Is it safe to eat fish packaged in cans, like salmon and sardines?
Food packaging of any kind can present health risks if there are unwanted substances in the packaging that come into direct contact with the food. These risk are not usually great enough for a person to automatically avoid the food, but if the food is a regular part of the diet (eaten several times a week or more over a long period of time), it may still be worth considering a change in the food selection.
With canned food, the risk is greater if the food inside the can is either watery and acidic (like canned tomatoes or canned tomato sauce) or if it is oily (like canned sardines and salmon). The risk is also greater when heating is involved. In general, we would place oily, canned fish like canned sardines and salmon in a higher-than-average risk category since there is often "double-cooking" involved (cooking prior to canning, and then heating in the can for sterilization purposes), and oils in and surrounding the fish can allow contaminants in the packaging to migrate from the can into the food.
Because many types of packaging can pose small levels of risk, the question is not whether canned foods like salmon and sardines can pose any health risk whatsoever, because we know that they may. The questions are really how much risk, whether the nutritional benefits of the canned food outweigh the risks, and whether there are any practical options for bringing these same foods into a diet in a different form. However with Tuna, remember the Mercury content should always be a concern.
Let's look specifically at canned salmon. We include salmon among the World's Healthiest Foods because this fish has so much to offer in terms of nourishment, especially in terms of its rare omega-3 fats. We believe it is always worth looking to find the least contaminated type of salmon (usually wild-caught Pacific salmon or organically farmed salmon). When it comes to fresh or frozen wild-caught Pacific salmon and organically farmed salmon, we believe the benefits outweigh the risks. We also believe this conclusion holds true for some canned salmon, but not in all cases, due to the issue of one particular toxin called bisphenol-A (BPA). BPA is a chemical used in the manufacturing of some vinyl can liners, including those found in some canned fish. Researchers classify BPA as an "endocrine disruptor" because it has the ability to disrupt activities in the body's endocrine (hormonal) system. We only seen a few studies that actually measured BPA in canned fish, and the results were mixed. Some of the studies showed contamination of the fish with BPA, and some did not. But to err on the safe side, we recommend that you avoid purchasing either canned salmon or canned sardines in vinyl-lined cans that contain BPA.
We recommend contacting the manufacturers of these products to find out which ones are using BPA-free cans. If you cannot find BPA-free cans, you may want to consider purchasing the fish in another (non-canned) form. The convenience of canned fish might make sense in certain circumstances, depending on where a person lives, the time of year, or other factors. In general, however, fish are like any other World's Healthiest food: we are better off consuming fish in a form that is as close as possible to the whole, natural form.
References Cabado AG, Aldea S, Porro C, et al. Migration of BADGE (bisphenol A diglycidyl-ether) and BFDGE (bisphenol F diglycidyl-ether) in canned seafood. Food Chem Toxicol. Food Chem Toxicol. 2008, May; 46(5):1674-80. 2008. Dionisi G, Oldring PK. Estimates of per capita exposure to substances migrating from canned foods and beverages. Joint Industry Group (JIG). Food Addit Contam 2002, 19(9): 891-903. 2002. Kipcic D, Vukusic J. Polychlorinated biphenyls in fresh and canned fish from the Central Adriatic. Food Addit Contam 1991; 8(4): 501-504. 1991. Simoneau C, Theobald A, Wiltschko D, et al. Estimation of intake of bisphenol-A-diglycidyl-ether (BADGE) from canned fish consumption in Europe and migration survey. Food Addit Contam 1999, 16(11): 457-463. 1999.