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Fish has become a go-to staple for Canadians who want to have a healthy diet. So it may come as a surprise to learn that eating farmed tilapia, a widely consumed fish that has been steadily growing in popularity, may be no better than dining on bacon, hamburgers or doughnuts.

New U.S. research has found that farmed tilapia have low levels of omega-3 fatty acids - and surprisingly high levels of potentially detrimental omega-6 fatty acids.

It is a finding that could have serious implications for people who suffer from arthritis, asthma and other illnesses or allergies because the omega-6 fatty acids may cause inflammation, which can damage blood vessels and vital organ tissue, according to the findings, published in last month's Journal of the American Dietetic Association.

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Omega-6 fatty acids are considered to be essential and must be obtained through diet because they can't be produced by the body.

But consuming too much omega-6 can contribute to cancer, asthma, depression and heart disease, among other ailments.

Excessive consumption of omega-6 is common in many Western diets, according to the University of Maryland Medical Center.

By contrast, omega-3 fatty acids are considered good for health because they help to lower the levels of LDL (low-density lipoprotein), also known as "bad" cholesterol, in the blood.

Tilapia, a lean white fish with a mild taste, is the second-most cultivated fish in the world, after carp, according to Fisheries and Oceans Canada. While China is the world's leading producer of tilapia, British Columbia and Nova Scotia also produce it on a commercial scale. The department said Toronto is North America's largest market for live tilapia, and the World Aquaculture Society predicts that production will rise steadily because of increased demand for the fish.

"Ten years ago, people wouldn't even know what the word [tilapia]meant," said Robert Ackman, professor emeritus in food science and technology at Dalhousie University, who studied fats and oils in fish. "It's on the tabletops here in Nova Scotia for heaven's sakes. It's a popular food that's been written up in food magazines. People come in and ask for it."

Canadians are often encouraged to increase their consumption of fish to take advantage of beneficial omega-3 fatty acids. But certain varieties of fish, and how they are raised, can make a major difference in its health benefits, according to the study.

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"For individuals who are eating fish as a method to control inflammatory diseases such as heart disease, it is clear from these numbers that tilapia is not a good choice," according to the study, conducted by researchers from the Wake Forest University School of Medicine in North Carolina.

The study singled out tilapia raised on fish farms as having high levels of the potentially dangerous omega-6 fatty acids. Although researchers didn't compare farmed tilapia with wild tilapia, they noted significant discrepancies between farmed tilapia and other types of farmed fish.

For instance, they found that farmed tilapia contained less than half a gram of omega-3 fatty acids per 100 grams, while farmed salmon and trout had nearly three and four grams per 100 grams, respectively. At the same time, farmed tilapia contained significantly larger amounts of omega-6 acids - higher than the levels found in doughnuts, pork bacon and hamburgers made with 80-per-cent lean ground beef.

One of the major reasons for the abundance of omega-6 is the fact the tilapia involved in the study were raised on farms, Prof. Ackman said.

"This is a serious problem because they tend to feed [the fish]vegetable oils for growth and that's not quite what the tilapia is accustomed to getting in its native state," he said.

Because the abundance of studies in recent years has made it difficult for consumers to decipher which types of fish may provide health benefits and how much they should be eating, Prof. Ackman said the best rule of thumb is to avoid farmed fish.

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"Generally speaking, wild fish is always the best bet," he said.

Even though wild fish has been associated with increased levels of mercury, he said, the amounts aren't great enough to cause serious issues in most people.

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