Salmon is prized for its health benefits.
This fatty fish is loaded with omega-3 fatty acids, which most people don't get enough of.
However, not all salmon is created equal.
Today, much of the salmon you buy isn't caught in the wild, but bred in fish farms.
This article explores the differences between wild and farmed salmon and tells you whether one is healthier than the other.
Wild salmon is caught in natural environments such as oceans, rivers and lakes.
But half of the salmon sold worldwide comes from fish farms, which use a process known as aquaculture to breed fish for human consumption ().
The annual global production of farmed salmon has increased from 27,000 to more than 1 million metric tons in the past two decades (2).
Whereas wild salmon eat other organisms found in their natural environment, farmed salmon are given a processed, high-fat, high-protein feed in order to produce larger fish ().
Wild salmon is still available, but global stocks have halved in just a few decades (4).
Summary The production of farmed salmon has increased dramatically over the past two decades. Farmed salmon has a completely different diet and environment than wild salmon.
Farmed salmon is fed with processed fish feed, whereas wild salmon eat various invertebrates.
For this reason, the nutrient composition of wild and farmed salmon differ greatly.
The table below provides a good comparison. Calories, protein and fat are presented in absolute amounts, whereas vitamins and minerals are presented as percent (%) of the reference daily intake (RDI) (5, 6).
|1/2 fillet wild salmon (198 grams)||1/2 fillet farmed salmon (198 grams)|
|Protein||39 grams||40 grams|
|Fat||13 grams||27 grams|
|Saturated fat||1.9 grams||6 grams|
|Omega-3||3.4 grams||4.2 grams|
|Omega-6||341 mg||1,944 mg|
|Cholesterol||109 mg||109 mg|
Clearly, nutritional differences between wild and farmed salmon can be significant.
Farmed salmon is much higher in fat, containing slightly more omega-3s, much more omega-6 and three times the amount of saturated fat. It also has 46% more calories — mostly from fat.
Conversely, wild salmon is higher in minerals, including potassium, zinc and iron.
Summary Wild salmon contains more minerals. Farmed salmon is higher in vitamin C, saturated fat, polyunsaturated fatty acids and calories.
The two main polyunsaturated fats are omega-3 and omega-6 fatty acids.
These fatty acids play important roles in your body.
They’re termed essential fatty acids, or EFAs, because you need both in your diet.
However, it’s necessary to strike the right balance.
Most people today consume too much omega-6, distorting the delicate balance between these two fatty acids.
Many scientists speculate that this can drive increased inflammation and may play a role in modern pandemics of chronic diseases, such as heart disease (7).
While farmed salmon has three times the total fat of wild salmon, a large part of these fats are omega-6 fatty acids (, 8).
For this reason, the omega-3 to omega 6 ratio is about three times higher in farmed salmon than wild.
However, farmed salmon’s ratio (1:3–4) is still excellent — it's just less excellent than that of wild salmon, which is 1:10 ().
Both farmed and wild salmon should lead to a large improvement in omega-3 intake for most people — and is often recommended for that purpose.
In a four-week study in 19 people, eating farmed Atlantic salmon twice per week increased blood levels of the omega-3 DHA by 50% ().
Summary Though farmed salmon is much higher in omega-6 fatty acids than wild salmon, the total is still too low to cause concern.
Fish tend to ingest potentially harmful contaminants from the water they swim in and the foods they eat (, 11).
Studies published in 2004 and 2005 showed that farmed salmon had much higher concentrations of contaminants than wild salmon (, ).
European farms had more contaminants than American farms, but species from Chile appeared to have the least (, 14).
Some of these contaminants include polychlorinated biphenyls (PCBs), dioxins and several chlorinated pesticides.
Arguably the most dangerous pollutant found in salmon is PCB, which is strongly associated with cancer and various other health problems (, , , ).
One study published in 2004 determined that PCB concentrations in farmed salmon were eight times higher than in wild salmon, on average ().
Those contamination levels are deemed safe by the FDA but not by the US EPA (20).
Researchers suggested that if the EPA guidelines were applied to farmed salmon, people would be encouraged to restrict salmon consumption to no more than once per month.
Still, one study showed that the levels of common contaminants, such as PCBs, in Norwegian, farmed salmon decreased significantly from 1999 to 2011. These changes may reflect lower levels of PCBs and other contaminants in fish feed ().
In addition, many argue that the benefits of consuming omega-3s from salmon outweigh the health risks of contaminants.
Summary Farmed salmon may contain higher amounts of contaminants than wild salmon. However, the levels of contaminants in farmed, Norwegian salmon have been decreasing.
The current evidence for trace metals in salmon is conflicting.
However, one study determined that wild salmon had levels three times higher (23).
All told, levels of arsenic are higher in farmed salmon, but levels of cobalt, copper and cadmium are higher in wild salmon ().
In any case, trace metals in either variety of salmon occur in such low amounts that they’re unlikely to be a cause for concern.
Summary For the average person, trace metals in both wild and farmed salmon do not appear to be found in harmful quantities.
Due to the high density of fish in aquaculture, farmed fish is generally more susceptible to infections and disease than wild fish. To counter this problem, antibiotics are frequently added to fish feed.
Unregulated and irresponsible use of antibiotics is a problem in the aquaculture industry, especially in developing countries.
Not only is antibiotic use an environmental problem, but it is also a health concern for consumers. Traces of antibiotics may cause allergic reactions in susceptible individuals ().
Overuse of antibiotics in aquaculture also promotes antibiotic resistance in fish bacteria, increasing the risk of resistance in human gut bacteria through gene transfer (, ).
The use of antibiotics remains poorly regulated in many developing countries, such as China and Nigeria. However, salmon is generally not farmed in these countries ().
Many of the world’s largest producers of salmon, such as Norway and Canada, are considered to have effective regulatory frameworks. Antibiotic use is strictly regulated and the levels of antibiotics in fish flesh need to be below safe limits when the fish are harvested.
Some of Canada’s largest fish farms have even been reducing their antibiotic use in recent years ().
On the other hand, Chile — the world’s second largest producer of farmed salmon — has been experiencing problems due to excessive antibiotic use ().
In 2016, an estimated 530 grams of antibiotics were used for each ton of harvested salmon in Chile. For comparison, Norway used an estimated 1 gram of antibiotics per ton of harvested salmon in 2008 (, ).
If you're concerned about antibiotic resistance, it might be a good idea to avoid Chilean salmon for now.
Summary Antibiotic use in fish farming is an environmental hazard as well as a potential health concern. Many developed countries strictly regulate antibiotic use, but it remains poorly regulated in most developing countries.
It is important to keep in mind that farmed salmon is still very healthy.
In addition, it tends to be much larger and provides more omega-3s.
Wild salmon is also much more expensive than farmed and may not be worth the extra cost for some people. Depending on your budget, it may be inconvenient or impossible to buy wild salmon.
However, because of environmental and dietary differences, farmed salmon contains much more potentially harmful contaminants than wild salmon.
While these contaminants appear to be safe for the average person consuming moderate amounts, some experts recommend that children and pregnant women only eat wild-caught salmon — just to be on the safe side.
It is a good idea to eat fatty fish such as salmon 1–2 times per week for optimal health.
This fish is delicious, loaded with beneficial nutrients and highly filling — and therefore weight-loss-friendly.
The biggest concern with farmed salmon is organic pollutants like PCBs. If you try to minimize your intake of toxins, you should avoid eating salmon too frequently.
Antibiotics in farmed salmon are also problematic, as they may increase the risk of antibiotic resistance in your gut.
However, given its high amount of omega-3s, quality protein and beneficial nutrients, any type of salmon is still a healthy food.
Still, wild salmon is generally better for your health if you can afford it.