flushed into the ocean along with chemicals and antibiotics used to prevent the spread of disease. Soon, wild fish, which had only gotten lice sporadically as adults, were covered in lice at a young age, and many were unable to survive. "It's the same story with closed-quarter industrial animals of any kind," says Bowman. "When you put a lot of animals together, disease tends to be higher. Fish in the wild don't tend to live that way. It's the same thing for parasites: They jump from host to host because they're close by."

Since farmers make their living from the fish, most aren't keen on reducing their numbers. But to have less of an impact on the oceans, many now use pens that are constructed on land, like giant aquariums. Still, farming requires feed (often smaller fish turned into pellets and sometimes including corn or soy), which means that even farmed fish use resources provided by the open waterways.

Despite the proliferation of fish farming, overfishing of wild species has reduced populations greatly. Wild salmon from the Atlantic is all but extinct. Grouper, shark, bluefin tuna, and dozens of other species are overfished.

Whether farmed fish or wild fish are better for the environment is still up for debate. The list of the most and least ocean-friendly fish changes often, but you can download a pocket guide from the Monterey Bay Aquarium's Seafood Watch, a program designed to help people make environmentally responsible decisions about fish. Click here to download the handy guide, or download the free Seafood Watch app for your iPhone or Android phone.

The Bottom Line

So, what kind of fish should you be eating? Unfortunately, there's no one answer to this question that will suit everyone. Instead, you'll need to weigh your nutritional and environmental concerns, check your food budget, and decide what works for your life. Someone who values taste above availability may buy wild. Another person who finds cost more important than environmental factors may buy farmed. In the end, what's most important is that you find ways to get the healthful benefits of eating fish.

A Buyer's Guide

Click here to learn what to look for and what to ask when purchasing fresh fish.



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