Salmon, whether canned, fresh or frozen, is a good source of important nutrients, such as omega-3 fatty acids and vitamins. It can be an important part of a healthy diet; however, you should follow the consumption guidelines published by the Environmental Protection Agency to avoid taking in too many contaminants, such as polychlorinated biphenyls, which may be found in farmed salmon.
Omega-3 Fatty Acids
Fish is an important source of omega-3 fatty acids, which improve memory function and help to prevent some health problems, such as heart disease and cancer. Salmon is rich in these fatty acids, but canned salmon contains more per serving than other types. The canning process removes water from the fish, concentrating the fatty acids. According to the Tufts School of Medicine Nutrition/Infection Unit, one 4 oz. serving of canned salmon contains about 2.2 grams of omega-3 fatty acids, while the same portion of fresh or frozen salmon contains about 1.7 grams. However, the fatty acids degrade quickly in frozen salmon, so fish that has been frozen for a long period of time will have lower omega-3 content than will fresh fish.
Salmon contains higher levels of vitamin C than do oranges and lemons. Fresh and frozen salmon have equivalent levels. The canning process destroys some of this nutrient; however, much of the vitamin C that is lost from the salmon flesh remains in the liquid. You can regain most of the vitamin C by using the liquid in your recipes instead of draining it off. After canning, the levels of vitamin C remain stable over the salmon's shelf life.
Fresh and frozen salmon do not have particularly high levels of calcium. Canned salmon, however, contains bones that have been softened by the high temperatures of the canning process. They can be eaten, and they provide a significant amount of calcium.
Canned salmon manufacturers often add salt to the fish before canning to improve the taste. This leads to high sodium levels in canned salmon that are not found in fresh or frozen salmon. You can avoid the extra salt by purchasing no-sodium-added canned products.
Bacteria and Spoilage
Canned salmon has a longer shelf life than fresh or frozen salmon. It is safe to eat for at least six years, but it may be good for as many as 10 years, depending on the conditions in which the can is stored. The high temperatures of canning destroy the bacteria that cause spoilage, preserving the fish. Frozen salmon may be stored for about six months, or up to a year in ideal freezing conditions. Fresh salmon must be refrigerated immediately and consumed within a few days of purchase.