Farm-raised tilapia fish contains potentially dangerous fatty acid combination

Published on July 8, 2008 at 6:23 PM · No Comments

Farm-raised tilapia, one of the most highly consumed fish in America, has very low levels of beneficial omega-3 fatty acids and, perhaps worse, very high levels of omega-6 fatty acids, according to new research from Wake Forest University School of Medicine.

The researchers say the combination could be a potentially dangerous food source for some patients with heart disease, arthritis, asthma and other allergic and auto-immune diseases that are particularly vulnerable to an 'exaggerated inflammatory response.' Inflammation is known to cause damage to blood vessels, the heart, lung and joint tissues, skin, and the digestive tract.

"In the United States, tilapia has shown the biggest gains in popularity among seafood, and this trend is expected to continue as consumption is projected to increase from 1.5 million tons in 2003 to 2.5 million tons by 2010," write the Wake Forest researchers in an article published this month in the Journal of the American Dietetic Association.

They say 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." Tilapia has higher levels of potentially detrimental long-chain omega-6 fatty acids than 80-percent-lean hamburger, doughnuts and even pork bacon, the article says.

"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 article says. "All other nutritional content aside, the inflammatory potential of hamburger and pork bacon is lower than the average serving of farmed tilapia."

The article notes that the health benefits of omega-3 fatty acids, known scientifically as 'long-chain n-3 polyunsaturated fatty acids' (PUFAs), have been well documented. The American Heart Association now recommends that everyone eat at least two servings of fish per week, and that heart patients consume at least 1 gram a day of the two most critical omega-3 fatty acids, known as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).

But, the article says, the recommendation by the medical community for people to eat more fish has resulted in consumption of increasing quantities of fish such as tilapia that may do more harm than good, because they contain high levels of omega-6 fatty acids, also called n-6 PUFAs, such as arachidonic acid.

"The ratio of arachidonic acid (AA) to very long-chain n-3 PUFAs (EPA and DHA) in diets of human beings appears to be an important factor that dictates the anti-inflammatory effects of fish oils," the researchers write. They cite numerous studies, including a recent one that predicts "that changes in arachidonic acid to EPA or DHA ratios shift the balance from pro-inflammatory [agents] to protective chemical mediators " which are proposed to play a pivotal role in resolving inflammatory response in the body.

For their study, the authors obtained a variety of fish from several sources, including seafood distributors that supply restaurants and supermarkets, two South American companies, fish farms in several countries, and supermarkets in four states. All samples were snap-frozen for preservation pending analysis, which was performed with gas chromatography.

The researchers found that farmed tilapia contained only modest amounts of omega-3 fatty acids - less than half a gram per 100 grams of fish, similar to flounder and swordfish. Farmed salmon and trout, by contrast, had nearly 3 and 4 grams, respectively.

At the same time, the tilapia had much higher amounts of omega-6 acids generally and AA specifically than both salmon and trout. Ratios of long-chain omega-6 to long-chain omega-3, AA to EPA respectively, in tilapia averaged about 11:1, compared to much less than 1:1 (indicating more EPA than AA) in both salmon and trout.

The article notes that "there is a controversy among scientists in this field as to the importance of arachidonic acid or omega-6:omega-3 ratios vs. the concentration of long-chain omega-3 alone with regard to their effects in human biology." Those issues are raised in an editorial in the same issue of the Journal.

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