Is Canned Salmon Bad For You?

Concentrated Contaminants

Fish have a habit of soaking up any nasty chemicals in their environment. Salmon are no exception. Farmed salmon exhibit this trait to an extreme. Since they're raised in a relatively small body of water, anything that winds up in the water will almost certainly make it to your plate. 

With salmon, you're mostly concerned with industrial chemicals. Polychlorinated biphenyls, or PCBs, are a type of toxic compound that's been banned in the US since the 1970's. Because PCBs don't decay very quickly, they tend to accumulate in the bottom of rivers and lakes. This makes it easy for salmon to soak them up. 

Other chemicals that can wind up in your salmon include pesticides and dioxins, a group of chemical toxins that are especially slow to decay. Until very recently, the conventional wisdom was that farmed salmon contain more contaminants than wild-caught salmon. A 2004 study found that farmed salmon had 8 times as much PCBs as a similar sample of wild-caught salmon. 

The good news is that we're getting much better at keeping contaminants out of fish. A 2011 Norwegian study found that contaminant levels had dropped significantly since 1999. The study concluded that a person could safely eat about 3 pounds of farmed Norwegian salmon each week. A more recent 2017 Norwegian study went further still, pointing out errors in earlier studies and claiming that farmed salmon are now safer to eat than wild-caught. 

PCBs, dioxins, and pesticides have very serious effects, especially at high doses. Exposure to PCBs can result in cancer, weight loss, liver damage, a weakened immune system, breathing problems, and death in more extreme cases. Dioxins can cause skin lesions, cancer, liver damage, nervous system damage, and reproductive damage. The effects of pesticides vary, but pesticides are deliberately designed to disrupt the systems of living beings and are very unsafe to eat. Pentachlorophenol kills your liver, for example, while organochlorines kill your brain. 

Canning Chemicals 

A compound called bisphenol A (or BPA) is used in small amounts in the lining of most canned food. While there's some contention about whether or not BPA is safe to eat, the European Food Safety Authority has repeatedly examined scientific evidence and concluded that it's safe to use in food. 

In high doses, BPA is an endocrine disruptor, which means it blocks your body's hormones. Endocrine disruptors can cause serious side effects, including mental health issues, developmental disorders, and cancers. 

While studies have linked low doses of BPA to dramatic changes in rats, there's some contention about the validity of those studies. BPA is found in the packaging of most canned food and drinks, making it difficult to isolate the effects of prolonged exposure in adults. 

Mercury Levels 

The amount of mercury in a can of salmon will vary, but it tends to be pretty low. A 2004 survey found that salmon's mercury content was between 20 and 70 parts per billion. The same survey found that tuna contained mercury levels between 42 and 338 parts per billion. Most experts classify salmon as a low-mercury fish and suggest that you can eat it for multiple meals each week. 

Nutrients, Vitamins, and Minerals 

Now the good side of canned salmon. Salmon is rich in omega-3 fatty acid. This compound helps your body lower levels of certain fats in your bloodstream, which in turn lowers your risk of heart attacks and other cardiovascular diseases. 

When it comes to vitamins, salmon is no slouch. It's got a surprisingly large amount of vitamin D, which helps you absorb calcium, manage inflammation, and grow strong bones. There aren't a lot of dietary sources of vitamin D. Usually, this isn't a problem since your body makes its own vitamin D when it's exposed to sunlight, but if you're inside a lot eating canned salmon can help. 

Salmon also contains a lot of vitamin B12 (about twice your daily value) and niacin (about half your daily value). B12 is important for producing red blood cells, while niacin helps keep your skin, nerves, and digestive tract healthy. 

Finally, salmon is very rich in protein, especially on a per-calorie basis. A 3 oz can of salmon has about 17g of protein in 177 calories. This is pretty comparable to a serving of your favorite protein shake. Protein is best known for building and maintaining your body's muscles, but it's also used to maintain your metabolism, carry information throughout your body, and perform other tasks.