Health & Family

All fish are not equal nutritionally

Just when you thought you were doing a great job eating fish twice a week to keep your heart healthy, a study hints that not all fish are created equal.

Fish is high in omega-3 fatty acids – an essential fatty acid. A diet high in omega-3 fatty acids has been found to reduce blood pressure, lower triglycerides, prevent further heart attacks and perhaps prevent heart attacks.

Omega-3s have also been found to decrease stiffness from arthritis, and probably also help prevent depression.

Omega-3s are important because they balance out omega-6 fats – the other essential fatty acid that humans need in their diets. Omega-6 fats, however, are overly abundant in our diets – especially in the form of harmful trans-fats in baked goods and processed foods. The recommended dietary intake of the two fats is a diet that contains at most a 4-to-1 ratio of omega-6 to omega-3.

But we typically eat 20 times more omega-6 than omega-3s.

So, how much fish must you eat to get enough omega-3s to protect your heart? The American Heart Association recommends eating fatty fish at least twice a week. Those with heart disease should get about 1 1 / 2 ounces of fish per day. Examples of fatty fish include anchovies, bluefish, carp, catfish, halibut, herring, lake trout, mackerel, pompano, salmon, striped sea bass, tuna (albacore), and whitefish.

Unfortunately, the July 2008 issue of the Journal of the American Dietetic Association suggests that two of the most commonly ingested fish — farmed tilapia and catfish — may actually be more harmful than healthful.

Why? It appears that these farmed fish varieties may contain more omega-6 than omega-3 fats. This is probably because these farmed fish were raised on commercial feeds that were high in omega-6 fats (wild fish feed on algae, which is high in omega-3s). Farmed trout and Atlantic salmon had relatively good concentrations of omega-3 fatty acids, however.

What's the take-home message from the study? Wild fish appear to have better concentrations of omega-3s than farmed fish. And tilapia and catfish, very common and increasingly popular fish on the American dietary menu, may not be all that healthful in terms of their omega-3 to omega-6 ratio. (Fish may also contain dioxins, methyl-mercury and polychlorinated biphenyls, and caution is warranted in young children and pregnant or breastfeeding women.)

Most fish oil supplements appear to contain little or no contamination, however.

Other good sources of omega-3 are flaxseed and canola oil, broccoli, cantaloupe, kidney beans, spinach, cauliflower and walnuts.