by Vicky Uhland

A group of university researchers has busted the commonly held conception that all fish is a good source of beneficial omega-3 fatty acids.

In a study published in the July issue of the Journal of the American Dietetic Association, Wake Forest University School of Medicine researchers found that farm-raised tilapia, one of the most popular types of fish in the U.S., not only has low levels of omega-3s, but also contains more omega-6s than bacon, doughnuts or 80 percent-lean hamburger.

Although both omega-3s and 6s are necessary for a healthy diet, a 2006 study conducted by The Center for Genetics, Nutrition and Health found that while humans evolved with a 1-1 ratio of omega-6s versus omega-3s in their diets, in today's Western diet, the ratio is between 15-1 to 16.7-1. A high omega-6 to omega-3 ratio promotes inflammatory and autoimmune diseases such as cardiovascular disease, cancer and osteoporosis, the researchers said.

The authors of the Wake Forest study, who tested a variety of fish obtained from seafood distributors, two South American companies, fish farms in several countries and supermarkets in four states, said their research revealed that farm-raised tilapia, as well as farmed catfish, "have several fatty acid characteristics that would generally be considered by the scientific community as detrimental."

Not only does farm-raised tilapia have high levels of omega-6s, the researchers said it also has less than half a gram of omega-3s per 100 grams of fish, similar to flounder and swordfish. Farmed salmon has 3 grams and farmed trout has 4 grams.

"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," the researchers wrote.

The main culprit behind the high omega-6 levels is the corn-based diet that is fed to farm-raised tilapia, said Floyd Chilton, Ph.D., senior author of the Journal article. This feed contains omega-6s that the fish store in their tissues.

Tilapia's ability to subsist on inexpensive feed, along with its capacity to grow under almost any conditions, keeps the market price low enough that the fish is rapidly becoming a staple in low-income diets, Chilton said. "Cardiologists are telling their patients to go home and eat fish, and if the patients are poor, they're eating tilapia. And that could translate into a dangerous situation."

However, "tilapia is still a decent fish to include on the dinner table" because it's a good source of protein and generally a healthy food, said Douglas MacKay, N.D., research adviser for Nordic Naturals, a Watsonville, Calif.-based manufacturer of omega-3 fish oil supplements.

Wild tilapia may be a better nutritional option than farm-raised because its diet is lower in carbohydrates and a little higher in protein, said Marisa Moore, an Atlanta-based spokeswoman for the American Dietetic Association. Consumers who want more omega-3s from their fish but like tilapia's less-fishy-tasting flavor might consider trout, which is also a mild fish, she said.