Q: Should I really eat fish twice a week for good health?

A: The American Heart Association recommends that we should be “eating fish (particularly fatty fish) at least two times a week.” This is because, in addition to fish being a good source of protein and relatively low in saturated fat, many varieties are high in omega-3 polyunsaturated fatty acids (PUFA), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). AHA released a scientific statement in 2002 to the effect that omega-3 fatty acids decrease atherosclerotic plaque, triglycerides and in some cases, heart arrhythmias. The risk of cardiovascular disease seems to be lowered when omega-3 PUFA are ingested in the amounts present in fatty fish such as trout, salmon, sardines and tuna.

According to Karen Hudson with Kansas State University’s human nutrition department, in the July 2008 issue of the Journal of the American Dietetic Association, researchers from Wake Forest Center for Botanical Lipids at the Wake Forest School of Medicine reported they had analyzed the polyunsaturated fats typically present in commonly eaten fish in the US. — farmed and wild. The wild fish tended to have high levels of omega-3 PUFA because their diets are based on algae, naturally rich in these fatty acids. They looked at four popular farmed fish in detail: Atlantic salmon, trout, tilapia and catfish. The farmed Atlantic salmon and trout also had a relatively high amount of omega-3 PUFA.

Interestingly, the farmed tilapia (and the catfish) had a surprisingly low amount of omega-3 PUFA (n-3) and a high amount of omega-6 PUFA (n-6). Although n-6 and n-3 are both “essential” fatty acids (i.e., must be obtained from our diets), n-6 competes with n-3, and if it is proportionately high relative to n-3, an inflammatory response is possible. The Wake Forest researchers are concerned that the high ratio between the two types of fatty acids found in tilapia may promote or exacerbate inflammation in certain vulnerable individuals who have an existing inflammatory condition such as cardiovascular disease (CVD) or even a genetic predisposition to one. The ratio of omega-6 fatty acids to omega-3 fatty acids in farmed salmon is 1:1; whereas the ratio in farmed tilapia is 11:1.

It is important to point out that the science is not “cut and dried” on this controversial issue. Some researchers contend that there is no increased risk of CVD from a high ratio of n-6:n-3. They point to the benefit of omega-6 PUFA (often found in vegetable oils like corn, sunflower, and soybean) in lowering LDL cholesterol, and thereby the risk of heart disease. Although the data are not all in, for most people the high ratio may not be problematic, but for a percentage of people at risk of an inflammatory disease, like heart disease, a lower ratio may be a healthier one.

Q: So what is the consumer supposed to do while we wait for consensus in medical science?

A: Tilapia is a popular fish in the U.S. for a number of reasons. It is mild-flavored, and it doesn’t accumulate mercury (as is the case in some fish) because it is fast-growing, short-lived and easy to raise. Although tilapia is not a rich source of omega-3 PUFA, it is still a good source of protein and is moderately priced. Consequently, for most people, after weighing the pros and cons, eating an occasional meal of tilapia is still a good choice.

— Susan Krumm is an Extension agent in family and consumer sciences with K-State Research and Extension-Douglas County, 2110 Harper St. She can be reached at 843-7058.