Functional Foods – Fish

We have been discussing functional foods and how the high potassium foods are functional foods. There are high potassium foods in all the major food categories, but there are also high potassium foods in these categories that have functional advantages beyond their potassium content. Some fish and sea food have functional effects beyond their high potassium content because of their high eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels.

Watch Out For High Sodium Sea Food

Not all seafood is high potassium food. Alaskan king crab is not a high potassium food, having an enormous content of sodium. Other seafood that has too much sodium includes shrimp and caviar. High potassium fish and seafood are discussed here and here. There are tables on these posts showing the amount of potassium and the monounsaturated, polyunsaturated and saturated fat content of various high potassium fish and seafood.

Functional Effects Of Fatty Fish

Fish and other seafood that contain large amounts of EPA and DHA have the functional effects of reducing cardiovascular disease (CVD). These fish are the fish that are fatty. They are high in several omega 3 fatty acids, including EPA and DHA.

In addition to EPA and DHA, they contain the essential fatty acid alpha linolenic acid (ALA), another omega 3 fatty acid. ALA is used to form a part of the structure of the cell membrane of our cells. When we get enough of it, the cell membranes are more fluid and function better. It is also a precursor of EPA and DHA, although very little of the ALA gets converted to EPA or DHA in our body.

The EPA and DHA are felt to lower CVD by reducing inflammation, reducing triglycerides and lowering LDL. This means less buildup of plaque in arteries, including the arteries in the heart. Less plaque results in fewer heart attacks.

Triglycerides are one of the contributors to arterial plaque accumulation. A meta-analysis of 65 studies (1) showed lower and lower triglyceride levels with greater and greater intake of omega 3 fatty acids.

The fish that are high in these components are the ones felt to confer the advantage of CVD reduction. Among the fish with the highest EPA and DHA are salmon, lake trout, tuna, and herring.

Fish oil high in EPA and DHA is also sold as a supplement. Since little ALA is converted in our bodies to EPA and DHA, it is best to get these two directly, either as a supplement or in fish. For those with no history of coronary heart disease, the American Heart Association has recommended eating fish twice a week.

Concerns About Fish

One concern with fish is the potential contamination with heavy metal, PCBs and dioxin. Fish raised on fish farms have little contamination, but may have a change in their fatty acid proportions. The least likely wild fish to have mercury, other heavy metals, PCBs or dioxin are those caught far from the coastal areas.

Another concern is potential rancidity of fish oil, whether the oil is in a supplement or in the fish itself. Fatty acids become rancid when exposed to oxygen in the air. The fatty acids become oxidized and become more like saturated fat. When the fatty acids become rancid they may create more free radicals in the body making the body more prone to some diseases. To prevent rancidity, eat only fresh fish and use fresh fish oil. Keeping fish oil cool and in a dark place will slow the oxidation of the oil.

1. P. M. Kris-Etherton and W. S. Harris, “Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease,” Circulation, vol. 106, no. 21, pp. 2747–2757, 2002.